The Dawn and Dusk of the Age of Mammals

In Beasts Before Us, paleontologist, Elsa Panciroli, traces the evolutionary history of the mammal class of the animal kingdom, of which humans are members, to its origins about 300 million years ago.  It’s a tedious recitation of multitudes of now extinct species from their earliest ancestors up to the dawn of the age of mammals that began 66 million years ago after the abrupt end of the age of dinosaurs. But it’s also a rewarding read because it reminds us of our close relationships with other animals as well as the ways in which we are different.  Those differences predict which mammals will survive the forthcoming sixth great extinction that humans have inflicted on life on Earth.

Mammals living today have in common only one characteristic that distinguishes them from other classes of close relatives.  The subdivisions of mammals alive today have mammary glands that produce milk to feed their young.  The three subdivisions of mammals are monotremes, marsupials, and placentals.  Monotreme species alive today are platypus and echidna whose young are hatched from eggs, but are milk fed by their mothers.  Marsupials are born at an undeveloped stage and carried to term in their mothers’ pouch.  By far the largest group, placentals carry their developing offspring inside the mothers’ abdomen until birth. 

The earliest ancestors of mammals were four-legged vertebrates called amniotes. Amniotes were named for the membrane that lined the hard shells of their eggs, protecting the embryo.  The development of the amniotic membrane provided protection needed to lay and hatch eggs on land rather than the ocean where earlier forms of life lived.  This evolutionary development was associated with the transition of life from the ocean to the land.  The earliest amniotes diverged to take two different evolutionary paths, one as reptiles and dinosaurs (sauropsids) and the other as mammals (synapsids).  Pause here briefly to contemplate our close relationships with other animals. 

The Science of Paleontology

Beasts Before Us is also interesting as a history of paleontology, the branch of science that studies fossils of plants and animals to determine the evolutionary history of life.  Beasts focuses on advances in modern paleontology, but this article takes readers further back in time to appreciate how recently we learned about the scale of past extinctions that predict future extinctions.

Prior to the 19th century, an understanding of extinction was inconsistent with prevailing Western belief that the world was created by God as complete, perfect, and unchangeable.  In the late 17th century fossils of extinct animals were discovered that appeared to be unlike any living species.  Inquiring minds began the search for an explanation for what happened to these unknown species. 

George Cuvier is credited with establishing the modern concept of extinction in a lecture to the French Institute in 1796.  Cuvier is sometimes called the “founding father of paleontology.”  He rejected the theories of evolution, believing instead that extinctions could be explained by “cyclical creations” and catastrophic natural events such as floods. 

The fossil record is limited in what it can tell us about life in deep time because it does not preserve the remains of extinct species with equal reliability.  Bones survive to tell the tale with greater accuracy than soft tissues and plants.  Paleontology is developing techniques to compensate for gaps in the fossil record, drawing from other scientific disciplines, such as botany, biochemistry, mathematics, and engineering. 

Since more than 99% of all species that ever lived on Earth—more than five billion species–are now extinct, we can only imagine the difficulty of the task of piecing together the complete phylogenetic tree of life.  Beasts Before Us gives us a current view of what has been accomplished to date.  Clearly it is not the end of the story and much of the story is still speculative. 

Divergent Evolution

The 300-million year journey from the first ancestors of mammals to modern mammals of today is a story of divergent evolution, the accumulation of differences between closely related populations within species that lead to new species. Tracing that long process was until recently dependent upon the fossil record and was therefore focused on changes in bone structure, particularly teeth, jaws, and skulls for which the fossil record is more intact. 

Evolutionary tree of mammals. Wikimedia Commons

These bone structures are important clues about the diet of animals. The teeth of herbivores, insectivores, and carnivores are different.  “Mammal fossils can be distinguished and named based on their teeth alone.” (1) Nearly half of all mammal species are rodents, a name that comes from the Latin word for gnaw.  Their long front teeth grow continuously as they are ground down by gnawing on tough plant material such as tree bark in the case of beavers or the wooden shingles on my home in the case of squirrels.

The digestive systems of mammals also diverged to accommodate their different diets (or vice versa).  Carnivores typically have a short intestinal track where digestion is accomplished with enzymes and resident microbial communities.  Herbivores have a longer digestive system in which plant material is fermented in a series of separate chambers in the case of ruminants (cows, sheep, deer, etc.). 

Divergent evolution creates diverse species with diverse abilities to exploit different ecological niches while reducing competition between species.  Shortly after the divergence of mammal and reptile lineages, the characteristic most consequential to the fate of those lineages was endothermy (warm-bloodedness) in mammals and ectothermy (cold-bloodedness) in reptiles. The divergence of this characteristic occurred about 250 million years ago, shortly after the divergence of mammal and reptile lineages. 

Only mammals and birds are generally capable of generating their body heat internally.  Over millions of years they also evolved insulation that conserves body heat with fur, feathers, and blubber in the case of marine mammals. A diet high in sugar and fat also helps to maintain body heat. Cold blooded animals depend on external heat sources such as sunlight to be active.  These crucial differences in mammals and reptiles relegate them to different ecological niches to which they are suited, for example:

  • Mammals and birds can survive in colder climates than reptiles.
  • Mammals and birds can be more active at night when it is cooler.
  • Mammals and birds can be more active for longer periods of time than reptiles.
  • Mammals and birds can live below ground where it is colder in summer and warmer in winter than above-ground temperatures.
  • On the other hand, mammals and birds must eat more and more frequently than reptiles. 

These significant differences are partly responsible for the sudden transition from the age of dinosaurs to the age of mammals 66 million years ago.  During the age of dinosaurs, mammals were small, lived below ground, and ate primarily insects.  This lifestyle avoided competition with huge dinosaurs that dominated the land. 

Scale diagram comparing a human and the largest-known dinosaurs of five major clades Creative Commons Attribution-Share Alike 4.0 International license.

When the asteroid hit the Earth 66 million years ago, the climate was suddenly and drastically transformed from a tropical climate to a cool, partly sunless climate.  Vegetation adapted to a tropical climate quickly died, depriving dinosaurs of their food if they weren’t killed outright by the impact. 

Beasts paints a vivid and dire picture of the cataclysmic event that ended the age of dinosaurs.  The asteroid created a crater almost 100 miles in diameter and 12 miles deep.  “An earthquake larger than any recorded in human history would have made the Earth reverberate like a bell.  The thermal shockwave would have flash-fried all life for hundreds of miles.  The blast of air probably flattened forests as much as 1,000 kilometers away…[the impact] created a mega-tsunami at least 330 feet in height…[that] mounted the coasts of North American and barreled inland like a liquid steam-roller…The dust in the atmosphere swirled its way around the planet until it enclosed all life in its smothering grip.  The sun rose, but as little as half of its light could penetrate the dust in the atmosphere.  The sulphur in the dust combined with water droplets to rain sulphuric acid on the land, burning away the green vegetation…Few animals bigger than a Labrador dog survived the extinction event.”  (1; not verbatim)

The fifth extinction predicts the consequences of the sixth extinction

Small mammals were safely below ground and they didn’t require the great quantities of plant food required by dinosaurs.  Mammals inherited the Earth and over millions of years they evolved into some 5,500 mammal species today of which 90% are still small bodied, most of them rodents.

The final chapter of Beasts uses the consequences of the fifth extinction that ended the age of dinosaurs to predict the consequences of the anticipated sixth extinction because “Humans are replicating many of the conditions of previous mass extinctions.” (1)

  • Animals are likely to become more active at night, when temperatures are cooler.
  • Animals are likely to find some respite by living below ground where temperatures are more moderate in winter and summer. 
  • Animals will move to more temperate regions if they can.

The animals that are most likely to survive will be small generalists, who need less food, are not fussy about what they eat, and are more capable of tolerating heat. Think rats. Beasts advises, “If I were you, I’d say goodbye to any wild animal bigger than a pig—zoos are likely to be the only refuges for them in the future we are creating.”

Birds were the only descendants of dinosaurs to survive the fifth great extinction.  They are expected to fare better in the sixth extinction for much the same reason:  they can be active at night; they eat insects as well as plants; they are more mobile than most classes of animals.  We often hear dire predictions of the fate of birds, but in fact they are less threatened than other classes of animals.  A recent study reported that 21% of reptiles are threatened with extinction, a higher risk than birds (of which about 13 percent of species are threatened with extinction) and slightly less than mammals (25 percent). Amphibian species are at highest risk with about 40 percent of species in danger of extinction.  We hear more about birds because their popularity motivates greater media coverage about them.

I will also presume to give my readers some advice. 

  • Quibbling about whether native plants are superior to non-native plants is like arguing about the color of the lifeboat. It really doesn’t matter.  Soon enough we will be glad to have ANY vegetation that is capable of living in the climate we have created. The universe is indifferent to the survival of any specific species of life.
  • You can do more for the environment and the animals that live in it by stopping the use of pesticides than by planting native plants. 
  • Be humble about what you think you know.  Many important scientific concepts such as evolution and extinction are less than 200 years old and the cause of the extinction of dinosaurs was discovered less than 50 years ago.  What you learned 50 years ago may need to be reconsidered and revised.  A rapidly changing situation requires that we keep an open mind to new information.
  • Set meaningful prioritiesClimate change is an existential threat to all life on Earth.  Ask yourself how we can justify the destruction of healthy trees that sequester the carbon that contributes to climate change? 

  1. Elsa Panciroli, Beasts Before Us: The Untold Story of Mammal Origins and Evolution, Bloomsbury Sigma, 2021

History of Earth predicts its future

My interest in the native plant movement began about 25 years ago when my neighborhood park was designated as a “natural area” by San Francisco’s Recreation and Park Department.  My park was only one of 33 parks in San Francisco that were designated as a “natural area.” 

What did it mean to be a “natural area?”  As I studied the plans, my reaction was primarily to the proposed destruction of non-native plants and trees.  Later I realized that the eradication of non-native plants and trees would be accomplished with herbicides. 

Stern Grove Park in San Francisco was my neighborhood park where I began my long journey to understand why anyone would want to destroy trees in a treeless neighborhood. 

How could the creation of native plant gardens justify the destruction of our urban forest using herbicides?  I have spent the last 25 years trying to answer that question.  There are many useful lines of inquiry in the search for the answer, but the approach that has been most helpful to my understanding of the futility of the undertaking has been the study of the physical and biological forces that created Earth and its inhabitants.  Today, I will take you on an abbreviated journey of the past 4.6 billion years of events on Earth that have resulted in present-day nature, drawing from A Brief History of Earth by Andrew Knoll, Professor of Natural History at Harvard University. (1)

Gravity “created” the Earth

“Gravity is the architect of our universe.”  Gravity is the attraction of objects to one another in proportion to their mass and proximity that over billions of years accumulated the elements dispersed in Earth’s universe.  As these dispersed objects coalesced into stars, planets, moons, and asteroids, Earth was formed about 4.6 billion years ago.

Cross-section of Earth. Source: USGS

“Earth is a rocky ball.”  Its inner core is solid, composed mostly of iron.  Earth’s molten outer core moves by convection as hotter, denser material near the base rises and cooler, less dense matter toward the top sinks.  This circular motion generates electrical current that creates the Earth’s magnetic field.  The mantle is composed of the molten magma that emerges on the surface crust of Earth where tectonic plates are separating and when volcanoes erupt where tectonic plates submerge into the mantle. The crust of Earth that is visible to us is only 1% of Earth’s mass.

Physical Earth

Simplified map of Earth’s principal tectonic plates, which were mapped in the second half of the 20th century (red arrows indicate direction of movement at plate boundaries).  Source:  USGS

The crust of Earth is composed of plates that are moved on the surface of the Earth by the convection current of the mantle.  Some of the plates are moving away from one another where they meet.  As the plates separate, molten magma from the mantle is pushed through the crust, forming new crust.  The North American and Eurasian plates are moving apart in the middle of the Atlantic Ocean at the rate of about 1 inch per year. 

Since the Earth is not getting bigger, the expanding crust collides with adjacent plates.  In some places, the collision of the plates pushes up the crust into mountain ranges.  The Himalayan mountain range is the result of the collision of the Indo-Australian and the Eurasian Plates, a process that continues today.

Map of subducted slabs, contoured by depth, for most active subduction zones around the globe. Source:  USGS

In other places, the expanding crust is pushed below the adjacent plate in subduction zones, where the crust dives below the crust into the mantle.  Earthquakes are common in subduction zones and the subducting plate triggers volcanic eruptions in the overriding plate.  Earthquakes are also common where adjacent plates are grinding against one another in opposite directions, as is the case on the coast of California.

Pangea super-continent

The movement of tectonic plates has assembled and reassembled the Earth’s continents many times. The entire history of the configuration of continents is not known to us because of the cycle of the crust emerging from the mantle only to return to the mantle about 180 million years later.  We know that all continents were fused into a single continent, named Pangea, about 350 million years ago and began to break up 200 million years ago.  Much of life as we know it evolved on Earth while the continents were fused, which is one of the reasons why all life on Earth is related.  Geographic isolation of species results in more biodiversity as genetic drift and different environments result in greater speciation.  Geologists believe such continental mergers are likely in the distant future.  

Earth’s oceans and atmosphere were formed within the first 100 million years of its birth.  Continents were visible above oceans, but small compared to their present size.  The absence of oxygen in the air at that early stage was the most significant difference between present and early Earth.

Biological Earth

Life, as presently defined, requires growth and reproduction, metabolism, and evolution. (I say, “presently defined” because debate continues about defining viruses as life since they do not meet all criteria.)  The chemical components required to perform the functions of life and the natural processes to combine them (such as heat and lightning) were available on Earth for millions of years before they combined to perform the functions of life.  Precisely how and when that happened on Earth is studied intensely, but not conclusively known, although Professor Knoll describes theoretical possibilities. 

The geological record suggests that “Earth has been a biological planet for most of its long history.” Microbes may have been living on Earth 4 billion years ago.  Climate on Earth was warm at that time for the same reason the climate is warming today.  The atmosphere was composed primarily of carbon dioxide (the greenhouse gas that traps heat on the surface of the Earth) and nitrogen:  “…life emerged on an Earth barely recognizable to the modern eye—lots of water and not much land, lots of carbon dioxide but little or no oxygen…”

Oxygen Earth

Phylogenetic tree of life based on Carl Woese et al. rRNA analysis. The vertical line at bottom represents the last universal common ancestor.

Two of the three domains of life were capable of living without oxygen:  archaea and bacteria.  Archaea are single-cells without nuclei.  We are all too familiar with bacteria, as they are as much a part of our bodies as our own cells.  Oxygen was the prerequisite for the evolution of the third domain of life, eukarya.  The kingdoms of eukarya most familiar to us are plants, animals, and fungi. 

Oxygen arrived on Earth when early life forms evolved the ability to photosynthesize, the process by which plants (and some other organisms) use sunlight to synthesize food from carbon dioxide and water, generating oxygen as a byproduct.  This transition occurred about 2.4 billion years ago, as measured by the absence of iron on the seafloor after that time. 

Photosynthesis alone could not have accomplished the transformation of Earth’s atmosphere to the balance of carbon dioxide and oxygen needed to support complex life on our planet because photosynthesis also requires nutrients as well as sunlight and water.  Phosphorous weathers from rocks, a process that was initially limited by the small amount of land above sea level.  As the planet matured, more land emerged from the sea, making more phosphorous available to photosynthesizing organisms.  Photosynthesis was also enhanced when some bacteria and archaea evolved the ability to convert nitrogen gas into biologically usable molecules, a process called nitrogen-fixing.  Many plants in the legume family are capable of nitrogen-fixing today.

Extinctions of the past predict extinctions of the future

There have been five major extinction events in the past 500 million years that changed the course of evolution of life on Earth and at least 20 mass extinctions in total (2).  The first representatives of all modern animal phyla (a taxonomic classification between kingdom and class) evolved during the Cambrian Period (541-486 million years ago).  All extinction events were associated with radical changes in the climate.  Many of the changes in the climate were caused by changes in the balance of carbon dioxide and oxygen in the atmosphere.  All these catastrophic events were natural events, not caused by the activities of humans because they all occurred long before the advent of human evolution. 

The third and biggest extinction event occurred 252 million years ago at the end of the Permian geologic period, when more than 90% of marine animals and 70% of terrestrial species disappeared.  At that time, continents were fused into the single supercontinent of Pangea.  The extinction of most life on Earth was caused by the sudden and catastrophic change in the atmosphere–and therefore the climate–by an episode of volcanism in Siberia “a million times greater than any volcanism ever witnessed by humans” or our primate ancestors.  Gases emitted by volcanism at the end of the Permian period rapidly increased the carbon dioxide content of the atmosphere and oceans by several times greater than before that event.  “It would take 10 million years for life to reassemble into something approaching the complexity of the ecosystems that preceded it. The world that emerged from the volcanic dust was unlike anything that came before.” (2) The current increase of carbon dioxide in the atmosphere caused by the burning of fossil fuels by human activities is comparable to this event and is expected to cause the sixth great extinction on Earth.  

The fifth and most recent massive extinction event occurred 66 million years ago, bringing 170 million years of dinosaur evolution to an abrupt end. The entire environment of the planet was radically and suddenly altered by the impact of an asteroid 7 miles in diameter that landed on what is now the Yucatan peninsula in Mexico.  The impact engulfed Earth in a dust cloud that precipitated the equivalent of a nuclear winterkilling most vegetation and animals adapted to a much warmer climate.  As with all massive extinctions, it took millions of years for plants and animals to slowly evolve adaptations to the new environment.  Dinosaurs did not evolve again, a reminder that evolution does not necessarily repeat itself (although birds evolved from dinosaurs).  Although there were small mammals during the dinosaur age, the disappearance of dinosaurs and corresponding changes in the climate introduced the age of mammals, including the human lineage about 300,000 years ago.  When multiple animal groups disappear it creates opportunities by reducing competition between groups.

What can we learn from the history of Earth?

If a native plant advocate were reading this abbreviated history of Earth, these are the lessons I would hope they might learn from it:


  1. Andrew H. Knoll, A Brief History of Earth, 2021.  All quotes in this article are from this excellent book unless otherwise indicated.
  2. Elsa Panciroli, Beasts Before Us: The Untold Story of Mammal Origins and Evolution, Bloomsbury Sigma, 2021.

A Natural History of the Future

“The way out of the depression and grief and guilt of the carbon cul-de-sac we have driven down is to contemplate the world without us. To know that the Earth, that life, will continue its evolutionary journey in all its mystery and wonder.” Ben Rawlence in The Treeline

Using what he calls the laws of biological nature, academic ecologist Rob Dunn predicts the future of life on Earth. (1)  His book is based on the premise that by 2080, climate change will require that hundreds of millions of plant and animal species—in fact, most species–will need to migrate to new regions and even new continents to survive.  In the past, conservation biologists were focused on conserving species in particular places.  Now they are focused on getting species from where they are now to where they need to go to survive.

In Dunn’s description of ecology in the future, the native plant movement is irrelevant, even an anachronism.  Instead of trying to restore native plants to places where they haven’t existed for over 100 years, we are creating wildlife corridors to bypass the obstacles humans have created that confine plants and animals to their historical ranges considered “native.” 

The past is the best predictor of the future. Therefore, Dunn starts his story with a quick review of the history of the science that has framed our understanding of ecology.  Carl Linnaeus was the first to create a widely accepted method of classifying plants and animals in the 18th century.  Ironically, he lived in Sweden, one of the places on the planet with the least plant diversity.  Colombia, near the equator, is twice the size of Sweden but has roughly 20 times the number of plant species because biodiversity is greatest where it is hot and wet.

Global Diversity of Vascular Plants. Source: Wilhelm Barthlott, et. al., “Global Centers of Vascular Plant Diversity,” Nova Acta Leopoldina, 2005

 

Humans always have paid more attention to the plants that surround us and the animals most like us.  Dunn calls this the law of anthropocentrism.  We are the center of our own human universe.  Consequently, our awareness of the population of insects that vastly outnumber us came late to our attention in the 20th century.  In the 21st century we learned that all other forms of life are outnumbered by the microbial life of bacteria, viruses, and fungi that preceded us by many millions of years.  Our knowledge of that vast realm of life remains limited although it is far more important to the future of the planet than we realize because those forms of life will outlast our species and many others like us.

Tropical regions are expanding into temperate regions

The diversity and abundance of life in hot and wet tropical climates give us important clues about the future of our warming climate.  We tend to think of diversity as a positive feature of ecosystems, but we should not overlook that tropical regions are also the home of many diseases, such as malaria, dengue fever, zika, and yellow fever that are carried by insects that prey on animal hosts, including humans.  In the past, the range of these disease-carrying insects was restricted to tropical regions, but the warming climate will enable them to move into temperate regions as they warm. The warming climate will also enable the movement of insects that are predators of our crops and our forests into temperate regions.  For example, over 180 million native conifers in California have been killed in the past 10 years by a combination of drought and native bark beetles that were killed during cold winters in the past, but no longer are.  Ticks are plaguing wild animals and spreading disease to humans in the Northeast where they did not live in the cooler past. 

Human populations are densest in temperate regions“The ‘ideal’ average annual temperature for ancient human populations, at least from the perspective of density, appears to have been about 55.4⁰F, roughly the mean annual temperature of San Francisco…” (1) This is where humans are most comfortable, free of tropical diseases, and where our food crops grow best.  As tropical regions expand into temperate regions, humans will experience these issues or they will migrate to cooler climates if they can.

Our ability to cope with the warming climate is greatly complicated by the extreme variability of the climate that is an equally important feature of climate change.  It’s not just a question of staying cool.  We must also be prepared for episodic extreme cold and floods alternating with droughts. Animals stressed by warmer temperatures are more easily wiped out by the whiplash of sudden floods or drought.

Diversity results in resiliency

Diversity can be insurance against such variability.  If one type of crop is vulnerable to an insect predator, but another is not, growing both crops simultaneously increases resiliency.  That principle applies equally to crops that are sensitive to heat, cold, drought, or floods. 

Agricultural biodiversity. Source: Number of harvested crops per hectar combining 175 different crops. Source: Monfreda et al. 2008. “Farming the planet: Geographic distribution of crop areas, yields, physiological types, and net primary production in the year 2000”. Global Biogeochemical Cycles, Vol. 22.

Historically, cultures that grew diverse crops were less likely to experience famine than those that cultivated monocultures.  The Irish potato famine of the mid-19th century is a case in point.  The Irish were dependent upon potatoes partly because other crops were exported to Britain by land owners. When the potato crop was killed by blight, more than one million people died in Ireland and another million left Ireland.  The population dropped about 20-25% due to death and emigration.  The diversity of crops in the United States (where corn is the commodity crop) and Brazil (where soy is the commodity crop) is very low, compared to other countries.  This lack of diversity makes us more vulnerable to crop failure and famine, particularly in an unpredictable climate.

Change in total use of herbicides, antibiotics, transgenic pesticide producing crops, glyphosate, and insecticides globally since 1990. Source: A Natural History of the Future

Instead of increasing crop diversity, we have elected to conduct chemical warfare on the predators of our crops by using biocides, such as pesticides for agricultural weeds and insects and antibiotics for domesticated animals.  The scale of our chemical warfare has increased in response to growing threats to our food supply.  This is a losing strategy because as we increase the use of biocides we accelerate evolution that creates resistance to our biocides. We are breeding superweeds, insects, and bacteria that cannot be killed by our chemicals.  This strategy is ultimately a dead end.

Evolution determines winners and losers

Inevitably, evolution will separate the survivors of climate change from its victims. Dunn reminds us that “The average longevity of animal species appears to be around two million years…” for extinct taxonomic groups that have been studied.  In the short run, Dunn bets on the animals that are most adaptable, just as Darwin did 160 years ago.  The animals most capable of inventing new strategies to cope with change and unpredictability will be more capable of surviving.  In the bird world, that’s corvids (crows, ravens, jays, etc.) and parrots.  In the animal world that’s humans and coyotes.  We aren’t helping adaptable animals survive because we are killing abundant animals based on a belief it will benefit rare animals.  Even in our urban setting, the East Bay Regional Park District contracts Federal Wildlife Services to kill animals it considers “over-abundant,” including gulls, coyotes, free-roaming cats, non-native foxes, and other urban wildlife throughout the Park District.  We are betting on evolutionary losers.

 

If and when humans create the conditions that cause our extinction, many of our predators are likely to disappear with us.  Bed bugs and thousands of other human parasites are unlikely to survive without us.  Many domestic animals will go extinct too, including our dogs.  On the bright side, Dunn predicts that cats and goats are capable of surviving without us.             

Timeline of the evolution of life. Source: CK-12 Foundation

However, in the long run Dunn bets on microbial life to outlast humans and the plants and animals with which we have shared Earth.  Humans are late to the game, having evolved from earlier hominoids only 300,000 years ago, or so.  The plants and animals that would be recognizable to us preceded us by some 500 million years, or so.  But microbial life that is largely invisible to us goes back much further in time and will undoubtedly outlast us.  Dunn says microbial life will give a big, metaphorical sigh of relief to see us gone and our environmental pollutants with us.  Then microbial life will begin again the long process of rebuilding more complex life with their genetic building blocks and the tools of evolution. 

Some may consider it a sad story.  I consider it a hopeful story, because it tells me that no matter what we do to our planet, we cannot kill it.  For the moment, it seems clear that even if we are not capable of saving ourselves at least we can’t kill all life on Earth.  New life will evolve, but its features are unfathomable because evolution moves only forward, not back and it does not necessarily repeat itself. 


  1. A Natural History of the Future, Rob Dunn, Basic Books, 2021

Words Matter: “Die-Off” vs. “Die-Back”

California has been in severe drought conditions for over 10 years.  Climate change is the underlying reason for the extremity of the drought.  Maintaining our carbon sinks that sequester greenhouse gases causing climate change is one of our most important defenses against climate change and forests are one of our primary carbon sinks.  Unfortunately, California’s forests are dying of drought and associated insect infestations. You might think that given these conditions, we would try to preserve our forests. 

In fact, the drought has accelerated the war on our non-native urban forest in the San Francisco Bay Area.  All trees and plants have suffered during our prolonged drought.  Where trees are not irrigated in our parks and open spaces, signs of drought stress are visible.  Today, I am publishing my letter to the IPM Director and Fire Chief of East Bay Regional Park District about the need to make a distinction between dead trees and trees that are not dead, but showing symptoms of prolonged drought. My letter explains why we must distinguish between dead (described as “die-off”) and living trees (described as “die-back”) when making commitments to destroy trees that we desperately need during this climate crisis.

Links are provided to email addresses of recipients of my letter.  Please consider writing a letter of your own.


To:   Pam Beitz, Aileen Theile

CC:  Natural and Cultural Resources Committee, Matteo Garbelotto

As you know, the Park District hired the Garbelotto Lab at UC Berkeley to evaluate two species of trees in the parks, acacia and eucalyptus.  The reports of the Garbelotto Lab were recently published on the Lab’s website.  I am writing to ask that responsible staff read those reports and make adjustments in plans to remove trees as needed, based on those reports. 

Source: Report of Garbelotto Laboratory
Acacia die-off in Leona Canyon, East Bay Regional Park District. Source: US Forest Service

The diagnoses for acacia and eucalyptus are entirely different.  The pathogens are different in the two tree species.  The pathogens killing acacia are new and they are lethal.  The pathogens found in eucalyptus are not new.  They have been latent and asymptomatic in eucalyptus for decades and have only become symptomatic because of the stress of drought. The pathogens found in eucalyptus disfigure leaves and twigs, but are not fatal. 

Much like the microbes (bacteria, viruses, fungi, parasites) in our bodies that outnumber human cells, every tree is inhabited by microbes that are usually asymptomatic.  If similar tests were done on other tree species in the Bay Area, similar results would be found where trees are not irrigated.  The pathogens are always there.  Drought has made them visible.  If we were obligated to destroy every tree in the parks showing signs of drought stress, we would be required to remove most trees in the parks. 

There are significant disadvantages to destroying living trees:

  • A dead tree is not capable of resprouting, but a living tree is capable of resprouting unless it is a species that is not capable of resprouting. Eucalyptus, acacia, redwoods (not candidates for removal, but dying of drought nonetheless) and bay laurels are all vigorous resprouters.  The stumps of these living tree species will require herbicide applications to prevent them from resprouting. 
  • The herbicides used to prevent resprouting travel through the roots of the tree to kill the roots. Herbicides used to prevent resprouting damage the roots of neighboring plants and trees connected by their mycelium networks. 
  • The trees that are destroyed release their stored carbon into the atmosphere contributing to the greenhouse gasses causing climate change. In the absence of those trees, less carbon dioxide is removed from the atmosphere in the future.  Since the underlying cause of increased frequency and intensity of wildfires is the warmer/drier climate, removing living trees increases wildfire risks in the future.
  • As more trees die, wood debris has accumulated to the point that there isn’t sufficient disposal capacity. When roadsides in the Berkeley hills were clearcut over one year ago, it took 9 nine months to dispose of the wood debris.  Huge piles of wood debris were stacked on roadsides, creating a fire hazard.  The more trees that are destroyed, the more wood debris is created.
One of many piles of logs, Claremont Ave, November 2020. Photo by Doug Prose, courtesy Hills Conservation Network.

I am therefore concerned about the Park District’s plans to remove one million trees from parks in the East Bay, according to press coverage: “In consultation with academics and state experts, they’ve identified a mass die-off of trees in the parks as a result of stress from drought, climate change and a proliferation of non-native species. Now they estimate they need to remove more than 1 million trees on their land, at a cost of $20 million to $30 million in one park alone. One area of the die-off, located between Mt. Diablo and communities in Oakland and Berkeley, is particularly concerning to Fire Chief Aileen Theile.”  

In an earlier media interview Fire Chief Theile included eucalyptus in the list of dead trees: “The die-off, first noticed last October, has mostly hit eucalyptus, acacias, pines and bay laurels and has expanded this summer amid an exceptional drought.”  Oaks are strangely absent from that list of dead trees, although it is well known that there are thousands of dead oaks in the Park District that have not been removed.

In summary, I ask for your reconsideration of Park District plans and public communications regarding tree removals in the parks:

  • The Park District should confine plans for tree removals to dead trees. Dead trees are public safety risks that should be mitigated. Drought stressed trees that may be unsightly are not a priority for removal.  Given our heavy rains in December, it is still possible that many will recover.
  • Park District communications with the public should make a distinction between “die-off” and “die-back.” Acacias are accurately described as experiencing a die-off.  Eucalyptus are accurately described as experiencing a die-back.

Thank you for your consideration.

Open Letter to California Native Plant Society

A diverse garden of native and non-native plants will be the most resilient to climate change. Photo credit Marianne Willburn, Garden Rant

In a recent edition of Nature News, Jake Sigg published an announcement of a new publication and a brief description of it that was apparently written by Susan Karasoff, Outreach Chair of the Yerba Buena Chapter of the California Native Plant Society:

San Francisco Estuary Institute (SFEI) developed Making Nature’s City: A Science-based Framework for Building Urban Biodiversity, which summarizes the key indicators supporting urban biodiversity. Local native vegetation is the base of the food web for our wildlife, including our local native pollinators, our native bees, butterflies and hummingbirds.

Biodiversity is biosecurity. Biodiversity only applies to locally native plants and wildlife. Introduced, invasive and non-local native plants contribute to landscape diversity, not to biodiversity. Our pollinators eat local native plants and pollen as caterpillar food. Introduced plant leaves feed few, if any, caterpillar species. Caterpillar species feed the rest of our local food web. Healthy urban ecosystems are measured by the health of contributors to their biodiverse food web and habitat.

Native plants planted in plant communities are resilient to climate change. Introduced and non-local native plants and trees are not resilient to climate change. San Francisco benefits from native plants planted in plant communities. San Francisco Estuary Institute (SFEI)’s Hidden Nature project, done in conjunction with the Exploratorium, maps the locations of plant communities in San Francisco prior to European arrival.

Jake Sigg’s Nature News, February 18, 2022

I compared the description to the SFEI document because the description contains several counterintuitive statements.  Although the SFEI document reflects a clear preference for native plants, it does not corroborate these specific statements:

  • “Biodiversity only applies to locally native plants and wildlife. Introduced, invasive and non-local native plants contribute to landscape diversity, not to biodiversity.”
  • “Introduced plant leaves feed few, if any, caterpillar species.”
  • “Native plants planted in plant communities are resilient to climate change. Introduced and non-local native plants and trees are not resilient to climate change.”

Here are a few studies, references, and public policies that explicitly contradict these counterfactual statements.

Biodiversity is not confined to native plants

“Biodiversity is the biological variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic, species, and ecosystem level.” (Wikipedia)  The Simpson index and the Shannon-Wiener index are the two most commonly used measures of biodiversity by ecological scientists.   Neither index makes a distinction between native and non-native species.  In fact, such a distinction is difficult to make and is often hotly debated. 

In San Francisco, home of the Yerba Buena Chapter of the California Native Plant Society, public policy explicitly acknowledges that non-native species contribute to local biodiversity:  “Parks and open spaces in San Francisco include both native and non-native species, both of which can contribute to local biodiversity.” (Policy 4.1, Recreation and Open Space of San Francisco General Plan)

 Non-native plants are host to many butterflies in the Bay Area

Butterflies lay their eggs on plants called their host plants. The eggs develop through several larvae stages into caterpillars that feed on the host plant that is often confined to a particular plant genus or family.  Few butterflies are confined to a single plant species. For example, plants in the milkweed genus are the host of monarch butterflies.  There are many species within the milkweed genus and many are not native to the San Francisco Bay Area.  An introduced milkweed species, tropical milkweed, is a particular favorite of monarchs and it has the advantage of being available throughout the year, unlike native milkweed species that are dormant during winter months. Some have attributed the recent comeback of the California monarch migration to the widespread planting of tropical milkweed in residential gardens.

This article from the UC Davis Bug Squad says they plant tropical milkweed and two species of native milkweed in their experimental garden. Monarchs show a strong preference for tropical milkweed in their experimental garden: “In July, we collected 11 caterpillars from the narrowleaf [native] milkweed; we rear them to adulthood and release them into the neighborhood. But in the numbers game, the tropical milkweed [A. curassavica] won. From July through today, we have collected a whopping 43 eggs or caterpillars from A. curassavica. How many from [native] A. speciosa? Sadly, none.”

Anise swallowtail butterfly is another common butterfly species in the Bay Area that is dependent upon a non-native host plant.  Before non-native fennel was introduced to California, anise swallowtail bred only once each year. Now it is able to breed year around on non-native fennel and is therefore more plentiful than it was in pre-settlement California.

These butterfly species in the San Francisco Bay Area are not unique with respect to their need for non-native plants:  “California butterflies, for better or worse are heavily invested in the anthropic landscape [altered by humans].  About a third of all California butterfly species have been recorded either ovipositing [laying eggs] or feeding on nonnative plants.  Roughly half of the Central Valley and inland Bay Area fauna is now using nonnative host plants heavily or even exclusively.  Our urban and suburban multivoltine [multiple generations in one year] butterfly fauna is basically dependent on ‘weeds.’  We have one species, the Gulf Fritillary that can exist here only on introduced hosts.  Perhaps the commonest urban butterfly in San Francisco and the East Bay, the Red Admiral is overwhelmingly dependent on an exotic host, pellitory.  And that’s the way it is.” (1)

During the butterfly phase of life, butterflies eat pollen and nectar of many different plants, not just its host plant.  When native plant advocates eradicate important sources of food for butterflies, they aren’t helping butterflies.  For example, butterfly bush (buddleia) is as popular with butterflies as they are unpopular with native plant advocates because they aren’t native.  Butterflies don’t care if they are native because they are an important source of food. 

Butterfly bush is the host plant of Variable checkerspot butterflies. It is also an important source of nectar for butterflies and bees. It is being eradicated on public land because it is not a native plant. butterflybush.com

Native plants are NOT more resilient to climate change

The most dangerous of the counter-factual statements by the spokesperson for the California Native Plant Society is the claim that native plants are resilient to climate change, but non-native plants are not.  That claim defies reality and it prevents us from responding effectively to climate change. 

Here are a few samples from scientific literature that contradict this inaccurate claim about native plants.  There are many others, just Google “Are native plants more resilient to climate change.” 

  • “As spring advances across the Midwest, a new study looking at blooming flowers suggests that non-native plants might outlast native plants in the region due to climate change.”
  • “Warming temperatures affect native and non-native flowering plants differently, which could change the look of local landscapes over time, according to new research.”
  • ”Whether in natural areas or in our gardens, climate change is affecting native plants. According to the Maryland Climate Summary, our temperatures are expected to increase 5⁰ F to 11⁰ F by 2100.
    1. “Higher temperatures cause native plants to experience more heat-related stress. Heat stress causes higher water demand, a situation made worse by longer droughts.
    2. “Higher atmospheric carbon dioxide (CO2) levels preferentially promote the growth of invasive plant species, decreasing the space needed to support natural areas.
    3. “Elongated growing seasons cause earlier leaf out and bloom times, which in turn affects the animal species synchronized to the life cycles of native plants, especially pollinators.”

An appeal to native plant advocates

I am publishing this article today as an open letter to the California Native Plant Society as an appeal to their leadership to make a new commitment to accuracy.  CNPS and native plant advocates enjoy a vast reservoir of positive public opinion.  However, they put their reputation in jeopardy by advocating for policies that are not consistent with reality, with science, or with public policy.  CNPS can’t distance itself from the Yerba Buena Chapter of CNPS because Susan Karasoff has made several presentations for CNPS that are available on its website.  Native plant advocates can best promote their agenda by providing accurate information.


California Natural Resources Agency writes a BIG blank check to the “restoration” industry

California Natural Resources Agency has published the draft of “Pathways to 30X30 California” and has invited the public to comment on the draft by February 15, 2022.  “Pathways to 30X30” is the last in a series of documents that defines the program before implementation in February 2022, when distribution will begin of $15 Billion dollars to public and non-governmental agencies to fund specific projects. 

To recap the process that began in October 2020 with the passage of an Executive Order:

  • In October 2020, Governor Newsom signed Executive Order N-82-20 “enlisting California’s vast network of natural and working lands – forests, rangelands, farms, wetlands, coast, deserts and urban greenspaces – in the fight against climate change. A core pillar of Governor Newsom’s climate agenda, these novel approaches will help clean the air and water for communities throughout the state and support California’s unique biodiversity.” The program and its implications are described by Conservation Sense and Nonsense HERE.
  • California Natural Resources Agency held a series of public workshops in summer 2021 that were theoretically an opportunity for the public to participate in the process of defining the program.  Conservation Sense and Nonsense identified potential opportunities as well as pitfalls of the program HERE.
  • California Natural Resources Agency published the first draft of implementation plans in fall 2021.  Conservation Sense and Nonsense published its favorable opinion of the first draft that is available HERE.

The draft of the final implementation document is disappointing.  My public comment on the draft of “Pathways to 30X30” is below.  To preview it briefly here, this is its concluding paragraph:  “California’s 30X30 initiative had great potential to improve the environment rather than damaging it further.  Instead, draft “Pathways to 30X30” suggests that opportunity may be squandered.  Of course, the proof will be in the projects, but for the moment it looks as though the lengthy public process may have been a charade intended to benefit the “restoration” industry, not the environment or the public.”

Please consider writing your own public comment by February 15, 2022.

  • Email: CaliforniaNature@Resources.ca.gov;
  • Letter via postal mail: California Natural Resources Agency, 715 P Street, 20th Floor, Sacramento, CA 95814;
  • Voice message: 1 (800) 417-0668.
  • There will be a virtual meeting on Tuesday, February 1, 2022, 3-6 pm in which the public will be invited to make 2 minute comments.  Register HERE.

TO:        California Natural Resources Agency

RE:         Public comment on draft “Pathways to 30X30”

I have attended the public workshops regarding the 30X30 initiative and sent written feedback when given the opportunity.  I am therefore in a position to tell you that the “Draft Pathways to 30X30” is a significant retreat from principles defined by previous drafts because it is so vague that it is meaningless. Any project could be approved within its limitless boundaries. The document puts CNRA in the position to do whatever it wishes, including violate principles defined in previous draft documents.

My public comment is a reminder of commitments made in previous drafts and a request that they be reinstated in the final version of the Draft “Pathways to 30X30” document:

  • “Pathways to 30X30” must confirm its commitment to reducing the use of pesticides on public lands.  The draft mentions the need to “avoid toxic chemicals” only in the context of working lands.  That commitment must also be made for public parks and open spaces because widespread pesticide use is exposing the public and wildlife to dangerous pesticides and killing harmless plants while damaging the soil.
  • Unlike the previous draft, “Climate Smart Strategy,” “Pathways to 30X30” requires the exclusive use of native plants, which contradicts the commitment to “promote climate-smart management actions.”  The ranges of native plants have changed and must continue to change because native plants are no longer adapted to the climate.  We cannot reduce greenhouse gas emissions causing climate change if we cannot plant tree species that are capable of surviving in our changed climate, as acknowledged by previous draft documents. As Steve Gaines said in the January 12th public meeting regarding “Pathways to 30X30,” “We must help species move [because the changing climate requires that they do].”

There are significant omissions in “Pathways to 30X30” that epitomize my disappointment in this draft:

  • The draft kicks the can down the road with respect to integrating climate change into consideration of projects funded by the initiative:  “Designations have not yet been established that emphasize climate benefits such as carbon sequestration or buffering climate impacts. While the definition of conserved lands for 30×30 builds upon existing designations, it will be important to integrate climate…” (pg 26)  Climate change is the underlying cause of most problems in the environment, yet “Pathways to 30X30” dodges the issue by declining to take the issue into consideration as it distributes millions of grant dollars to projects that are toxic band aides on the symptoms of climate change.
  • The 30X30 initiative made a commitment to protecting 30% of California’s land and coastal waters.  At 24%, we are close to that goal for land, but at only 16% we are far from the goal for coastal waters.  Yet, the draft declines to protect more marine waters:  “MPA [Marine Protected Areas] Network expansion will not be a component of meeting the State’s 30×30 marine conservation goals.” (pg 29, deeply embedded in fine print) The excuse for this omission is that the decadal review of existing MPAs won’t be completed for another year.  That is not a legitimate reason for refusing to designate new MPAs.  The evaluation of existing MPAs can and should be completed and inform the management of new MPAs going forward. 

The lack of guidance in “Pathways to 30X30” is particularly dangerous because California law has recently been revised to exempt projects considered “restorations” from CEQA requirements for Environmental Impact Reports for three years, ending January 1, 2025. An Environmental Impact Report is the public’s only opportunity to preview planned projects and challenge them within the confines of CEQA law.  The public is effectively shut out from the process of distributing millions of grant dollars of the public’s tax money by this blanket exemption on CEQA requirements for an EIR. 

The Draft of “Pathways to 30X30” writes a big blank check for projects that will potentially increase the use of pesticides on our public lands and increase greenhouse gas emissions by destroying plants and trees that sequester carbon and are capable of surviving our current and anticipated climate. 

California’s 30X30 initiative had great potential to improve the environment rather than damaging it further.  Instead, draft “Pathways to 30X30” suggests that opportunity may be squandered.  Of course, the proof will be in the projects, but for the moment it looks as though the lengthy public process may have been a charade intended to benefit the “restoration” industry, not the environment or the public. 

The need for diverse urban forest and the obstacles to achieve that goal

Matt Ritter is a professor of biology at Cal Poly San Luis Obispo and Director of Cal Poly Plant Conservatory.  He is the author of several books about California’s unique flora, including A Californian’s Guide to the Trees Among Us.  He is considered an expert on the horticulture, ecology and taxonomy of the Eucalyptus genus.

Click on picture to view Professor Ritter’s presentation

In October 2021, Professor Ritter gave a presentation to the California Urban Forests Council, entitled “Underutilized Species for the Future of Urban Wood and Urban Forestry.”   He began by explaining why it is important to identify new tree species for our urban forest.

  • “Baja is moving to Oregon,” said Ritter to set the stage.  Within 50-80 years trees living in California now will no longer be adapted to the anticipated warmer, drier climate.  Trees killed by wildfire in California are not returning.  Forests are quickly converting to grassland and shrub.  As of 2018, California had lost 180 million trees to drought, disease, bark beetles, heat, and wildfire, which is nearly 5% of the total tree population in California.  Adding subsequent years to date, we have probably lost 7% of all of our trees.
  • Trees in urban areas will help Californians cope with warmer conditions because they cool our cities and reduce energy consumption.  Fewer trees will mean a lower quality of life, for us and for birds.  The loss of our trees reduces carbon storage, which contributes to more climate change. 

Ritter then explained why we must diversify tree species in our urban forests.

  • There are over 60,000 tree species in the world and only 7% of tree species are found in urban areas around the world.  In California our urban forests are even less diverse.  There are only 234 tree species on average in California’s urban forests.  The average number of approved tree species for planting in California’s municipalities is only 49 and few species on those approved lists are native to California.
  • Diversity of tree species ensures greater resiliency that enables our urban forests to survive changing conditions.
  • Only 9% of tree species in California’s urban forests are native. 
The native ranges of tree species in California’s urban forest.

An inventory of Oakland’s urban forest (street trees, medians, and landscaped parks only) was recently completed.  With 535 tree species, the diversity of Oakland’s urban forest is greater than average for California.  With 14% native trees, Oakland’s urban forest is more native than average. There are 59 species on Oakland’s list of approved trees, of which only 4 are native to Oakland.  The most significant finding of Oakland’s tree inventory is that our urban forest is only 64% “stocked,” meaning that of existing tree wells, only 64% are currently planted with trees.  When trees die in Oakland, they aren’t being replaced.  I don’t doubt there is a will to plant trees in Oakland.  I assume it is a question of means in a city with more pressing needs than resources.

Ritter and his colleagues at Cal Poly have created a website called SelecTree to help Californians choose the right tree for the right site and conditions.  There are 1,500 tree species described on SelecTree, using 60 characteristics, such as drought tolerance.  SelecTree rates blue gum eucalyptus “medium” for drought tolerance, the same rating as native coast live oak and bay laurel.  Ritter clarified that drought tolerance on SelecTree is a measure of how much water the tree species uses.  Claims that eucalyptus uses more water than native trees is bogus, like most bad raps about eucalyptus.  

Ritter recommended specific tree species, based on their drought and heat tolerance.  He said that when diversifying our urban forests “we have to think about Australia” because it is the hottest, driest, flattest, and oldest place on the planet, which is another way of saying that tree species in Australia have survived terrible conditions that are comparable to the challenging conditions in urban environments.

Ritter recommended oak species that are native to Texas; eucalyptus and closely related tree species; and several tree species in the legume family, especially acacia.  In each case he mentioned the suitability of tree species based partly on the quality of its wood.  Apparently, I’m not the only person in California who is disturbed by huge piles of wood chips wherever trees have been destroyed.  Ritter also thinks we should be thinking about how we can use wood when trees are destroyed, rather than building potential bonfires.  

Obstacles to diverse urban forests in California

When Professor Ritter took questions from the audience, we learned that the main obstacle to a diverse urban forest in California, adapted to our climate conditions, is the myopic focus of native plant advocates:

Question:  “Are we introducing new pathogens to our natives by importing new species?”

Answer:  There are many laws and rules that restrict the importation of plants to prevent that from happening.  We also import only the seeds of plants, not grown plants.  The seeds are sterilized and they don’t carry the pathogens that may exist on grown plants in their native ranges.

Question:  “Do we know how quickly birds and insects adapt to new species?”

Answer:  “No we don’t, but who cares?  We are facing a climate emergency.   We have 50 years before life in our cities becomes hell.  We have a responsibility to protect the quality of life in our cities.  We should stop developing the wild, but cities are different.” 

Ritter anticipated a question that is often a concern of native plant advocates by saying we should not be concerned about “weediness,” AKA “invasiveness.”  He said, “That should be far down on our list of priorities of what to worry about.  We need to be primarily concerned about what tree species will grow in our changed climate.”

Rhetorical Question:  “But insects need native plants!

Answer:  Ritter instantly recognized the mantra of Doug Tallamy.  He replied that it is not well established that there are more insects living on native plants than on introduced plants.  He mentioned a single study that inventoried plant and animal species in eucalyptus compared to oak forests, presumably Dov Sax’s study which concluded:  “Species richness was nearly identical for understory plants, leaf-litter invertebrates, amphibians and birds; only rodents had significantly fewer species in eucalypt sites.  Species diversity patterns…were qualitatively identical to those for species richness, except for leaf-litter invertebrates, which were significantly more diverse in eucalypt sites during the spring.” 

Rhetorical Question:  “We are still dealing with a legacy of blue gum eucalyptus in the Bay Area.  Why should we repeat that mistake?”

Answer:  Ritter agreed that blue gum eucalyptus is “inappropriate” in many places where it was planted in the Bay Area, but we’re not planting blue gums.  There are 800 eucalyptus species and many are ideal for our conditions.  He said, “Why not plant eucalyptus?  It would be dumb not to plant suitable eucalyptus species just because it shares a name.”

Ritter added that, “Planting only natives just doesn’t work in San Francisco.  There would be no trees in Southern California because we don’t have very many native trees in California.”  The pre-settlement coast of California was virtually treeless in most places and that’s a fact. For example, a study of historic vegetation in Oakland, California reported that only 2% of pre-settlement Oakland was forested with trees. “Vegetation before urbanization in Oakland was dominated by grass, shrub, and marshlands that occupied approximately 98% of the area.” (1)

San Francisco in 1806 as depicted by artist with von Langsdoff expedition. Bancroft Library

Oakland as a case in point

The San Francisco Chronicle recently published an article about a guerilla tree-planter in Oakland who is planting native oak trees on public land, wherever he wants.  Oakland’s Director of Tree Services, David Moore, gently suggests that many of these tree plantings are ill-advised:  “‘There is a part of all of us that loves with our hearts the coast live oak tree because of its heritage, the symbolism of our city, and just the legacy that they have,’ Moore said. ‘But we have to diversify, and we are diversifying to other ones that are recommended to be more adaptable to climate change…The reality is that we have created a world that is not the native conditions of these plants,’ Moore said. ‘If we want trees to survive in these non-native conditions, we have to pick trees from around the world that can survive these conditions.’…Moore said oaks, while beautiful, are not the ideal tree for today’s hot, dry and cramped urban landscape. Without careful and costly maintenance, he said, oaks could destroy sidewalks, block light from street lamps and grow their branches into streets and walkways, creating hazards for motorists and pedestrians. The city still plants oaks, but mainly in parks rather than streets because that’s where they do better, Moore said…”

Stalemate

So, here we are.  We have a pressing need for a more diverse urban forest that is adapted to present and anticipated conditions, but we are paralyzed by the ideological commitment of native plant advocates who are demanding that we destroy our urban forest because it is predominantly non-native.  In a recent edition of Nature News, Jake Sigg said, “Hysterical tree planting is worse than a waste of time and resources…”

I am grateful to Professor Ritter for being bluntly frank with members of the arborist community who should know better.  Dare we hope they learned something from that presentation? 

I wish you Happy New Year.  Please join me in my hope for a more peaceful year.  Thank you for your readership.


(1) Nowak, David, “Historical vegetation change in Oakland and its implications for urban forest management,” Journal of Arboriculture, 19(5): September 1993

Draft of California’s Climate Smart Strategy looks promising

California has made a $15 Billion budget commitment to address climate change and protect biodiversity. The California Natural Resources Agency (CNRA) held a series of workshops to explain the initiative and give the public an opportunity to provide feedback to CNRA.  Sixteen hundred Californians participated in those workshops, including me. 

California Natural Resources Agency recently published a draft of the first installment of implementation plans:  “Natural and Working Lands Climate Smart Strategy.”  The public is invited to comment on this draft.  The deadline for comment is November 9, 2021.  There are three ways you can send your comments and feedback:  Email: CaliforniaNature@Resources.ca.gov; Letter via postal mail: California Natural Resources Agency, 715 P Street, 20th Floor, Sacramento, CA 95814; Voice message: 1 (800) 417-0668.

Update: The deadline for public comment has been extended to Wednesday, November 24, 2021.

Below is the comment that I submitted today.  I focused my attention on the portions of the draft that are relevant to my urban home, such as developed land and urban forests.  My comment may not be relevant to your concerns, so I encourage you to write a comment of our own.  If you find issues in the draft that I haven’t mentioned please post a comment here to alert other readers.


TO:  California Natural Resources Agency

RE: Public Comment on “Natural and Working Lands Climate Smart Strategy”

Thank you for this opportunity to comment on the draft of California’s Climate Smart Land Stretegy.

I find much to like in the draft of California’s Climate Smart Land Strategy.  In particular:

  • The draft makes a commitment to reduce pesticide use on public lands, for example:

Priority nature-based solutions for developed lands: 

“low-chemical management of parks and open spaces in and around cities to beneft underserved communities who are often the most negatively affected by health impacts related to air pollution and extreme heat caused by urban heat islands.”

“Prioritize protection of public safety by ecologically treating vegetation near roads and energy infrastructure.”

“Utilize safer, more sustainable pest management tools and practices to combat invasive species and accelerate the transition away from harmful pesticides.”

  • The draft makes a commitment to expanding, maintaining and preserving urban forests:

Priority nature-based solutions for developed lands: 

“Increase development and maintenance of both urban tree canopy and green spaces to moderate urban heat islands, decrease energy use, and contribute to carbon sequestration.”

“Maintain urban trees to provide vital ecosystem services for as long as feasible”

  • The State of California defines the urban forest broadly and the draft acknowledges its importance in climate smart land management:

“California Public Resources Code defines urban forests as “those native or introduced trees and related vegetation in the urban and near‐urban areas, including, but not limited to, urban watersheds, soils and related habitats, street trees, park trees, residential trees, natural riparian habitats, and trees on other private and public properties.”  Urban forests are our opportunity to apply climate smart land management in the places most Californians call home. The character of urban forests is diverse, which heavily influences the localized selection of management options and outcomes related to both carbon storage and co-benefits.”

  • The draft acknowledges that suitability to a specific location and climate are the appropriate criteria for planting in the urban forest.  Because native ranges are changing in response to changes in the climate, whether or not a tree is native to a specific location is no longer a suitable criterion.

Utilize place-based tree and plant selection and intensity, to ensure the species selection process considers climate, water, and locally-specific circumstances.”

  • The draft acknowledges the importance of forests to maintain carbon sinks to reduce greenhouse gas emissions that cause climate change.  The urgent need to address climate change must trump nativists’ desire to replicate treeless historical landscapes. 

“Healthy forests can serve as reliable carbon sinks, both because they are able to store significant amounts of carbon and because they are at a lower risk of carbon loss due to climate impacts such as wildfire and drought. After large, high-severity fires, some of California’s forests may convert to shrublands and grasslands59 that are not capable of supporting the same level of carbon storage as forests.

“…shrublands and chaparral store substantially less carbon, and the dynamics of their growth and disturbance are less well known. Evidence indicates that shrublands in California are burning more frequently than they would have historically, leading to degraded conditions, possible conversion to grasslands, and reduced carbon storage in above ground biomass.”

Making these commitments operational implies that the State must also make these commitments:

  • The State of California should not fund projects that destroy healthy trees for the sole purpose of replicating treeless historical landscapes, especially on developed lands.
  • The State of California should not fund projects that destroy functional landscapes and healthy trees, particularly by using herbicides.

Suggested improvements in the draft

These commitments in the draft should be revised:

Implement healthy soils practices, including through native plant landscaping and mulch and compost application.”

The word “native” should be deleted because the nativity of a plant is irrelevant to soil health.  Introduced plants do not damage soil, but using herbicides to kill them does damage the soil by killing beneficial microbes and mycorrhizae.   

“Increase drought-tolerant yards and landscaping through, for example, native plant species replacements and lawn removal and by adopting, implementing and enforcing the State’s Model Water Efficient Landscaping Ordinance.”

The word “native” should be replaced by “drought-tolerant,” which would include many native species, but not all.  Redwoods are an example of a native tree that is definitely not drought-tolerant.  Many species of drought-tolerant plants have been introduced to California from other Mediterranean climates that are well adapted to our climate and the anticipated climate in the future.

California’s urban forest is predominantly non-native because these are the tree species that are adapted to our climate and can survive harsh urban conditions. Professor Matt Ritter of CalPoly is the source of these data. He presented this slide at a conference of the California Urban Forest Council on October 14, 2021.

Where appropriate and applicable, Departments should rely on the Class 33 categorical exemption for small habitat restoration projects in the CEQA Guidelines”

Such exemptions should not be granted to projects that will use pesticides because they will damage the environment, including the soil, and the wildlife that lives there.  Such a specific limitation is consistent with commitments in the draft to reduce pesticide use in parks and open spaces around cities because those are the places where such small projects (5 acres or less) are likely to be proposed.  Such a limitation on the use of this exemption to CEQA requirements should be added to the final draft because it does not explicitly exist in the code.

The importance of setting priorities

The strength of the draft is its emphasis on addressing the sources of climate change.  All projects funded by this initiative must be consistent with that over-riding mission because climate change is the primary threat to all ecosystems. Reducing the sources of greenhouse gases causing climate change is a prerequisite for protecting biodiversity.

I appreciate the mention of opportunities to remediate brownfields, but I believe a broader commitment to addressing sources of pollution is needed:

“Ensure brownfield revitalization supports community efforts to become more resilient to climate change impacts by incorporating adaptation and mitigation strategies throughout the cleanup and redevelopment process. These efforts also increase equity, as many climate vulnerable communities live close to brownfields and other blighted properties.”

Julie Bargmann was recently awarded the Oberlander Prize in Landscape Architecture for her ground-breaking work to bring blighted land back to useful life in the heart of post-industrial cities. Her work is unique because it transforms abandoned industrial land into beautiful public space while honoring and preserving its history.  She brings new meaning to the word “restoration.”  She does not begin by destroying functional landscapes.  She provides a model for a new approach that is particularly important to underserved inner-city communities.  I live in Oakland, where I see many such opportunities to restore public land to useful life without the scorched-earth strategies commonly used by ecological “restorations.”

Julie Bargmann projects. Source: NPR News Hour

When ecological restorations are funded without addressing sources of pollution, valuable resources are often wasted.  The recent oil leak from an oil platform off the coast of Southern California is a case in point.  Millions of dollars were spent restoring a wetland that was doused with oil for the second time. Yet, some of the oil platforms in California waters are no longer productive, but have not been safely decommissioned.  This is putting the conservation cart before the horse. 

Talbert Marsh. Source: Huntington Beach Wetland Conservancy

We are about to make enormous investments in the expansion of wetlands, as we should.  At the same time, we should address the sources of pollution that will despoil those wetlands, such as many miles of impaired waters in the watersheds that drain into the wetlands.  For example, the draft touts seagrasses as carbon sinks and acknowledges pollution as one of the major threats to seagrass:  “The leading causes of seagrass loss are nutrient pollution, poor water clarity, disease, and disturbance.”

At every turn, climate smart solutions should stay focused on the underlying causes of problems in the environment, rather than cosmetic solutions that don’t address those causes.  Quibbling about whether or not marsh grass is native or non-native is like arguing about the color of the lifeboat. Let’s focus on whether or not a landscape is functional as a carbon sink.

In conclusion

The draft gives me hope that the State of California can do something useful with our tax dollars to address climate change without damaging the environment further.  The draft shows the influence of learned hands with good intentions.  Now let’s see specific projects funded that are consistent with the goals defined by the draft.  That’s where the rubber meets the road.

Spartina eradication is now a zombie project

Over 20 years ago the governors of California, Oregon, and Washington made a commitment to eradicate non-native spartina marsh grass on the entire West Coast of the country.  Intensive aerial spraying of herbicide killed over 95% of non-native spartina about 10 years ago, but the project continues in the San Francisco Bay.  The goal is now the eradication of hybrid spartina that grows at the same marsh elevations as native spartina and is so visually similar that it requires 500 genetic tests every year to determine that it is a hybrid before it is sprayed with herbicide (1). This article will explain why the Invasive Spartina Project in the San Francisco Bay Estuary is now a zombie project, a project that is dead, but is not being allowed to rest in peace.

Click on the picture to see the presentation of the Invasive Spartina Project to the California Invasive Plant Council on June 11, 2021. This is the source of some of the information in this article. Answers to questions at the end of the presentation are particularly important.

Hybridization is the boogey man of plant nativism

Hybrid spartina is being hunted because it outcompetes native spartina.  Nativists fear the loss of native spartina as a distinct species.  Rather than seeing the potential for a new, improved species of spartina, they see it as a loss of biodiversity, rather than an increase in biodiversity. 

Non-native spartina is also accused of “invading” mudflats where some animal species require that type of environment. However, that accusation is contradicted by these photos where native spartina has been planted on mudflats at Eden Landing. The source of these photos is the June 2021 presentation of the Invasive Spartina Project.

Hybridization is an important evolutionary tool that frequently increases biodiversity by creating new species on the margins of ranges where closely related species encounter one another.  For example, hybridization is credited with creating over 500 species of oaks all over the world that are well-adapted to their respective microclimates.  The rapidly changing climate and the globalization of trade have created more opportunities for hybridization and resulting speciation. 

Advances in molecular analysis has informed us of the frequency of hybridization and its benefits to biodiversity:

“With the growing availability of genomic tools and advancements in genomic analyses, it is becoming increasingly clear that gene flow between divergent taxa can generate new phenotypic diversity, allow for adaptation to novel environments, and contribute to speciation. Hybridization can have immediate phenotypic consequences through the expression of hybrid vigor. On longer evolutionary time scales, hybridization can lead to local adaption through the introgression of novel alleles and transgressive segregation and, in some cases, result in the formation of new hybrid species.” 

Restoration and expansion of wetlands is extremely important as we prepare for anticipated rising sea levels.  If hardier, denser, stronger hybrid species of marsh grass are available why would we reject that opportunity?  Nativist ideology should not deprive us of this opportunity. 

Native species are not inherently superior to species that are better adapted to present environmental conditions.  The rapidly changing climate requires corresponding changes in vegetation to adapt to present conditions.  Extreme weather events are natural selection events that kill species that are no longer adapted to the climate.  We cannot stop evolutionary change, nor should we try.

Why does this matter?

If herbicides were not required to eradicate hybrid spartina perhaps I could shrug and move on.  Hundreds of gallons of imazapyr herbicide were used by East Bay Regional Park District to aerial spray non-native spartina for the first few years of the eradication project.  In 2020, EBRPD used 43 gallons of imazapyr for “ecological function,” a nebulous category that includes spartina eradication. 

When the Invasive Spartina Project (ISP) made a presentation to the California Invasive Plant Council in June 2021, the public asked several questions about the toxicity of the herbicide (imazapyr) that is used to eradicate spartina (1). The ISP mistakenly claimed that imazapyr is not harmful to humans and wildlife because it uses a different metabolic pathway to kill plants that does not exist in animals.  They probably believe that claim, but they are wrong.

 A similar claim was made for glyphosate for 40 years.  We now know that the claim about a “unique pathway” for glyphosate existing only in plants is not true.  In 2020, plaintiffs in a class-action suit against Monsanto alleging that it falsely advertised that the active ingredient in Roundup only affects plants were awarded $39.5 million.  The settlement also requires that the inaccurate claim be removed from the labels of all glyphosate products: “…[plaintiff] says Monsanto falsely claimed through its labeling that glyphosate, the active ingredient in Roundup, targets an enzyme that is only found in plants and would therefore not affect people or pets. According to the suit, that enzyme is in fact found in people and pets and is critical to maintaining the immune system, digestion and brain function.”

I asked Beyond Pesticides for help to determine if the exclusive pathway claim was true of imazapyr.  Beyond Pesticides informs me that both imazapyr and glyphosate use metabolic pathways that exist in animals. I summarize their response:  “You asked about the ALS pathway that is the target of imazapyr—is there a comparison to glyphosate?  [According to] the research I found, I think the comparison is valid.  This early paper appears to clearly state that ALS is a pathway found in yeast and bacteria as well as plants (2). Another early paper which identified ALS as coming from bacteria, fungi, and plants (3).”  These pathways exist in bacteria that reside in our bodies and perform important functions, particularly in our digestive and immune systems.  When we damage those bacteria, we are damaging our health.

Please note that both of these studies of imazapyr are nearly 40 years old.  If pesticides were being evaluated and regulated, the public and the users of imazapyr might know that it is harmful to animals.  I provided this information to the Invasive Spartina Project.  They responded that their use of imazapyr is legal.  Unfortunately, they are right.  Because there is no regulation of pesticide use in the United States, the Invasive Spartina Project has the legal right to use it.  But is it ethical?  I asked the Invasive Spartina Project to quit making the inaccurate claim that imazapyr kills plants, but cannot harm animals.  They did not respond to that request.

Unfortunately the judicial system is our only recourse to take dangerous chemicals off the market.  For example, chlorpyrifos that is known to damage children’s brains was finally banned as the result of a court order.  The EPA refused to ban chlorpyrifos, but a lawsuit finally resulted in a judge requiring that the EPA either provide studies proving its safety or ban its sale.  The EPA could not prove its safety, so it had no choice but to finally ban it. 

What about the animals?

Ridgway rail. Source: Cornell Ornithology Laboratory

The only issue that temporarily brought the spartina eradication project to a halt was the impact it has had on endangered Ridgway rail. Ridgway rail is a close relative to the Clapper rail on the East and Gulf coasts where the spartina species considered non-native here (S. alterniflora) is native.  Clapper rails are abundant where S. alterniflora resides.

“Fig. 2.  In marshes where invasive Spartina was present in large densities, populations declined rapidly commensurate with the amount of Spartina removed [from 2005 to 2011].” (4)

The eradication of Ridgway rail breeding habitat in the San Francisco Bay reduced the rail population significantly by 2011, according to the US Geological Service and the US Fish and Wildlife Service (4). The loss of rails was greatest where the most non-native spartina was killed with herbicide.  In response, USFWS mandated a moratorium on eradication in areas where rails were nesting (5). According to the ISP 2020 survey of rails in the project areas, the rail population rebounded where eradication was stopped.  When treatment resumed in 2018, the number of Ridgway rails in the previously restricted areas declined by 9% in the following year.  That outcome was predicted by the USFWS Biological Opinion: “In the 2018 Biological Opinion, the Service estimated that rails inhabiting the nine previously-restricted sub-areas may be lost due to mortality or exhibit decreased reproductive success due to loss of hybrid Spartina cover when treatment of these sub-areas resumed.”

Clearly, the endangered Ridgway rail has been harmed by spartina eradication, as USGS and USFWS concluded in their analysis that was published in 2016 (4):

“California [now known as Ridgway rail] rail survival was higher prior to invasive Spartina eradication than after eradication or compared to survival in a native marsh. The combined indication of these studies is that tall vegetation structure provides California rails with both higher quality nesting substrate and refuge cover from predation, particularly during high tides. Thus, habitat structure provided by invasive Spartina in heavily infested marshes may facilitate California rail survival, and continued efforts to remove invasive Spartina from tidal salt marshes could lead to further California rail population declines….” (4)

Given that Ridgway rail is protected by the Endangered Species Act, it is difficult to understand why this project is allowed to continue.  Much like the unregulated use of pesticides, it will probably take a lawsuit to enforce the Endangered Species Act on behalf of endangered Ridgway rail. When government is not functional, the judicial system can sometimes compensate.

Let’s bury this zombie project

The US Geological Service and the US Fish and Wildlife Service have put their finger on the failure of the Invasive Spartina Project.  The same could be said of many other pointless eradication projects:

“Removing the source of that novel habitat without addressing pre-existing native habitat quality limitations threatens to re-create an ailing landscape for California rails by dogmatically adhering to specific management approaches. In essence, the conservation community is choosing the winners and losers in this ecosystem by failing to solve the underlying problems that will support a healthy species community with all constituent members.” (4)

The spartina eradication project serves no useful purpose.  In fact, it damages the environment and the animals that live in it.  We cannot stop evolution, nor should we try.  Let natural selection determine the plant species that are best adapted to our environment and the animals that live in it.  Not only would we benefit from better protection for our coastline from rising sea levels, we could reduce our exposure to dangerous pesticides that are harmful to our health, as well as improve habitat for wildlife.  This project is doing more harm than good. 


  1. Presentation of Invasive Spartina Project to California Invasive Plant Council, June 2021 
  2. Falco, S.C., Dumas, K.S. and Livak, K.J., 1985Nucleotide sequence of the yeast ILV2 gene which encodes acetolactate synthase
  3. LaRossa, R.A. and Smulski, D.R., 1984. ilvB-encoded acetolactate synthase is resistant to the herbicide sulfometuron methylJournal of bacteriology160(1), pp.391-394.
  4. M.L. Casazza, et.al., “Endangered species management and ecosystem restoration: finding the common ground,” Ecology and Society, 2016, 21(1):19. http://dx.doi.org/10.5751/ES-08134-210119
  5. Adam Lambert et.al., “Optimal approaches for balancing invasive species eradication and endangered species management,” Science, May 30, 2014, vol. 344 Issue 6187

“A history of food, from sustainable to suicidal”

“A brilliant and insightful explanation of the food system. Bittman’s writing is succinct and entertaining, and his recommendations are spot on.” –David Kessler, MD, former FDA commissioner

Mark Bittman’s new book, Animal, Vegetable, Junk, is best described by its subtitle, A history of food, from sustainable to suicidal.  Bittman starts the story at the beginning, nearly 300,000 years ago when humans were hunter/gatherers.  The transition from a hunter/gatherer to an agricultural society began only 10,000 years ago.  It was a long, slow transition that happened unevenly all over the world.  Hunter gatherer societies still exist in the Amazon and perhaps elsewhere.  Where nature was generous, hunting/gathering persisted longer.  For example, indigenous people in California were still hunters/gatherers when Europeans arrived and indigenous people on the East coast had developed agricultural societies.

The conventional wisdom has been until recently that sedentary agriculture is superior to hunting/gathering as a lifestyle and a producer of food.  Bittman and Yuval Harari in Sapiens—the sweeping history of human civilization—disagree.  The diets of hunters/gatherers are more diverse, which makes them healthier and less vulnerable to famine.  If you can’t find what you need in one place, you move to another.  Families of hunter/gatherer societies are small because mothers can’t carry more than one child at a time, so there is no advantage to the large families required by farming.  Women’s role as gatherer is as important as man’s role as hunter, making the family less patriarchal than agriculture societies.  A mobile society has less impact on the land and is less likely to deplete resources, such as water and soil.  Communities were smaller, making them less vulnerable to communicable diseases.

The invention of the plow more than 2,000 years ago was one of the first significant turning points in the development of agriculture.  The plow requires the strength of men to operate, making the participation of women in food production less important.  A division of labor between the genders developed, along with the gender power hierarchy that persists today.  This division of labor was consistent with the need for families to have more children and therefore more farm hands. 

As the population of humans in agricultural society increased, so did the pressure on the land to be more productive.  Farmers knew and still know that the soil requires regeneration if it is to remain fertile.  Such practices as planting cover crops between cash crops to return vegetation to the soil, are not new.  Farmers also knew that leaving land fallow for a season or two enables the soil to recover from the loss of nutrients required to grow crops.  Rotating crops helps to control pests and diseases that are usually associated with one type of crop, but not another.  But the pressure to produce more food as the population increases puts pressure on farmers to squeeze more from the soil than it has to give in the long term.

Mechanization of agriculture

Mechanization was the most significant incremental step on the long road to the dead end that we now face in agriculture.  John Deere introduced his steel-bladed plow in the middle of the 19th century that was capable of breaking the tough sod of the Mid-Western prairie.  Deere mass-produced the steel plow using the assembly-line methods of the industrial revolution.  By 1859 John Deere was making 10,000 plows in a year. 

Although the Deere plow was a significant invention, the advent of the steam and then gas-powered tractor shortly thereafter were the true game changers that started the transition from family farms to the corporate agriculture of today:  “In 1830 it took a farmer and a horse at least seventy-five hours to produce a hundred bushels of corn.  BY 1930 that same task took as little as fifteen hours.  Production grew in parallel, from 173 million bushels of wheat in 1859 to 287 million by the century’s end.  The big difference was the tractor.”

The tractor was only the beginning of mechanization of agriculture.  There are now enormous machines, such as harvesters that cost half a million dollars and more.  Family farmers can’t afford to buy these machines.  They aren’t useful to small land-holders because huge farms are needed to pay for the cost of these machines.  Farmers who tried to stay in the game took huge loans to buy them.  Agriculture is risky business because the climate is changeable and unpredictable.  In drought years, many farmers with small holdings lost their land because they couldn’t repay their loans. 

Cornfield

Corporate interests are in a position to obtain the necessary loans and buy out the small land-holders.  Family farms are a thing of the past.  The romanticized notion of family farms is a fiction. Family farmers understand that destroying their soil is not in the interests of their family. Corporate interests have a short-term perspective when making business decisions.  Therefore, regenerative agricultural methods such as cover crops, rotating crops, and leaving land fallow are also a thing of the past.   

The Green Revolution

The so-called “green revolution” was the response to the destruction of agricultural land.  By the 1930s, the soil in agricultural America was exhausted.  The result of a century of short-term perspective agriculture that didn’t give back to the soil what was taken from it was the Dust Bowl of the 1930s. 

The Dust Bowl

Instead of returning to regenerative agricultural methods, the response was the introduction of chemical fertilizers and pesticides. Sixty years of pesticide use has bred many weed and insect species that are resistant to pesticides because no amount of chemistry can outwit evolution. In addition to introducing toxic chemicals into the environment, these chemicals exacerbated the trend toward bigger, corporate-owned agricultural lands because chemicals are expensive.  They must be purchased in advance of realizing the income of selling a crop, requiring bigger loans. According to Bittman, John Deere company makes four times as much money from financing these loans as from selling farm equipment. More family farms failed and their land was consolidated into huge acreages owned by corporate interests with short-term goals for higher profits.

The chemical warfare waged by industrial agriculture escalated greatly when Monsanto’s Roundup Ready seeds were introduced in 1996.  These genetically modified seeds enabled the indiscriminate spraying of the non-selective herbicide, glyphosate on commodity crops.  The seeds are expensive and their patents require that they only be used once.  They greatly increased farmer’s dependence on loans to finance the planting of their crops.  This indiscriminate spraying of glyphosate on commodity crops used in all processed food and animal feed means that we are now eating and drinking food laced with glyphosate, a probable carcinogen.

Chemical fertilizers deliver phosphorous to the soil, needed for plant growth.  Run off from agricultural land pollutes our lakes and rivers, killing fish and making water unsafe to drink or swim in.  Pesticides are indiscriminately killing insects, many of which are beneficial, such as our pollinators.  Pesticides are found in our water, our soil, and our food.  Little is known about the effects of these chemicals on our health or on wildlife, but what we know suggests they are probably more dangerous than we realize.  For example, recent research suggests that chemicals that disrupt our endocrine systems are probably reducing fertility, causing birth defects and contributing to gender dysphoria. 

Consequences of agricultural surpluses

Bigger is not better in agriculture because bigger also means that only a handful of crops are grown on huge corporate farms.  It is more expensive to grow diverse crops, requiring different cultivation methods and inputs.  Huge machines are operated more efficiently on huge plots of land.  Most agricultural land in America is devoted to growing crops of corn, soy beans, and wheat.  So much of America’s farm land is devoted to these commodity crops that they produce huge surpluses that require a global market to sell them to.

The global marketplace for commodity agricultural crops has fundamentally changed many countries.  The North American Free Trade Agreement (NAFTA) forced farmers in Mexico to abandon their small farms and move to cities to take low-paying manufacturing jobs because they could not compete against cheaper American corn.  The diet and health of the Mexican people has deteriorated significantly because they no longer have access to the variety of fruit and vegetables their small properties produced.  Their healthy fruit juices have been replaced by sodas made from corn syrup, resulting in high rates of obesity and diabetes.

Children’s cereals. Glyphosate residues are found in most cereal.

The diet of Americans has also been changed radically by the marketing campaigns designed to sell surplus commodities.  A surplus of milk produced the “Got milk?” advertising campaign that sold milk to adults for whom milk is rarely healthy.  Bittman says that 65% of adults are lactose intolerant, which he knows from personal experience.  He was forced to drink milk until he left home.  He was plagued by indigestion until he was able to quit drinking milk as an adult. 

Far more pernicious, is the advertising campaign that convinced mothers to quit breast feeding in favor of feeding formula.  This insidious campaign used guilt to pressure mothers by making the inaccurate claim that formula is healthier for their babies.  Breast feeding is the primary means that a baby’s immune system develops.  Formula contains higher levels of sugar that sets the stage for life-long eating habits that are not healthy.  High levels of obesity and diabetes begin at childhood and are very difficult to change later in life.  The advertising campaign was global and it did more damage in undeveloped countries where the water needed to dilute formula is often not safe.  Although the health consequences of using formula are well known, the advertising campaign continues to this day.  The New York Times ran a full-page advertisement for formula recently, using convenience as its approach, suggesting that modern mothers should not be guilt-tripped into breast feeding. 

Not the end of the story

We landed in this dietary and environmental disaster zone over thousands of years of small, incremental changes that were imperceptible at the time.  We could not foresee the consequences of the cumulative effect of each small step along the road to this dead end.  And Bittman says we can back out of this dead end in the same way, by making small steps back to regenerative farming.  Bittman’s final chapters are devoted to the many projects all over the world devoted to restoring our agricultural land, our diets, and our health. 

This brief summary of Bittman’s book does not do it justice.  There are a multitude of other important factors to consider, such as the huge contribution that industrial agriculture is making to climate change and the changes in raising animals that are just as unhealthy as how we are growing our plant-based food.  I can’t say that Bittman’s book is a pleasant read, but I assure you that it is important.