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