Ecology – Page 25 – Conservation Sense and Nonsense

Relentless war on eucalyptus

A new front has opened in the relentless war on eucalyptus in California. The drought has given native plant advocates an opportunity to develop a new narrative to justify their demands for eradication of eucalyptus. The opening gambit in this new strategy is an item in Jake Sigg’s “Nature News” of May 16, 2014:

“The prolonged drought of the last 2-3 years seems to be taking its toll. The Tasmanian blue gums in Glen Canyon along O’Shaughnessy Boulevard strongly show drought stress. The stress is more evident from the high cliffs above O’Shaughnessy than it is at ground level. Thinning crowns and discolored foliage was striking. And that was before the recent heat wave.

Barring substantial rains–unlikely, but not impossible–the trees are in serious trouble. The City could have an emergency situation and no money to address it.”

Recap of the war on eucalyptus

When public land managers began the war on eucalyptus in the 1980s it did not occur to them that the public would object. So deep was their prejudice against eucalyptus, that they assumed the public shared their opinion. The first two massive projects in the 1980s on National Park Service and State Park properties were greeted with angry public protests. Land managers quickly learned that it was not going to be as easy to eradicate eucalyptus as they had thought. They developed a series of story-lines to justify their projects, which were designed to convince the public that the eradication of eucalyptus is both necessary and beneficial. This is a summary of some of their cover stories with links to articles that debunk them:

Based on our experience, we were immediately suspicious of the new claim that San Francisco’s eucalyptus forest is dying of drought. We know that our predominant species of eucalyptus—Tasmanian blue gum—grows successfully throughout California, all the way to the Mexican border in climates that are much hotter and drier than the Bay Area. We also know that the central and north coast of California is foggy during the dry summer months, which doubles the amount of annual precipitation in the eucalyptus forest. All reliable sources of horticultural information describe blue gum eucalyptus as drought tolerant. Frankly, we couldn’t see how our eucalyptus could be dying of drought.

What is wrong with our eucalyptus forest in Glen Canyon?

The picture became clearer when Jake Sigg posted the following on his “Nature News” on June 12, 2014:

“The June 10 newsletter [see below*] included an editorial on an evolving catastrophe, mostly involving our numerous plantations of Tasmanian blue gums. The editorial focused primarily on the plantations on O’Shaughnessy Blvd in Glen Canyon and on Mt Sutro, and included a photo of a grove of Mt Sutro dying trees. Here is a photo of the Glen Canyon plantation, taken from above the high cliffs on O’Shaughnessy. The damage is most visible from high, looking down.

The discoloration of leaves was very dramatic, but the foliage color and condition is not fully conveyed in the photograph. Some trees defoliated entirely in the prolonged winter dry spell. Look very closely at the juvenile blue leaves of the coppice shoots; anything that appears faintly bluish are new coppice shoots which grew in response to the late rains we had in February and March. Once you see coppice shoots on old trees you know the trees are in trouble. These trees are in double jeopardy, as they invested energy in new shoots, but were betrayed by another dry spell which, under normal circumstances, will last until autumn. Note that you can now see the grassland through the trees; that slope was not previously visible. Even a casual inspection of these groves reveals dead, dying, and stressed trees, and under normal circumstances we will have four or five months of dry. The fire situation is serious right now and is likely to become worse.”

View of west side of Glen Canyon Park from Marietta Drive, June 2014

With more specific information in hand about what Jake Sigg is looking at, we went to see for ourselves. We could see what he was describing from a vantage point on Marietta Drive, west of Glen Canyon Park. We could see lighter colored leaves, but they were more localized than Jake Sigg’s description implied. We didn’t feel qualified to speculate about why the leaves were lighter colored so we recruited an arborist to help us figure out what is happening there. We were fortunate to enlist the help of a certified arborist who has been responsible for urban forests on public lands in the Bay Area for several decades. This is what we learned.

Epicormic Sprouts

Looking through binoculars from our vantage point on Marietta Drive, the arborist said immediately, “Those are epicormic sprouts.” The leaves of epicormic sprouts are distinctively lighter colored than the darker green of mature eucalyptus leaves. They are also a more rounded shape than the long, pointed mature leaves of eucalyptus. This is how Wikipedia describes epicormic sprouts:

“Epicormic buds lie dormant beneath the bark, their growth suppressed by hormones from active shoots higher up the plant. Under certain conditions, they develop into active shoots, such as when damage occurs to higher parts of the plant. Or light levels are increased following removal of nearby plants.”

Epicormic sprouts on trees in Glen Canyon Park, June 2014

The remaining question was why some of the eucalypts, were producing these epicormic sprouts, when most were not. We went down to O’Shaughnessy Blvd to get a closer look, hoping to answer that question. This is what we learned:

The understory of non-native shrubs between O’Shaughnessy Boulevard and the trees with epicormic sprouts has been cleared in the past year. We could see the dead brush piled up next to the trees. We had to wonder how people who claim to be concerned about fire hazard could think such huge piles of dead brush were nothing to be concerned about.

Remains of dead non-native brush destroyed along O'Shaughnessy Boulevard, June 2014 — Remains of dead non-native brush destroyed along O’Shaughnessy Boulevard, June 2014

We could see the stumps of some of the dead brush and we wondered if the stumps had been sprayed with herbicides after they were cut. Pesticide use reports for Glen Canyon indicate that O’Shaughnessy was sprayed several times in the past year, twice with products containing imazapyr. Imazapyr is known to be harmful to trees if sprayed in proximity to their roots. The trees with epicormic sprouts were downhill from the understory shrubs that were destroyed, in the probable direction of water and herbicide flow.
We found several trees that had been girdled in the past and are now dead.

Girdled tree in Glen Canyon Park, now dead, June 2014

The trees in Glen Canyon Park

Then we walked into Glen Canyon Park from its southern end. It’s not a pretty sight. Many huge, old eucalypts have been destroyed. When they were destroyed, their stumps were immediately sprayed with herbicide to prevent them from resprouting. The stumps are simultaneously painted with dye so that workers can tell which trees have been sprayed. The dye is no longer visible, but regular visitors took photos of the painted stumps before the dye faded. The spraying of the stumps do not appear on the pesticide use reports of the Recreation and Park Department. We assume that’s because the spraying was done by the sub-contractors who destroyed the trees.

Poisoned and dyed eucalyptus stump, Glen Canyon Park, 2013. Courtesy San Francisco Forest Alliance

The arborist who walked in the forest with us said, “The painting of stumps with RoundUp or Garlon in proximity to trees that are being preserved can kill the neighboring preserved tree. Stumps near living, residual (preserved) trees should not be painted with RoundUp or Garlon if the stumps are within 40’ of mature, blue gums that are slated for preservation.” If the remaining trees are damaged by herbicides, their mature leaves fall and epicormic sprouts will then emerge as the tree recovers.

Some of the stumps of the trees that were destroyed in Glen Canyon Park in 2013. Taken June 2014

While the trees were being destroyed in 2013, the Natural Areas Program was eradicating non-native vegetation in the Canyon. They sprayed ivy, blackberry, and valerian with Milestone, which is another herbicide that is known to damage trees if sprayed near their roots. In addition to these official applications of herbicide in this park, there is a long history of unauthorized, illegal herbicide applications by “volunteers,” more appropriately called vandals.

We saw a lot of epicormic growth in the Canyon, sprouting from stumps that must be cut back and resprayed with herbicides. It usually takes several retreatments to successfully kill the roots of eucalypts that are destroyed. We also saw epicormic growth from eucalypts that had been severely pruned and were also exposed to a great deal more light because they had lost the shelter of their neighboring trees.

Epicormic growht, Glen Canyon Park, June 2014 — Epicormic growth, Glen Canyon Park, June 2014

Wrapping up

The trees in Glen Canyon are reacting to the traumas to which they have been subjected: the loss of their neighbors that were either girdled or cut down thereby exposing them to more light and wind, the loss of the shelter of their understory, the application of herbicides known to be harmful to trees.

The good news is that there are still plenty of trees in Glen Canyon that have not yet been destroyed and they are in great shape. Here is the view of the tree canopy in Glen Canyon taken from the east side of the park near Turquoise Way. The first picture was taken in December 2012 (before the current round of tree destruction in Glen Canyon Park) and the second picture was taken in May 2014.

Eucalyptus canopy on east side of Glen Canyon Park, taken from Turquoise Way December 2012, before tree destruction began. Courtesy San Francisco Forest Alliance

Same perspective of Glen Canyon tree canopy, taken May 2014. Courtesy San Francisco Forest Alliance.

These trees are doing just fine because the Natural Areas Program has not yet gone that deeply into the park. But NAP intends to destroy many more trees in Glen Canyon (and elsewhere) when the Environmental Impact Report (EIR) for their management plan (SNRAMP) is finally approved. Then we will see more consequences of the destructive practices of the Natural Areas Program and we will probably hear more bogus explanations for that damage.

We expect the EIR to finally be considered for approval at the end of 2014. [Update: now predicted for fall 2015] We will do whatever we can to convince San Francisco’s policy makers that they should approve the “Maintenance Alternative” which would enable NAP to continue to care for the native plant gardens they have created in the past 15 years, but prevent them from expanding further. We hope that our readers will help to accomplish this important task.

*Jake Sigg’s Nature News of June 10, 2014, introduced the theories of Craig Dawson about the health of the Sutro Forest. Mr. Dawson’s speculations are different from Mr. Sigg’s and we will not address them in this post. You can find an analysis of Mr. Dawson’s theories on Save Sutro Forest HERE.

Mulberries: Red, white and goo

This is a guest post by Mark Spreyer, Director of the Stillman Nature Center in Barrington, Illinois. He can be reached at: stillmangho@gmail.com

We publish his article about mulberries as our July 4^th gift to our readers.

Thy stout heart

Now humble as the ripest mulberry

That will not hold the handling

–Coriolanus, Shakespeare

For those of us of a certain age, mulberries and childhood went hand in hand. Whether it was singing “Here we go round the mulberry bush” or reading Dr. Seuss’ And to Think That I Saw It On Mulberry Street, the word mulberry was all around us.

I was an adult before I learned that actual mulberry trees were all around us as well. We have two species, one red and one white, one native and one introduced. Both are wildlife favorites, and both grow here at Stillman. So, let’s take a walk down our local Mulberry Street.

Mulberry Leaves

White mulberry - Creative Commons Attribution 3.0 — The variously lobed red and white mulberry leaves look but don’t feel alike. White mulberry leaves are smoother to the touch than red mulberry leaves. Creative Commons Attribution 3.0

I have often had students, from elementary school to college, identify trees by looking at their leaves. Some have teeth, some have lobes, and some have neither.

Those that have lobes often have a set number. Sugar maple, for example, usually has five lobes.

Enter the mulberry. Whether red or white, mulberry leaves can be unlobed to variously lobed. No, they aren’t about to be limited by a set number!

Yet some tree books seem desperate to quantify the number of lobes. One source writes that mulberry leaves are “sometimes 2-lobed, sometimes 3-lobed, often unlobed….” Well, isn’t that helpful?

There is a pattern to the location of the different leaves. Multiple-lobed leaves are more likely to be found on young trees and root sprouts while unlobed leaves are found in the crowns of mulberry trees.

Red Mulberry (Morus rubra)

This is our indigenous mulberry. It ranges from southern Vermont down to southern Florida across to central Texas and back north to southeastern Minnesota.

In Illinois, red mulberries can be found growing in almost every county.

These trees prefer moist woodlands and deciduous bottomlands rubbing branches with American elm, hackberry, silver maple, and box elder.

Red mulberry is a medium-sized tree that can reach a height of fifty feet with a diameter of two feet. Its broad rounded crown makes red mulberry a useful shade tree.

Both red and white mulberry trees are named after the color of their fruit but be forewarned: when red mulberries are red, they are NOT ripe.

The tasty mulberries are ripe when they are purple-black, like a blackberry. When reaching for that first juicy handful, do remember that Shakespeare (as usual) was right. A ripest mulberry easily crumbles in your soon-to-be purple palm.

Not just humans enjoy a handful of sweet mulberries, but wildlife dines on mulberry street as well. A partial list of birds enjoying a midsummer meal of mulberries would include eastern kingbird, American robin, gray catbird, wood duck, starling, Baltimore oriole, northern cardinal, cedar waxwing, brown thrasher, plus red-bellied and red-headed woodpeckers.

Some mulberry munching mammals include opossum, raccoon, fox, skunk, an assortment of squirrels, plus a few dogs I know!

Simply put, red mulberry is one of the best summer fruit trees for wildlife.

White Mulberry (Morus alba)

Now that I think of it, it doesn’t matter to hungry animals if the berries are red or white. This brings us to white mulberry.

Like its red counterpart, white mulberry is a medium-sized tree with variously lobed leaves. It was introduced to N. America during colonial times (see below). It can now be found growing from Maine to Minnesota, south to Texas and east to Georgia. It also is naturalized across most of Illinois.

When white mulberries are ripe, they are indeed white or sometimes pink. The closer you look, though, the more confusing it gets since red and white mulberries freely hybridize. The resulting hybrid fruits come in a variety of colors between white and purple.

White mulberries will grow in almost any upland habitat being particularly at home in urban environs.

Silk Road to Mulberry St.

If you break the leafstalk of a white mulberry, milky sap exudes. This Elmer’s goo is the foundation of a multi-cultural exchange that dates back thousands of years.

Take white mulberry leaves and add the domesticated Chinese silkworm caterpillar (Bombyx mori) and the result are large cocoons spun of the finest silk.

Unwrap that silk and one can weave it into garments that were desired by traders around the world.

What comes next? The ancient and famed silk road (trade routes actually) that crossed Asia from China to Europe.

Others thought there might be an easier way to get their silk. After it was discovered that imported silkworm caterpillars found native red mulberry leaves to be too tough, tens of thousands of white mulberries were being raised by nurserymen in colonial Virginia.

Some of those who planted these promising saplings were Ben Franklin, George Washington, and Thomas Jefferson.

While a few American entrepreneurs succeeded in this labor-intensive silk business, the growing textile industries soon found ways to make quicker profits.

The neglected white mulberry trees fed birds and mammals that, in turn, spread white mulberry seeds around a good chunk of the continent.

Back on Mulberry Feet

Mulberries are indeed good street trees. Once established, they can withstand salt, drought, air pollution, and soil compaction. Some will say, there is little need to plant mulberries as wild animals are doing a fine job at that.

However, when the berries fall thick from the trees they can make you feel like you have double-sided tape on the soles of your shoes. Your gooey shoes pick up bits of gravel and so it goes.

Keep in mind that mulberries are dioecious meaning there have separate male and female plants. Planted male mulberries, of course, won’t bear fruit.

With apologies to Dr. Seuss– perhaps you like sticky feets or just want handfuls for eats, either way visit Stillman for treats along our Mulberry Streets.

Mulberry Jam Recipe

Mr. Spreyer’s note: This recipe comes from the Illinois Department of Natural Resources. In particular, the cooking credit belongs to Deb Singer and Kathy Andrews.

I expect that red mulberries are used more often than white mulberries in this recipe.

I say this because I think we are used to ripe berries being red or darker in color (i.e. blackberries, blueberries, strawberries, raspberries). However, I bet if you hybridize your jam with some white mulberries, it would taste just as good.

Oh yes, a mulberry pie would also be a nice summer treat.

3 cups crushed mulberries

½ cup lemon juice

1 package (1.75 ounces) powdered pectin

6 Cups sugar

Bring berries, lemon juice and pectin to a rolling boil. Add sugar. Return

to a boil and boil for 1 minute. Skim off foam. Ladle into prepared jars and process in a water bath for 10 minutes

HAPPY FOURTH OF JULY!

Climate Change vs. Biodiversity: NOT!!

A new study reported changing public and scientific interest in biodiversity compared to climate change. Using reports in the media and scientific journals in the United Kingdom and the US, as well as funding of scientific studies by the World Bank and the National Science Foundation, the study reports that the interest in climate change has increased and the interest in biodiversity has decreased in the past 25 years.

This analytical approach seems to suggest that these two environmental issues are mutually exclusive, that the interest in one is at the expense of the other. We find this both unfortunate and unnecessary because we consider these two issues intimately related. Climate change is increasingly the biggest threat to biodiversity. If plants and animals are unable to adapt to climate change, they are doomed to extinction.

Therefore, we believe that science should study these topics together. In fact, the study on which we are reporting acknowledges the relationship between these topics: “Dual-focus projects are being funded more often, but… ‘this is relatively small and does not mitigate the plateauing expenditure on biodiversity research.’” (1)

Conservation in a changed climate

As long as conservation and “restoration” projects are devoted to replicating historic landscapes, they are likely to be unsuccessful. The climate, atmosphere, and soil conditions are no longer suited to a landscape that existed hundreds of years ago, particularly in urban environments. Therefore, if biodiversity is to be preserved by conservation and restoration, such projects must look forward, not backwards.

We have been watching the Nature Conservancy closely for signs that it is adapting to climate change. We look to the Nature Conservancy to lead the way because they employ hundreds of scientists. In contrast, many mainstream environmental organizations employ more lawyers than scientists.

We have reported that the Conservancy’s Chief Scientist, Peter Kareiva, is at least paying lip service to an approach to conservation that takes into consideration the profound changes in the environment caused by the activities of man. This acknowledgement of the irreparably altered environment is encapsulated by the proposal to name a new geologic era, the Anthropocene.

Unfortunately, the old guard of conservation biology has engaged in a vigorous campaign to silence the Conservancy’s new approach. This conflict between the old guard and scientists who have proposed a more realistic approach to conservation was recently reported by the New Yorker. (2) According to that article, Peter Kareiva has made a commitment to the old guard to quit publishing anything regarding the Anthropocene and its implications for conservation practices.

The Nature Conservancy has responded to the article in the New Yorker in its on-line blog. It doesn’t explicitly address the question of whether or not a commitment has been made to quit advocating for a more realistic approach to conservation. However, it implies that the Conservancy plans to continue on a course of scientific innovation and experimentation, which it describes as “practical.” Here is a specific choice made by the Conservancy that typifies this approach:

Monarch butterflies roosting in eucalyptus tree.

“We know it was worth spending millions of dollars to rid Santa Cruz Island of non-native pigs. But we are pretty sure it would not be worth spending what could be hundreds of millions of dollars to rid California of non-native Eucalyptus trees (which also happen to harbor wildlife and monarch butterflies.)” (3)

Although the Nature Conservancy’s Chief Scientist may have agreed to “shut up,” we see signs of the Conservancy’s new approach in its latest magazine. In a brief article entitled “Forests of the Future,” the magazine reports that they are no longer planting the species of trees that existed in the past in one of their properties in Minnesota, because they don’t believe that species is adapted to current or predicted future conditions. Instead they are actively engaged in reforestation of the land with new species:

“Over the past two springs, the team planted 88,000 tree seedlings across 2,000 acres in the northeastern corner of the state. The seedlings consisted of species that should survive better in a warmer and drier climate—trees, such as red oak, found in higher numbers just south of the area. For a team accustomed to restoring forests to match historical landscapes, helping the North Woods [of Minnesota] adapt to a predicted future climate is a new but necessary idea. [The Conservancy’s science director in Minnesota] says, ‘All of our modeling is saying the same thing,’ she adds, ‘We needed someone to actually go out and start trying some of this stuff.’” (4)

Looking forward not back

We are very encouraged by the Conservancy’s new approach and we hope that other land managers will be inspired by it. We are also reminded of a recent visit to a nature reserve near San Luis Obispo managed by the local chapter of the Audubon Society. We reported about this reserve in a recent article because the land managers had planned to destroy all eucalyptus trees on that property but were forced to scale back their plans in response to a noisy negative reaction from the public.

Dying oak tree, Sweet Springs Nature Reserve

On our recent visit, we learned that this was a wise choice because many of the oak trees that were planted on this reserve by those who wish to “restore” it are quite dead despite the fact that the reserve has an extensive irrigation system. These land managers looked back and the result of that retrospective thinking is a landscape of dead native trees.

Irrigated native plant garden, Sweet Springs Nature Reserve

Climate change requires land managers to wake up to the realities of what will grow where. Land managers in the San Francisco Bay Area appear to be blind to that reality. They repeatedly plant species where they grew hundreds of years ago and we are forced to watch the plants die repeatedly.

(1) “Climate change beats biodiversity as a press, scientific, and funding priority,” Science Daily, June 11, 2014

(2) D.T. Max, “Green is Good,” New Yorker, May 12, 2014

(3) Mark Tercek and Peter Kareiva, “Green is Good: Science-Based Conservation in the 21st Century,” May 5, 2014

(4) “Forests of the Future,” Nature Conservancy, June/July 2014

Ants used to scapegoat our urban forest

Ants are important members of the ecosystem. They improve the fertility and consistency of the soil. They distribute plant seeds. They are both predators of and food for other insects as well as birds and omnivorous mammals. Therefore, their abundance in an ecosystem is often considered an indicator of its health.

Today we will report on a study of ant populations in San Francisco’s “natural areas,” parks that were designated over 15 years ago for restoration and preservation of native plants. This study reaches this conclusion:

“The results of this study indicate that natural areas within urban parks play a critical role in supporting ant biodiversity. Many habitats in the natural areas of San Francisco’s parks support healthy, diverse ant communities. Areas of non-native forest, however, reduce this diversity. Maintaining open grasslands, reducing tracts of non-native forest, removing the invasive understory, and thinning forest canopy may all help support a healthier ant community and ecologically valuable parks.” (emphasis added) (1)

Could this ant study be the first example we have found of evidence that native plants benefit wildlife and conversely that our non-native urban forest is less valuable for wildlife? We have examined this study to determine how it reached this conclusion. We have compared this study to similar studies that report different findings. We reached the conclusion that this study does not support its conclusion that “reducing tracts of non-native forest…may…help support a healthier ant community and ecologically valuable parks.”

The relationship between ant communities and soil moisture

The ant study used pitfall traps to survey the abundance and diversity of ant populations in 24 “natural areas.” It also measured the moisture of the soil in proximity of the traps. The ant study found that soil moisture and ant abundance and diversity were positively correlated at low levels of moisture, but that high levels of moisture found in eucalyptus forest were negatively correlated with abundance and diversity of ants:

We will tell you how this ant study used this empirical observation of the relationship between soil moisture and ant populations to reach its conclusion that non-native forests must be “reduced” to achieve “ecologically valuable parks.”

Generalizing about “urban forests”

This study of San Francisco’s ant population asks us to believe that its negative assessment of San Francisco’s urban forest applies to all urban forests: “Urban forests are structurally different than natural forests. Besides being smaller, fragmented, and more isolated than non-urban forests, urban forests also show increased canopy cover, greater disturbances due to human traffic and pollution, and differences in leaf litter accumulation.” (1)

We don’t think it is possible to generalize about all urban forests. Here are two sources which suggest that the ant study has over-generalized about urban forests and ants found in them:

According to the US Forest Service survey of urban forests, San Francisco has one of the smallest tree canopies in the country. Only 11.9% of San Francisco is covered by the tree canopy, compared to 20.9% of New York City. According to that survey, San Francisco’s urban forest removes 141 tons of pollutants per year compared to 1,677 tons of pollutants removed by New York City’s urban forest.
Ants are found in some urban forests. A study in Toledo, Ohio and Detroit, Michigan compared ant populations in urban habitats (forests in city parks, community gardens, and vacant lots). (2) The study found greater diversity of ant species in forests than in other habitat types, but fewer ants. They found 26 species of ants in the forest, 20 in vacant lots, and 14 in gardens. They found no correlation between various characteristics of vegetation and ant diversity or abundance. Soil moisture was not measured by this study. Generalizations about urban forests derived from one study in San Francisco clearly do not apply to Toledo and Detroit.

More soil moisture in forest with a closed canopy

The ant study in San Francisco predicts greater soil moisture in a forest with a closed canopy and dense understory:

“A combination of high soil moisture, dense canopy cover, and dense understory (habitat complexity) may help explain the lack of ground-foraging ants in urban forests.” (1) The study associates those characteristics specifically with the eucalyptus forest: “Within forest types examined, eucalyptus forests contained significantly more soil moisture than other forest types and also had lower ant richness and abundance.” (1)

We don’t think these generalizations can be applied neither to all eucalyptus forests nor solely to eucalyptus forests:

The density of eucalyptus forest in the San Francisco Bay Area varies widely according to data presented recently by Professor Joe McBride to the Commonwealth Club:

Location	Average Number of Trees per Acre
Presidio, San Francisco	163
Land’s End, San Francisco	364
Tilden Park, Berkeley	540
East Ft Baker, Marin County	1795

In other words, not all eucalyptus forests have closed canopies.

The density of understory in the eucalyptus forests of the Bay Area also varies widely. One of the densest understories exists on Mount Sutro, which is the location of the Interior Greenbelt, where the ant study reports finding no ants. In drier locations, such as Bayview Hill, there is little understory in the eucalyptus forest, which may be why the ant study reports finding ants there. Bayview Hill is on the east side of San Francisco and therefore receives much less fog than Mount Sutro, which is closer to the ocean.
Eucalyptus forest is not unique in often having a closed canopy. Native redwood forest also has a closed canopy: “Many meters above the ground, the branches of trees, especially those of redwood, merge to form a ceiling, or canopy.” (3)

Fog and soil moisture

The ant study describes the relationship between fog and soil moisture in San Francisco: “The increased moisture in eucalyptus is due to the fact that summer fog tends to condense on eucalyptus leaves and branches and drip down to the soil below. Such fog drip can add as much as 42 cm of water to eucalyptus forest during a single summer.” (1)

Fog in San Francisco is unrelated to the fact that its forest is predominantly eucalyptus:

Redwood forest. NPS

Although redwoods did not live in San Francisco when Europeans arrived in 1769, they lived there in the distant past. Native redwoods now exist only on the coastal fog belt of California. Fog is essential to their survival: “During the study period, 34%, on average, of the annual hydrologic input was from fog drip off the redwood trees themselves. When trees were absent, the average annual input from fog was only 17%, demonstrating that trees significantly influence the magnitude of fog water input to the ecosystem…The results presented suggest that fog, as a meteorological fact, plays an important role in the water relations of the plants and the hydrology of the forest.” (4)
Fog exists along the northern coast of California because the interior is hot and the ocean is cool. When the cool ocean air meets the hot air from the interior, fog forms. The existence of fog has nothing to do with the species composition of the forest. Any tall tree is capable of condensing the fog, which then drips to the forest floor, providing water to both the trees and their understory. The eucalyptus forest is not to blame for this sequence of events.

The nativity of the urban forest is irrelevant to the ants

The ant study implies that there are few ants in San Francisco’s urban forest because the forest is not native to San Francisco: “…reducing tracts of non-native forest…may all help support a healthier ant community and ecologically valuable parks.”

Soil moisture is the operative variable in predicting abundance and diversity of ant populations. The nativity of the vegetation is irrelevant to the ants:

If the urban forest in San Francisco was native redwoods, it would precipitate equal amounts of fog, resulting in equal amounts soil moisture. The ant population would probably be similar.
A study of ant populations in the central Appalachian Mountains found the same relationship between soil moisture and ant populations in native forests: “Fewer ants, lower number of species, and lower ant diversity were found at sites with higher elevation and soil moisture.” (5)
A study of ant populations in Northern California grasslands found that the characteristics of the soil were better predicators of ant populations than the types of vegetation: “Plants were less important than soil attributes in explaining variation in overall ant species richness and abundance…” (6) Chemical composition and consistency (sand vs. clay) of soils were evaluated by this study, but not soil moisture

“Science” in the service of nativism

We consider this ant study a classic demonstration of nativism. In this case, soil moisture was confounded with the non-nativity of forest in San Francisco. The nativity of San Francisco’s forest is irrelevant to the amount of soil moisture. Any closed canopy forest of tall trees would precipitate equal amounts of fog and have a similar impact on ant populations.

The study speculates that the allelopathic properties of eucalyptus may have a negative impact on the ants, but offers no evidence. We have found no evidence of allelopathic properties of eucalyptus. Nor do we think that the existence of ants should be the sole criterion for “ecological health.” Would we demand the destruction of redwood forests so that we could have more ants? We doubt it.

However, we must also give credit where credit is due. The ant study reports that the existence of the non-native Argentine ant does not have a negative impact on the populations of native ants. They report that the Argentine ants occupy the perimeter of the “natural areas” where native ants generally are not found. This is a refreshing departure from the usual nativist claims that all non-native plant and animal species have negative impacts on native species.

(1) Kevin M. Clarke, et. al., “The influence of urban park characteristics on ant communities,” Urban Ecosyst, 11:317-334, 2008

(2) Shinsuke Uno, et. al., ”Diversity, abundance, and species composition of ants in urban green spaces,” Urban Ecosyst, 13:425-441, 2010

(3) UC Berkeley Botanical Garden, “Plants and Their Environments”

(4) T.E. Dawson, “Fog in the California redwood forest: ecosystem inputs and use by plants,” Oecologia, 117-4:476-485, December 1998

(5) Changlu Wang, et. al., “Association Between Ants and Habitat Characteristics in Oak-Dominated Mixed Forests,” Environmental Entomology, October 2001

(6) April Boulton, et. al., “Species Richness, Abundance, and Composition of Ground-Dwelling Ants in Northern California Grasslands: Role of Plants, Soil, and Grazing,” Environmental Entomology, February 2005

“Restoring” vegetation does not restore an ecosystem

One of the persistent questions in our interminable debate with native plant advocates is whether or not native vegetation provides superior habitat for wildlife compared to existing non-native vegetation. At the heart of that question is the closely related question of whether or not more insects are found in native vegetation than in non-native vegetation. That’s because insects (and other arthropods) are near the bottom of the food web. If there are fewer insects, there are probably fewer birds and other animals that eat insects. We have told our readers about many studies that find equal abundance and diversity of insects in native compared to non-native vegetation, so we won’t repeat them, but here’s a brief list of those studies and links to them for new readers:

Does “restoration” of native vegetation increase insect populations?

Arthropods - Creative Commons Share Alike — Arthropods – Creative Commons Share Alike

In this post we will consider this issue from a slightly different angle: can insect population or diversity be increased by “restoration” of native vegetation? Even if we accept the premise of native plant advocates that native vegetation supports greater abundance and diversity of insects, can that population be “restored” by eradicating non-native vegetation and replacing it with native vegetation? That question is answered with a resounding “NO” by a study that compared arthropod abundance and diversity in undisturbed (predominantly native vegetation), disturbed (predominantly non-native vegetation), and disturbed sites 5 and 15 years after restoration. (1) Restoration methods described in the study are mowing followed by disking and seeding, disking and seeding, planting of container stock, and clearance by hand. All sites were irrigated initially. No mention is made of herbicide use or prescribed burns to eradicate non-native vegetation. The vegetation type in all 15 sites in Southern California was coastal sage scrub. This is the dominant vegetation type along the coast of California and is the goal of many restoration projects in the San Francisco Bay Area. Many species of both native and non-native vegetation in the study sites also exist in the Bay Area.

Coastal sage scrub in Southern California - Creative Commons Share Alike — Coastal sage scrub in Southern California – Creative Commons Share Alike

The study used pitfall traps to collect arthropods in these sites. Arthropods are invertebrates that include insects, arachnids (spiders), and crustaceans (aquatic species not relevant to this study). Arthropods are further divided into guilds such as herbivores, predators, scavengers, and parasites. Because of the method of collecting in pitfall traps, few herbivores were found. Here are some of the findings of this study:

“Arthropod diversity at undisturbed and disturbed sites was greater than at sites that were 5 and 15 years following restoration.”
“Number of arthropod species was not significantly different among undisturbed, disturbed, and restored sites.”
“Vegetation at disturbed and undisturbed sites differed significantly; older restorations did not differ significantly from undisturbed in diversity, percent cover, or structural complexity.”
“Vegetation characteristics did not differ significantly between the newly restored site and disturbed sites.”
“…arthropod communities at all restored sites were, as a group, significantly different from both disturbed and undisturbed sites.”
“As found in other studies of other restoration sites, arthropod communities are less diverse and have altered guild structure.”

Here is the concluding discussion of this study:

“Of the restoration sites sampled, none had developed an arthropod community that resembled undisturbed or disturbed native coastal sage scrub. Restoration sites in general exhibited lower arthropod diversity and a preponderance of exotic arthropod species. The time elapsed since revegetation effort had no discernible effect on arthropod community structure; there was no gradual return of the community to a more natural structure over time”.

“Restorations” do not improve arthropod abundance or diversity

This study found that arthropod population and diversity was the same in disturbed (non-native) and undisturbed (native) vegetation. When disturbed vegetation was “restored” arthropod population was maintained but the composition of the arthropod community was significantly changed even 15 years after the restoration was completed. There were more “exotic” species of arthropods in the restored sites even though the vegetation was similar to the undisturbed sites of native vegetation. The restored vegetation was native, but its arthropod occupants weren’t.

However, the birds and other animals that prey on those insects don’t care if the insects are native or non-native. Much like humans, animals are not concerned with the nativity of their food. The non-native apple you are eating is just as tasty whether you are eating it in its native range in Central Asia or where it has been introduced. If you have an apple tree, you know the birds and squirrels enjoy the apples too and the bees and other pollinators enjoy the apple blossoms. Most of what we eat is not native, yet many people are obsessed with the nativity of vegetation, claiming that animals require native vegetation even though humans don’t.

An important caveat

The predominant vegetation type in the San Francisco Bay Area is coastal scrub, which is also the vegetation type in the study of arthropod populations. This suggests that if a similar study were conducted here, the results might be similar. However, there is one very important difference between the restorations studied in Southern California and the restorations in the Bay Area. Land managers in the San Francisco Bay Area are using large amounts of herbicides to destroy non-native vegetation. The study in Southern California reports no herbicide use in restoration sites. It seems likely that herbicides sprayed in restoration projects in the Bay Area would decrease the population of arthropods. We would like to see a study that tests that hypothesis.

There is more to an ecosystem than plants

The veneration of native plants has become a national obsession. Demands for eradication of non-native plants are supported by many fictions to justify these destructive projects. One of those fictions is that wildlife requires native vegetation. We have found no empirical evidence to support that assumption. The study we are reporting today is yet more evidence that restoring native plants does not restore an ecosystem. In this case, after 15 years of effort, land managers were eventually successful in establishing a population of native plants. However, these “restored” native landscapes did not support a population of insects and spiders that were comparable to either the undisturbed native landscape or the unrestored non-native landscape. We have been looking for some legitimate reason to engage in these destructive projects for over 15 years. We have yet to find any justification for spraying our public lands with herbicides or destroying hundreds of thousands of healthy trees. We will keep looking.

(1) Travis Longcore, “Terrestrial Arthropods as Indicators of Ecological Restoration Success in Coastal Sage Scrub (California, USA),” Restoration Ecology, December 2003, Vol. 11 No 4, pp.397-409

Spartina eradication: Herbicides are their dirty little secret

This is a good news/bad news story about the eradication of non-native Spartina marsh grass and the impact it has had on the population of endangered California Clapper Rail:

Spartina alterniflora, Smooth Cordgrass. USDA photo

The good news: US Fish & Wildlife has temporarily halted efforts to eradicate non-native Spartina (Spartina alterniflora) in the San Francisco Bay Area because the population of endangered California Clapper Rail has declined by 50% during the period of eradication efforts from 2005 to 2011. (1) This problem was identified several years ago and was attributed to the lack of cover for the rail as a result of eradication of non-native Spartina, which grows more densely, taller, and doesn’t die back in winter as the native Spartina does. (2)
The bad news: US Fish & Wildlife attributes this negative impact on the Clapper Rail population on the slow recovery of native Spartina (Spartina foliosa).
Spartina foliosa – USFWS

They do not acknowledge that non-native Spartina provides superior cover compared to the native species. Nor do they acknowledge that non-native Spartina was killed with herbicides. Therefore, they do not consider the possibility that the slow recovery of native Spartina may be attributable to the herbicides that were used to kill the non-native plant. They also continue to claim that the recovery of the endangered California Clapper Rail depends upon the return of native Spartina, despite the overwhelming evidence to the contrary. The California Clapper Rail is a sub-species of Clapper Rail; the Clapper Rail is abundant on the East and Gulf Coasts and not endangered perhaps because of the superior cover provided by Spartina alterniflora on those coasts. (3) Based on these fictions, US Fish & Wildlife proposes a new strategy that will simultaneously eradicate non-native Spartina while intensively planting native Spartina. (1)

We have been following the Spartina eradication project since 2011. For the benefit of new readers, we will review the issues with a few excerpts from previous posts on Million Trees.

Spartina alterniflora: Treasured on the East Coast, reviled on the West Coast

Spartina alterniflora (Smooth Cordgrass) is a species of marsh grass native to the Atlantic and Gulf coasts of the United States, where it is considered a valuable plant making important contributions to the coastal ecology:

Its dense growth provides protection against storm surge and “erosion control along shorelines, canal banks, levees, and other areas of soil-water interface.” (4)
It filters nutrients, sediments and toxins from the water that flows off the land before reaching the ocean, acting as a natural water treatment facility.
It provides cover and food for birds, mammals and marine animals that live in the coastal marsh.

Where Smooth Cordgrass has died back in its native range, the dieback has been considered a serious environmental threat:

In 2001 the Governor of Louisiana declared a “state of emergency” when Smooth Cordgrass declined and the state obtained $3 million of federal funding to study and hopefully reverse the decline. This study resulted in the development of a method of aerial seeding of Smooth Cordgrass to restore declining areas of marshland. (5)
A similar, but smaller dieback of Smooth Cordgrass in Georgia led to a collaborative research and on-going monitoring effort by 6 research institutions in Georgia.
Similar dieback of Smooth Cordgrass has been reported as far north as the coast of Maine. A researcher at the Connecticut Agricultural Experiment Station is quoted in that report as saying, “In New Orleans, if their marshes were intact, the storm surge of Katrina would not have reached the levees.” (6)

The war on Smooth Cordgrass on the West Coast

Smooth Cordgrass is not native on the Pacific Coast of the United States. Therefore it is treated as an alien invader to be eradicated with herbicides:

$24 million was spent to eradicate Smooth Cordgrass in San Francisco Bay and Willapa Bay from 2000 to 2010 (7)
$16.3 million is projected to be spent on the entire West Coast from 2011 to 2020 (7)

Spartina is being eradicated with an herbicide, imazapyr. This is a new herbicide about which little is known. The analysis that was done to justify its use in the Spartina eradication project admits that no studies have been done on its effect on shorebirds, including the endangered Clapper Rail.

The Material Safety Data Sheet mandated by the Environmental Protection Agency tells us that imazapyr is “not readily biodegradable.” So, in the event that we eventually learn that this herbicide is harmful to shorebirds and/or to us, we probably should assume that it will still be in the environment in the nearly 200 sites in the San Francisco Estuary on which it has been sprayed. Imazapyr is also being sprayed–sometimes from helicopters–in hundreds of places along the West Coast, including Oregon and Washington.

Imazapyr is often mixed with glyphosate by the Spartina eradication project. Glyphosate is a non-selective herbicide. That is, it kills any plant it is sprayed on at the right stage of its growth. But imazapyr is far more insidious as a killer of plants because it is known to travel from the roots of the plant that has been sprayed to the roots of other plants. For that reason, the manufacturer cautions the user NOT to spray near the roots of any plant you don’t want to kill. For example, the manufacturer says explicitly that imazapyr should not be sprayed under trees, because that tree is likely to be killed, whether or not that was the intention.

Furthermore, no tests have been conducted on the toxicity of combining multiple pesticides in a single application. Therefore, we know nothing about the possible synergistic effects of combining imazapyr and glyphosate.

These facts about the herbicides used to eradicate non-native Spartina bear repeating. The main herbicide being used is known to be mobile in the soil and persistent in the environment. The herbicide with which it is often mixed is an indiscriminate killer of any plant on which it is sprayed. Therefore, the likelihood that these herbicides will prevent the establishment of the new plantings of native Spartina should be taken into consideration. The entire enterprise seems deeply flawed, both harmful and futile.

Bringing it home to the Bay Area

So, what does this have to do with you? If you are concerned about pesticide use, you might be interested in the fact the East Bay Regional Park District (EBRPD) used 203 gallons of imazapyr in 2009 and 121 gallons in 2010 for the sole purpose of eradicating Spartina on their properties. We don’t know how much imazapyr EBRPD used in 2011, 2012 and 2013, because they haven’t published a report of pesticide use since 2010. Since their properties are only on the east side of the San Francisco Bay, we should assume that at least that much imazapyr was used by land managers on the west side of the Bay.

Displacement of Clapper Rails in San Francisco

California Clapper Rail. British Wikipedia

In July 2011, a Clapper Rail was seen and photographed at Heron’s Head in southeastern San Francisco. There was quite a bit of excitement about this sighting because a Clapper Rail had not been seen in San Francisco for decades. That excitement dissipated when we learned more about where this bird came from, which provided a probable reason for its arrival.

The Clapper Rail was wearing a radio collar that had been put on him and 109 other rails by the USGS to track their movements. He had moved from Colma Creek, 11 km south of Heron’s Head, which is one of nearly 200 Spartina “control sites” in the San Francisco Estuary. The bird sighted at Heron’s Head is one of three Clapper Rails that have left Colma Creek since 2007, when the radio collars were placed. The Spartina control project has been going on for over 10 years, so we have no way of knowing how many Clapper Rails were displaced prior to 2007. In 2012, non-native Spartina at Heron’s Head was sprayed with herbicides. Where did the Clapper Rails go from there? Was there anywhere left for them to hide?

Pesticide Application Notice, Heron's Head, 2012 — Pesticide Application Notice, Heron’s Head, 2012

As our readers know, native plant advocates claim their “restoration” projects benefit wildlife. They can offer no evidence for this claim. But there is considerable evidence that proves them wrong. The endangered California Clapper Rail is one such case.

(1) Adam Lambert et.al., “Optimal approaches for balancing invasive species eradication and endangered species management,” Science, May 30, 2014, vol. 344 Issue 6187

(2) “West Coast Governors’ Agreement on Ocean Health, Spartina Eradication Action Coordination Team Work Plan,” Released May 2010, page 12

(3) Cornell Ornithology Lab: http://www.allaboutbirds.org/guide/clapper_rail/id

(4) “Smooth Cordgrass,” USDA/NRCS Plant Fact Sheet.

(5) Dorset Hurley, “Geogia’s Marsh Die Back and Louisiana’s Marsh Browning,” Altamaha Riverkeeper

(6) “What’s killing off our salt marshes,” Going Coastal Magazine, September 15, 2008

(7) “West Coast Governor’s Agreement on Ocean Health,” May 2010, page 5-6

Krakatoa: A case study of species dispersal

Islands are intensively studied by ecologists because they are hothouses for evolution. Physical isolation results in the evolution of new species that are related to their mainland ancestors and the result is many endemic species of plants and animals which exist only on that island.

Some islands originated when continents broke up into smaller pieces as a result of continental drift. Madagascar and New Zealand are examples of islands that were originally attached to a continent. These islands brought some of the inhabitants of the continent with them. But many islands arose from the ocean as a result of volcanic activity and were therefore born bare as a newborn babe without vegetation or inhabitants. All subsequent life on these volcanic islands arrived by dispersal from elsewhere via ocean currents, winds, or carried by traveling animals, most recently by humans.

Krakatoa is such a volcanic island in the Indonesian archipelago. It has a long record of volcanic eruptions which both destroyed much of the island and created new islands. Many of these eruptions occurred during prehistoric periods, but many have been recorded by human history. These recent eruptions have created an evolutionary laboratory that enables us to answer the perplexing question of how quickly the dispersal of species occurs.

The cataclysm of 1883

In August 1883 a series of volcanic eruptions on Krakatoa produced one of the most cataclysmic events of recorded human history. The force of the blast was the equivalent of 13,000 times the nuclear bomb that devastated Hiroshima in 1945. The blast could be heard as far as 3,000 miles away. Shock waves from the blast reverberated around the planet 7 times. The blast sent an ash cloud 50 miles into the atmosphere. The weather of the entire planet was altered by the ash cloud. The temperature dropped by 1.2 Degrees Celsius in the year after the eruption and the climate did not return to normal until 1888. The blast and subsequent tsunami killed over 36,000 people and destroyed two-thirds of the island.

Scientists believe that nothing living survived the blast: “no plant, no animal, no seed, no spore.” (1) The first scientists visited Krakatoa nine months after the blast. They reported finding nothing alive except a single spider. Spiders are notoriously successful dispersers because the webs they weave can become sails on the wind.

Krakatoa is quickly repopulated

In 1886—three years after the eruption—the first botanical expedition arrived on Krakatoa. They found mosses, algae, flowering plants and eleven species of fern. They speculated that the arrival of algae enabled the spores of ferns to become established on the otherwise bare ground. Amongst the plants there were two species of grasses. Scientists assume that most of these plants arrived via wind, but some species could have arrived as seeds carried by the surf.

Further colonization of the barren island then began to accelerate. By 1887, young trees were found as well as dense grassland and many ferns. Butterflies, beetles, flies and a single monitor lizard were found in 1889. The species of monitor lizard found in 1889 is known to be a good swimmer and is a “versatile opportunist” on land, which means it’s not a fussy eater and it can eat less often than other lizards.

By 1906, there were a hundred species of vascular plants, covering the summit in green and a grove of trees along the shore, including tamarisk and coconut palm. The coconut is found on virtually any sunny beach in the Pacific because its seeds float in their large protective shell wherever the current carries them.

Fifty years after the eruptions of 1883, the island was home to 171 species of plants. One botanist estimated that 40% of the plants came on the wind, 30% floated on the sea and most of the remainder were brought by animals. The eruption of 1883 produced huge quantities of pumice–a lightweight, sponge-like volcanic glass—that floated on the ocean creating rafts that were observed for years after the eruption: “…a ship’s captain…who encountered pumice on the Indian Ocean, lowered a boat for a closer look, ‘It was curious and interesting to note how it had been utilized by animals and low types of life as habitations and breeding places.’” (1)

These early arrivals were effective dispersers, but they also had to be capable of surviving inhospitable conditions on arrival. The order of arrival is therefore an important factor in determining successful establishment. For example, animals won’t survive if they arrive before needed food resources. The plants most likely to survive are capable of self-pollinating, that is they don’t require a partner to reproduce.

San Francisco is not an island

How does this experience on Krakatoa compare to our experience in the San Francisco Bay Area? We’re so glad you asked!!

The many projects all over the Bay Area that destroy non-native vegetation are not isolated islands. They are surrounded by more non-native vegetation which quickly re-populates the bare ground created by these projects. Dispersal into small plots of land within San Francisco is much easier than onto isolated Krakatoa. The majority of these projects do not have the resources to replant the areas in which non-native vegetation is eradicated. The fiction is that native plants will magically reappear when non-natives are destroyed. But we can see that the result is the return of the hardiest non-native weeds such as hemlock, star thistle, oxalis, and broom. These hardy creatures don’t need to be planted. Their seeds are carried by the wind or remain dormant in the ground to germinate when someone foolishly destroys the trees that provide shade and suppress germination of weeds.

California Academy of Sciences, April 2011

Even when natives are planted, they are quickly out-competed by non-natives. The best local example of that hard, cold fact is the living roof on the California Academic of Sciences. When the California Academy of Sciences reopened in San Francisco in August 2008, its “living roof” was considered its most unique feature. Thirty species of native plants were candidates for planting on the roof. They were planted in test plots with conditions similar to the planned roof and monitored closely. Only nine species of native plants were selected for planting on the roof because they were the only plants that were capable of self-sowing from one season to another, implying that they were “sustainable.” A living demonstration of “sustainability” was said to be the purpose of the living roof.

Two of six of the predominant species on the roof after 2-1/2 years were native. Four of six of the predominant species were mosses that are “cosmopolitan,” which means they are found everywhere. They weren’t planted on the roof and were therefore “volunteers.”

The monitoring project divided the roof into four quadrants. In February 2011, non-natives outnumbered natives in two of the quadrants. Although natives outnumbered non-natives in the other two quadrants, non-natives were also growing in these quadrants.

The consultant who advised the Academy about what to plant on the roof would not be surprised by this monitoring report. He advised the Academy to walk the streets of San Francisco and identify the plants growing from the cracks in the sidewalks. These are the plants he advised the academy to plant because these are the plants that are adapted to current conditions in the city. The Academy rejected this advice because they were committed to planting exclusively natives on the roof.

The many projects that are destroying non-native vegetation are not sustainable. They are surrounded by non-native vegetation which is better adapted to current climate, soil, and atmospheric conditions. Non-native vegetation will out-compete the natives that are not adapted to current conditions. If these projects were merely futile, perhaps we could shrug and move on. But we can’t turn a blind eye because these projects are harmful to the environment. They use huge quantities of toxic herbicide and they are destroying healthy trees that are performing many valuable ecological functions. These are not harmless experiments.

(1) David Quammen, Song of the Dodo, Scribner, 1996.

(2) Some information for this post is from Wikipedia

The Monkey’s Voyage: How plants and animals are dispersed throughout our planet

The Monkey’s Voyage (1) is as much a history of the science of evolution and ecology as it is a report of the prevailing scientific opinion of the means by which plants and animals were dispersed around the world. Just as life has evolved, so too has the science that studies it.

In the beginning….

The story begins with Charles Darwin, the author of the first publications that identified natural selection as the mechanism that drives the evolution of life on the Earth. These ideas came to him as the result of a five-year voyage around the world in 1831-1836: down the coast of Africa, across the Atlantic, down the coast of South America, around the horn, to the Pacific Ocean to many islands—most famously the Galapagos—to New Zealand, Australia, islands in the Indian Ocean, round the horn of Africa to home.

Voyage of the HMS Beagle, 1831-1836. Creative Commons - Share Alide — Voyage of the HMS Beagle, 1831-1836. Creative Commons – Share Alike

He spent 3-1/2 of the 5 years on land, collecting plant and animal specimens, including many fossils. The fossils suggested to him the existence of animals no longer occupying the land. He also observed many similar plants and animals with slightly different forms around the world. The classic example of closely related, but widely dispersed animals is a family of large, flightless birds: the ratite family.

These similarities suggested a common ancestry to Darwin. Yet, their dispersal across oceans was puzzling to him because at that time the continents were considered fixed in place both going back in time and going forward into the future. Nothing was known at the time about the constant movement of continents, known as continental drift, because the movement was too slow to be observed by humans.

Darwin’s theory about the similarities he found in widely dispersed plants and animals was consistent with his perception of the fixed nature of the geography in which they were found. He theorized that the common ancestors of the similar plants and animals had been dispersed by wind, ocean currents, carried by birds, or other means of transportation.

He conducted experiments to determine how long seeds could survive in sea water to test his theory and he examined migrating birds for evidence of seeds and small animals in their feet and feathers. What he found supported his theory that it was physically possible for plants and animals to be dispersed across oceans to new ranges where subsequent evolution in a different environment would eventually result in alterations of form. When plants and animals are moved from their home ranges and are physically isolated, their genetic compositions diverge. Over time they are sufficiently genetically and morphologically distinct to be considered different species.

Continental Drift

Around the turn of the 20^th century, scientists began to theorize that Africa and South America may have been merged at one time because maps revealed that they fit together like pieces of a puzzle. Alfred Wegener is best known for his pursuit of this theory. He visited both sides of the Atlantic and observed that seams of rock and sediments lined up on the two shores, suggesting their past connections. Although Wegener’s theory gained considerable traction, he did not propose an equally compelling theory about the physical mechanism that would be capable of moving the continents apart.

The mechanism that moves the continents was identified about 50 years later when the ocean floor was studied as a result of developments in radar and sonar. These analytical tools eventually identified seams running the length of the oceans that separate the tectonic plates on which continents ride. Beneath the crust of the earth magma of molten material moves in a current, emerging through the seams of the Earth’s crust as volcanic activity. As molten material emerges from this seam between the tectonic plates, it cools on the ocean floor to form new sea floor. The expansion of the sea floor moves the plates away from the seams, which moves the continents. This is the engine that drives continental drift.

Tectonic Plates - USGS — Tectonic Plates – USGS

By the late 1960s there was scientific consensus about plate tectonics and consequent continental drift. That knowledge led to an understanding of the history of the continental configuations. About 300 million years ago, all continents were fused into one, called Pangaea. Pangaea began to break up about 100 million years later. However, South America, Africa, Madagascar, Australia, New Zealand, and Antarctica remained fused in a continent called Gondwana until about 100 million years ago.

“The history of life is the history of the earth.”

This new understanding of the history of the earth’s geology resulted in a paradigm shift in scientific theories regarding dispersal of life forms. Very quickly, scientific consensus formed around the theory that life moved as a result of movements in the continents. This theory was succinctly expressed as “The history of life is the history of the earth.” That is, where life is found depends upon changes in the geology of the earth. For example, scientists assumed that life found on Madagascar originated in Africa before Madagascar separated from the African continent. Similarly, scientists assumed that life found in New Zealand originated in Australia before New Zealand separated from the Australian continent. In other words, life migrated from the continent along with the land, like Noah’s ark carrying the animal kingdom. Previous theories about trans-oceanic voyages of plants and animals were quickly abandoned in favor of this new, elegant theory which seemed so much more plausible than its predecessor.

DNA analysis trumps elegant theory

Although scientists were comfortable with their new theory of how life was dispersed, the inexorable forward movement of human knowledge intervened to disrupt their complacency. The new analytical tool that overturned this theory was DNA analysis which enabled scientists to study the genetic composition of life forms.

When there are two morphologically similar species in physically isolated locations, their common ancestry can now be determined by DNA analysis. And the genetic distance between the species can help scientists determine when those species became physically separated. When populations become separated their genetic pools become progressively more distant from one generation to another. This rate of genetic change is called the “molecular clock” and it can be used to determine when the physical separation occurred if the rate of change is known. Unfortunately, the molecular clock varies from one lineage to another, so first scientists must calibrate the clock and when they do they can estimate the arrival of a specific plant or animal in a new territory that is physically isolated from its former range and therefore its ancestors.

Genetic analysis has overturned former theories of how life was dispersed on the earth. In most cases, plants and animals arrived in their present locations long after the continents separated into their present configuration. Plants are more likely to have been dispersed by wind and ocean currents than animals. New ranges of plants are often on the receiving end of ocean currents and plumes from big rivers.

Also, new understanding (1980s) of the most recent mass extinction approximately 65 million years ago—when dinosaurs disappeared from the earth—would predict the same result. The mass extinction at the end of the Cretaceous period occurred after the separation of the continents. Therefore, most life forms that moved along with the separating continents were wiped out by the mass extinction about 65 million years ago. Life forms found now are more likely to have arrived after present continental configurations formed and therefore are more likely to have arrived by long-distance dispersal.

Evolutionary science comes full circle

Olive baboon, Old World monkey by Mohammad Mahdi Karim — Olive baboon, Old World Monkey by Mohammad Mahdi Karim

There are some die-hard scientists that have not made the transition from the “life-moves-with-the earth” theory. However, the molecular evidence that life has dispersed across vast expanses of ocean is mounting and most scientists have accepted the reality of the evidence. Science has come full circle, to return to Darwin’s original theory. As improbable as it may seem, monkeys made the voyage from Africa to South America, across the Atlantic Ocean.

Brown spider monkey, New World monkey. Creative Commons - Share Alike — Brown spider monkey, New World monkey. Creative Commons – Share Alike

But is that voyage really so improbable? Within the past decade, we have witnessed two massive earthquakes that caused massive tsunamis. In December 2004, a tsunami following an earthquake in Asia killed approximately 200,000 people. A few survivors tell harrowing stories of clinging to rafts of debris at sea to arrive many days later on a foreign shore. And less than 10 years later, in March 2011, an earthquake and tsunami in Japan killed tens of thousands of people. Over a year later, huge rafts of debris washed ashore on the West Coast of America, encrusted with sea life that accumulated on that long trip. They were called “invasive species” when they arrived. But were they really? After all they arrived as the result of a natural occurrence with no assistance from humans.

These may seem rare events to us because of our short time perspective. Multiply those two catastrophic disasters by the millions of years of life on earth to arrive at the conclusion that these events are routine when put into the context of the lifespan of the earth rather than the lifespan of humans.

Bringing it home

What we learn from The Monkey’s Voyage is relevant to the concerns of Million Trees:

Life is constantly in motion whether we are capable of perceiving it or not. To choose some specific landscape that existed in the distant past as an ideal to be re-created is to deny the reality of nature. The concept of “native plants” is meaningless. Native to where? Native to when?
Change in nature is random and therefore unpredictable. Cataclysmic events render humans impotent to manipulate complex ecosystems. Human attempts to “manage” nature are arrogant at best and harmful at worst. For example, when we kill one animal based on a belief that it will benefit another animal, we haven’t sufficient knowledge to predict the outcome with certainty.
Science is constantly evolving, just as nature is evolving. Invasion biology is stuck in a cul-de-sac that is contradicted by the reality of the dynamism and complexity of nature. There is little scientific evidence that supports the assumptions of invasion biology.

(1) Alan de Queiroz, The Monkey’s Voyage: The improbable journeys that shared the history of life, Basic Books, New York, 2014

“Gardening for Climate Change”

The White House recently released the National Climate Assessment which was prepared by a panel of scientists convened by the federal government. This report informed us that average temperature increase of only 2° Fahrenheit over the entire country in the past century has produced these changes in the environment:

“Summers are longer and hotter, and extended periods of unusual heat last longer than any living American has ever experienced.”
“Winters are generally shorter and warmer.”
“Rain comes in heavier downpours.”

If greenhouse gas emissions continue to increase at the same pace, the report predicts an increase in average temperature of as much as 10 degrees by the end of the century. If an increase of only 2 degrees is capable of producing the extreme weather we are experiencing, it is difficult to imagine what we can expect if the temperature increases 10 degrees.

President Obama announced the report: “This is not some distant problem of the future. This is a problem that is affecting Americans right now. Whether it means increased flooding, greater vulnerability to drought, more severe wildfires—all these things are having an impact on Americans as we speak.”

The impact of climate change on plant life (1)

Henry David Thoreau recorded the arrival of spring at Walden Pond in Concord, Massachusetts in the 1850s. His data has been incorporated into the records of his successors, creating a continuous record across 160 years. Spring arrives in Concord, Massachusetts about three weeks earlier than it did in the 1850s. This pattern mirrors the changes occurring around the planet according to field studies and satellite images taken from space.

The response of plants to this change in seasons has varied, according to a study published recently by the Proceedings of the National Academy of Sciences. Some species of plants reach their flowering peak earlier in the year, while other species are extending their flowering into later in the fall.

Another study speculates that increased temperature isn’t the only factor influencing these changes in flowering patterns. Increased levels of carbon dioxide also may be affecting plants. Earlier snow melt may be another trigger for changes in timing of flowering. The availability of pollinators at the time of flowering is assumed to influence the long term survival of flowering plants. In other words, the affects of climate change on plants are complex and imperfectly understood.

The implications for gardeners who care about wildlife

The New York Times recently published an op-ed which offered an answer to this question: “How do we garden in a time of climate change?” There are probably many answers to that question, so we should understand the perspective of the author of the op-ed, James Barilla. He describes his background on his website: “… James Barilla held a variety of posts in wildlife research and management, crossing paths with wolves and mountain lions in remote wilderness and promoting “mini-beast” habitat in urban schoolyards. He first became intrigued by backyard wildlife while working in England for a land trust, where his job was to create wildlife habitat on the outskirts of a city.” He has a Master’s Degree in Environmental Science from University of Montana and a Ph.D. in English from UC Davis. He now teaches creative and environmental writing at University of South Carolina. He has written a book about gardening to support urban wildlife and articles published by Atlantic and National Geographic Magazine.

One of Mr. Barilla’s goals as a gardener is to provide habitat for wildlife. Million Trees is therefore very interested in his answer to the question, “How do we garden in a time of climate change?” because we are always responding to the perception of native plant advocates that the eradication of non-native plants will benefit wildlife. Mr. Barilla shares our view that, particularly at a time of a rapidly changing climate, it no longer makes sense to limit ourselves to native plants if we are to provide useful habitat to wildlife:

“In [the] microclimate [of our backyards], extreme gardening means making the yard hospitable for as many species as possible, without worrying so much about whether they originally belonged here or not. I used to think that tearing out turf and making room for native species like purple coneflower and switchgrass was the best thing I could do. But things aren’t that simple anymore. It doesn’t make sense to think in terms of native and nonnative when the local weather vacillates so abruptly. A resilient garden is a diverse garden.” (emphasis added)

Mr. Barilla also acknowledges the changing ranges of plants and animals in response to climate change and the need to accommodate those changes if species are to survive: “…species are disappearing across their native range but flourishing outside it…This phenomenon of species movement and adaptation is likely to become commonplace as the climate changes.”

Finally, Mr. Barilla appeals to us on moral grounds: “…we humans are responsible for the current changes. So we must also be responsible for helping other species survive them.” He uses the needs of the monarch butterfly as an example of a species that has been particularly hard hit by both climate change and the agricultural practices of humans. He urges gardeners to plant milkweed—the host plant of monarchs—in their yards.

Scientists in Ohio have concluded that episodes of extreme heat have reduced the population of native butterflies. Here in California, we can help monarchs by stopping the many projects that are destroying eucalyptus because monarchs use eucalyptus in several hundred locations along the coast of California as their overwintering roost.

Native plant advocates are putting their heads in the sand

We (and thousands of people with whom we have collaborated in the past 15 years) have made every effort to inform native plant advocates that they are mistaken in their assumption that native plants provide habitat superior to non-native plants. We have provided them with the many empirical studies that prove otherwise, including one cited by Mr. Barilla in his op-ed: “One study in Davis, California, found that 29 of 32 native butterflies in that city breed on nonnative plants. Thirteen of these butterfly species have no native host plants in the city; they persist there because nonnative plants support them.” This study by Professor Arthur Shapiro and his graduate student was published over 10 years ago. (1) It is only one of 5 local studies that report similar findings for every taxon of wildlife: benthic microorganisms, insects, amphibians, reptiles, birds, mammals.

Anise Swallowtail butterfly in non-native fennel

There are similar studies elsewhere in the country and around the world that also find equal numbers of insects in native and non-native vegetation. The British Royal Horticultural Society is conducting a 4-year study of insect use of plants. Their preliminary findings are that insects are equally likely to use native and non-native plants. Even Doug Tallamy was unable to find evidence to support his mistaken assumption that more insects use native plants than non-native plants.

Yet, native plant advocates refuse to consider the damage they are doing to both the environment and wildlife that is struggling to survive the destruction of their habitat. They demand the destruction of thousands of healthy trees, storing millions of tons of carbon dioxide that is released into the atmosphere when the trees are destroyed, thereby contributing to climate change. They demand that herbicides be used to eradicate non-native vegetation and kill the roots of the trees that are destroyed to prevent them from resprouting.

Here are a few specific examples of native plant advocates– and the environmental organizations that support them– refusing to consider the damage being done to the environment and wildlife:

Neighbors of Mount Davidson in San Francisco have been trying for several years to discuss plans of the Natural Areas Program to destroy 1,600 trees on Mount Davidson with the Bay Area Chapter of the Sierra Club, which supports those plans. The Chapter Sierra Club leadership has repeatedly refused to even discuss the issue with the neighbors who are members of the Sierra Club. The final response came from the Sierra Club Executive Director, Michael Brune who supports the refusal of Chapter leadership to discuss the issue with Club members.
The Sierra Club recently announced in its newsletter, The Yodeler, that it has asked the East Bay Regional Park District to destroy 100% of all eucalyptus trees on over 1,200 acres of park land. East Bay Regional Park District has estimated the average density of the eucalyptus forest on their properties at 650 trees per acre, which means that the Sierra Club is demanding that over 780,000 trees be destroyed in the East Bay.
The Sierra Club recently announced that it has asked UC San Francisco to implement its original plan to destroy over 30,000 trees on Mount Sutro in San Francisco. In making this request, they claim that such destruction will benefit native plants, although the original plan did not propose to plant any native plants. (These plans are presently on hold, although UCSF is now in the process of destroying about 180 trees they consider hazardous, in the height of nesting season.)
San Francisco’s Department of the Environment has submitted an application for funding to create a Biodiversity and Ecology Master Plan which proposes to treat all open space in San Francisco as “natural areas” using the Natural Areas Program as its model. The Natural Areas Program is presently restricted to 1,100 acres of city-managed park land. If implemented, this plan could eradicate non-native plants on all city-owned open space as well as private backyards.

The changing climate requires that we reconsider the commitment to native plants in historic ranges because they are probably no longer adapted to those ranges. They must move if they are to survive and we must accommodate that movement if we want them to survive. Likewise, we must reconsider everything we are doing to contribute to climate change, including our use of fossil fuels and deforestation.

Taking action

If you are a member of the Sierra Club, please tell them your opinion of their recent demands to destroy more trees in San Francisco and the East Bay than is presently planned by the owners of those properties. Also, urge them to listen to the concerns of their members regarding the plans for tree removals by San Francisco’s Natural Areas Program. Their address is: San Francisco Bay Chapter Sierra Club, 2530 San Pablo Ave. Suite I, Berkeley, CA 94702-2000

If you live in San Francisco and don’t want all open space in the city to be treated as native plant museums, please write to Polly Escovedo (who is considering the grant application to create a Biodiversity and Ecology Master Plan) by May 14, 2014: polly.escovedo@resources.ca.gov

(1) This section is from: Carl Zimmer, “Springing Forward, and Its Consequences,” New York Times, April 23, 2014

(2) SD Graves and AM Shapiro, “Exotics as host plants of the California butterfly fauna,” Biological Conservation, 110 (2003) 413-433

Dr. Arthur Shapiro: Composition of ecological communities is dynamic

We are republishing an article from the San Francisco Forest Alliance with permission. This excellent summary of Professor Shapiro’s presentation was approved by him. Professor Shapiro is an expert on the butterflies of California. We have had the great pleasure of attending some of his lectures at UC Davis. He is a gifted educator with a deep and profound knowledge of ecology.

Recently, UC Davis Professor Art Shapiro gave a talk at the Commonwealth Club. It was a tour-de-force. He described it as a very quick resume of a course he’s been teaching for 40 years at UC Davis.

The takeaway: The conventional wisdom about ecology is often wrong.

[You can listen to the one-hour audio recording of his talk HERE.]

SPECIES THROWN TOGETHER

Nativists idealize an ecosystem as a community of plants, animals, fungi, and other organisms that have evolved together over many thousands of years in a particular place so that they fit like a complicated jigsaw – the balance of Nature. (We’ve heard them use phrases such as “lock and key” to describe the effect of this co-evolution.) When non-native and invasive species enter, nativists believe, they destroy this intricate mechanism, resulting in an impoverished and simplified ecosystem with fewer species and no natural balance – and even the dire possibility of ecosystem collapse. They talk in terms of plants and animals that “shouldn’t be there” – usually, immigrant species brought in by humans.

But it’s not often true. What the scientific data show is that “communities” of that interdependent kind are unusual. Instead, most ecosystems are groups of plants and animals that happen to be in a place where they can thrive. When they interact, it’s usually because of “ecological fitting” – they can use the other plants and animals in that area to help them survive. Depending on how ancient they are, communities may include tightly co-evolved mutually interdependent multispecies systems. But these make up only a fraction of the community as a whole.

Anise swallowtail butterfly breeds on fennel

Here’s the evidence against the concept of tight-knit interdependent “communities”:

1. There’s no functional difference between a heritage ecosystem and one with exotic species. If there was, scientists should be able to tell an undisturbed “community” from an invaded one without knowing its history. In fact, they can’t. There are no consistent functional differences once an “invading” species has been established. Some ‘invaders’ can drastically transform the systems they enter – an example is cheatgrass in the Western deserts, which greatly amplified fire risk there. But most do nothing of the sort.

2. Species recolonize open land at different rates. “Species move, communities don’t.” If a landscape is wiped clean – say by glaciers or a volcanic eruption – nature begins to move back in almost immediately. The pollen record allows scientists to understand which species of trees arrived at which time. It shows that tree-species move individually, not as communities.

3. Species that now don’t exist in the same place did so in the past, which would not be true if plants and animals normally lived in fixed communities. One example: the wood turtle and the southern toad are not found in the same areas now – but the fossil record shows that in the past, the ranges did overlap. This couldn’t have happened if they needed to be part of different communities. Vast areas were occupied in the past by “no-analogue” communities – ones that simply don’t exist anywhere at all today.

He ended by pointing out that we – humans – are an invasive species. So are most things, at least at one time.

Read on for detailed notes from Professor Shapiro’s talk at the Commonwealth Club.

Again, you can listen to an audio-recording of the whole talk HERE (on the Commonwealth Club website).

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NOTES FROM ART SHAPIRO’S TALK:

ECOLOGICAL COMMUNITIES AND THE MARCH OF TIME

(The talk was dedicated to Prof Shapiro’s late neighbor, Steven Warnock.)

commonwealth club motto — Commonwealth Club motto

The talk was in three parts: The first laid out the historic context for two opposing schools of thought about ecology. The second examined the data, and concluded that the evidence supports Gleason. The third part looked at the future, which includes climate change.

ECOLOGICAL “COMMUNITIES” OR “ASSEMBLAGES” ?

Here’s the conventional wisdom about ecology, associated with Frederic Clements: Plants, animals, insects, fungi and microscopic creatures form interdependent groups, or “communities.” The process by which this happens is “co-evolution” (sometimes described as evolving a “lock and key”), leading to an ecology where all the species fit together like a jigsaw puzzle. (“Co-evolution” is associated with Peter Raven and Paul Ehrlich, who described it in butterflies and plants that evolved together.) If an area is disturbed, it will go through a predictable process of “natural succession” that will lead to a stable “climax” situation, with all its species again interacting as a community.

This stable ecosystem is sometimes called “the balance of nature.” Tamper with it, this theory says, and you could destabilize the whole community, even leading to ecological collapse.

The opposing view, associated with Henry Gleason, is that plants and animals do not necessarily form ecological communities. Instead, groupings or “assemblages” of plants and animals occur mainly by accident. They happen to arrive in that space at that time, and find conditions that allow them to survive and thrive. The species in such an assemblage will interact, not because they co-evolved, but because they find an opportunity to do so.

These theories about how species fit within an ecosystem were quantified when several ecologists – including the famous Robert McArthur – introduced mathematical models that looked at populations of plants and animals and their interactions. They used these models to look at Species Packing – i.e., how many different species of plants and animals could live in a particular ecosystem. Assembly rules says that the distribution of plant and animals species in a given area isn’t random: both competition and cooperation between plants and animals affect what you find. Competing species can’t all live in the same area, but their niches can overlap. Where they do overlap, the two species may evolve more differences (“character displacement“) so they compete less. These mathematical models assumed a condition of equilibrium, i.e. stability. Opponents have argued that ecological niches are seldom stable because the physical environment is not stable for very long.

R.H. Whittaker introduced the idea that the levels of dependency could vary within communities. For any two species, you could assign a number: +1 meant that the species needed each other to survive; -1 meant that they could not live in the same space. He speculated that these relationships tended to be distributed in a bell curve – meaning that most species in a group didn’t depend on the presence or absence of another species. But some subsets of the community were tightly integrated.

How adaptable are living things? They can evolve, but only in certain ways. Niche conservatism is the idea that most species cannot change very much or very fast in response to changes in their ecological niches.

The idea of co-evolution was fine-tuned with John Thompson’s concept of Geographic Mosaics. Co-evolution between two species can happen differently in different geographic areas. So, for example, a plant in one place might depend totally on one insect for pollination, but elsewhere, the same species of plant might find alternative pollinators available. Such Fine-Tuning is the opposite of Niche Conservatism – and both occur in Nature.

TESTING THESE IDEAS

Cladistics (i.e., the system of showing how related species evolved from common ancestors) provided a way to test the Ehrlich-Raven co-evolution hypothesis. If one kind of animal or plant developed into a separate species (“speciation”) then did the plants and animals depending on it also co-evolve into a separate species? There was no evidence that this happened. Co-evolution was a lot sloppier and more unpredictable than that!

Every time you see two organisms working together, it doesn’t necessarily mean they are co-evolved. Dan Janzen, a great tropical ecologis, pointed out that organisms could be taking advantage of niches and resources that appear through Ecological fitting, with no history of coevolution at all. We see this happen when introduced pests attack native plants, and native insects attack introduced plants, forming brand-new associations. It happens all the time.

pacific reed grass under eucalyptus — Pacific reed grass thrives in eucalyptus fog drip

Is there really a difference between “intact” ecosystems and ones that are disturbed or invaded? Mark Sagoff pointed out that if there really is a functional difference between “invaded” and “co-evolved” ecosystems, then scientists should be able to tell them apart without knowing their history.

“The theory that evolutionary processes structure ecosystems and endow them with a mathematical organization (e.g., rule-governed patterns that ecologists can study) has the following implication….scientists should be able to tell by observation whether a given ecosystem is heavily invaded or remains in mint condition…

“In fact, once non-native species have become established, which may take only a short time, ecologists are unable by observing a system to tell whether or not a given site has been heavily invaded. Invaded and heirloom systems do not differ in pattern or process, structure or function, in any general ways.”

There’s more evidence against the idea of stable interdependent communities as the norm in nature. For example: pollen core data shows that trees recolonizing lands after glaciation don’t move in “communities.” The tree species migrate at different rates. Only those species that have mutualistic relationships move together (for example, mycorrhizae and trees).

“Communities” are like still shots from a movie. They show a set of relationships at a particular point in time. That doesn’t mean the relationships are stable or unchanging. Many species show different sets of relationships in the past. For instance: at present, the wood turtle and the southern toad have completely different ranges – but in the past, those ranges overlapped in places. In the UK, workers building Hadrian’s Wall nearly 2000 years ago left middens that have remains of beetles of species now found only in Lapland. When an event that wipes out an ecosystem and recolonization starts, it takes trees 50-100 years to leave a pollen signature. Bufo_terrestris public domain Norman Benton sm Beetles that can fly get there in months to a few years.

If communities were stable groupings of interdependent co-evolved species, then we would expect to see the same communities repeated in similar conditions. But in fact, we often see different groupings in similar conditions.

THE FUTURE

Decisions about what ecosystems should look like are subject to human preferences. For most people, what they grew up with is “normal.” But the world has changed. The climate is changing. The pool of available species has increased enormously. In terms of trying to “restore” an earlier ecosystem – there’s no going back.