One of Woody Allen’s running jokes in the movie "Sleeper" is the schlep who woke up 200 years into the future and discovered how many of our accepted medical and other scientific “facts” were upended. A similar thing is happening with invasive species and ecological restoration; a growing chorus is proclaiming that “novel ecosystems”—landscapes in some cases dominated by non-native, invasive species—are nothing to fear.
Dr Agon: Has he asked for anything special?
Dr. Melik: Yes, this morning for breakfast. He requested something called wheat germ, organic honey and tiger milk.
Dr. Agon: [laughs] Oh, yes. Those were charmed substances…That some years ago were felt to contain life-preserving properties.
Dr. Melik: You mean there was no deep fat? No steak or cream pies? Or hot fudge?
Dr. Agon: Those were thought to be unhealthy, precisely the opposite of what we now know to be true.
Dr. Melik: Incredible.
Dr. Orva: Here. You smoke this, and be sure to get the smoke deep down into your lungs.
Miles Monroe: I don’t smoke.
Dr. Orva: It’s tobacco. It’s one of the healthiest things for your body. Now go ahead. You’ll need all the strength you can get.
— From Woody Allen’s “Sleeper”
Ecological restoration is glorified gardening and we need to focus on the new sustainability: one that accepts and embraces exotics. On the far end of the “acceptanistas” are those who think that invasive species-being more tolerant of humans—and are in fact nature’s saviors, hardworking and providing invaluable ecosystems services and the working material for new species to evolve.
Those working to eliminate these invasive non-native species are romantics who have scary similarities to the Nazis and other ethnic cleansers, and do not recognize that, in reality, “native species” do not exist. In fact because humans are a product and part of nature, landscapes dominated by humans and exotic species introduced by humans are completely “natural”. While the last idea might sound like something from a late-night, cannabis-fueled college bull-session (“Hey man, when you think about it , an industrial brownfield is just as “natural” as a coral reef!”), a published conservation scientist recently made this case (ok, not the brownfield point, but more about Dr. Chris Thomas later).
Let me be clear: I love a lot of non-native species. The area around the steward’s house at Ramsey Creek (including the parking lot) has a lot of exotics including ginko, Asian magnolias, dawn redwood, evergreen azaleas and daffodils. When we made this area a part of the Preserve, we did not rip out these plants, although if we were starting with a blank slate we would NOT use them for landscaping. People who see daffodils in the parking lot see this as a license to plant exotic bulbs on graves.
I don’t have trouble with the Queen Ann’s lace in our “natural” meadows at Ramsey Creek. Unlike in other areas of the country, wild carrot seems to behave itself—at least on our poorly drained clay soils. Native wasps (at least at Ramsey Creek) use the flowers and voles eat the roots.
European honey bees have been here for almost 500 years-and while they might have impacts on some of our native pollinators in the wild, at this point it is pretty much a done deal (by the same token, we will not keep domestic honey bees at Ramsey Creek-which could compete with native pollinators).
I realize that with all of the non-native species, we will never be rid of them entirely; many like Queen Ann’s lace are at the very least benign. Others could certainly be beneficial: a recent study out of Duke University shows that an invasive species of Japanese seaweed (Gracilaria vermiculophylla) benefits native species where native “foundation species” on the sea floor have been lost (http://www.pnas.org/content/114/32/8580).
I also agree that those species present in 1492 were not always here, and many species had disappeared in the previous 20,000 years or so, especially the megafauna including horses. Horses, (the genus Equus-including zebras, asses, and horses) originated here in North America about 4 million years ago, and the modern horse species (E. caballus) arose here, and crossed to Eurasia maybe 1-2 million years ago. The last Equus in N. America did not die out until 11-13,000 years ago. Some people out west think of wild horses as horrible non-natives but the Equus has been absent only .3% of the years since it evolved here.
Canids evolved in North America and never went extinct here: an animal very much like the coyote was in the southern US over 10 million years ago. The gray wolf was an invasive species in the early Pleistocene, having evolved in Asia from canids that had traveled across the land bridge from North America. In our area, people complain about coyotes (or coy-wolf-dogs since they carry gray wolf and dog genes) being an invasive species. Considering that a coyote-like animal was roaming this area 3 million years before chimpanzees and humans went their separate evolutionary ways, it might be short term thinking to object to wild canids returning. Yes, they occasionally carry off cats and other small pets, but they also provide natural control of deer-especially in areas where hunting pressure is low.
So yes, I get all that. But we spend a lot of time and money at Ramsey Creek controlling non-native invasive species like kudzu, Asian honeysuckle and privet, and we are working hard to restore (or recreate) piedmont grasslands-a once wide-spread habitat now almost extinct. Novel ecosystems advocates might say we are not only wasting our time, we are harming the environment.
To be sure, some critics of native plant advocates have a point. Evolutionary biologist Steven J. Gould held that some proponents misused evolutionary reasoning to make a case for preserving native plants (“An Evolutionary Perspective on Strengths, Fallacies and Confusion in the Concept of Native Plants”, Arnoldia (58)1, 1998). His criticism centered on what he described as two fallacies.
The Functional Argument Based on Adaptation
Gould says: “If natural selection works for the best forms and most balanced interactions that could possibly exist in any one spot, then the native must be best, for the native has been honed to optimality in the refiner’s fire of Darwinian competition.”
But locally evolved natives are not “optimized” as much as they prevail over local competition. In some cases, like relatively small islands where the competition is pretty slack , natives are particularly vulnerable to exotics that evolved under much more competitive conditions. It’s like the old joke with a bear approaching two people, one says “I’m going to run.” The other says “You can’t outrun a bear”, and the first man says “I just have to outrun you.”
The Geographic Argument Based on Appropriate Place
This argument, as Gould says, is less clearly linked to a Darwinian postulate, but goes like this: “Why would a plant live only in this or that region of 500 square kilometers unless the domain acted as its natural home?” The idea is old, and was advocated by Willam Paley in his 1802 book Natural Theology: God made each creature for its proper place.
It is easy to come up with counter-examples. Torreya taxifoliain and Taxus floridana (gopher yew and Florida yew) are both endangered conifers limited to a 10 square kilometer area along the Apalachicola River in the northern Florida panhandle, and both are in decline and facing extinction.
Torreya is down to a few hundred stems, most of these not reproducing. Interestingly, the most successful, naturally reproducing grove is outside of Highlands, NC, where botanist Thomas Grant Harbison planted seeds around 1920. This small grove is at 3,300 feet elevation and hundreds of miles north, reinforcing the idea that Torreya is an ice age relict that became “stuck” in Florida as the climate warmed. While some in the native plant / invasive science community oppose the idea of “assisted migration” and “re-wilding” of Torreya and Florida yew, to me it makes sense in a warming climate. Torreya has not become invasive in 100 years in and fossil evidence shows that at least one species of Torreya lived in Georgia and North Carolina as far back as the Cretaceous era (some 70 million years ago or more). We would very much like to plant a few Torreya at Ramsey Creek, if anyone wants to sponsor one for a grave. Gould probably overstates the case for accidents of history and geology, and took a rather dim view of “community ecology”.
Of course some species-like those adapted to serpentine soils rich in metals most plats find downright poisonous-are specially adapted to a specific place, and we are only now beginning to unravel mutualistic and semi-parasitic relationships between plants and between plants and fungi (not to mention how vertebrates and invertebrates play into this). Tree gall communities, for example, are incredibly complex with foundational wasps making the galls, insects that feed on the gall, and parasitic wasps that feed on the original wasp larvae and the larvae of the “gall parasites”, and vertebrates that feed on all of the above.
But Gould was not opposed to protecting native plants, controlling exotic species or protecting natural areas. As he said in the 1998 paper: “A preference for natives does foster humility and does counteract human arrogance-for such preference provides the only sure protection against our profound ignorance of consequences when we import exotics.”
Like Gould’s analysis, much of the criticism of invasion science (the science of invasive species) and restoration ecology is valuable to the young sciences; some criticism is just plain bad science and science journalism: full of straw-men, ad hominem attacks and the occasional redutio ad Hitlerum (in on-line arguments this is known as Godwin’s Law).
For those who want to skip more specific examples and long, geeky exploration of these ideas (that will be part 2), invasion scientists David Richardson and Anthony Ricciardi did us a service in publishing “Misleading Criticisms of Invasion Science: A Field Guide” ( Diversity and Distribution, (2013) 19, 1461-1467). Their short paper outlines 6 basic criticisms and 6 rebuttals—and provides almost 3 pages of references.
The (abridged) arguments are :
I think that conservation burial has a role to play with ecological restoration and promoting native species, and I think we all understand that we are not trying to go back to some pure, romantic ideal of pre-Columbian landscapes. But dense thickets of privet crowding out rare native trilliums are something we can try to control. We can get rid of the loblolly pine plantations without pulling up every Queen Anne’s lace plant.
Dr. Billy Campbell is the co-founder of Ramsey Creek Preserve, with his wife, Kimberley. His informed perspective is deeply valued in the conservation burial community.