In Defense of Invaders, and a rebuttal
(reposted from The Economist)
ArcheWild Note: ArcheWild does not agree with the points of view in this article and is drafting a rebuttal for submission to the editors at The Economist
Most campaigns against foreign plants and animals are pointless, and some are worse than that
EVERYBODY loves to hate invasive species. Americans battle rampant plants such as kudzu, a Japanese vine; Europeans accuse the American grey squirrel of spreading disease and damaging forests. As The Economist went to press, a scientific committee was expected to sign off on Europe’s first invasive-species blacklist. Cross-border trade in 37 species will be banned (the list is bound to grow longer as conservationists add more troublemakers). Where it is not already too late to wipe out these alien invaders, EU member states will be required to do so.
Europeans are restrained in comparison with other countries. The international list of invasive species—defined as those that were introduced by humans to new places, and then multiplied—runs to over 4,000. In Australia and New Zealand hot war is waged against introduced creatures like cane toads and rats. In 2013 New Zealand used helicopters to drop a poison known as 1080 on 448,000 hectares of land—an area about the size of Yosemite and Sequoia national parks put together. Just four public objections were recorded.
Some things that are uncontroversial are nonetheless foolish. With a few important exceptions, campaigns to eradicate invasive species are an utter waste of money and effort—for reasons that are partly practical and partly philosophical.
ArcheWild Note: Campaigns to eradicate invasive species ARE effective when implemented by professionals with good techniques. The staff at ArcheWild, for example, has safely and effectively eliminated infestations of Japanese stiltgrass, lesser celandine, phragmites, garlic mustard, and many others by applying persistent, low-cost, low-impact methodologies.
Start with the practical arguments. Most invasive species are neither terribly successful nor very harmful. Britons think themselves under siege by foreign plants like Japanese knotweed, Rhododendron ponticum and Himalayan balsam. In fact Britain’s invasive plants are not widespread (see article), not spreading especially quickly, and often less of a nuisance than vigorous natives such as bracken. The arrival of new species almost always increases biological diversity in a region; in many cases, a flood of newcomers drives no native species to extinction. One reason is that invaders tend to colonize disturbed habitats like polluted lakes and post-industrial wasteland, where little else lives. They are nature’s opportunists.
ArcheWild Note: The claims that invasive species do not spread quickly, that they are less of a nuisance than natives, and that they increase biodiversity is patently untrue, especially in the Northeastern United States. Our forests are overrun with privet, burning bush, multiflora rose, and barberry. Our streams and rivers are choked with Japanese knotweed and phragmites. These invasive species, and many more, are fundamentally changing the diversity of our forests and riparian areas rendering them unavailable to the native species that birds, insects, and amphibians rely upon them for their survival.
New arrivals often turn out to be useful, even lovely. Americans fret about the decline of a vital crop-pollinator known as the American honey bee. Apis mellifera is actually an invader from the Old World: having buzzed from Africa to Europe, it was brought to America by colonists and went wild. Invasive plants provide food and nests for vulnerable natives; invasive animals can help native species by killing their predators, as the poisonous cane toad has done in Australia.
ArcheWild Note: Some new arrivals do provide ecosystem services, such as Queen Anne’s Lace (from Afghanistan), but it does so at the expense of the native species it replaces in a meadow, whose flower parts are better matched to the mouth parts of our native pollinators, thus reducing overall ecosystem performance. Holding up the European honeybee as an example of good invasive species ignores the fact that honeybees are neither invasive nor displace native species.
Another practical objection to the war on invasive species is that they are fiendishly hard to eradicate. New Zealand will not get rid of its rats any more than Britain could wipe out its grey squirrels. Culls tend to have a short-term effect at best. It is, however, sometimes possible to get rid of troublesome immigrants on tiny oceanic islands. Because the chances of success are higher, and because remote islands often contain rare species, efforts there are more worthwhile.
ArcheWild Note: Temporary efforts to control invasive species can fail due to incomplete/ineffective eradication methods or ignoring the weeds across the street. Only long-term, systemic approaches have worked well, in our experience.
The philosophical rationale for waging war on the invaders is also flawed. Eradication campaigns tend to be fuelled by the belief that it is possible to restore balance to nature—to return woods and lakes to the prelapsarian idyll that prevailed before human interference. That is misguided. Nature is a perpetual riot, with species constantly surging, retreating and hybridizing. Humans have only accelerated these processes. Going back to ancient habitats is becoming impossible in any case, because of man-made climate change. Taking on the invaders is a futile gesture, not a means to an achievable end.
ArcheWild Note: Evidence abounds of the capacity of nature to rebound after the removal of invasive species. Returning to a pre-Columbian state is indeed fantasy but ignoring the problem of invasive species because they somehow are additive is not only an uninformed opinion but irresponsible. Invasive species removal is a proven and fundamental first step to restoring natural function and expanding ecosystem services.
No return to Eden
A rational attitude to invaders need not imply passivity. A few foreign species are truly damaging and should be fought: the Nile perch has helped drive many species of fish to extinction in Lake Victoria. It makes sense to keep out pathogens, especially those that destroy whole native tree species, and to stop known agricultural pests from gaining a foothold. Fencing off wildlife sanctuaries to create open-air ecological museums is fine, too. And it is a good idea for European gardeners to destroy Japanese knotweed, just as they give no quarter to native miscreants like bindweed and ground elder. You can garden in a garden. You cannot garden nature.
ArcheWild Note: Yes, you can garden nature. The ecological restoration industry, including native plant suppliers, is large and growing rapidly. The Army Corp of Engineers is restoring the dunes along nearly the entire coast of New Jersey. The US Forest Service is reclaiming hundreds of acres of abandoned coal mines in West Virginia. The Chesapeak Bay Foundation is well on its way to restoring the entire Bay watershed.
ArcheWild Note: Perhaps the best example that people can visit is Bowman’s Hill Wildflower Preserve, located in New Hope, Pennsylvania, which is the largest (more than 130 acres) and oldest deer-fenced wildflower preserve in the northeast. Invasive species, including deer, are managed using good techniques with the result being that there are over 700 native plant species growing inside the fence and about two dozen growing outside the fence. A commensurate ratio of bird and insect species can also be found within the fence. Yes, you can garden nature.