Ecologists: Time to End Invasive-Species Persecution

Ecologists: Time to End Invasive-Species Persecution: "


They’re treated as outsiders, as opportunity-stealing intruders who ought be greeted with government crackdowns rather than open arms.


They’re immigrants — immigrant species, that is. And some ecologists say it’s time to declare amnesty, demilitarize our environmental borders and accept the inevitable reality of non-native invasion.


“People like to have an enemy, and vilifying non-native species makes the world very simple,” said ecologist Mark Davis of Macalester University. “The public got sold this nativist paradigm: Native species are the good ones, and non-native species are bad. It’s a 20th century concept, like wilderness, that doesn’t make sense in the 21st century.”



Davis is one of 18 ecologists to sign a June 9 Nature essay entitled, “Don’t judge species on their origins.” They argue that while some non-natives are indeed destructive, such as Guam’s brown tree snakes and Great Lakes zebra mussels, they’re the exception.


Most are actually benign, relegated to a lower-class status that reflects prejudice rather than solid science, write the authors. Non-natives are assumed to be undesirable, and their benefits go ignored and unstudied.


‘To value the nature we actually have, and are creating, we need to think broadly…. Nature is something we create now.’

As examples of unfairly maligned invaders, the authors mention Australia’s devil’s claw plants, subject to a 20-year-long plant hunt that’s done little to contain a species that may cause little ecological disturbance. In similar fashion, tamarisk trees in the U.S. southwest have been targeted for 70 years by massive eradication programs, but are now seen as providing important bird habitat. Ditto the honeysuckle, banned in many U.S. states, but providing an apparent boost to native bird biodiversity.


“Classifying biota according to their adherence to cultural standards of belonging, citizenship, fair play and morality does not advance our understanding of ecology,” wrote the essay’s authors. They also consider ecological nativism to be hypocritical — nobody’s complaining about lilacs or ring-necked pheasants — and a form of denialism: In a globalized, human-dominated world, plants and animals will get around.


“Most human and natural communities now consist both of long-term residents and of new arrivals,” they wrote. “We must embrace the fact of ‘novel ecosystems.’”


Many other ecologists, however, were dismayed by the essay. David Pimentel of Cornell University said many invasive benefits are indeed recognized: Ecologists hardly complain about corn and other non-native crop plants. He said Davis and colleagues cherry-picked their examples.


“This article … is biased and is not a fair representation of the risks and benefits,” said Pimentel, who has estimated invasive species damage in the U.S. at between $100 billion and $200 billion. His point was echoed by by University of Notre Dame ecologist Jessica Gurevitch. “I think they downplay some of the problems and uncertainties,” she said. “That we should just get used to it, is not correct.”


Davis said that non-native species need to be addressed on a case-by-case basis. “We’re not saying, ‘Everything is okay, let’s open the doors,’” he said. “What’s frustrated us is that the actual data has often been misrepresented. People have heard that non-native species represent the second-greatest extinction threat in the world, and it’s just not true.” Davis noted that in many places, non-native species actually increase total biodiversity.


But a different criticism came from David Lodge, a Notre Dame ecologist who studies Great Lakes Asian carp invasion and coined the term ‘homogecene’ to describe how habitat disruption and non-native species flow reduces ecological uniqueness. Even as local biodiversity increases, each locale may come to resemble the next. “The researchers focus on biodiversity as the fundamental good. But what if that’s not the goal?” said Lodge.


There is, however, a common ground for these arguments: Each reflects the basic fact that, early in the 21st century, humanity is the driving force of nature on Earth. Whether species are classified as native or non-native, whether they’re accepted or rejected, reflects a choice. Philosophy guides stewardship, and stewardship is global.


“Humans are managers, humans are gardeners. We make the decisions about what species we want, and where,” said Lodge.


“To value the nature we actually have, and are creating, we need to think broadly,” said earth scientist Erle Ellis of the University of Maryland, Baltimore County, who invented the term ‘anthrome’ to define the hybrid human-natural systems that now dominate Earth’s surface. “Nature is something we create now.”


Images: Tamarisk trees along the Colorado river (Steven Damron/Flickr)


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Citation: “Don’t judge species on their origins.” By Mark Davis, Matthew K. Chew, Richard J. Hobbs, Ariel E. Lugo, John J. Ewel, Geerat J. Vermeij, James H. Brown, Michael L. Rosenzweig, Mark R. Gardener, Scott P. Carroll, Ken Thompson, Steward T. A. Pickett, Juliet C. Stromberg, Peter Del Tredici, Katharine N. Suding, Joan G. Ehrenfeld, J. Philip Grime, Joseph Mascaro, John C. Briggs. Nature, Vol. 474, June 9, 2011.







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