Response to New York Times article
Above photograph: Goats and feral cats introduced in the late 1800’s devastated the biodiversity on Guadalupe Island, Baja Mexico. Once invasive goats were fenced out of a section of the island, rare, native plants remerged! In 2003, Conservación de Islas removed invasive goats from the entire island.
By Dr. Dan Simberloff & Bill Waldman
Erica Goode’s February 29 NYT article, Invasive Species Aren’t Always Unwanted, wisely recognizes “Islands and mountaintops are especially vulnerable to damage from invaders [invasive species] because their native species often evolved in isolation and lack natural defenses against predators or immunity to exotic disease.” But this article, and others she cites, confuse introduced, non-native species, which may be benign (or even beneficial), with invasive species, which are, by definition, harmful.
The distinction has long been widely recognized by invasion scientists and policymakers. It was codified in United Nations’ 1992 Convention on Biological Diversity, which engages 194 signatory nations to “Prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species” (emphasis added). A preeminent authority on biodiversity conservation, the International Union for the Conservation of Nature, defines an invasive species as one “that has been introduced to an environment where it is non-native, or alien, and whose introduction causes environmental or economic damage or harm to human health.”
Goode’s article does not go far enough. All native species—not only those on islands and mountaintops—lack a co-evolutionary history with species from elsewhere. This is why non-native species are far more likely to cause ecological damage than native ones (up to 40 times more likely in comprehensive reviews of data). Further, the relatively new science of invasion biology is not yet adept at predicting which non-natives will cause problems, and many non-natives that ultimately become invasive do so only after long time lags and in unpredictable ways. This is why the 2002 expansion of the Convention on Biological Diversity advocates not waiting to see if a non-native has a harmful impact, but rather a precautionary approach of preventing all introductions, and if this proves impossible, attempting to detect non-natives early and eradicate them before they are widely established.
Failing to recognize the distinction between non-native and invasive, the article further muddies an already cloudy debate amongst mainstream biodiversity conservationists and skeptics who cite possibly benign (or beneficial) introductions to argue against early and aggressive intervention against non-native species. These misguided arguments ignore the fact that we are in the midst of a sixth mass extinction precipitated by humans and that introduced species are a major contributor. We know that about 80% of all extinctions recorded since 1500 occurred on islands. Two papers recently analyzed extinctions events and concluded that invasive species were cited most frequently as the cause of island species extinctions and invasive species are the most common threat associated with vertebrate extinctions globally. Other recent research shows that many more non-native species than previously realized cause substantial, inimical ecological impacts, on continents as well as islands. The charge of xenophobia voiced in the article is particularly insidious, as no evidence supports it and it ignores the wealth of devastating impacts wrought by non-natives that motivate the increasing response to them.
We are puzzled by those few who ignore the preponderance of scientific evidence and hypothesize that the anthropogenic diaspora of non-native species is nothing more than ‘nature’s’ work, the next, natural stage of our evolving ecosystems. After all, they argue, humans are animals, a part of nature, too. It appears such critics are content to live in a world of diminishing species and deteriorating ecosystems regardless of the costs.
We, however, are unwilling to accept a depauperate future for our planet. We believe biodiversity conservation is a moral imperative and necessary for the wellbeing of humanity. To us, safeguarding biodiversity means preventing extinctions, protecting ecosystems, and sustaining critical resources that nature and people rely on. This is our line in the sand. Surely, we can debate the relative impacts of particular introductions, whether they are benign, harmful, or even beneficial. This is where this debate should be centered—it has been for years, every time action is proposed against a particular introduced species. This is where we should decide when, where, and how intervention is warranted.
Unfortunately, some leading journalists and editors are fanning the flames of this ill-advised, unsubstantiated debate. Most of the opinions and examples Goode sites to corroborate the “good” invasive species side of this argument are not, in fact, about invasive species. They are simply harmless introduced species. This confusion is a disservice to our world’s most imperiled species and only leads conservationists, scientists, and academics to continue to talk past each other.
The conservation outcomes of our work (preventing extinctions by removing invasive species from islands) is perhaps the most poignant response to the confusion promulgated in Goode’s article. Picture this: Before Darwin was even born (1809), invasive Black rats were introduced to Pinzón Island in Ecuador’s Galapagos Archipelago (probably by whalers or pirates). Invasive rat predation was so severe that not a single Pinzón Giant Tortoise egg or hatchling survived for over 100 years and it was declared Extinct in the Wild. The species was only preserved through 80 plus years of captive breeding. That is, until we and our partners eliminated this threat in 2012. Today, hatchlings like this one can be found emerging from nests and flourishing on an invasive predator free island.
We continue to stand behind all those around the world working to remove harmful invasive species and to prevent introduction of new ones. In our case, we do this for unique island species often found nowhere else in the world. Others engaged in similar missions have a much wider ambit, working at local, regional, national, and global scales toward the same ends. The increased effort at all these levels, even during the recent global recession, belies Goode’s suggestion that scientific and public support for this mission is waning.
Dr. Dan Simberloff, is the Nancy Gore Hunger Professor of Environmental Studies and director of the Institute for Biological Invasions at the University of Tennessee in Knoxville. He is a biologist and ecologist who earned his PhD from Harvard University in 1969. He studied ecology as a student of the biologist EO Wilson, one of the coauthors of the theory of island biogeography.
Bill Waldman is the CEO for Island Conservation, the only global biodiversity conservation organization whose sole mission is to prevent extinctions by removing invasive species from islands.
- Invasive species are, by definition, harmful. Period. - March 9, 2016
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- Do you know where the real wild things are? - October 14, 2015
- ¿Sabes dónde están los verdaderos animales salvajes? - October 13, 2015
- Protecting the Dominican Republic’s Native Species - May 19, 2015