The Editor of an academic journal, Diversity and Distribution, wrote and published a defense of invasion biology (which he prefers to call “invasion science”) entitled, “Misleading criticisms of invasion science: a field guide.” (1) We recently critiqued a similar defense by other invasion biologists, so we’ll “cherry-pick” a few issues from this publication which weren’t covered in our earlier critique.
“Costs and Benefits?”
The authors begin by describing their academic discipline: “Invasion science is the study of the causes and consequences of the introduction of organisms to the areas outside their native ranges. It concerns all aspects relating to the transport, establishment, and spread of organisms in a new target region…and the costs and benefits of invasion with reference to human value systems.” However, the publication makes no mention of any benefits of non-native species nor does it mention the costs to the environment associated with the attempts to eradicate non-native species, such as herbicide use. Non-native species are said to be “far more likely to cause substantial ecological and socio-ecological damage” than to benefit ecosystems and, in any case, if there are any benefits they are said to be “transient.”
Actually, there is empirical evidence that the negative impacts of non-native species are transient. For example, the population of zebra mussels in the Great Lakes began to decrease significantly within three years when the population of migrating ducks discovered them and altered their migratory route to take advantage of that new food source. And the negative effects of garlic mustard on forest regeneration were significantly decreased within 50 years of its arrival in North American forests.
Evidence of the benefits of non-native species is too voluminous to enumerate, so we will just offer our local example of the services to wildlife provided by eucalyptus in California. It is one of the few sources of nectar in the winter and is therefore essential to the survival of honeybees and hummingbirds. Eucalyptus is the over-wintering roost of 75% of monarch butterflies in the California migration. It is the preferred nesting habitat for raptors.
We see no evidence in this publication that “costs and benefits” of non-native species have been considered.
Are most “invasions” benign?
The authors respond to the defenders of non-native species who say that most non-native species are benign:
- “The impacts of most invasions have not been studied, and so important effects may remain undetected,
- Invaders that are apparently innocuous in one region can be disruptive in other regions,
- Subtle impacts that may be unrecognizable without careful technical study can produce enormous ecosystem changes over time, and
- Many non-native species that currently appear innocuous may become damaging many years later—when it is no longer feasible to eradicate them.” (1)
Here’s how we paraphrase this defense: “We may not have much evidence that non-native species are doing any harm, but we are sure they are doing harm and even if they aren’t doing any harm, we’re sure they will eventually do a great deal of harm.” Does this seem an adequate defense of projects that are eradicating all non-native plants on thousands of acres of public land, using harmful methods such as herbicides and prescribed burns? We think a higher standard of proof is needed to justify such damage to our public lands.
Invasion biologists chastise critics
Invasion biologists are angry that their academic turf is being challenged by other academic scientists:
“In our view, the escalation of cavalier bashing of the discipline is undermining systematic science-based efforts to improve the efficiency of management of problematic non-native species and invaded ecosystems.” (1)
We have seen no “cavalier bashing” of invasion biology. What we have seen, and provided to readers of Million Trees, are many scientific studies which show that the hypotheses of invasion biology are often not supported by evidence from the field. Most of the papers don’t even mention “invasion biology,” they just present their evidence in scientific journals.
We wish it were true that these studies were “undermining management” of non-native species. Unfortunately, we see no evidence that criticisms of invasion biology by academic scientists have any impact on public policy. Every project in the San Francisco Bay Area which is eradicating or proposing to eradicate all non-native species on our public lands is moving inexorably forward. There is no apparent connection between the revision of the hypotheses of invasion biology by academic scientists and the practical application of those out-dated hypotheses by managers of public lands. If the primary goal of invasion biologists is to eradicate non-native species rather than to defend their academic discipline, they seem to have nothing to fear. They would be wise to shut up and let the destruction continue quietly under the public’s radar.
A new round of criticism of invasion biology
Meanwhile, the angry reaction of invasion biologists to criticism of their discipline has not stopped that criticism. Hardly a day goes by without the publication of new critiques of invasion biology by other scientists. Where do camels belong? by Ken Thompson was published in September 2014. It is a full frontal assault on the unfounded assumptions of invasion biology. It is a hard-hitting, often amusing summary of the flaws in the reasoning on which invasion biology was constructed. Although Mr. Thompson is a British academic scientist, his book is written for the general public, drawing on the scientific studies of his colleagues who share his opinion of the fallacies of invasion biology. The book is also unique in mentioning the damage that is done by the fruitless attempts to eradicate firmly entrenched non-native species.
Mr. Thompson was recently interviewed by Canadian public radio. Here is a choice excerpt from that interview:
“He also cautions that our efforts to control or eliminate invasive species can be tremendously expensive, are rarely successful, and often have damaging unintended consequences. For example, the herbicides used to try to eliminate invasive plants often have devastating impact on vulnerable native species. The cure, in some of these cases, is worse than the disease, he says. Professor Thompson says the invasive species we might worry about most is actually us. Humans have spread to every corner of the globe, and altered a huge amount of the planet. ‘We’ve chopped down forests, built dams and turned the whole world into a giant cattle pasture, and then we’re surprised that some species quite like what we’ve done. We shouldn’t be surprised.’”
The publication of Where do camels belong? is one of the few bright spots in 2014, a year full of disappointments for those who value our urban forest in the San Francisco Bay Area. We recommend it to our readers. It may cheer you up as it did us.
Update: Professor Richardson recently published (February 11, 2015) an article in Ensia, an on-line science blog, which was written in response to an earlier article(January 21, 2015) in Ensia by Daniel Simberloff. Professor Simberloff’s article defended “invasion biology” and criticized any acceptance of “novel ecosystems.” Professor Richardson’s response seems to defend “novel ecosystems.” It seems that Professor Richardson has altered his views regarding novel ecosystems since writing his article two years ago about “Misleading criticism of invasion science.” Welcome to reality, Professor Richardson. Updated 4/8/15
- David Richardson and Anthony Ricciardi, “Misleading criticisms of invasion science: a field guide,” Diversity and Distribution, 19: 1461-1467, 2013