Academic blacklisted over threat of invasion

Ecologists have been accused of allowing emotions and aesthetics to colour warnings about the environmental threat posed by non-native species.

The scholar at the centre of the dispute said he had been prevented from publishing his thesis by outraged members of the scientific community.

Most experts believe the global movement of plants and animals, often inadvertently carried by ships and planes, to colonise unfamiliar ecosystems is a principal culprit in the loss of native biodiversity. They argue for measures to prevent new waves of invasive species - such as the green crab in the US, the mink in the UK and the zebra mussel on both sides of the Atlantic - from driving out native species as well as harming human health and the economy.

But some scientists are arguing that the threat has been exaggerated.

Philosopher Mark Sagoff said the scientific community had pilloried his insistence that the distinction between native and non-native species as a group had no ecological or economic basis and had in effect blocked publication of his full thesis.

His latest submission to a journal was rejected last month by a majority of the reviewers.

One reviewer called Dr Sagoff's paper "egregious" and complained of "half-truths, statements out of context and twisted logic".

Dr Sagoff, a senior research scholar at the University of Maryland in the US and former president of the International Society of Environmental Ethics, said he admired many of his critics and had been surprised at the strength of the reaction.

He felt that the established line was influenced by aesthetic, cultural and spiritual arguments to conserve native ecosystems. These were valid reasons but should be acknowledged as non-scientific arguments.

While he supported efforts to prevent the spread of known pests, Dr Sagoff argued against a general presumption among ecologists that non-native species were "guilty until proven innocent" and observed that his was not supported by research.

Mark Davis, professor of biology at Macalester College in the US, said this argument threatened deeply held beliefs. "Ecologists have been guilty of overgeneralising and categorising beyond what the data actually say," he said. "An emotional response is the best indication that you really are onto something."

Professor Davis said that many ecologists revealed their feelings by using pejorative metaphors such as "invasive meltdown" and "pollute" in scientific discourse.

"I'm not welcoming all invasive species with open arms - I'm arguing for sound scientific comments based on data and a more sensible perspective."

Professor Davis added that this would enable the limited resources available for control to be better focused on serious problems.

David Lodge, professor of biological sciences at the University of Notre Dame in the US, accused Dr Sagoff of drawing illogical conclusions in a journal six months ago.

He told The THES there was a kernel of truth in Dr Sagoff's claims, but that he was none-theless attacking a straw man as few, if any, ecologists believed non-native wholly equalled bad.

Professor Lodge said the priority had to be to push for risk assessments to identify those new species likely to cause damage.

"It is important to get beyond Sagoff's and Davis' arguments and address the very many serious threats that invasive nonindigenous species pose to human commerce, human health and environmental health," he said.

David Pimentel, professor of entomology at Cornell University in the US, said: "Personally, I like Mark Sagoff, but ecologically several of his arguments have serious errors. This is why not a single biologist that I know supports his position and assessment."