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Last Updated: Friday, 27 January 2006, 09:51 GMT
All is silent down at the pond
Professor Tim Halliday.  Image: Open University
Tim Halliday

Conservationists are mistaken, argues Professor Tim Halliday in this week's Green Room; many animals and plants cannot be saved from extinction, and the job of conservation scientists is to document them as they disappear.

Panamanian frog (undescribed species of Eleutherodactylus) dead from fungal disease in river.  Image: Image: Forrest Brem/Roberto Brenes
There is a profound malaise affecting fresh water, on which all terrestrial biodiversity and human life depends

As long ago as 1952, Rachel Carson predicted a "Silent Spring" if humans did not change their relationship with the natural environment.

For many amphibians, the silent spring is now a reality, and in many parts of the world the calls of frogs have been silenced.

This is happening at a time when public and scientific interest in biodiversity has reached an unparalleled level, as realisation increases that planet Earth is entering the sixth major episode of extinction in its history.

My own interest is in amphibians (frogs, toads, salamanders, newts and caecilians), a group of animals that appears to be bearing the brunt of the current biodiversity crisis.

In the last 20 years, several species have gone extinct, most famously the Golden Toad (Bufo periglenes) of Costa Rica.

The Golden Toad's disappearance around 1989 exemplifies two important features of amphibian declines:

  • first, it happened very quickly, the species going from relative abundance to extinction over only three or four years
  • second, it occurred in a national park, a protected area set up to preserve biodiversity
It was thus clear, 15 years ago, that the Earth's amphibians are subject to a process that cannot be explained simply in terms of habitat destruction.

Dirty water

Amphibians on leaves.  Image: Don Church/Conservation International

The recent Global Amphibian Assessment co-ordinated by IUCN, the World Conservation Union, concluded that a third of the world's 5743 known amphibian species are threatened with extinction.

At the level of individual populations the situation appears equally dire.

Data gathered by the IUCN Species Survival Commission's Declining Amphibian Populations Task Force (DAPTF) reveals that of 3020 amphibian populations monitored in recent years, over 20% have declined, and one in 10 has become extinct.

These figures are clear evidence that natural systems which support amphibian life are collapsing.

Amphibians are dependent, to varying degrees, on access to clean fresh water habitats for their survival; the recent dramatic amphibian decline suggests that all is not well in these ecosystems.

In 2004, WWF reported that biodiversity in the world's fresh water habitats halved between 1970 and 2000.

This makes fresh water the most threatened of the world's natural resources, more threatened even than tropical forest.

Amphibian declines are thus but one symptom of a profound malaise affecting global supplies of fresh water, on which all terrestrial biodiversity, and human life, depends.

Mallorcan midwife toad.  Image: Durrell Wildlife
Perhaps it is time to face reality and replace the 'conservation paradigm' with the 'extinction paradigm'
Concern for biodiversity has long been the domain of conservationists, and the dramatic decline among amphibian species suggests that the efforts of the conservation community are failing.

It is clear that the mainstay of conservation, the protection of habitat, is no longer sufficient to ensure the survival of many species.

There is a widespread culture of denial about this situation, not least among conservationists, who must take a lead in alerting humanity to the current extinction crisis.

The reality is that many thousands of species will become extinct in the near future; so perhaps it is time to face this reality and to replace the "conservation paradigm" with the "extinction paradigm".

Tangled threats

For recent extinctions, such as those that wiped out many island birds at the turn of the 19th and 20th centuries, identifying the causes was a relatively simple matter.

Human settlers and their attendant rats, cats and dogs destroyed their habitat and hunted them to extinction.

For frogs and toads that rapidly vanish from apparently pristine, protected areas, the causes are much less easy to identify.

Technician holds water flask.  Image: China Photo/Getty Images
Pollution is part of a complex web of threats facing wildlife
The accumulating evidence, from many scientific studies, reveals a complex of interacting and largely invisible factors, including climate change, chemical contamination and elevated ultra-violet radiation, against which protected-area status is totally ineffective.

To make matters worse, many amphibians are becoming prey to a highly virulent disease called chytridiomycosis which, probably with the help of humans, has found its way to almost all parts of the world.

Similarly enigmatic declines and extinctions are occurring in other habitats, notably in the oceans.

Even if they had plenty of time and money, conservationists can only hope to protect a few of the many species that face imminent extinction.

It is the responsibility of biologists, I suggest, to admit that the conventional view of conservation - that we can and should preserve at-risk organisms - is simply untenable.

What we can and must do is document the decline and disappearance of species that cannot be saved, so that at least some kind of record of them will be preserved.

Tim Halliday is Professor in Biology at the Open University in the UK, and International Director of the IUCN/SSC Declining Amphibian Populations Task Force

The Green Room is a new series of environmental opinion articles running weekly on the BBC News website

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