http://www.independent.co.uk/story.jsp?story=297239
05 November 2002 07:43
BDT
How one creature
drives so many species to extinction
Scores of animals
and plants are being driven out of
existence each year - and scientists say that mankind
is almost always to blame
By Steve Connor Science
Editor
21 May 2002
Planet Earth is going
through its sixth and probably its
most devastating period of mass extinction with scores,
and possibly hundreds of species of animals and plants
dying out each year. But unlike the previous five extinction
waves, this time the culprit is just another lifeform,
Homo sapiens.
A United Nations report
on the environment, to be published
tomorrow, will highlight the scale of a problem many
conservationists believe is likely to rapidly worsen
over 30 years as wildlife congregations are destroyed
or invaded by a less diverse range of species.
Some scientists believe
the "sixth wave" of mass extinction
is between 1,000 and 10,000 times greater than the normal
"background" rate at which species are lost naturally.
Such a dramatic fall
in biological diversity is identified
as one of the most pressing problems facing humanity,
by the scientists who contributed to the Global Environment
Outlook-3 (Geo-3) report of the United Nations Environment
Programme (Unep).
The report will identify
some 11,046 species of plants
and animals known to face a high risk of extinction,
including 1,130 mammals - 24 per cent of the total - and
12 per cent, or 1,183 species of birds.
Human activities, from
habitat destruction to the introduction
of alien species from one area to another, are listed as the
main causes of this dramatic loss in biodiversity. In the report,
scientists also identify 5,611 species of plants known to be
on the verge of extinction. They say the true figure is likely
to be far higher, given that only 4 per cent of the world's
known plant species have been properly evaluated.
The Geo-3 report covers
almost every aspect of environmental
degradation, from forest destruction to water pollution.
It is designed to set the framework for the world summit
on sustainable development to be held this summer in Johannesburg.
Geo-3 looks back on
the past 30 years of environmental
degradation, since the 1972 Stockholm conference on the
human environment, to assess the likely prospects for the
next 30. It is likely to warn that many of the factors that
led to the extinction of species in recent decades continue
to operate with "ever-increasing" intensity.
Serious threats to
life on Earth are over-exploitation of
natural resources, pollution, habitat destruction, the
introduction of alien species and global climate change,
say the scientists who advised Unep.
They identify the loss
of habitats by human encroachment as one
of the most pervasive threats to wildlife. Habitat loss and
fragmentation of breeding grounds are behind the precarious
predicament of 89 per cent of threatened birds, 83 per cent
of threatened mammals and 91 per cent of endangered plants,
the Unep scientists say.
In addition to growing
poverty and climate change caused
by global warming, Unep has identified alien invasive species
as another serious threat to biodiversity, affecting 30 per cent
of threatened birds and 15 per cent of threatened plants.
The black rat, which
since 1800 has stowed away on ships
sailing to the remotest corners of the world, is held responsible
for the biggest slaughter of birds, especially those on uninhabited
islands.
Another of man's hitchhikers
has caused havoc to native wildlife
from Hawaii to the Seychelles and Zanzibar. The crazy ant,
so called because of its frenetic movements, killed three
million crabs in 18 months on Christmas Island alone.
A host of other invasive
aliens have also inflicted enormous
environmental and economic damage throughout the world.
The list includes the brown tree snake, the small Indian
mongoose, the Nile perch, the strawberry guava, the water
hyacinth, the zebra mussel and the brushtail possum.
Several species of
animals and plants in Britain are
threatened by a similar invasion of aliens. The water
vole is being killed off by the American mink, the eggs
of rare wading birds nesting in the Outer Hebrides are
being eaten by hedgehogs introduced from the mainland,
and the wetland habitats of the Norfolk Broads suffered
decades of destruction by the coypu, a South American rodent.
Jeff McNeely, chief
scientist at the International Union
for Conservation of Nature in Geneva, said the next 30 years
could be the defining moment for life on Earth. Either
we can finally recognise the problems and do something
about them, or we do not, he said.
"It could go either
way. It could be a golden age of
nature conservation, or it could be a disaster scenario.
If we assume a doomsday scenario then we're going to live
in a greatly oversimplified world.
"Most of the remaining
species are going to be widely
dispersed and cosmopolitan. We will have lost many of
the large mammals and birds, and life in general will
be more homogeneous, with a smaller capacity to adapt
to a changing environment."
Within the next 30
years, if the biodiversity crisis
is not addressed, it is likely that the last tiger,
rhinoceros, Asian elephant, cheetah and mountain gorilla
will have been lost in the wild, Dr McNeely added.
Often it is the well-known
animals and plants which
are at greatest risk. The Chinese alligator is the
most endangered crocodilian, with only 150 individuals
in the wild. Half of the world's insect-eating pitcher
plants are threatened and one, the green pitcher plant,
is critically endangered because of the loss of its
wetland habitat.
Scientists have identified
and named about 1.5 million
species but they believe that between 5 million and
15 million species have yet to be formally classified.
It is now generally assumed that many unnamed animals,
plants and micro-organisms are going extinct before
they are even known to science.
Lord May, an Oxford
zoologist, believes present extinction
rates are likely to increase further over the next century.
He said: "This represents a sixth great wave of extinction,
fully compatible with the big five mass extinctions of the
geological past, but different in that it results from the
activities of a single other species rather than from
external environmental changes."
This catalogue of extinction
is in danger of going
unrecorded as fewer scientists are being trained in
the field of taxonomy, the science of systematic
classification.
Last week, the House
of Lords Select Committee on
Science and Technology warned that a shortage of
taxonomists and underfunding of the research centres
for systematic biology was jeopardising efforts to
protect wildlife. How can biodiversity be protected
if no one is recording what is there? "We have a
cultural and moral obligation, as well as a pragmatic
economic need, to record and, as far as possible,
conserve the diversity of life with which we share
the planet," the committee said.
The Natural History
Museum and Kew Gardens in London
are two world-reknowned centres for animal and plant
taxonomy yet the committee found that both were finding
it difficult to provide a service because of financial
constraints. "It has also placed the reference collections
of specimens comprising a wide range of biodiversity,
which are housed in these institutions, at considerable
risk," the committee added.
Professor Paul Henderson,
director of science at the
Natural History Museum, said systematics and the description
of species was critical to the preservation of animals and
plants, and the key to economic prosperity for many of the
poorer nations in the world. He said it was at the heart of
the sustainable development theme of the forthcoming world
summit.
"We helped to
identify the screw-worm when it invaded
African livestock from South America," Professor Henderson
said. "Without recognising it early on, it would have
wreaked havoc with enormous economic consequences,"
Yet being able to name
species will not, in itself,
stop the inexorable decline, he said. "In 30 years?
We'll still be heading for very fast rates of extinction
comparable to today simply because we're not doing
anything about it," the professor said. "I have to
be a bit gloomy on the 30-year time-scale. There's
not been very much action to justify being optimistic."
