Resources for a sustainable future

8/3/2010 Guardian For the first time since the dinosaurs disappeared, humans are driving animals and plants to extinction faster than new species can evolve, one of the world’s experts on biodiversity has warned.Conservation experts have already signalled that the world is in the grip of the
“sixth great extinction” of species, driven by the destruction of natural
habitats, hunting, the spread of alien predators and disease, and climate
change.
However until recently it has been hoped that the rate at which new species were
evolving could keep pace with the loss of diversity of life.
Speaking in advance of two reports next week on the state of wildlife in Britain
and Europe, Simon Stuart, chair of the Species Survival Commission for the
International Union for the Conservation of Nature – the body which officially
declares species threatened and extinct – said that point had now “almost
certainly” been crossed.
“Measuring the rate at which new species evolve is difficult, but there’s no
question that the current extinction rates are faster than that; I think it’s
inevitable,” said Stuart.
The IUCN created shock waves with its major assessment of the world’s
biodiversity in 2004, which calculated that the rate of extinction had reached
100-1,000 times that suggested by the fossil records before humans.
No formal calculations have been published since, but conservationists agree the
rate of loss has increased since then, and Stuart said it was possible that the
dramatic predictions of experts like the renowned Harvard biologist E O Wilson,
that the rate of loss could reach 10,000 times the background rate in two
decades, could be correct.
“All the evidence is he’s right,” said Stuart. “Some people claim it already is
that … things can only have deteriorated because of the drivers of the losses,
such as habitat loss and climate change, all getting worse. But we haven’t
measured extinction rates again since 2004 and because our current estimates
contain a tenfold range there has to be a very big deterioration or improvement
to pick up a change.”
Extinction is part of the constant evolution of life, and only 2-4% of the
species that have ever lived on Earth are thought to be alive today. However
fossil records suggest that for most of the planet’s 3.5bn year history the
steady rate of loss of species is thought to be about one in every million
species each year.
Only 869 extinctions have been formally recorded since 1500, however, because
scientists have only “described” nearly 2m of an estimated 5-30m species around
the world, and only assessed the conservation status of 3% of those, the global
rate of extinction is extrapolated from the rate of loss among species which are
known. In this way the IUCN calculated in 2004 that the rate of loss had risen
to 100-1,000 per millions species annually – a situation comparable to the five
previous “mass extinctions” – the last of which was when the dinosaurs were
wiped out about 65m years ago.
Critics, including The Skeptical Environmentalist author, Bjørn Lomborg, have
argued that because such figures rely on so many estimates of the number of
underlying species and the past rate of extinctions based on fossil records of
marine animals, the huge margins for error make these figures too unreliable to
form the basis of expensive conservation actions.
However Stuart said that the IUCN figure was likely to be an underestimate of
the problem, because scientists are very reluctant to declare species extinct
even when they have sometimes not been seen for decades, and because few of the
world’s plants, fungi and invertebrates have yet been formally recorded and
assessed.
The calculated increase in the extinction rate should also be compared to
another study of thresholds of resilience for the natural world by Swedish
scientists, who warned that anything over 10 times the background rate of
extinction – 10 species in every million per year – was above the limit that
could be tolerated if the world was to be safe for humans, said Stuart.
“No one’s claiming it’s as small as 10 times,” he said. “There are uncertainties
all the way down; the only thing we’re certain about is the extent is way beyond
what’s natural and it’s getting worse.”
Many more species are “discovered” every year around the world, than are
recorded extinct, but these “new” plants and animals are existing species found
by humans for the first time, not newly evolved species.
In addition to extinctions, the IUCN has listed 208 species as “possibly
extinct”, some of which have not been seen for decades. Nearly 17,300 species
are considered under threat, some in such small populations that only successful
conservation action can stop them from becoming extinct in future. This includes
one-in-five mammals assessed, one-in-eight birds, one-in-three amphibians, and
one-in-four corals.
Later this year the Convention on Biological Diversity is expected to formally
declare that the pledge by world leaders in 2002 to reduce the rate of
biodiversity loss by 2010 has not been met, and to agree new, stronger targets.
Despite the worsening problem, and the increasing threat of climate change,
experts stress that understanding of the problems which drive plants and animals
to extinction has improved greatly, and that targeted conservation can be
successful in saving species from likely extinction in the wild.
This year has been declared the International Year of Biodiversity and it is
also hoped that a major UN report this summer, on the economics of ecosystems
and biodiversity, will encourage governments to devote more funds to
conservation.
Professor Norman MacLeod, keeper of palaeontology at the Natural History Museum
in London, cautioned that when fossil experts find evidence of a great
extinction it can appear in a layer of rock covering perhaps 10,000 years, so
they cannot say for sure if there was a sudden crisis or a build up of
abnormally high extinction rates over centuries or millennia.
For this reason, the “mathematical artefacts” of extinction estimates were not
sufficient to be certain about the current state of extinction, said MacLeod.
“If things aren’t falling dead at your feel that doesn’t mean you’re not in the
middle of a big extinction event,” he said. “By the same token if the
extinctions are and remain relatively modest then the changes, [even] aggregated
over many years, are still going to end up a relatively modest extinction
event.”
Species on the brink of being declared extinct
The International Union for the Conservation of Nature (IUCN) lists 208 species
as “possibly extinct”, more than half of which are amphibians. They are defined
as species which are “on the balance of evidence likely to be extinct, but for
which there is a small chance that they may still be extant”.
Kouprey (or Grey ox; Bos sauveli)
What: Wild cattle with horns that live in small herds
Domain: Mostly Cambodia; also Laos, Vietnam, Thailand
Population: No first-hand sightings since 1969
Main threats: hunting for meat and trade, livestock diseases and habitat
destruction
Webbed-footed coqui (or stream coqui; Eleutherodactylus karlschmidti)
What: Large black frog living in mountain streams
Domain: East and west Puerto Rico
Population: Not seen since 1976
Main threats: Disease (chytridiomycosis), climate change and invasive predators
Golden coqui frog (Eleutherodactylus jasperi)
What: Small orange frog living in forest or open rocky areas
Domain: Sierra de Cayey, Puerto Rico
Population: No sightings since 1981
Main threats: Unknown but suspected habitat destruction, climate change, disease
(chytridiomycosis) and invasive predators
Spix’s macaw (or little blue macaw; Cyanopsitta spixii)
What: Bright blue birds with long tails and grey/white heads
Domain: Brazil
Population: The last known wild bird disappeared in 2000; there are 78 in
captivity
Main threats: Destruction of the birds’ favoured Tabebuia caraiba trees for
nesting, and trapping
Café marron (Ramosmania rodriguesii)
What: White flowering shrub related to the coffee plant family
Domain: Island of Rodrigues, Republic of Mauritius
Population: A single wild plant is known
Main threats: Habitat loss, introduced grazing animals and alien plants
Source: IUCN and Royal Botanic Gardens Kew. To mark the International Year of
Biodiversity, the IUCN is running a daily profile of a threatened species
throughout 2010. See iucn.org.

Go to: http://www.guardian.co.uk/environment/2010/mar/07/extinction-species-evolve