Humans Causing The sixth great wave of Extinction

[Guest guest]

Biodiversity: The sixth great wave

As part of Planet Under Pressure, a BBC News Online

series looking at some of the biggest environmental

problems humanity faces, Alex Kirby considers the

current increase in extinction rates.

 

Source >

http://news.bbc.co.uk/1/hi/sci/tech/3667300.stm

 

 

 

By Alex Kirby

BBC News Online environment correspondent

 

Indochinese tiger cubs

A quarter of all mammals face some extinction risk

All the creatures we share the Earth with are

important in some way, however unprepossessing or

insignificant they may appear. They and we are all

part of the web of life.

 

From the dawn of time, extinction has usually

progressed at what scientists call a natural or

background rate. Today the tempo is far faster.

 

Many scientists believe this is the sixth great wave -

the sixth mass extinction to affect life on Earth.

 

We were not here for any of the previous mass

extinctions, but this time our sheer preponderance is

driving the slide to oblivion.

 

 

LIVING PLANET INDEX

The index tracks the size of specific populations of

selected species

It shows them as a percentage of the 1970 populations

It shows falling population levels in all three

ecosystem types studied

We have more than doubled our numbers in half a

century, and that is the most obvious reason why there

is less room for any other species.

 

We are taking their living room to grow our food,

their food to feed ourselves. We are exploiting them,

trading in them, squeezing them to the margins of

existence - and beyond.

 

Often the choice is hard: conserve a species or feed a

community, tourists' dollars or turtles' nests.

 

In 2003 the World Conservation Union's Red List said

more than 12,000 species (out of 40,000 assessed)

faced some extinction risk, including:

 

* one bird in eight

* 13% of the world's flowering plants

* a quarter of all mammals.

 

That gives you a ballpark figure. Science has

described 1.75 million species, some experts estimate

that there may be 13 or 14 million in the world in

total - but until they are catalogued, nobody knows.

 

 

FIVE MASS EXTINCTIONS

Cretaceous (About 65 million years ago)

Triassic (About 208 million years ago)

Permian (About 245 million years ago)

Devonian (About 360 million years ago)

Ordovician (About 438 million years ago)

Our pillage of the natural world has been likened to

burning down the medieval libraries of Europe, before

we had even bothered to catalogue their contents.

 

Many species keep us alive, purifying water, fixing

nitrogen, recycling nutrients and waste, and

pollinating crops.

 

Plants and bacteria carry out photosynthesis, which

produces the oxygen we breathe. Trees absorb carbon

dioxide, the main greenhouse gas given off by human

activities.

 

Pandas and microbes

 

Some years ago, when the global annual gross product

was about $18 trillion, US researchers calculated the

value of the goods and services provided by the Earth

to the world economy: $33 trillion.

 

Tropical cone snails contain toxins which show promise

for treating some forms of cancer and heart

irregularities. One toxin may be a thousand times more

potent than morphine for pain relief.

 

But millions of cone snails are now killed annually

for their shells, and their habitats are under

pressure.

 

That is the argument for utility. But the creatures we

can see, and those we can use directly, are just the

start of the story.

 

Lord May, president of the Royal Society (the UK's

national academy of sciences), has said: " Most

conservation effort goes into birds and mammals -

creatures like the panda, a dim, dead-end animal that

was probably on the way out anyway.

 

" Yet arguably it's the little things that run the

world, things like soil microbes. They're the

least-known species of all. "

 

Complex network

 

And we continue to tug at the loose threads of the web

of life, thinking we can split it into its separate

parts.

 

Pearl bordered fritillary

71% of UK butterfly species are reported to be

declining

Brazil nuts are a lucrative harvest in the Amazon. But

an experiment to produce them in plantations failed,

because the trees bear a good crop in the forest, but

are barren in isolation.

 

We are not removing individual species from the

Amazon: we are destroying the entire forest. US

researchers estimate that by 2020 less than 5% of it

will remain in pristine condition.

 

Within 15 years, about a fifth of central Africa's

forests will have gone, by one estimate. And the

forests of Indonesia are in headlong retreat.

 

Some species are bucking the trend towards extinction.

In 1953 there were about 2.5bn people: today there are

6bn.

 

Ensuring other species keep their living space is not

sentimental. It is the only way we shall survive.

 

Extinction, whatever Steven Spielberg says, really is

for ever. The web is unravelling.

 

 

 

 

 

 

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