Fewer species, less stability

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Fewer species, less stability

 

Posted Jan. 26, 2005

Courtesy Nature

and World Science staff

 

A study of ancient coral reefs has shown that a greater number of more

diverse species can promote a stable environment over million-year

timescales, experts say.

Angelfish at a coral reef (image courtesy National Oceanographic Data

Center, U.S.A.).

 

 

Coral reefs are underwater ridges of hard material built up from the

skeletons of reef-building coral, a small primitive marine animal, and

other marine animals and algae over thousands of years. They occur in

clear, shallow and sunlit seas. They are one of the world's most

productive and diverse ecosystems.

 

Wolfgang Kiessling of Humboldt University in Berlin extracted data on

the diversity of species living on ancient coral reefs from a database

of fossil records called PaleoReefs.

 

Over ten-million-year periods, he found that a higher average

diversity of reef-building species produced smaller changes in the

reef's skeleton, architecture and species in subsequent time intervals.

 

Because this rule held true over a wide spectrum of different reef

types, it supports the hypothesis that species richness can promote

ecological stability, he said.

 

The findings are published in the Jan. 27 issue of the research

journal Nature. Commentators writing in a separate article in the

journal observed that the study is a much scaled-up version of smaller

experiments that previously had reached similar conclusions.

 

" It is remarkable that Kiessling's findings agree with those derived

from mathematical models, bottles, Petri dishes, aquaria, growth

chambers and field plots, which often run for only a handful of

generations, " wrote the commentators, Shahid Naeem and Andrew C. Baker

of Columbia University in New York City.

 

The findings also come at a time when experts are warning that the

world's species are dying off at unprecedented rates (see Nov. 18

World Science, Species dying off at unprecedented rate, researchers say).

 

Species dying off at unprecedented rate, researchers say

15,589 species are at risk of extinction and least 15 have gone

extinct in the past 20 years, conservationists say

 

Posted Nov. 18, 2004

Courtesy World Conservation Union

and World Science staff

 

From the mighty shark to the humble frog, species are dying off faster

than ever before, according to a new report billed as the most

comprehensive evaluation ever conducted of the world's biodiversity.

 

The announcement was made at the World Conservation Union's World

Conservation Congress in Bangkok, Thailand, this week. The findings

are based on a report called the Global Species Assessment, released

by a consortium of conservation groups in conjunction with the union's

annual " Red List " of threatened species.

 

" There is some good news, " said a statement released by the World

Conservation Union, an environmental organization, this week regarding

the findings. " Conservation measures are already making a difference –

a quarter of the world's threatened birds have benefited from such

measures. What is needed is more of them, and to focus them better. "

 

The Global Species Assessment shows trends in biodiversity over four

years since the last major analysis in 2000, and it includes, for the

first time, complete assessments of amphibians, cycads (an ancient

group of plants) and conifers, as well as regional case studies. It

also highlights which species are at greatest risk of extinction,

where they occur, and the many threats facing them.

 

" Governments are starting to realise the value of biodiversity and the

critical role it plays in their peoples' well-being. Species provide

food, medicine, fuel, and building materials. They help filter water,

decompose waste, generate soil and pollinate crops. Recognition of

this is growing but governments need to mobilize far more resources, "

said David Brackett, Chairman of IUCN's Species Survival Commission.

 

In 1996 it was revealed that one in eight birds (12%) and one in four

mammals (23%) were threatened with extinction (falling into the

Critically Endangered, Endangered or Vulnerable categories). This

infamous line-up has now been joined by one in three amphibians (32%)

and almost half (42%) of turtles and tortoises, according to the World

Conservation Union.

 

With amphibians relying on freshwater, their catastrophic decline is a

warning about the state of the planet's water resources, the report

said. Even though the situation in freshwater habitats is less well

known than for terrestrial, early signs show it is equally serious.

More than half (53%) of Madagascar's freshwater fish are threatened

with extinction.

 

The vast ocean depths are providing little refuge to many marine

species which are being over-exploited to the point of extinction.

Nearly one in five (18%) of assessed sharks and rays are threatened.

 

Many plants have also been assessed, but only conifers and cycads have

been completely evaluated with 25% and 52% threatened respectively.

 

For the first time, the assessment includes the Red List Index, a new

tool for measuring trends in extinction risk. This shows overall

changes in threat status (projected risk of extinction) over time for

a particular group. It will be important for measuring changes in

biodiversity. Red List Indices are currently available for birds and

amphibians, and show that their status has declined steadily since the

1980s.

 

" Although 15,589 species are known to be threatened with extinction,

this greatly underestimates the true number as only a fraction of

known species have been assessed. There is still much to be discovered

about key species-rich habitats, such as tropical forests, marine and

freshwater systems or particular groups, such as invertebrates, plants

and fungi, which make up the majority of biodiversity, " says Craig

Hilton-Taylor, the World Conservation Union's Red List Programme Officer.

 

People, either directly or indirectly, are the main reason for most

species' declines. Habitat destruction and degradation are the leading

threats but other significant pressures include over-exploitation for

food, pets, and medicine, introduced species, pollution and disease.

Climate change is increasingly recognised as a serious threat.

 

" It is clear that the situation facing our species is serious and

getting worse. We can continue to assess and bemoan the loss of the

world's biodiversity or we can act! We must refocus and rethink the

way in which society must respond to this global threat, " says Achim

Steiner, the World Conservation Union's Director General.

 

" While most threats to biodiversity are human-driven, human actions

alone can prevent many species from becoming extinct. There are many

examples of species being brought back from the brink including the

southern white rhino and black-footed ferret, and thousands of

dedicated people around the world are doing their utmost to reverse

the extinction rate, " he added. " But this cannot continue to be the

task of the environmental community alone. Governments and business

must commit to these efforts as well " .

 

Since the release of the 2003 Red List, more than 15,633 new entries

have been added and 3,579 species reassessed. There are now 7,266

threatened animal species and 8,323 threatened plant and lichen

species. A total of 784 plant and animal species are now recorded as

Extinct with a further 60 known only in cultivation or captivity.

 

Since 2003, there have been some notable changes to the list,

including some marked deteriorations, like the St Helena olive (from

Extinct in the Wild to Extinct), the Hawaiian crow (from Critically

Endangered to Extinct in the Wild), the Balearic shearwater (From Near

Threatened to Critically Endangered), the giant Hispaniolan galliwasp

lizard (from Near Threatened to Critically Endangered), and an African

begonia, Begonia oxyanthera (from Near Threatened to Vulnerable).

 

But there have also been some improvements, such as the European otter

(from Vulnerable to Near Threatened) and the Christmas Island Imperial

pigeon (from Critically Endangered to Vulnerable).

 

The 2004 assessment shows that threatened species are often

concentrated in densely populated areas, particularly in much of Asia

and parts of Africa. A major conservation challenge will therefore be

to reconcile the demands of large numbers of people on the

environment, whilst protecting the biodiversity upon which so many

people's livelihoods depend.

 

The importance of international support in safeguarding biodiversity

is critical says the assessment. Many countries with a high

concentration of threatened species have a low Gross National Income

(GNI) per capita and are unable to implement the required conservation

measures without international assistance.

 

Some key findings from the Global Species Assessment

 

* Numbers of threatened species are increasing across almost all

the major taxonomic groups.

* The marine environment is not as well known as the terrestrial

environment but initial findings show that marine species are just as

vulnerable to extinction as their terrestrial counterparts.

* Freshwater habitats are also poorly known, but recent surveys

reveal that many aquatic species are threatened with extinction.

* Most threatened birds, mammals, and amphibians are located on

the tropical continents - Central and South America, Africa south of

the Sahara, and tropical South and Southeast Asia. These regions

contain the tropical broadleaf forests which are believed to harbour

the majority of the earth's living terrestrial and freshwater species.

* Australia , Brazil, China, Indonesia and Mexico hold

particularly large numbers of threatened species.

* Countries with high numbers of threatened species and relatively

low GNI include Brazil, Cameroon, China, Colombia, Ecuador, India,

Indonesia, Madagascar, Peru and the Philippines.

* The world's list of extinctions increases – from 766 in 2000 to

784 documented extinctions since 1500 AD.

* Although estimates vary greatly, current extinction rates are at

least one hundred to a thousand times higher than background, or

" natural " rates.

* Over the past 20 years, 27 documented extinctions or extinctions

in the wild have occurred but this underestimates the true number that

have taken place.

* While the vast majority of extinctions since 1500 AD have

occurred on oceanic islands, over the last 20 years, continental

extinctions have become as common as island extinctions.

* Humans have been the main cause of extinction and continue to be

the principle threat to species at risk of extinction.

* Habitat loss, introduced species, and over-exploitation are the

main threats, with human-induced climate change becoming an

increasingly significant problem.

 

A comprehensive information kit including profiles, case studies,

photos, and graphics is available on the IUCN website: www.iucn.org

 

The Global Species Assessment is available from the IUCN Bookstore

http://www.iucn.org/bookstore/ or can be downloaded from the IUCN

website: www.iucn.org

 

The IUCN Red List is available as a searchable database online at

www.iucnredlist.org