New Scientist, May 16, 2008

GLOBAL BIODIVERSITY SLUMPS 27% IN 35 YEARS

[Rachel's introduction: Ground-living vertebrates have declined by 25%, with most of the slump occurring since 1980. Marine species held fairly steady until the late 1990s before falling sharply to give an overall drop of 28%. Freshwater species have decreased by 25%, primarily since the late 1980s.]

By Michael Marshall

The latest data on the global biodiversity of vertebrates shows that it has fallen by almost one-third in the last 35 years. But experts say it may still underestimate the effect humans have had on global species counts.

The Living Planet Index (LPI) follows trends in nearly 4,000 populations of 1,477 vertebrate species and is said to reflect the impact humans have on the planet. It is based on a wide range of population datasets, such as commercial data on fish stocks and projects such as the Pan-European Common Bird Monitoring scheme.

New figures show that between 1970 and 2005, the global LPI has fallen by 27%. This suggests that the world will fail to meet the target of reducing the rate of biodiversity loss set by the 2002 Convention on Biological Diversity.

The results were released as part of a WWF report entitled 2010 and Beyond: Rising to the biodiversity challenge [1.5 Mbyte PDF].

"Governments have signally failed to deliver on their biodiversity commitments, and biodiversity declines are continuing," Jonathan Loh, a researcher at the Institute of Zoology and the editor of the report, told New Scientist.

Global picture

Ground-living vertebrates have declined by 25%, with most of the slump occurring since 1980. Marine species held fairly steady until the late 1990s before falling sharply to give an overall drop of 28%. Freshwater species have decreased by 25%, primarily since the late 1980s.

Loh says the most dramatic declines have been observed in the tropics. Tropical ground-living species have seen an average population drop of 46%, while their temperate cousins have shown no overall change.

Freshwater vertebrates show different trends in different regions, leading to "no obvious signal", says Loh. European and North American populations show no overall change, but Asian-Pacific populations have declined steeply since the late 1980s.

In the world's oceans, northern vertebrate populations have held fairly steady over the entire period, but may have entered a downward trend since 1990. By contrast, southern populations have fallen precipitously, although because less data is collected there the trend is less certain.

Rose-tinted view

The LPI focuses exclusively on vertebrates, which are relatively well- monitored. Loh says, "We started collecting data on invertebrates, but it's very patchy and not good enough as yet."

The survey may be "bird-biased", he adds, because their populations are well-monitored. The LPI tracks 811 bird species but just 241 fish and 302 mammals.

Fish should actually comprise the bulk of the Index. The world's 30,000 species of fish compare to just 10,000 bird species and 5,400 mammals.

Loh says this suggests that the situation is worse than the data shows. "Birds are doing better than fish," he says, "so if anything, by biasing the survey towards them we're underestimating the global decline."

Incomplete picture

There is also a lack of good data for Latin America and Africa. Loh says that, frustratingly, "the more species there are in an area, often the less data there are on how they're doing. For instance the UK is well-monitored, but has relatively few species. It's a priority for us to find out what's happening in areas like the Amazon Basin."

The WWF report was published ahead of a worldwide conference on biodiversity, the ninth meeting of the Conference of the Parties on 19-30 May. The conference will assess what has been achieved by the Convention on Biological Diversity.