Scientists report that the diversity of bees and the flowering plants they pollinate has declined in Britain and the Netherlands, a possible indicator of the problem worldwide. Other scientists worried about species extinction call for the formation of an international body to monitor such threats to biological diversity, similar to one that now tracks global warming.

Bees and other insects are essential to the reproduction of many agricultural crops and wild plants. At the University of Leeds in Britain, researcher William Kunin explains. "Pollinators are intrinsically tied to interactions with plant species, and so the pollination of crop plants and wild plants is of both ecological value and economic value. Estimates go up to about 150-billion dollars a year in economic value that is provided by wild pollinators," he said.

Researchers and policymakers have raised concerns for years that such insects are in decline. The 1999 Sao Paulo Declaration and the 2000 International Initiative for the Conservation and Sustainable Use of Pollinators seek urgent attention to the possible worldwide decline of pollinator diversity.

Yet, there has been little evidence that such declines are under way. Now, Kunin and British, German and Dutch colleagues have published evidence in the journal "Science" that gives the concerns validity.

They analyzed observations of bees and hoverflies recorded from 180 sites in Britain and the Netherlands before and after 1980. Kunin told Science magazine that they found local bee diversity had declined in both countries. The hoverfly trends were more variable. "But in both countries and in both groups, the tendency was for local communities of insects to become simpler, to have fewer species that dominated the collections. So about 30 percent fewer species would make up half the observations, again, in both countries and in both types of pollinators," he said.

Not surprisingly, plant species reliant on the declining pollinators have themselves declined. Kunin says it is not clear whether the plants or the pollinators declined first, or whether they both responded to some other factor, such as pesticide use, changes in land use, or climate change. "A loss of pollinators in the U.K. and the Netherlands is not a global pollination crisis as some people have suggested. But I would be surprised if there aren't some similar patterns elsewhere," he said.

The pollinator problem is a part of a broader trend in species loss noted in a 2004 report of the World Conservation Union. It says extinction threatens one-eighth of all bird species, a fourth of mammal types, a fourth of evergreen species called conifers and a third of amphibian species.

For this reason, 19 leading biologists warn that the Earth is on the verge of a major extinction crisis. Writing in the journal "Nature," they say biological diversity is undervalued and call for a global coordinating body to provide an authoritative voice to inform government decision makers around the world. Their model is the United Nations Intergovernmental Panel on Climate Change.

Their appeal has the support of the French government, which is funding talks on establishing such an expert panel.