Animal, farm

SCIENCE & TECHNOLOGY
Land-use change

Feb 3rd 2005 PARIS
From The Economist print edition

New data are finally revealing global patterns of habitat loss

WHEN economists, scientists and governments want to study the state of the environment, and reach sensible decisions, they have a problem. Most of the data available concern local areas or regions, so it is difficult to get a global picture. But in late January, provisional data from the Millennium Ecosystem Assessment (MEA), an international effort launched by the United Nations in 2001, were presented to a conference on biodiversity, held in Paris.

Georgina Mace, of the Institute of Zoology in London, told the meeting that each year, 0.5% of the area of natural habitats on land is lost, largely due to conversion to farmland. The rate is consistent across most of the world's major “biomes”—such as grasslands, boreal forest and tropical moist forest. Furthermore, Dr Mace said, such losses look set to continue.

Within the 14 different terrestrial biomes the study identified, most have been greatly modified by humans. Between 20% and 50% of nine biomes have been transformed into croplands. Tropical dry forests are the worst hit, while 35% of temperate grasslands and broadleaf and Mediterranean forests have been converted.

What makes the MEA particularly interesting is that the goal of the overall report, due out in March, is to give a picture of how changes to the environment affect humans through degradation of the services that it provides. These would include things like watershed protection, pollination and protection from coastal erosion.

The report will differ from efforts to determine how much biological diversity a region holds. This is because an area may have many rare species, but not enough living matter to, say, prevent a coastline from being eroded. The starkest findings from the MEA, though, are to be expected in oceans. On land, the huge patterns of habitat loss have been offset by gains in food production. In water, though, the story is very different. Not only is there dramatic evidence of damage to marine ecosystems, but this has not been offset by similar gains in productivity.

There is a phrase that says what matters gets measured. It thus seems odd that nobody had yet done this kind of audit. The resulting lack of information seems to have led to the true value of many ecosystems being ignored or underestimated. Perhaps later this year the MEA will prove the opposite also to be true, that what is measured starts to matter.

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