Ecologists must work faster

With global farming projected to double by midcentury, researchers seek quicker ways to assess the impact of land use on wildlife.

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As farming ramps up to meet new demands for food and fuel, ecologists have to act fast to assess the impact on wildlife. Tim Benton at England's University of Leeds notes that "we may not have the luxury of spending years collecting biological information."

Ecologists need what he calls "quick and dirty" ways to give timely guidance for land-use policy.

They also need more knowledge of how land use changes affect food webs and other subtle wildlife interrelationships. Recent research reports illustrate how those needs are being met.

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Writing in Science two weeks ago, Dr. Benton was commenting on the new "quick and dirty" risk-assessment technique reported in that issue. Simon Butler at England's University of Reading and colleagues have developed a strategy for using readily available information on farming practices to come up with numbers that correlate with species' risk of decline or extinction.

They tested their technique on bird species whose risk of decline had already been assessed by direct observation in the field. Their alternative assessment focused on six components of the intensified farming that has developed in Britain over the past 40 years – switching from spring to autumn sowing, using more chemicals, the loss of unfarmed land, increased drainage, switching from hay to silage for animal feed, and more intense grassland management.

The researchers used available data on how these practices changed the environment to assess how each of them would affect the availability of food and nesting sites for each bird species.

Combining these assessments in their mathematical scheme, they came up with a risk index – expressed as a number – for each species. Those numbers neatly correlated with species that were already listed as doing OK, the ones deemed at moderate risk of decline, and those in the "red zone" – at serious risk of extinction. In other words, the research showed that if those risks had not already been determined by years of field research, the Reading team's technique could have determined the risks quickly with enough reliability to guide land-use planning.

While the team focused on birds, their risk-assessment technique can be used for many animals. This is not deep ecological knowledge. It is practical guidance for planners.

Benton notes that "a quick answer that is good enough may be more influential on policy than a better answer supplied years later."

That deeper knowledge, however, is needed to find a sustainable balance between intensified farming and a healthy environment. In a report in Nature three weeks ago, Jason Tylianakis and colleagues at Germany's Georg August University in Goettingen pointed out that subtle changes in food webs, host-parasite relationships, and other aspects of an interconnected community represent "an insidious ... hidden effect of habitat modification by humans."

They used a region in southwestern Ecuador to study this effect for bees and wasps that nest in cavities. The area has environments ranging from intensively cultivated rice fields to untouched forest. Summarizing the study of 48 sites in that area, the scientists say they found enough food-web changes to prove that studies focusing solely on species richness "may overlook important alterations to community structures."

Global farming is expected to double by midcentury. Ecologists must scramble to keep up.

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