Farming Risks

A new model for risk assessment promises to help scientists and policymakers evaluate the dangers of agriculture to wildlife - as well as the potential success of government programs designed to redress the damage from traditional farming.  The new method takes a simple approach.  It evaluates the likelihood that a species will become less prevalent by examining how many of its needs - for food, nesting sites, and so on - will be impacted by a given farming practice.  The more requirements that are in jeopardy, the higher the risk of decline.

After developing their model, ecologist Simon Butler of the University of Reading, U.K., and his colleagues gave it a test run.  They mined the literature on the ecological needs of 62 species of British birds that live in and around farm fields.  Many of these birds, such as the skylark, have become much scarcer since the 1970s, when U.K. farmers began to intensify their operations.  The researchers looked at six variables, such as spraying insecticides and herbicides that deprive birds of food.  The model did a good job, Butler says; species predicted to be at a higher risk of decline were in fact more likely to be listed as “most threatened” by the U.K. government than were species at low risk.

Next, the group evaluated two relatively new approaches to agriculture. For genetically modified crops that tolerate herbicides, Butler and his colleagues concluded that they would “only have a limited effect” on birds.  Although 39 species would have slower population growth rates, just one species would warrant a change in its official conservation status.  The group also looked at a farm-management program, called entry-level stewardship (ELS), which has paid $92 million in conservation incentives to U.K. farmers since August 2005.  The analysis showed that the program is unlikely to halt the decline in bird populations. “Hopefully, this will cause a redress of how ELS is implemented,” Butler says.

Tim Benton, a population ecologist at the University of Leeds, says that the model will help researchers compare the response of different species to a possible threat, including the impact of global warming and invasive species. “Why hasn't anyone thought of such a quick-and-dirty technique before?  My personal feeling was that if my mind strayed down that direction, I'd laugh at myself and say, ‘Of course it couldn't work, it is too crude!’” he says.  In fact, says Benton, the model works well.  (ScienceNOW Daily News, 1/18/07).