Friday, 17 October 2008

No Link Found Between Pollinator Declines and Agriculture

Considerable research efforts have suggested that there is, or could be a link between insect pollinator decline and agricultural output. The body of science on the subject of pollinators and agriculture has influenced policy at the highest level; the creation of the International Initiative for the Conservation and Sustainable Use of Pollinators (IPI) at a United Nations meeting in 2000.

However, new research published in Current Biology suggests that agriculture has not been affected by the decline of key insect pollinators.

Examining a period spanning over 40 years, Alexandra Klein's research time investigated agricultural productivity of crops requiring pollinators with those that do not. Contrary to popular belief, the researchers found that crop yields have gone up consistently, with growth rates of up to 1.5%, despite the falling numbers of pollinators. Focusing on tropical agricultural regions, no difference in yields were found between breeze and insect pollinated crops, (though it is not known whether these regions had experienced significant concurrent pollinator declines).

It is possible that the researchers, having grouped together all crops globally, might not be picking up on detail happening at finer spatial scales.

The results of this work are out of sync with the work of many others such as Taylor Ricketts, director of WWF's conservation science programme. Rickett's group found that coffee plantations were 20 per cent more productive when grown within 1km of forested areas. Other work has also suggested that an abundant diversity of pollinators increases crop yields.

Some scientists remain sceptical. Jaboury Ghazoul, a plant ecologist at ETH Zurich, Switzerland, believes that few crop species actually depend on pollinator species.

Klein however does not rescind the notion that pollinators are very important for agriculture. She suggests that actions by farmers at the local level, (such as hand pollination or pollinator transplantation) may mask the extent of pollinator decline. Klein anticipates that a crop productivity crash could occur any time soon - many major crop plants now are pollinator dependent, 15% up from 8% in 1961.

Do blog readers think that agricultural productivity can continue with a concurrent decline in pollinators? Is there an optimum spatial scale to conduct this kind of research? Is pollinator diversity important?

Source: Aizen M. A., Garibaldi, L. A., Cunningham, S. A. & Klein, A. M., 2008, Current Biology, doi:10.1016/j.cub.2008.08.066

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