(via Nature 2.0beta)
By Christiane Galus | Le Monde – Original | Saturday 22 July 2006
Pollinating insects are indispensable to the reproduction of the 80% of terrestrial vegetation represented by flowering plants that produce seeds: flying from flower to flower to gather pollen (the male fertilizing material), they transport it to the stigma of a female flower, allowing fertilization to occur. For several years now, scientists have thought that this free service nature has offered the last 140 million years is being threatened by the decrease in biodiversity.
A study conducted by Jacobus Biesmeijer and William Kunin (Leeds University, United Kingdom) and a team of British, German, and Dutch researchers and published in the July 21 issue of Science confirms that the threat is serious. By studying different areas of Great Britain and the Netherlands, scientists observed that wild bees have paid the heaviest toll, with a 52% reduction in their diversity with respect to their situation in 1980 in Great Britain and a 67% reduction in the Netherlands. On the other hand, the situation is less catastrophic for pollinating flies, the numbers of which have declined by 33% in Great Britain, but increased by 25% in the Netherlands.
The researchers also studied the influence of this situation on the plants visited by these insects. Thus, they observed that in Great Britain, the distribution of 75 wild plants which must be pollinated by insects decreased, while the distribution of 30 others that are pollinated by wind or water, was, on the contrary, more widespread. In the Netherlands, only plants pollinated by wild bees have declined. Jacobus Biesmeijer and William Kunin consequently suspect a cause and effect link between the pollinating insects’ decline and that of the pollinated plants, without being able to specify what the engine of the decline is: the evolution of agricultural methods, the use of chemicals in agriculture, or global warming? They are worried because “whatever the cause, the study strongly suggests that the decline of several species can set off a cascade of local extinctions among other associated species.”
For Guy Rodet, entomologist at the National Institute for Agricultural Research (INRA) of Avignon (in the plant and environmental health section), this article is important since “it’s the first to scientifically establish the decline of pollinating insects. And that with a large amount of data over a long-scale period.” The authors of the Science article have, in fact, worked with a million records effected by naturalists in the past, some of which go back to Queen Victoria’s reign. By applying techniques designed to make the data comparable, the researchers divided Great Britain and the Netherlands into 10 kilometer square plots and compared the density of pollinating insects before and after 1980. That is a date to remember, because there have been great changes in agriculture during this period.
This study was conducted in the framework of the European program “Alarm,” intended to evaluate the risks incurred in the realms of terrestrial and aquatic biodiversity. In France, a similar study on insect pollination has been started by the research team from INRA-Avignon, led by Bernard Vaissi’re, the objective of which is to evaluate the decline of pollinators over a very short period. Ten parcels, spread out between France, Germany, Poland, Sweden and the United Kingdom, have been chosen to accomplish the study.
The reduction in the diversity of pollinating insects can have a variety of impacts. It may, first of all, translate into a “change in the landscape,” Guy Rodet explains, “since there is a risk of seeing different plant species disappear.” Still more serious, “we can have problems producing fruit and vegetables, even though in some cases we can make up for the reduction in wild pollinators with cultivated insects,” Guy Rodet notes. “But for large cultivated areas, as in the United States, that could be very expensive.”