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Pollinators vital for crop yields are dying out New Scientist 14 Feb 98

A WORLDWIDE decline in bees, bats, butterflies, birds and other pollinators is threatening the yields of major food crops and the biodiversity of wild plants. A study published in this month's Conservation Biology (vol 12, p 240) says that the most immediate cause for concern is an epidemic of varroa mites. The mites have wiped out millions of colonies of honeybees in Europe and North America, where the bees are the prime method of pollination for more than a hundred commercial crops. A quarter of North America's wild and domesticated honeybees have disappeared over the past eight years, the report finds. According to Gary Nabhan of the Arizona Desert Museum near Tucson, the study's lead author, the disappearance of honeybees has increased production costs for many major American crops, notably California almonds. 'Impacts may be felt more strongly in home gardens and on small farms that do not rent managed honeybees," he says. The paper puts the cost to American farmers of the declining honeybee population at $5.7 billion a year. The study also reports a 'long-term decline' in other pollinators across the world, including 1200 wild vertebrate pollinators known to be at risk of extinction. The authors say these declines, often caused by pestidde use, explain depressed ali yields of blueberries in New Brunswick, cherries in Ontario, pumpkins in New zcs York, cashew nuts in Bomeo, and Brazil nuts in Bolivia and Brazil. Declining bat populations threaten the survival of many tropical fruit trees, including durians and wild bananas, as well as neem and eucalyptus. In Central America, many plants are pollinated by threatened species of hummingbirds. And the dextrous fingers of primates, such as the endangered black and white ruffed lemur of Madagascar, are uniquely fitted to open the buds of Ravenala madagascariensis, the traveller's tree. The researchers wam that, apart from honeybees, data on invertebrate [email protected] are hard to come by British ecologists agree that there are similar threats in Europe, where honeybees are also in decline because of varroa mites. According to David Sheppard of Enghsh Nature, the government's conservation agency, a quarter of Britain's 250 native bee species are now classified as rare or threatened. 'These bees are responsible for most of the pollination of native wild plants, including fruit crops such as strawberries, apples and pears," he says. Wild plants around the world endangered by the lack of pollinators include the Japanese primrose, Arizona agave and Hawaiian sflversword. In some case, the loss of a single pollinator species can cause the collapse of entire ecosystems. On some Pacific islands, Nabhan and his colleagues say, the loss of flying foxes could lead to cascades of extinctions, including mammals that depend on the fruit of trees pollinated by the bats. Nabhan wants to see schemes to reduce the spraying of pesticides and to plant native nectar-bearing wild flowers in fields and gardens, where modern artificially propagated hybrids are often less attractive to pollinators. One suggestion is the creation of "nectar corridors" along which pollinators can migrate. Fred Pearce