28 July 2010

Shade-Coffee Farms Support Native Bees That Help Maintain Genetic Diversity

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Shade-grown coffee farms support native bees that help maintain the health of some of the world's most biodiverse tropical regions, according to a study by a University of Michigan biologist and a colleague at the University of California, Berkeley.

The study suggests that by pollinating native trees on shade-coffee farms and adjacent patches of forest, the bees help preserve the genetic diversity of remnant native-tree populations. The study was published online Monday in the Proceedings of the National Academy of Sciences.

"A concern in tropical agriculture areas is that increasingly fragmented landscapes isolate native plant populations, eventually leading to lower genetic diversity," said Christopher Dick, a U-M assistant professor of ecology and evolutionary biology.

"But this study shows that specialized native bees help enhance the fecundity and the genetic diversity of remnant native trees, which could serve as reservoirs for future forest regeneration."

An estimated 32.1 million acres of tropical forest are destroyed each year by the expansion of cropland, pasture and logging. Often grown adjacent to remnant forest patches, coffee crops cover more than 27 million acres of land in many of the world's most biodiverse regions.

Over the last three decades, many Latin American coffee farmers have abandoned traditional shade-growing techniques, in which plants are grown beneath a diverse canopy of trees. In an effort to increase production, much of the acreage has been converted to "sun coffee," which involves thinning or removing the canopy.

Previous studies have demonstrated that shade-grown farms boost biodiversity by providing a haven for migratory birds, nonmigratory bats and other beneficial creatures. Shade-coffee farms also require far less synthetic fertilizer, pesticides and herbicides than sun-coffee plantations.

In the latest study, U-M's Dick and UC-Berkeley's Shalene Jha investigated the role of native bees that pollinate native trees in and around shade-grown coffee farms in the highlands of southern Chiapas, Mexico. In their study area, tropical forest now represents less than 10 percent of the land cover.

(TerraDaily)

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