FOR generations, forests have been steadily converted to farmland to provide food and fuel for expanding populations. Researchers estimate the conversion process has happened more drastically in South Asia and Southeast Asia, raising concerns about the loss of native species and biodiversity in those local ecosystems. According to a worldwide census published in the journal Science last month, roughly 20 percent of mammalian species worldwide are threatened with extinction.

Conservation biologists have historically tended to think of agricultural areas in tropics as not having much diversity because native species don?t adapt very well to changes in their ecosystems. Recent work published online the week of Nov. 3 in the journal Proceedings of the National Academy of Sciences of the United States suggests however, that it is possible to have agricultural areas and native species in the same ecosystem.

Biodiversity of bird species

Jai Ranganathan from the University of California at Santa Barbara?s Ecological Analysis and Synthesis and colleagues from India-based institutions Care Earth and the Environmental Management and Policy Research Institute looked at the biodiversity of bird species found in an Indian farming region. They studied a 20-kilometer farmed region on a mountain range in southwestern India that has been continuously cultivated for more than 2,000 years.

The area has rice paddies, peanut fields and arecanut palm plantation. The nut is more commonly known in South Asia and Southeast Asia as the stimulant that produces a red-stained mouth when paired with betel leaves and then chewed. There are also forests, which were divided into two categories: those that remained untouched; and those from which only nontimber products such as leaf litter for mulch could be removed.

To measure biodiversity the researchers counted the number of bird species in the area, identifying more than 100 bird species. They then compared the figures to those recorded for a similar census in the 1880s at the site, and found that approximately 90 percent of the bird species sighted then still remained in the area.

Ranganathan and his colleagues attribute the thriving diverse bird populations to the arecanut plantations for two reasons. By sticking to the traditional method of cultivating the arecanut palms, the Indian farmers were used to collecting leaf litter from the nearby forests. The trees provided the native bird species with a protected home.

The second reason was that the palms had such high water requirements that farmers who cultivated the crop grew them on lowland regions that would have been used for ricefields. If the ricefields had been maintained instead, the bird populations would have been greatly decreased, the researchers noted.

?Consequently, arecanut adds to the conservation case for traditional agriculture, which has been used in India and elsewhere in the tropics to support local livelihoods and biodiversity,? Ranganathan and his colleagues noted in their study.

Promoting bioconservation

The plant, they said, could be useful in promoting bioconservation efforts in South Asia and Southeast Asia, much like shade grown coffee has been promoted for biodiversity conservation efforts in Latin America.

Many coffee farmers have turned away from the traditional technique of growing coffee beans beneath a canopy of trees, choosing instead to increase their crop production by thinning or removing the canopy completely and using coffee plant strains that produce high yields in direct sun.

For years conservationists and scientists have worked to promote a return to shade grown coffee. In the October issue of the journal BioScience, researchers from the University of Michigan reported that unlike the so-called ?sun coffee,? the traditional technique of growing coffee beans actually protects the crop from extreme weather such as floods or storms.

E-mail the author at massie@massie.com.