ECOLOGY/EVOLUTION

Beneficial Birds and Bees

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Science  20 Dec 2002:
Vol. 298, Issue 5602, pp. 2285
DOI: 10.1126/science.298.5602.2285a

Agricultural intensification, urban sprawl, and deforestation are all examples of processes that are likely to lead to loss of ecosystem services: the material benefits that natural or seminatural landscapes provide for the human population. Yet the effects of these processes—and hence the economic values of the lost benefits—are often hard to quantify.

An example of such a service is the pollination of crop plants by native bees, leading to the production of fruit. Kremen et al. compared the efficacy of bee pollination of watermelon in intensive and organic farms in California, which varied in their proximity to bee habitat (woodland and chaparral). Only in the organic farms close to native habitat were full pollination services (in terms of maximized fruit production) achieved by native bees; in organic farms far from native habitat, and in all intensive farms, supplementary pollination by managed, introduced honeybees was necessary to improve fruit yields. Fruit production can also be enhanced by the presence of vertebrate predators of pest species. Mols and Visser found that simply constructing nest boxes for great tits in Netherlands apple orchards significantly increased fruit yield per tree. These results add to the evidence that conservation or promotion of natural biological diversity in an agricultural landscape can be economically advantageous. — AMS

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.262413599 (2002); J. Appl. Ecol.39, 888 (2002).

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