intensive, industrial-scale farming may be damaging one of the very natural resources that successful farming requires: bees that help in pollination. A study by scientists at the us-based Princeton University found that native bee populations plummet as agricultural intensity goes up. In farms studied in and around the Sacramento Valley in California, usa, concentrated farming appeared to reduce bee populations by eliminating natural habitats and poisoning them with pesticides. The farmers may not have noticed this effect because they achieve much of their harvests with imported bees. Even population of these bees is declining because of pesticide usage and diseases.

The researchers spent two years examining watermelon farms located at varying distances from oak woodlands and chaparral habitats that are native to the Sacramento Valley. They also looked at land that was farmed with pesticides and without pesticides. They focused on watermelon because it requires a lot of pollen and multiple bee visits to produce marketable fruit. They found that native bee visits were less in the farms that were distant from natural habitats and that used pesticides.

It would take careful land use to combat the situation, the researchers conclude, because current high-density, pesticide-dependent agriculture cannot support native bees. "This is a valuable service that we may actually be destroying through our own land management practices,' says Claire Kremen, who co-authored the study.