Here's an exercise in deductive logic, with implications for our food supply.

Fact: Insects such as bees and butterflies are helpful, and sometimes essential, for producing much of our food, including a majority of our fruits, vegetables and nuts.

Fact: Many of these pollinators, especially wild ones such as bumblebees, are in trouble. In Europe, where the phenomenon has been studied most carefully, about a third of all bee and butterfly species are declining, and 9 percent are threatened with extinction.

The seemingly logical conclusion? Food production will decline along with the pollinators.

This is the basis of a headline-generating summary of a new and massive scientific report prepared by 80 scientists around the world, and sponsored by the United Nations. Only a summary of the report has been released at this point.

According to the summary, fewer pollinators could lead to food shortages, "impacting health and nutritional security."

This simple, logical deduction, however, is bedeviled by many complicating factors.

First, the world's biggest crops, the ones that billions of people still depend on for most of their calories, don't rely on insects or other pollinators. These crops include corn, wheat, soybeans and rice.

That still leaves a lot of other crops, though, and many of them are growing in popularity. Berries, vegetables, fruits and nuts tend to benefit most from pollinators. Marcelo Aizen, a researcher at Universidad Nacional del Comahue in Argentina and co-author of the U.N. report, has reported that the amount of land devoted to these "pollinator-dependent" crops has been increasing at a much faster rate, globally, than pollinator-indifferent grains.

According to Aizen, the surging popularity of these nutritious crops could run headlong into the roadblock of vanishing pollinators. With fewer bees or butterflies available, yields could fall, making these valuable foods even more expensive.

The degree of probable damage, however, is largely a matter of speculation. According to Jaboury Ghazoul, an ecologist at ETH Zurich, a leading university in Switzerland, "in most farming systems, production is limited by other, far more important factors" — such as pests and diseases, weather, and access to fertilizer.

Some crops, meanwhile, like almonds and greenhouse-grown tomatoes, rely on pollination by highly managed colonies of bees that are multiplied in captivity and hauled by the truckload to farms where they are needed. This can be expensive, but those pollinators — unlike wild species — are not likely to disappear.

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