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If only Congress could be as efficient as bees. Some of the healthiest foods you can think of - blueberries, squash, almonds - would never get to your plate without the help of insects. No insects, no pollination. No pollination, no fruit. Farmers who grow these crops often bring in honeybees to do the job. And farmers get bigger harvests if there are wild bees around, like bumblebees. Yet those wild bees are getting harder to find. NPR's Dan Charles reports.

DAN CHARLES, BYLINE: A century ago, a man named Charles Robertson, a teacher of biology and Greek at Blackburn College in Carlinville, Illinois, was fascinated by the close connection between insects and flowers.

LAURA BURKLE: He's described as sort of one of America's great scientists that nobody knows about.

CHARLES: That's Laura Burkle, an ecologist at Montana State University. She says Charles Robertson spent years in the forests around Carlinville carefully taking notes on which insects visited which wildflowers at what time of year. Robertson's notes eventually were published. A few years ago, when Burkle was at Washington University in St. Louis, she and a colleague were reading about them and they wondered, where is Carlinville anyway?

BURKLE: You know, typed it into Google Maps and all of a sudden we realized that it's an hour and a half away from St. Louis.

CHARLES: So they jumped into a car and went for a visit. Much of the forest around Carlinville has disappeared. It's turned into corn or soybean fields or suburbs, but small wooded patches remain and Burkle and her colleague realized they could follow in Robertson's tracks. They could see if the same insects still are pollinating the same flowers.

They decided just to concentrate on wild bees, not other insects. They released their results this week in the journal Science. All of the wildflowers that Robertson saw still are there. But of the 109 species of bees that Robertson observed, half of them cannot be found anymore.

BURKLE: We don't know why they've gone extinct or at least locally extinct.

CHARLES: One possibility might be there's so little forest left there aren't enough places for wild bees like bumblebees or carpenter bees to nest. But it might also be related to a change in climate, Burkle says. The bees that disappeared tended to be species that depended on just a few kinds of flowers for food. For those bees to survive, the right flowers have to blooming when those particular bees start flying and need food.

Maybe the warming trend has thrown off that timing. In fact, Burkle says, if you map the interactions between flowers and bees, they seem more tenuous now. Flowers in a particular place may get visited by just one or two kinds of bees and maybe just for one week.

BURKLE: And so I don't know that these systems can take a lot more environmental change without something drastic happening.

CHARLES: Burkle's report was released this week side by side with another study which says wild bees aren't just good for flowers in forests, they also help put food on our plates. Dozens of scientists from 14 different countries looked at all kinds of crops that require pollination by insects, like almonds, blueberries, coffee, pumpkins, onions and strawberries. Farmers who grow these crops often pay beekeepers to bring in honeybees.

But the scientists found, even when there were plenty of honeybees, most crops produced a bigger harvest more reliably when native wild insects were visiting as well. Marla Spivak, a specialist on bees at the University of Minnesota, says this is really important.

MARLA SPIVAK: The surprising message in all of this is that honeybees cannot carry the load. Honeybees need some help from their cousins and relatives, the other wild bees. And let's do something so that we can promote it, so that we can keep our honeybees healthy and our wild bee populations healthy.

CHARLES: Some of the scientists who wrote this paper are also trying to figure out how farmers can attract more of these wild bees. Claire Kremen at the University of California, Berkeley says one big problem is specialization, huge farms of just one crop. The almond groves of California, she says, are a sea of blossoms in February, a feast as far as the eye can see for honeybees that come here from all over the country.

CLAIRE KREMEN: But for the rest of the year, there's really nothing blooming on that farm field.

CHARLES: So no bees.

KREMEN: Yeah, no bees. And in fact, in places where we do have very large monocultures of almond, we don't find any native bees anymore.

CHARLES: Having other flowers in and around these orchards, maybe as hedgerows, blooming all summer long, would help, she says. Even better would be farms with smaller fields and lots of different crops. Wild bees, she says, need diversity. Dan Charles, NPR News, Washington.

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