Wild bees add about $1.5 billion to yields for just six U.S. crops

U.S. cherries, watermelons and some other summertime favorites may depend on wild bees more than previously thought.

Many farms in the United States use managed honeybees to pollinate crops and increase yields, sometimes trucking beehives from farm to farm. Now an analysis of seven crops across North America shows that wild bees can play a role in crop pollination too, even on conventional farms abuzz with managed honeybees. Wild volunteers add at least $1.5 billion in total to yields for six of the crops, a new study estimates.

“To me, the big surprise was that we found so many wild bees even in intense production areas where much of the produce in the USA is grown,” says coauthor Rachael Winfree, a pollination ecologist at Rutgers University in New Brunswick, N.J.

That means threats to wild bees could shave profits even when farms stock honeybees, the researchers report July 29 in Proceedings of the Royal Society B. Both honeybees (Apis mellifera), which aren’t native to the United States, and wild pollinators such as bumblebees (Bombus spp.) face dangers including pesticides and pathogens (SN: 1/22/20).

To see what, if anything, wild native bee species contribute, researchers spot-checked bee visits to flowers at 131 commercial farm fields across the United States and part of Canada. In a novel twist, the researchers also calculated to what extent the number of bee visits limited yields.

These intensive farms with plenty of fertilizer, water and other resources often showed signs of reaching a pollinator limit, meaning fields didn’t have enough honeybees to get the maximum yield, and volunteer wild bees were adding to the total. Then the team estimated what percentage of the yield native bees were adding — versus just doing what honeybees would have done anyway.

Wild bees don’t seem to help California’s almond orchards. But based on orchards in Michigan and Pennsylvania, some $1.06 billion of apples depends on native pollinators, the researchers say. Watermelons, particularly in Florida, get an estimated $146 million benefit, and sweet cherries $145 million. Native bees also boost tart cherries and blueberries and dominate pumpkins.