Wild insects pollinate major agricultural crops—from cotton to blueberries—more effectively than hives of honeybees managed by humans, according to a massive international study.
In their report in the 1 March issue of Science, Lucas Garibaldi of Universidad Nacional de Río Negro in Argentina and colleagues also conclude that honeybees only add to the pollinating power of the wild insects, and can’t replace their pollination services.
When wild bees, flies and other insects pollinate crops, the researchers discovered, they lead to twice as much fruit set as managed honeybees. Fruit set refers to the number of flowers on a plant that develop into mature fruits and seeds, a process largely aided by insect pollination in agricultural crops.
Even crops that get most of their pollination from managed honeybees, such as almonds and blueberries, are less productive when the plants aren’t visited by wild insects as well.
Contrary to what some researchers and agricultural managers believe, Garibaldi said, it won’t be enough to increase the number of honeybees working the fields to make up for any decline in wild pollination services. “We are not against honeybees,” he said in a Science Podcast interview, “but we do find that the current paradigm is not correct, because honeybees cannot replace wild insects. You need both.”
Wild pollinator services are declining in spots around the world, as another Science story reports this week. Laura Burkle of Montana State University and colleagues examined networks of plants and wild pollinators in Illinois using a historical data set stretching back to the late 1800s. They found a significant disruption in pollination services over time, due in part to the eradication of half of the original bee species in the area.
Wild insects, like the bee Eulaema nigrita (left), provide critical pollination services that cannot be replaced by managed honeybees hives (right), seen here in an almond grove. | CREDIT: Bee photo by Breno M. Freitas; Almond grove photo by Saul Cunningham
Changes in climate and land use have also played a role, Burkle and colleagues said. Earlier spring warming can lead to a mismatch between plant flowering times and peak bee activity, and shrinking woodlands have made it more difficult for some bees to find materials to build nests.
Until recently, Garibaldi said, researchers and others have seen the threats against wild pollinating insects as “more of a problem of conservation and not a problem of agricultural production.”
He hopes agricultural managers will now take steps to encourage wild pollinators, by growing a diversity of plants around their fields, rotating crops and reducing pesticide use, especially during critical flowering periods.
Jason M. Tylianakis, an ecologist from the University of Canterbury in New Zealand, said in a related article in Science that the new studies will help to show that biodiversity directly impacts food production, “and that a few managed species cannot compensate for the biodiversity on which we depend.”
Read the abstract, “Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance,” by Lucas Garibaldi and colleagues.
Read the abstract, “Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence and Function,” by Laura Burkle and colleagues.
Listen to a related Science Podcast interview with Lucas Garibaldi.