Pollinators Are Responsible for One Third of the Global Production

Animal pollinators, like insects, birds and bats, are responsible for 35 % of the world's crop production.

Recently, the first global estimate of crop production reliant upon animal pollination was made by scientists from Berkeley University. In North America, pollinators are a key factor for such crops as fruits, vegetables, nuts, spices and oilseed. E.g.: 1.4 million colonies of honey bees are necessary to pollinate 550,000 acres of California's almond trees.

Alexandra-Maria Klein, an agroecologist from the University of Goettingen in Germany, and Claire Kremen, an assistant professor at UC Berkeley's Department of Environmental Science, Policy, and Management, have conducted an analysis of studies from 200 countries and for 115 crops to see how crop production is linked to pollinators worldwide. "There's a widely stated phrase in agriculture that you can thank a pollinator for one out of three bites of food you eat," said Kremen.

"However, it wasn't clear where that calculation came from, so we set out to do a more thorough and reproducible estimate, and we wanted to look at the impact on a global scale."

87 from 115 studied crops, accounting for one third of the global production, need to some degree animal pollination. 13 crops were entirely dependent on animal pollinators, 30 are highly pollinator dependent and 27 were more or less dependent. Interesting enough, main staple crops, represented by cereals, like wheat, corn and rice, are not dependent on animal pollinators.

But ultimately, many important pollinators, like the honey bee, are suffering a steep decline in North America. Colonies have been decimated by parasitic mites introduced inadvertently to the continent, antibiotic-resistant pathogens and competition from Africanized "killer bees."

Wild native bees (4,000 species in North America) and savaged honey bees are affected by habitat loss and non-sustainable farming practices, like the use of fertilizers and pesticides. "We've replaced pollination services formerly provided by diverse groups of wild bees with domesticated honey bees," said Kremen.

Previous studies showed that wild bees can lead to a five-fold increase in pollination efficiency of the honey bees when interacting with them. "The problem is, if we don't protect the wild pollinators, we don't have a backup plan."

"Some changes may involve mere tweaks to current practices, such as allowing weeds and native plants to grow and prosper along the border of the primary crop," said Kremen.

Wild plants, usually destroyed by herbicides, support many pollinator insect species whilst the crops are not in bloom. "Another change could be to switch from flood irrigation, which drowns bee species that nest in the ground, to spray irrigation when feasible," said Kremen.

Pollinator biodiversity can have in many occasions a deep economic importance. "Passion fruits in Brazil are hand-pollinated through expensive day-laborers as the natural pollinators, carpenter bees, are hardly available because of high insecticide use in the agricultural fields and the destruction of the natural habitats," said Klein.

Klein said that, in the cities of Brazil, the high cost of manpower for these agricultural tasks rises the fruit and vegetable prices, turning the people to more harmful less expensive aliments, including fatty meats and sugars. "As a result, she said, obesity rates seem to be rising."

"The stability of crop yields not only depends on pollination, but also on further ecosystem services," Klein added.

"Therefore, we need landscapes carefully managed for a diversity of functionally important groups of organisms that sustain many important ecosystem services such as pollination, pest, pathogen and weed control, and decomposition."

Photo: Raspberries after self-pollination (left and middle) and insect pollination (right).