Just two percent of wild bee species do almost 80 percent of their work in pollinating crops, according to a study on Tuesday that outlined simple measures for farmers to attract star insects to safeguard food production.
The international report, based on 90 studies on five continents, said governments should also conserve the apparently less valuable bees as they might play a bigger role in the event of environmental shocks, such as from climate change.
Many types of wild bees, which count 22,000 species worldwide, are in decline because of factors such as pesticides and habitat loss, raising uncertainty about how best to protect insects vital to human food production.
Lead author David Kleijn, of Wageningen University and Research Center in the Netherlands, said bees were like soccer players.
"There are a few who really make a lot of money, like [Cristiano] Ronaldo and [Lionel] Messi, then another large group who can make a living from football. And then there's 99.9 percent who just play for fun," he told Reuters.
The study in the journal Nature Communications said just two percent of species, usually the most common such as bumblebees or solitary bees, did almost 80 percent of the work by wild bees in pollinating crops such as potatoes, beans or apples.
The report, examining wild bees rather than managed honey bees kept in hives, said farmers could easily attract the best wild insect pollinators by planting wild flowers or strips of grass alongside their crops.
"It should be helpful to farmers to know that the simple and cheap measures can give them what they need for pollination," said Pat Wilmer of Scotland's University of St. Andrews, who was not among the authors.
The study estimated that wild bees' work contributed more than $3,000 per hectare (2.5 acres) in helping to produce crops, comparable to the economic value of managed honey bees.
The most industrious wild species was the North American bumble bee, with work worth $963 a hectare, it said.
One study in 2008 estimated that insect pollination, mainly by bees, is worth 153 billion euros ($171.54 billion) a year for human crop production.
But the authors said purely economic arguments about the current value of bees would wrongly overlook many species.
"We need a large and diverse group of species on the substitutes' bench," said Professor Simon Potts, a co-author at the University of Reading.