In one way or another, nearly all the buzz on bees these days is about us humans being in deep trouble. Bee populations, both in managed honeybee colonies and in the wild, are dying in alarming numbers and the food system, which depends on those bees for pollination, is in big trouble.
But a new study published today in Nature Communications offers some reassurance, at least for the wild bees our food supply depends on. When it comes to pollinating food crops, it turns out not all bees are created equal: Only 2% of wild bee species are responsible for pollinating nearly 80% of crops in North America and Europe—and within that 2%, few are actually threatened.
These wild bee species are able to withstand agricultural expansions and the populations can even grow, with “simple conservation methods.” This finding is especially important as bee experts have pointed to an increasingly monoculture-saturated landscape as one of the challenges for bees, because it often encroaches on their natural habitat.
(Many experts and studies point to neonicotinoid pesticides, frequently used in modern agriculture, as the culprit behind bee deaths. This study does not shed much light on that question, says author Rachael Winfree of Rutgers University, as the researchers didn’t collect or analyze data on that point. However, she adds, “we found that many bee species DID decline with increasing agricultural intensification—just the more common bee species that pollinate many crops did not decline.”)
The researchers used data from 90 studies and 1,394 crop fields across five continents. To determine how many bee species were pollinating human crops, they counted up the number of species represented in the studies and found 785, representing only 12.6% of the known bee species in the regions where those studies took place. When they figured out which of those species were doing most work, the “dominant crop-visiting species” making 5% or more of the total crop visits in any one study, they found that those came from just 2% of the regions’ total bee species. That small percentage of bee species was responsible for nearly 80% of all the visits to pollinate crops. This was true across different crops, years, and geographical regions.
Next, the researchers looked to see how many of those bee species were threatened within their regions. Four countries—Germany, Netherlands, Sweden, and the United Kingdom—had Red Data Books cataloguing threatened bee species. Using that information and the 19 studies undertaken in those countries, they determined that only 0.3% of bees observed on crops came from threatened species.
The researchers then looked to determine whether this pattern would hold true in other regions. Using independent data from 264 agricultural sites in Europe and North America, they found the dominant crop-visiting species made up approximately 75% of the bees at sites in Europe and 59% of those in North America, suggesting “that the species that are the dominant crop pollinators are the most widespread and abundant species in agricultural landscapes in general.”
The authors don’t contend that all bee species are safe, or that modern agriculture is not contributing to the decline of some bee species—which is having a dire effect on biodiversity. Rather, they found that the specific bee species most important to agriculture are not currently threatened.
Their argument has implications beyond bees. From an environmental advocacy point of view, the authors question the reliance on the concept of “ecosystem services”—the value that a natural system delivers to humans—as an argument for biodiversity. “Many experimental studies show that biodiversity increases the magnitude and/or stability of ecosystem functioning (of which ecosystem services are the subset that benefit people), and that most species contribute to ecosystem functioning in some way,” they write.
In short, there’s a value to biodiversity beyond any direct “services” it delivers to people and our farming. So we should focus our efforts on saving the bees that are threatened, whether or not they are pollinating our crops.