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What We Know About the Decline of Bees

Two new studies summarize trends in honeybee populations—they’re doing pretty well in some places, actually—as well as the ongoing challenges bees face.

By Nathan Collins


(Photo: Joe Raedle/Getty Images)

Honeybee populations are in decline worldwide, and, because we need them to pollinate fruits and vegetables, that spells big trouble for our food supply. But there’s a glimmer of good news: Researchers are finally starting to get a handle on the exact challenges bees face and how to deal with them, according to two recent surveys published in the journals Nature and Science.

The bee situation is nothing if not complicated. Things started to look dire around a decade ago, when unusually large numbers of bees essentially were lost to an odd phenomenon called colony collapse disorder—odd because there’s little evidence the bees actually died. Instead, they just went missing. Since that time, however, managed bee populations (as opposed to wild ones) seem to have recovered.

There’s no one explanation for bee populations’ ups and downs. It’s thought that neonicotinoids, a class of insecticides introduced in the 1990s, play a role, but their impact depends on the crops involved. Other pesticides, parasites, and maybe even climate change could be involved, but no one’s quite sure how exactly. It’s important that we get to the bottom of this decline because most of our fruits and vegetables—around 5 to 8 percent of our food supply—need bees and other insect pollinators to reproduce.

Now, Lynn Dicks, Rosemary Hill, Simon Potts, and their colleagues have managed to summarize what’s known with a paper published this week in Nature. The study builds on a recent report for the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, one of the most comprehensive to date.

In Europe, 57 percent of bee species can’t be assessed because there simply isn’t enough data.

The researchers argue that, although our understanding has improved, the state of affairs remains complex. For one thing, despite what you may have read, there isn’t one overall trend in bee populations. Colonies of the most common managed bee, the western honeybee, have increased 45 percent in the last 50 years.

Wild bee populations, on the other hand, are in decline both in terms of size and diversity. And good data is hard to come by: In Europe, 57 percent of bee species can’t be assessed because there simply isn’t enough data.

The team also identified a number of factors that drive bee populations up and down, among them land use policies that affect bee habitat, insecticides, invasive species, and disease. Genetically modified crops designed to resist certain herbicides may have an effect as well—not because the plants or herbicides are toxic to bees, but because they make it easier to remove weeds that would otherwise benefit bees and other pollinators.

There is also good reason to believe climate change will affect bee habitat and populations—in fact, there’s some evidence that’s already happening, the team writes, though the full consequences “may not be fully apparent for decades.”

In a separate paper published last week in Science, Dicks, Hill, Potts, and nine others suggest 10 policy measures that could help safeguard bees and the food they pollinate. The team’s recommendations include improving pesticide regulation worldwide—right now, only a few countries tightly regulate neonicotinoids and other bee-harming pesticides—and promoting less pesticide-heavy pest management strategies. “Green infrastructure,” or networks of bee-friendly habitats on public and private land, would also encourage bee conservation, the researchers write.