Pollinators thrive in diverse habitats with a mix of native vegetation. But converting land for agriculture often destroys that biodiversity, reducing pollinator health.
DISEASE AND PARASITES
Bees in particular have been victimized by a range of microscopic threats, which can weaken them–and leave them more vulnerable to other dangers.
Pesticides like neonicotinoids can kill not only the insects that destroy harvests but also some of the bees, bats and other bugs that help crops reproduce.
Rising global temperatures shift the range of habitats where bees and other pollinators can survive. Scientists fear current trends could worsen as the world warms.
This appears in the March 14, 2016 issue of TIME.