An international panel of scientists found that more than a dozen factors, ranging from insecticides that damage a bee's memory to climate change, are causing dramatic declines in bee populations.
Achim Steiner, the executive director of the U.N. Environment Program, said 70 percent of the world's major food crops rely on bees for pollination.
"The way humanity manages or mismanages its nature-based assets, including pollinators, will in part define our collective future in the 21st century," he said in a statement.
The bee report, Global Bee Colony Disorders and other Threats to Insect Pollinators, concludes that bees are early warning indicators of the health of animal and plant life.
Work to increase the number of bees will help address food security concerns, scientists said.
Scientists who wrote the report said farmers and landowners should get incentives to create pollinator-friendly habits by planting flowering plants next to their crops.
"Human beings have fabricated the illusion that in the 21st century they have the technological prowess to be independent of nature," said Steiner. "Bees underline the reality that we are more, not less dependent on nature's services in a world of close to 7 billion people."