The UN on Thursday expressed alarm at a huge decline in bee colonies under a multiple onslaught of pests and pollution, urging an international effort to save the pollinators that are vital for food crops.
Much of the decline, ranging up to 85 percent in some areas, is taking place in the industralised northern hemisphere due to more than a dozen factors, according to a report by the UN's environmental agency.
They include pesticides, air pollution, a lethal parasite that only affects bee species in the northern hemisphere, mismanagement of the countryside, the loss of flowering plants and a decline in beekeepers in Europe.
"The way humanity manages or mismanages its nature-based assets, including pollinators, will in part define our collective future in the 21st century," said UNEP executive director Achim Steiner.
"The fact is that of the 100 crop species that provide 90 percent of the world's food, over 70 are pollinated by bees," he added.
Honey bee colony declines in recent years have reached 10 to 30 percent in Europe, 30 percent in the United States, up to 85 percent in Middle East, said scientist Peter Neumann, one of the authors of the first ever UN report on the issue.
But in South America, Africa and Australia there were no reports of high losses.
"It is a very complex issue. There are a lot of interactive factors and one country alone is not able to solve the problem, that's for sure. We need to have an international network, global approaches," added Neumann of the Swiss government's Bee Research Centre.
Some of the mechanisms behind the four decades old trend, which appears to have intensified in the late 1990s, are not understood. UNEP warned that the broad issue of countryside management and conservation was involved.
"The bees will get the headlines in this story," UNEP spokesman Nick Nuttall told journalists.
"But in a sense they are an indicator of the wider changes that are happening in the countryside but also urban environments, in terms of whether nature can continue to provide the services as it has been doing for thousands or millions of years in the face of acute environmental change," he added.
Explore further: Rising ocean acidification leads to anxiety in fish