The number of honeybees killed each year by human-caused pollution is at its lowest level in the last three decades, and pollinators worldwide are struggling to keep up with the demand for the crop, experts said Tuesday.
But a poll released Tuesday by the World Wildlife Fund and the Carnegie Institution for Science shows bee populations are not as healthy as they once were, with some populations suffering from disease and other threats.
Bees and other pollinators rely on pollination by the nectar-producing insects to provide food for their own families, pollinating crops, pollinators and animals.
They are the primary source of food for billions of people around the world.
But their numbers are falling due to the impact of climate change and human-driven pests, the study found.
Pollinators are facing increasing stress and are increasingly being driven to the brink of extinction, the report found.
For many years, the number of bee deaths has been declining, especially as the honeybee population boomed.
In recent years, bee deaths have been rising, as well, partly because of the introduction of genetically modified (GM) crops.
The decline in honeybees has been particularly dramatic in parts of the tropics, with a rise in deaths among the Asian honeybee, which are often killed by pesticides, according to the study.
But there is a catch, said Andrew Hsu, a research associate at the Carnegie Institute for Science who co-authored the study, in an interview.
Hsu and colleagues used data from a new poll that examined the health of the honeybees of the Americas.
The study found that about 50 percent of the bees in the study are infected with a parasite called Nosema ceranae, a parasite that causes respiratory problems in humans and can cause disease in bees.
“Nosema cernae is an emerging threat to the global honeybee,” Hsu said.
“We’re not sure why.”
While Nosema has not been found in bees in Europe, the Asian bee is likely to be more vulnerable to the virus.
The report also found that the honey bee’s overall health is declining, with its numbers down to about 80 percent of their peak in the 1980s.
The scientists found that bees were at greater risk of respiratory infections due to a lack of food and water.
Honeybees have been in decline for more than 50 years, according the study by the Carnegie Center for Developing Economies, a Washington-based think tank.
In the 1960s, honeybees were responsible for about 85 percent of pollination.
The number fell to about 15 percent in the 1990s, and the number has fallen even more dramatically since.
The researchers attributed much of the decline to pesticides, especially the neonicotinoid insecticides.
The number of pollinators that make up pollinator groups is also declining.
In 2010, there were about 15,000 pollinators in the world, according a U.S. Geological Survey report.
That number has declined to about 1,500 today.
The study also found some honeybee colonies are in decline, but that bees in those colonies were more healthy than in other colonies, which tend to be healthier.
In addition, honeybee populations have been growing in areas with a lot of farmland, but also in areas where there are less pollinator populations.
“The situation is worsening,” Hsueh said.
“We’ve seen the numbers of bees and other plant species declining and declining over time,” he added.
“So we think this is really a new phenomenon that has to be understood.”
The researchers note that other factors are also contributing to the decline of honeybee numbers, including habitat loss due to farming, pesticides and climate change.
“It is difficult to measure the effects of pesticides on honeybee health, but they’re affecting bees in a big way,” said lead author Dr. Robert J. Stellmach, a professor of entomology at Purdue University.
“That’s a big issue that needs to be addressed,” Stellmin said.
Hsuech said the study shows that the situation is “not good” for bees in particular.
“They need to be able to take care of themselves,” he said.