SINGAPORE: The first map of its kind detailing the distribution of bee species around the globe has been created by a team of researchers from several countries, including from Singapore.
There are more than 20,000 known species of bees, but accurate data about how they are spread across the world is sparse.
To create the global map, researchers combined a global checklist of the known bee species with almost six million additional public records of where individual bee species have appeared around the world, said scientific journal publisher Cell Press in a media release.
The map provides a "much clearer picture" of how many species of bees are distributed in different geographic areas, said the release. A research paper containing the map was published in science journal Current Biology on Friday (Nov 20).
The study involved a team of researchers from Singapore, the United Kingdom, China and the United States.
The checklist of 20,000 bee species used in creating the map was compiled by Dr John Ascher, an assistant professor at National University of Singapore's (NUS) department of biological science. He has been working on the checklist since 2003.
"People think of bees as just honey bees, bumble bees, and maybe a few others, but there are more species of bees than of birds and mammals combined, said Dr Ascher.
Speaking at a media briefing held at NUS on Tuesday before the report was released, Dr Ascher noted that studies on where species are living can allow researchers to assess reports of a decline in bee populations around the world.
"We can use that as a benchmark to get at what we really want to know down the road, which is what is driving alleged bee declines," Dr Ascher said.
"A lot of these reports (of declines) are based on ... England or the Netherlands ... very few places. And they have very sparse coverage for most of the rest of the world. So they're reporting global declines but their data set is not really global."
BEES, THEIR DISTRIBUTION AND CLIMATE CHANGE
Findings from the researchers found that there are more species of bees in the Northern than Southern Hemisphere and more bees in arid as well as temperate environments as compared to the tropics.
While most animals and plants follow a pattern known as a latitudinal gradient where diversity increases toward the tropics and decreases towards the poles, bees are an exception to the rule.
There are far fewer bee species in forests and jungles than in arid desert environments because trees tend to provide fewer sources of food for bees than low-lying plant and flowers.
"When it rains in the desert, there are these unpredictable mass blooms that can literally carpet the entire area," said the study's first author Michael Orr, a postdoctoral fellow at the Institute of Zoology at the Chinese Academy of Sciences in Beijing.
"There's a much higher turnover in the desert because of how patchy the resources are year after year. So there's a lot of potential for new species there."
Climate change has also been another factor which some have said affects the population and distribution of bees globally. However, Dr Ascher noted that such studies may not be entirely representative of the current situation.
"Some studies have claimed to show (the impact of) climate change for bees - especially bumblebees, but in my opinion, they're not well done for a number of reasons," he told reporters.
"Sometimes they're mixing up a situation in Europe and North America ... the data sets (in these two regions) are very different, and the environments are quite different. The other thing is that you have confounding factors ... especially the spread of epizootics, so you have fungal pathogens and other things that are wiping out a lot of bumblebees."
There has however been changes in the distribution of bees, noted Dr Ascher. This could be due to a number of different factors, he noted.
"I'm most familiar with eastern North America, and I'm in a way a bit pessimistic about detecting climate change there just because there's been massive changes in land use," Dr Ascher explained.
"Also the eastern United States was deforested, and now it's reforesting with second growth vegetation, so you detect big changes over time in the bee fauna, but to attribute them to a particular cause very difficult in my opinion."