Overheating of hives associated with global warming will become the main cause of mass death of bees on all continents of the Earth in the coming years, ecologists say in an article in Functional Ecology.
“If temperatures on Earth rise as much as climatologists predict, then bees will be on the verge of extinction as they push against their physiological limits. Bees will completely disappear in the warmer regions of their habitat. This prospect is sobering and scaring us,”said scientist Paul Caradonna of Northwestern University in Evanston (USA).
In recent years, scientists have noted a rapid decline in the number of domestic and wild bees on all continents, except for Antarctica, where bees simply do not live, RIA Novosti notes. Over the past five to ten years, the population of wild bees has declined by 25-30%, and the number of their domestic relatives in the United States has halved in 2015 alone.
In the list of the main "killers" of bees, several circumstances are named at once - global warming, parasitic mites from the Varroa genus, spreading viruses, deforming insect wings, pesticides and a mysterious "colony collapse syndrome", during the development of which worker bees suddenly abandon their queen and leave the hive.
Caradonna and his colleagues tried to find out what role climate can play in all these processes. To do this, scientists carved several "mini-hives" from wooden blocks and installed them in one of the arid mountain regions of Arizona, where the last colonies of wild osmia bees (Osmia ribifloris), the main pollinators of blueberries, are now disappearing.
These insects, unlike their domestic "cousins", lead a solitary lifestyle and rarely meet with other individuals. They build their nests inside tree stumps, snail shells, cracks in rocks, and other natural nooks where bees build up small food supplies and lay eggs.
Environmentalists decided to check what happens if the temperature inside such "incubators" rises or falls, while the larvae begin to grow. To do this, scientists painted a third of the hives black, raising the temperature in the hives by several degrees, and leaving other hives colorless or covered with white paint, which "returned" the bees to the climatic conditions that existed in Arizona in the middle of the last century.
The "decorative" changes seriously affected the life of the bees over the next two years. Insects that lived in black hives almost completely died out: in the first year, 35% of the bees died, and in the second, over 70% of the rest. However, osmium living in normal or white hives continued to thrive, and only 1–2% of them died before the bees could reproduce.
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The reason for the mass death of bees was that the high temperatures inside the hive "deceive" the insects' organism and prevent them from completely dormant. As a result, bees quickly burn fat reserves and wake up in spring in a very weakened state. So far, this phenomenon has almost no effect on the life of bees in natural hives, but the situation may become catastrophic in the coming years, when the temperatures of the "black" hive will become the norm for the entire planet. In this case, many species of bees can disappear from all warm regions of the planet, where a temperate climate previously dominated, scientists conclude.