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Climate change is killing bumblebees around the world, new study finds

For decades now, human agricultural methods, including the use of harmful pesticides, have led to a diminishing bumblebee population. As it turns out, that hasn't been the only way that human behavior has done a number on the essential insect. A new study published in the journal Science this week found that extreme weather linked to human-caused climate change has been wreaking havoc on bees, shrinking the population of dozens of species across North America and Europe and leaving them with a declining chance at survival in the long term.

To check up on how bees have been handling the changing climate, researchers looked at 66 bumblebee species across North America and Europe. They compared baseline population data collected between 1901 and 1974 to modern data, collected between 2000 and 2014. Then they looked at how bee populations changed during some of the hottest and coldest months, and months with the most and least amount of precipitation. What they found was not particularly promising. The probability of bees occupying a given region declined by 46 percent in North America and 16 percent in Europe — in large part due to extreme heat linked to climate change. The researchers suggested that bees are not colonizing and repopulating during months where they experience heat that pushes past their typical thermal limits. In fact, some species are abandoning hotter regions, resulting in a 30 percent decline in the likelihood of seeing bumblebees in a given location.

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That is some bad news for bees at a time when it seems like things couldn't get much worse for the little creatures. Basically everywhere they turn, humans have started to cut into their environment in some way. In more commercial settings like on farms, bees are being devastated by the use of pesticides. A number of studies have found that commonly used insecticides and weed killers have had adverse effects not only on bees themselves but also on the plants that they count on as a food source. This has become a global epidemic as more and more developing countries embrace the use of these chemicals to help keep up with the needs of a growing population and increased demand for food crops. In Brazil, for example, pesticide use has skyrocketed by more than 770 percent over the last two decades, according to Bloomberg. The result is a shocking drop in the bee population. The insects are dying by the millions in the country. More than 500 million honey bees were found dead across four states in the country in the spring of 2019, largely the result of exposure to harmful chemicals. Even when those chemicals don't kill bees outright, they effectively maim them, weakening them to the point of being unable to reproduce. This can lead to a phenomenon known as colony collapse disorder, wherein thousands of bees die suddenly and seemingly all at once. The use of pesticides has largely been thought responsible for pushing pollinators and other insects to the brink of extinction. A 2019 study published in the journal Biological Conservation found that as much as 40 percent of all insects are threatened with complete extinction simply because of exposure to chemicals found in insecticides and pesticides.

That doesn't even account for loss of land, which also affects bees and other insects. As with the increase in pesticides, modern agriculture is largely to blame. According to a study published by Greenpeace, croplands and pastures now occupy about 35 percent of all ice-free land surface on Earth. What has been sacrificed to allow farmers to occupy that space is the natural ecosystems that came before it. Farming is in large part responsible for deforestation, and has pushed flora and fauna — including bees — out of land that they would otherwise have occupied. Bees in the wild have seen their food sources greatly diminished, their behavioral patterns completely interrupted, and their natural lifecycle thrown for a loop as they try to adjust to human occupation of these regions.

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The trouble for humans is that these agricultural build outs provide a short-term solution to needs while also destroying the very creatures that we need in order to preserve our long-term viability. Bees are essential to the agricultural process — about one-third of all global food supply is enabled by pollination provided by bees. According to the BBC, bees pollinate about 70 of the top 100 crops that feed about 90 percent of the world's population. Honey bees in particularly are responsible for about $30 billion a year in crops. Everything from almonds to apples to coffee to cashews rely on bee pollination, and a disappearance of these essential insects could spell disaster for those crops and plenty of others. The loss of bees could also hurt livestock, as the insects are often responsible for pollinating things like alfalfa hay used to feed dairy cows. Losing bee populations would require a dramatic shift in food sources. The end of bees could mean the end of lots of familiar foods.

Unfortunately, all of these losses were already occurring before extreme heat joined into the mix. According to researchers, hot temperatures create a unique threat to bees because they aren't built to perform their duties in heat. Flying becomes challenging as they run the risk of overheating. This also makes them more susceptible to predators, which can eat into their population, and makes it harder for them to find necessary food resources to stay alive.

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It doesn't seem likely that extreme temperatures around the globe are going to stop any time soon. Climate change appears to be accelerating, according to scientists, and previously unheard of weather events are sure to follow. More than 120,000 weather records were broken in the United States alone in 2019, and a number of regions across the world including Europe and Australia experienced nearly unprecedented heat waves over the course of the last year. Experts project that similar heat waves will plague the U.S. in coming years, assuming dramatic changes aren't made almost immediately to address climate change. Now we know that those temperatures won't just be difficult for humans to deal with — they may also result in killing off large portions of already shrinking bee populations. Even if we manage to stop the worst-case climate change scenarios by shrinking our greenhouse gas emissions, we may be dealing with a dramatically different world going forward, where bees are a rare sight and where their essential service as pollinators is not available to us.