Modern food consumption may seem driven solely by factory farms, assembly lines, and plastic containers but, at its heart, the food system remains highly dependent upon the natural process of pollination — powered largely by the western honey bee.
For the last decade, those bees have been dying off in massive numbers, with beekeepers in the United States losing about 30 percent of their colonies every year since 2006. One of the causes is parasites, and, according to a new study from Queen’s University Belfast, climate change may help to drive one of the more virulent ones farther into Europe and North America, where bees are already suffering.
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“Something like 10 percent of the value of agricultural production is reliant upon insect pollination,” Robert Paxton, a biologist and co-author of the study, told VICE News. “It’s quite a sizeable economic concern that we’ve got.”
The study, published in the Proceedings of the Royal Society B, looked at two species of parasites, both of which infect the western honey bee: Nosema apis, which is native to the western honey bee’s range, and Nosema ceranae, which is not.
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The later parasite once infected Asian honey bees and was first discovered in Beijing in 1994. By 2007, however, the global trade in hives and honey had spread the parasite to Taiwan, Vietnam, and Europe.
“We collected samples from around the world and found, ‘My goodness, it’s absolutely everywhere,’” Paxton told VICE News.
In Spain and other southern Europe countries, as well as in the southern United States, Nosema ceranae has taken over. But in the northern United States, Canada, and northern European countries like Germany, Britain, and Norway, the native species still dominates, a distribution that had puzzled bee researchers for years.
In the laboratory, Paxton and his team fed bees sugar solutions contaminated with both parasites, alternating which species infected the bees first. In both cases, the second species introduced struggled to take hold inside the bees, but Nosema ceranae was much better than Nosema apis at preventing its competitor’s growth. That means a higher likelihood of Nosema ceranae spreading through bee populations.
‘So what’s going to happen with climate change?’
Next, the researchers built a mathematical model based on their infection results and previous research from Germany’s Institute for Bee Research that linked colder temperatures to lower levels of Nosema ceranae. The model allowed the scientists to simulate how frequently a colony might become infected under different temperature scenarios as the spread of Nosema ceranae outpaced that of its rival. The results showed that cold weather helped to block the spread of the more intrusive parasite.
“So what’s going to happen with climate change?” Paxton said. “Clearly, in Britain and the United States, if the temperature is warmer, it means that the exotic parasite, which has been suggested to be more virulent, will predominate or become more prevalent.”
In the United States, honey bees pollinate more than $15 billion worth of fruits, vegetables, and nuts every year, directly or indirectly contributing to at least 90 of the country’s commercial crops. The California almond industry alone, which relies heavily on bee pollination, lost about $445 million from 2005 to 2010 to Colony Collapse Disorder (CCD), one of the more mysterious causes of declining bee numbers.
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Aside from CCD, the loss of bees has also been attributed to Varroa mites, which were introduced in Florida in the 1980s and have since spread through the United States, pollution, and pesticides, which may not kill bees outright but can make them more susceptible to parasites like both species of Nocema.
“With pesticides, the analogy is to people with AIDS,” Dennis vanEngelsdorp, an entomologist at the University of Maryland, College Park, told VICE News. “You don’t die from AIDS, you die from pneumonia. The Nosemas tend to be the pneumonia.”
Paxton and his colleagues demonstrated in the laboratory what beekeepers had already seen in the field, vanEngelsdorp said, which helps to close the gap in understanding the parasites’ distribution. It may also provide practical guidance for beekeepers, such as understanding that freezing honeycombs can kill off Nosema ceranae.
“Part of the problem is, if you don’t know what’s killing bees, how can you do anything about it?” Paxton told VICE News. “At least now we’re more aware that this parasite potentially could be a serious threat, particularly with warmer temperatures.”
Follow Laura Dattaro on Twitter: @ldattaro
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