Bees' average lifespan has halved in fifty years. That could be bad news for humanity

One-third of the human diet comes from plants pollinated by bees

It is a public health triumph that human life expectancy has increased linearly since the year 1800, rising about 30 years in that span. Imagine, then, if human life expectancy were to spontaneously halve, and the degree of panic that would ensue.

Alarmingly, this precise scenario is playing out among honeybees — a species on which humans are utterly dependent for our survival, given that one-third of the human diet depends on honeybee pollination, and bees pollinate more than 100 different crops worth about $6.4 billion. The bee lifespan crisis was discovered in a new study published in the scientific journal Scientific Reports, which found that honey bees today live only half as long as their counterparts in the 1970s.

The reasons for this dramatic shift may relate to humanity's demand for honey. Beekeepers need to account for the fact that bees die periodically in the course of their hive-rearing; since the 1970s beekeepers have been forced to replace their bee colonies more frequently to stay afloat.

To understand why bees are dying younger, entomologists at the University of Maryland studied bee pupae that were collected within 24 hours of emerging from their wax cells. Those bees were raised in special conditions that included better water, which they hoped would closely mimic bees' natural conditions. Soon, however, they noticed that the median lifespan of all their bees remained half of that of bees from the 1970s, with the average bee lifespan dropping from 34.3 days to 17.7 days. This was stunning because, historically, bee lifespans in laboratories have closely mimicked their wild lifespans.

"We're isolating bees from the colony life just before they emerge as adults, so whatever is reducing their lifespan is happening before that point," Anthony Nearman, a Ph.D. student in the Department of Entomology and lead author of the study, said in a press statement.

Researchers believe that the problem could be genetic, meaning something in their DNA is giving them a shorter lifespan.

"This introduces the idea of a genetic component," Nearman continued. "If this hypothesis is right, it also points to a possible solution. If we can isolate some genetic factors, then maybe we can breed for longer-lived honey bees."

This would be a boon for beekeepers, who struggle financially when they have a high turnover in their colonies.

As the authors pointed out, their findings about declining bee lifespans are consistent with beekeepers' own observations, and offer ominous implications about the future of beehives — and by extension, the future of human food, given bees' role in pollination of crops.

"Modeled colony lifespans allowed us to estimate colony loss rates in a beekeeping operation where lost colonies are replaced annually," the study states. "Resulting loss rates were reflective of what beekeepers' experience today, which suggests the average lifespan of individual bees plays an important role in colony success."

In addition to being ecologically and economically important, bees are also among the more intellectually complex insects. A study released earlier this month in the journal Science found that bees enjoy play, which is considered to be a sign of intelligence. Bees were trained to associate rolling wooden balls with eating delicious food; then it was discovered that they would go out of their way to move the balls around even if doing so delayed receiving food, suggesting they enjoy the activity.

Yet bees, despite being intelligent, have been just as vulnerable to human-caused environmental problems as most other species. While the new study suggests that their declining lifespan may be caused by genetic rather than environmental factors, bees struggle today due to everything from climate change to the overuse of dangerous pesticides. In the latter case, a class of man-made insecticides called neonicotinoids has been linked to colony collapse disorder and plummeting bee populations. They have also had a negative impact on other kinds of wildlife, including harming bird communities, seeping into national wildlife refuges and perhaps affecting human brain development.

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