Air pollution harms (also) butterflies and bees


“It is estimated that more than a hundred thousand varieties of plants would disappear if bees did not visit them.” So wrote, in 1901, Nobel laureate in literature Maurice Maeterlick in his The Life of Bees (a quote that over the years, curiously enough, has been distorted several times, until one version of it was even attributed to Albert Einstein; but that’s another story). And indeed this is the case: bees-as well as all other pollinating insects-are absolutely indispensable to the ecosystem, both because of their role in the food chain and, more importantly, because of their importance in plant reproduction. Well, air pollution is putting them at risk, too: according to the results of a study just published in the journal Enviromental Pollution, insect pollination of flowers is significantly lower where there is more air pollution.

“We have confirmed,” explain James Ryalls and Robbie Girling, two of the authors of the paper, affiliated with the University of Reading, “that pollution has a very significant effect on insects, and especially on bees, bumblebees and wasps. Other species are affected to a lesser degree, and it all seems to depend on how strongly they base their behavior on olfactory stimuli.” To find out, the scientists measured the frequency with which bees, flies, butterflies, bumblebees and other insects visited flowers for pollination in different scenarios, characterized by different concentrations of two very common pollutants, nitrogen oxide and ozone: and it turned out, precisely, that the species that rely primarily on odors to reveal the presence of flowers are the most affected by exposure to pollution. These species, unfortunately, are also those that pollinate the most, i.e., those most important for flower and plant reproduction.

According to the scientists, unsurprisingly, the presence of pollutants-even at lower concentrations than those generally predicted by the guidelines of health care institutions-would destructively interfere with the ability of the infected to smell the olfactory signals of flowers, and consequently significantly reduce pollination rates. “The decrease in the frequency of visits to flowers by insects due to pollution,” the authors explain, “is almost certainly associated with the interference of pollutants with the olfactory signals of plants. Should this problem be shown to exist on a larger scale, and should pollution continue to increase, we would certainly see very negative consequences for the growth and reproduction of many insect-pollinated crops in the near future.” We are warned.

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