Bees – pests, pesticides and climate change

Bees – pests, pesticides and climate change

Chuck Dinerstein*

Image : marian anbu juwan de Pixabay

Bees are vital for us; without them, there would be no almonds, and few apples, onions, blueberries, carrots or even – God forbid – coffee. According to Center for Biological Diversity« more than half of North America’s 4,000 native bee species are in decline, and one in four species is threatened with extinction “. According Food and Water Watch« bee colonies are dying massively, due to dangerous pesticides that are poisoning them and destroying their habitats “. A new study published in Nature defeats this idea.

There is no doubt that honey bees (Apis mellifera) are dying out, with the United States having recorded a 43% loss of bee colonies in one year. As reported by the New York Times, almond trees, whose pollination depends entirely on bees, use 30,000,000,000 bees per year. This requires 2,000,000 hives. In reality, bees are bred and moved around the country to pollinate crops. In February, they go to California to pollinate almond trees; in March, they go to the Pacific Northwest to pollinate plum, cherry, and apple trees; in April, they arrive in Maine to pollinate blueberries, then in Florida to help citrus trees, and finally they rest in Dakota to pollinate clover and sunflowers in May.

The study published in Nature used a series of data to describe the losses of our “livestock » beekeeping and identify the causes. First, bee losses are largely seasonal; most deaths occur during the overwintering period, before the initial push into California. They tend to decrease in spring, during periods of active pollination until May. Then there is always colony attrition during the time they are among clover and other field crops in the Dakota. The three main causes of death are pests and pathogens, pesticides and climate. The study of Nature gives us their relative contributions.

Parasites – Varroa destructor

Varroa destructor is a parasitic mite that clings to the bee and draws its energy from sucking the fat from the bee. It breeds in the colony’s brood cells and spreads, weakening the bees and eventually killing the colony. The populations of V. destructor rise and fall with colony populations, exerting their greatest effect in late fall and overwintering.

Pesticides

As with all creatures, it is the dose that makes the poison, and bees are sensitive to pesticides sprayed on crops and to those spread on the ground and found in the flowers and pollen of plants. Neonicotinoids, derivatives of nicotine, are considered the ” bad actor of the disappearance of bees and the collapse of colonies.

Climate

Bees are affected by the weather, which influences the availability of food, the ability to thermoregulate during the winter and the initial period of brood rearing in the spring “. The study provides fascinating information regarding the climate and its changes. Rather than just looking at temperature averages, the researchers looked at two other measures of data centrality [1]. They studied the asymmetry of temperatures, accumulated ” at either end of the observed range of minimum temperatures as well as kurtosis, a measure of how extreme values ​​are at these skewed ends.

The researchers pooled the data in a regression model. I use the coefficients of this model as the relative contribution of these three factors. For the purposes of this discussion, pests will be the benchmark for honey bee losses. Pesticides contributed 17% compared to V. destructor – which is not insignificant, possibly avoidable, but certainly not the “ bad actor that has been portrayed. The standard range of minimum temperatures contributed 25%, but extreme temperatures, these climatic changes, contributed 90% of the losses caused by pests. More importantly, the extremes of these changes were almost three times greater as a factor in honey bee loss when they were present.

Parasites and the climate have contributed more to the death of bees than pesticides. Let’s not forget that honey bees are farm animals, kept in man-made structures, much like chicken coops where disease can spread quickly. Bees move just like livestock from one climate to another. Is it possible that humans who ” raise » honey bees are a bigger problem than we thought?

Bee keepers do their best to protect colonies from parasites. The states with the lowest losses, Montana and Wyoming, have the most stable climate; the states with the highest losses, such as New Mexico, have the largest and most extreme variations. A stable climate allows beekeepers to better predict the housing conditions of their colonies.

The collapse of colonies and the disappearance of honey bees are not only due to pesticides. They are linked to the evolution of the climate and to our agricultural methods. Honey bees are another form of livestock, and how we house and move them is just as manageable as how we deploy pesticides.

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[1] If we consider a bell curve, the mean is a good representation of the most common central value. But when the curve is distorted towards either end, the mean is no longer such a good representation of that central value.

Source : Honey bee colony loss linked to parasites, pesticides and extreme weather across the United States, Nature Scientific Reports DOI : 10.1038/s41598-022-24946-4

* Director of Medicine. Dr. Charles Dinerstein, MD, MBA, FACS, is the medical director of theAmerican Council on Science and Health. He has over 25 years of experience as a vascular surgeon.

Source : Bees – Parasites, Pesticides, and Climate Change | American Council on Science and Health (acsh.org)