The Effect of Climate Change on Pollinators and the Implications for Global Agriculture

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Jeffrey Park
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More than one-third of global food crops depends on commercial bees for pollination, but over 30% of domesticated honey bee colonies collapse each year due to poor nutrition, spread of pathogens, exposure to pesticides, and transportation stress. To avoid a pollination crisis that would cripple global agriculture, farmers can introduce diverse populations of wild bees by simply planting pollen-rich wildflowers near the cropland. Diverse bee populations not only supply higher crop yields and larger fruit set (compared to single-species management), but the differential responses among species to climate change and other perturbations provide a buffer against disastrous declines in any one species. In this essay, I analyze the effect of climate change on wild pollinators in montane meadows at the H.J. Andrews Experimental Forest in Oregon. Globally, warming temperatures have confused plants into flowering earlier each spring, which can cause temporal mismatches with pollinator species. Asynchronies can hinder plant reproduction and limit the food resources necessary for pollinator survival. At the study site, springtime temperatures rose significantly from 2011 to 2015, and the snowpack melted from the ground consistently earlier over the five years. In response to this climate variability, the median date of peak flower abundance and the median date of peak plant-pollinator interactions both shifted earlier by about five weeks from 2011 to 2015. Despite sustained synchrony between the plants and pollinators, the median flower abundances declined by 68% and the median number of interactions declined by 73%. Although the data suggest that the wild pollinators are trying to adapt to shifts in timing of flowering, the dwindling interaction counts indicate that the populations are still suffering. These findings reinforce the importance of cultivating a diverse set of wild bee species for agriculture. Even if a few individual species decline as a result of climate change and harmful agricultural practices, pollinator biodiversity can mitigate systemic crop pollination failures.