Declines in bee populations and other pollinators could negatively affect crop yields in the US, according to new research published in the journal Proceedings of the Royal Society B: Biological Sciences. The study led by Rutgers University researchers found that a lack of pollinators could translate directly into decreased yields of key crops such as apples, cherries and blueberries. “We found that many crops are pollination-limited, meaning crop production would be higher if crop flowers received more pollination,” said senior author Rachael Winfree from the School of Environmental and Biological Sciences at Rutgers University–New Brunswick. “We also found that honey bees and wild bees provided similar amounts of pollination overall,” she added. The authors stress that their study is the first to evaluate the contribution of wild pollinators to crop pollination at the national scale in the US in such a comprehensive way.

The importance of pollinators for crop production is well-known. “Pollination by insects is a critical ecosystem service that is necessary for production of most crops, including those providing essential micronutrients, and is thus essential for food security,” the study notes. In the US alone, the production of pollinator-dependent crops is valued at over $50 billion per year. And recent evidence suggests that both European honeybees and some native wild bee species are declining. The authors highlight, however, that a decline in pollinators will only affect crop yield if yield is limited by a lack of pollination. In order to get more information, the researchers established a nationwide study to assess the extent of pollinator limitation in seven crops at 131 farms across the United States and in British Columbia, Canada. Through this multi-state Integrated Crop Pollination Project, coordinated by Michigan State University, the scientists collected data on insect pollination of crop flowers and yield for apples, highbush blueberries, sweet cherries, tart cherries, almond, watermelon and pumpkin. “For each crop, we selected study farms within economically important areas for the national production of that crop, so these farms were representative of the majority of production in terms of growing conditions, pollinator communities and farm management practices,” they outlined in the study design.

The researchers found that apples, sweet cherries, tart cherries and blueberries showed evidence of being limited by pollination, indicating that yields are currently lower than they could be if pollinators were more abundant. Another finding is that wild bees and honeybees provided comparable amounts of pollination for most crops, even in agriculturally intensive regions. However, the proportion of visits by honeybees or wild bees differed greatly by crop. Wild bees accounted for the largest proportion of pollination visits in pumpkin (74.6%) but did not visit almond trees. The proportion of wild bee visits was higher for cherry and apple than for blueberry. The economic value of honeybees and wild bees was also estimated based on their relative contributions to crop pollination. The researchers estimated the nationwide annual production value of wild pollinators to the seven crops they studied at over $1.5 billion. “At the national level, we estimated the value of wild pollinators to be highest in apple, with a value of $1.06 billion, with significant value also in sweet cherry ($145 million), watermelon ($146 million), pumpkin ($101 million), blueberry ($50 million) and tart cherry ($32 million),” they wrote in the paper. The value of wild bee pollination of all pollinator-dependent crops would be much greater.

The findings of the study suggest that adopting practices that conserve or augment wild bees, such as enhancing habitat to support blooming trees and shrubs and wildflowers, or using managed pollinators other than honey bees, is likely to boost yields. Increasing investment in honey bee colonies is another alternative growers can consider to reduce the risk of limited pollination. “Managing habitat for native bee species and/or stocking more honey bees would boost pollination levels and could increase crop production,” said professor Rachael Winfree. The study also points to the fact that pesticides are a major threat to pollinators. According to data cited in the study, US farms currently spend about $9 billion annually on pesticides and about $23 billion on fertilizer. “In cases where pollination is limiting, there may be little benefit to spending large amounts of money on pest control,” the authors conclude. (ab)