The sting of drought: Fewer flowers for bees means increased disease

06/23/2021

A honeybee zips by to forage on the bright orange pollen of a California poppy. A bumblebee bumbles past on its way to a California lilac. A carpenter bee bites on the base of a sage bud to slurp its nectar, too large to fit inside the flower. A sweat bee is barely noticeable as its small size gets lost behind the anthers of a buttercup. All of these species are doing the same job of pollinating flowers while looking for food for themselves, their hives or their babies. This year is more difficult for many animals, including bees, as blooms dry up along with wilting grasses, turning the hills to the familiar straw color much earlier than anticipated. 

In this ecosystem, one of the species is not like the others. Honeybees (Apis mellifera) are not native to North America; they were brought over by European colonizers in the 17th century. Today they are effectively considered livestock in the United States and are critical for crop pollination. Although subject to high overwintering die-offs, honeybee populations in the U.S. and worldwide are increasing as the demand for animal-pollinated crops rises. Over the last 50 years, demand for animal-pollinated crops has nearly tripled, and there are concerns that honeybee populations may not be rising enough to meet demand. Marin is home to honeybees tended by both hobbyists and honey producers, as well as commercial beekeepers responsible for pollinating crops like almonds and citrus.  

But did you know that not a single native flower in the U.S. requires a honeybee to pollinate it? There are native bee species that do that job; the U.S. boasts over 4,000 different species of them. So how are those bees doing? For them, the story is complicated. As for most species, we lack data to understand whether or not they are in decline. We need to know a species’ population status at some point in the past in order to understand if it has decreased today. Some species invariably show that they are threatened, such as the western bumble bee (Bombus occidentalis), which has shown sharp population declines in California. In Marin, there are over 240 different bee species, but how their populations are doing is largely unknown. 

Droughts mean a general lack of resources, and this negatively impacts every bee species. Studies show that droughts cause plants to produce fewer flowers with less nectar and nutritious pollen. This has cascading effects onto bees, leading to overall decreased survival rates. Having quality food is critical for bees to grow and perform their daily tasks, and it helps them fight off disease. Research shows that when bees are starved, they exhibit worse symptoms of infectious disease. That means that with this drought, not only do all bees have less food, they also will likely be hit even harder with diseases. 

The periwinkle blue blush of lupine on grazed hillsides sits in stark contrast with low water levels in the Nicasio Reservoir, acting as a forewarning of a very dry summer ahead. It may be a particularly challenging year for beekeepers who will have to supplement the diet of their honeybees earlier than usual in the season. Although the extra sugar water will get them through, it does not provide the same nutrition as wildflowers, and honey production and honeybee survival will certainly be impacted. Native bees will likely be hit hardest, as they have no beekeepers to provide extra food and medicine. If there was ever a year to try to help save both honey and native bees, it would be this year. 

So, what can we do? Since bees can fend off diseases better when they are well fed, we must have focused management on increasing floral forage for pollinators. West Marin offers a unique opportunity to make positive change for pollinator health due to the environmentally minded stewardship of the people, the unique floral and bee diversity, and the ecologically minded agricultural systems. Pollinator-focused land management must occur at all scales, from rangelands to city greenspaces to your own backyard. This will allow as many species as possible to weather this drought, and future droughts, too.  Management strategies must incorporate pollinator-friendly habitat measures to increase floral resources in order to satiate and maximize health outcomes of bee populations. 

Are you interested in learning more about the bees of Marin? You can join research efforts at the University of California, Berkeley, to see how flowers are influencing bee health. This sort of research requires full partnership with locals through community science endeavors. By helping gather data and quantifying which species are found in Marin at different times of the year, you can contribute to helping protect these critically important pollinators. 

 

Nina Sokolov is a Ph.D. student at the University of California, Berkeley, studying bee health. If you want to be involved in this research, reach out to her by email at nsokolov@berkeley.edu.