3-minute read

Whether you look forward to the first spring flight of the bumblebee (Bombus) as a reassuring sign of nature’s capacity for renewal or are simply grateful for the fruits of the fuzzy pollinator’s labor, the recent study documenting its climate change-induced decline was a definite buzzkill. The new analysis of 66 bumblebee species across North America and Europe from researchers at the University of Ottawa and University College London reveals that over the last five decades, the growing number of unusually hot days is increasing local bumblebee extinction rates. Heatwaves and rising average temperatures have led to widespread loss of populations—an estimated 46% in North America and 17% in Europe.

Bumblebees evolved in cooler regions of the world over a period of about 100 million years, and scientists now believe that warmer winters and hotter summers resulting from global heating may exceed the iconic insect’s ability to adapt. At the current rate of emissions, it’s estimated that climate change may have greater negative impacts on the bee species than habitat loss, potentially resulting in mass extinction.

Like honey bees (Apis mellifera), wild bumblebees are important pollinators of crops and native plants, providing critical ecosystem and economic benefits for people and planet—absolutely free of charge. Both honey bees and bumblebees are accidental pollinators. In the process of drinking nectar and harvesting pollen for food, they pick up the finely-grained plant dust on their bodies or leg hair and transfer it from the anther to the stigma of the flower.

However, compared to its honey-producing cousin, the bumblebee is equipped with a few extra features that make it especially efficient at pollen gathering. Because bumblebees are bigger than honey bees, they can pick up and transfer more pollen per flower fly-by. Some species of bumblebees also have longer tongues than honey bees, not as long as this creature’s, but pretty impressive by bee standards. Longer-tongued bees are particularly skilled at lapping up nectar and pollen from hard-to-reach places in tubular flowers like honeysuckle and salvia. Bumblebees also have another expert tool in their pollen-gathering arsenal—buzz pollination, or sonication. By holding the flower with its legs or mouthparts and rapidly vibrating its flight muscles, the bumblebee can dislodge pollen from plants that can’t be pollinated through garden variety bee pollination methods. About eight percent of plants rely on this shake-and-take method of pollen gathering, including eggplants, tomatoes, potatoes, blueberries, and cranberries. In addition to its bigger size, longer tongue, and sonication skills, the bumblebee has an extended pollination season and can visit twice as many flowers per day as the honey bee.

Although bumblebees have an exceptional aptitude for pollen gathering, like many animal and plant species, their ability to adjust to the unprecedented environmental stressors of climate change is limited. Uncommonly warm winter temperatures can trick queen bumblebees into emerging from the hive well before pollen is available for food, leaving them too weak to return to the hive to lay eggs—no eggs, no bees. Come spring, higher-than-normal temperatures alter the scent, nectar, and pollen production of flowers, making them less attractive to foraging bees. And increased C02 in the atmosphere also reduces the protein level of pollen, resulting in smaller bumblebees. Smaller bees travel shorter distances, carry less pollen, and pollinate fewer flowers. To put these climate change casualties in perspective, 75 percent of the world’s flowering plants rely on pollinators for reproduction, including more than two-thirds of the world’s crops.

Unfortunately, less than one percent of bumblebee hotspots are currently protected. In a rapidly warming world, conservation aimed at maintaining habitats for the 250 species of bumblebees and assisting the insects with colonization beyond their normal range is crucial to their survival. If you’d like to help ensure that bumblebees have a soft landing wherever they roam and continue to contribute to everyday essentials, here are some tips on what to plant on your city or country patch to keep these precious pollinators buzzing:

Bumbles prefer:

Perennials because they produce more nectar than annuals
Native perennials because they produce more nectar and pollen than sterile hybrids
Symmetric two-sided flowers
Pink and violet-colored flowers

And here’s a short list of the bumblebees’ perennial favorites that you can plant from rooftop to roadside:

Daisy family (Asteraceae)
Common daisies, cornflowers, chamomile,
yarrow, fleabane, asters, dahlias, coneflowers

Flowering pea family (Fabaceae)
Lupine, mimosa, wisteria, clover

Mint family (Lamiaceae)
Sage, mint, rosemary, lavender, thyme,
lemon balm, hyssop, chaste, patchouli

You can learn more about what makes the bee bumble and how you can become a citizen conservationist from the Xerces Society and the Bumblebee Conservation Trust. For a deeper drill-down into the fascinating world of bees of all sorts, we highly recommend The Bee, A Natural History.

If you’ve got access to a front, back or side yard, or any other personal patch, you can find out how to grow climate-resilient, environmentally beneficial communities of plants that you, the bees, and other wildlife will love living within the excellent Bringing Nature Home and Planting in a Post-Wild World. And if you’re a city dweller in need of some perennial planting inspiration, visit the elevated gardens at the High Line in NYC (online or in-person) created by Dutch perennial plant master, Piet Oudolf. We may have a slight hometown bias, but as gardens go, it truly is the bee’s knees.