All Creatures, Especially Small
By Kathleen Tarlow, Education Manager
On a recent Thursday night, a group of local nature lovers gathered over a potluck dinner at Grassroots Ecology headquarters to learn more about the variety of our native bees from Sara Witt, our staff bee expert. Sara introduced us to different groups of locally native bees, whose beauty and unique natural histories had us rapt.
When most people think of bees, they tend to think of honeybees—the familiar amber-banded ones who live communally in a large nest, produce honey and wax that humans have harvested for millennia, and pollinate our crops and gardens. These honeybees—rightly appreciated for their service to humans— are actually imports from Europe from centuries past that have since naturalized here.
What most people don’t realize is that for many thousands of years before the honeybee arrived, a different and varied set of bees had been hard at work in our local ecosystems. There are about 4,000 bee species in North America, with an impressive 1,600 native to California.
Sweat bee (genus Agapostemon) males sleeping on Juncus patens. Photo by Sara Witt.
There are wool carder bees (Anthidium spp.), who scrape the hair off fluffy plants like hedge nettle and use the fluff to line the nurseries of their developing larvae. There are leaf-cutter bees (Megachile spp.) who delicately cut leaf segments to create a kind of origami tube, complete with a cake of nectar and pollen, to raise and nourish their young inside. There are metallic green and blue and purple bees, bees smaller than a grain of rice, bees that will drink your sweat, and bees so large and fuzzy they’ve been nicknamed teddy bear bees!
In addition to their beauty and fascinating behavior, these bees serve critical roles pollinating our wildlands, crops, and gardens. Appreciating this amazing group of animals is critical, because they are just one part of an alarming decline in invertebrate biodiversity.
Invertebrates don’t always get the attention of some of the larger, more obviously charismatic animals of the world like polar bears, elephants, and koalas. Research is catching up, however, and the news is disheartening. The best studied group of invertebrates, the Lepidopterans (butterflies and moths) have globally seen a 35% decline since 1970, and non-lepidopteran insects may be faring even worse. The International Union for Conservation of Nature (IUCN) has only assessed an estimated 1% of known invertebrate species, and of this small number, 40% are considered threatened with extinction in the coming decades (1).
A bee fly (Bombylius incanus) at a hillside gooseberry. Photo by Jeremy Merckling.
As bad as these numbers sound, it’s possible things are actually worse for insect abundance overall. Long-running insect surveys are hard to come by, but of those that exist, the picture is decidedly grim. One 27-year study conducted in Germany in a network of protected areas recorded a decline of over 75% insect biomass during the study period (2). This decline in insect abundance is no doubt happening in America as well, and it’s happening silently and unremarked in many cases. Where people are watching, however, the numbers are on par with the German study, if not more alarming.
The rusty-patched bumblebee, a Midwestern native bee, has declined by 87% in the past 20 years (3). A more familiar local example is the precipitous decline of monarch butterflies. This year’s January monarch counts showed Western monarch populations to be critically low for the second year in a row (4). The combined effects of habitat destruction, pesticides, and climate change threaten the existence of this marvel of nature.
This silent loss of insect abundance doesn’t affect just the beautiful and charming insects we know, but also the hidden, strange, and nameless insects that we don’t. Of nearly one million species of named insects, experts estimate that there are at least twice that number as yet unidentified (5). These insects are the pollinators of crops and wildlands, recyclers of ecosystems, and the base of the food webs that affect the animals many people find easier to appreciate, like birds and fish.
It’s all connected: A black-tailed bumblebee (Bombus melanopygus) in the grasp of a crab spider that is living on a pink-flowering currant. Photo by Jeremy Merckling.
In January of this year, an international team of scientists published a letter in Nature: Ecology and Evolution urging immediate action to slow the decline of insects and promote their recovery (6). They created a “global roadmap” for action, including increasing ecologically sustainable agriculture, creating and maintaining natural areas and habitat, and expanding outreach and awareness programs.
The good news is that, while this is a global problem, there are lots of actions you can take locally to help our native insects (and the food webs they support!). Join us to learn what invertebrates populate our creeks by coming to Bug Club, a group of community scientists helping to assess the diversity of benthic macroinvertebrates in our watersheds. Restore habitat with us for a few hours, planting and maintaining the native plants with which our local insects have co-evolved. Create your own insect oasis in your garden with native plants and fallen leaves that provide food and living space for these important members of our ecosystems. The next time you see leaf holes in a plant that you love, try to see it as a sign that a local insect has enjoyed a healthy meal and perhaps, in turn, been enjoyed by a bird or fish. And the next time a bee is buzzing nearby, fight the common urge to yelp and swat it. It’s likely minding its own life’s business; finding food, caring for its young, looking for a safe place to call home.
Sources Cited:
Dirzo, R et al, “Defaunation in the Anthropocene” Science 345, 401 (2014)
DOI: 10.1126/science.1251817Hallman, CA et al, “More than 75 percent decline over 27 years in total flying insect biomass in protected areas” PLoS ONE 12(10): e0185809. https://doi.org/10.1371/journal.pone.0185809
“Rusty Patched Bumble Bee” U.S Fish & Wildlife Service, (https://www.fws.gov/midwest/endangered/insects/rpbb/)
“Western Monarch Butterfly Population Still at Critical Level,” Xerces Society, https://www.xerces.org/press/western-monarch-butterfly-population-still-at-critical-level
“Numbers of Insects (Species and Individuals)”, Smithonian, https://www.si.edu/spotlight/buginfo/bugnos
Harvey, J et al, “International scientists formulate a roadmap for insect conservation and recovery,” Nature Ecology & Evolution, 4, 174-176 (2020) https://www.nature.com/articles/s41559-019-1079-8.pdf
