Insect populations are at risk around the globe, with 40% of all insect species in decline and roughly one third of all species endangered. Between the loss of habitat, climate change, and the extensive use of pesticides, our bees, butterflies, and beetles are dying off in unprecedented numbers.

This seems an overwhelming problem, but it is one that all gardeners can begin to remedy. As Archbishop Desmond Tutu once said, “There is only one way to eat an elephant: a bite at a time.” No matter the size of the garden, every gardener has steps they can take in order to make positive changes for the insects we all need to keep our planet healthy.

Let’s focus on two insect populations: bees and caterpillars.

Bees

The majority of flowers and about one third of all crops depend upon pollination. When these populations are threatened, so is food security. For an extreme example, consider the farmers of Sichuan province in China who hand paint pollen onto their fruit trees because insecticides have killed off bee populations. 

Somewhere between 60-70% of bee species dig burrows in the ground, while the remaining 30-40% nest in cavities such as holes in trees or hollow stems. 

A Few Solutions for the Home Gardener:

• For ground-nesting bees, provide areas in your garden with undisturbed soil, keeping insecticides away.

• For cavity-nesting bees, leave stems of varying lengths (8-24”) over winter and don’t trim back until after spring. Provide a water source for mud-building bees. 

• For bumblebees who need insulation to build nests, provide a brush pile with sticks and leaves.

• Consider a bug hotel to provide more spaces for cavity-nesting bees—you can build one yourself or find a ready-made bug hotel for purchase.

Caterpillars

While most gardeners love bees, caterpillars are often seen as a problem in the garden—and for a good reason. Hornworms decimate tomato plants and cabbage loopers devour all sorts of edible greens. However, entomologist and conservationist Doug Tallamy argues that since caterpillars dominate the nesting diets of the majority of birds, these insects are necessary for healthy bird populations. For example, 75% of the food chickadees bring their young is caterpillars.

While some caterpillars eat a variety of plants and can be considered generalists, many caterpillars are specialists that only eat one particular plant. Monarch butterflies, of course, rely upon milkweed flowers alone, while goldenrods are eaten by 80-plus different kinds of caterpillars.

A Few Solutions for the Home Gardener:

• Go to Native Plant Finder (https://www.nwf.org/NativePlantFinder/Plants/Flowers-and-Grasses) to look up which flowers best attract beneficial caterpillars in your area as generalists.

• Consider specialist caterpillars you want to attract and plant the flower or tree they rely upon.

• Convert some of your lawn to native wildflowers and grasses.

• If you don’t have a lawn, try a container garden of native wildflowers.

• Add a bed of native wildflowers and grasses below any trees that host caterpillars; this provides a soft, protected space for the caterpillars’ transformation.

• Use mosquito dunk tablets instead of mosquito sprays to control those populations. Even sprays that say they only target mosquitos have been shown to hurt other insects.

For More:

Bee Lab (University of Minnesota). https://beelab.umn.edu

Davies, Dave. “The World's Insect Population Is in Decline—And That's Bad News for Humans,” Fresh Air, (February 24, 2022). https://www.npr.org/sections/goatsandsoda/2022/02/24/1082752634/the-insect-crisis-oliver-milman

Habitat Installation Guide: Upper Midwest. Xerces Society. https://xerces.org/sites/default/files/publications/15-042.pdf

Homegrown National Park. https://homegrownnationalpark.org/

Millman, Oliver. The Insect Crisis: The Fall of the Tiny Empires That Run the World. New York, NY: W.W. Norton & Company, 2022.

Native Plant Finder. https://www.nwf.org/nativeplantfinder/

Photo Credit: John McLinden (https://www.flickr.com/photos/fogey03/34605941461) (1)