For gardeners – and anyone else concerned about the future of life on Earth – a recent article on the “insect apocalypse” is essential reading (New York Times Magazine, Nov. 27, 2018).
Researchers in Germany found that the number of insects is less than one-fifth of what it was 50 years ago. If you’re lucky enough to have lived that long, remember how many insects got plastered against your windshield on long car trips? Or how many bugs you couldn’t help but swallow on bike trips?
When the numbers of insects decline, the wildlife that depend on them also declines, often more precipitously. Insects are essential to ecological food webs and support not only birds, bats and amphibians, but also possums and bears.
Reasons for dwindling numbers of wildlife are complex and may include climate change, habitat loss and pesticides, as well as starvation. The ecosystem services provided by a functioning natural food web are, in turn, crucial to human survival: purifying water, cycling nutrients, controlling erosion, pollinating food crops, and so on.
If you are looking for a way to make a difference, planting native plants can have a considerable impact. In a talk at last year’s California Native Plant Society Conservation Conference, entomologist Doug Tallamy noted that residential landscapes are “a very powerful conservation tool.” For instance, the soft bodies of caterpillars are the primary food for baby birds, delivering a substantial meal that’s loaded with fat and protein. They need hundreds of caterpillars a day, over a couple of weeks or so, foraged locally by the parents, before they can leave the nest.
But landscapes dominated by plant species from outside California are largely unable to host the abundance needed. Planting the right native plants, which have co-evolved with native insects, can provide that abundance, one yard at a time. Tallamy cited a study of 18 pairs of native versus non-native plants (the same genus, with “presumably similar leaf chemistry”) that showed only half the number of insects using the non-natives.
Several online resources can help you learn more about which native plants can host the greatest diversity. Plug in your ZIP code and get prioritized lists of host plants (by genus) that support the most species of butterflies and moths at the National Wildlife Federation Native Plant Finder (nwf.org/nativeplantfinder). These critters lay their eggs on specific host plants, and most of the caterpillars that hatch are essential food for birds. (A small number will become butterflies or moths.)
You can also survey your own plants in midsummer, counting the number of caterpillars – the most important food for birds – you see, looking closely. As Tallamy said, step back 10 feet, and you won’t see any!
Audubon also has a native plants database (audubon.org/native-plants) that asks for your ZIP code and lets you choose several filters: type of bird attracted, type of plant and plant resources (nectar, fruit, butterflies, caterpillars, nuts and seeds). The database lists plants by species.
To learn how to attract a variety of native bees to your garden, visit the UC Berkeley Urban Bee Lab website at helpabee.org and click the “Gardening” tab.
In addition, explore the websites of Tree of Life Nursery (californianativeplants.com) and Las Pilitas Nursery (laspilitas.com) to find out more about growing specific natives.