Eight simple actions that individuals can take to save insects from global declines

Common beneficial and intriguing insects.* (Key below)

Excerpt from Opinion published in the Proceedings of the National Academy of Sciences of the United States of America, January 12, 2021.** (Full citation below):

1. Convert lawns into diverse natural habitats.

Traditional European or Western lawns are biodiversity deserts (15). There are more than 40 million acres of lawns or turf grass in the United States alone (16), and these groomed/mowed monocultures support few insects and other wildlife. With increasing global fragmentation of natural environments, insects will need quality habitat to be preserved and restored, including travel corridors and stepping stones to allow movement across the landscape (5, 7, 17). Because many insects need little space to survive, even partial conversion of lawns to minimally disturbed natural vegetation—say 10%—could significantly aid insect conservation, while simultaneously lowering the cost of lawn maintenance through reduced watering, and requisite herbicide, fertilizer, and pesticide applications. If every home, school, and local park in the United States converted 10% of their lawn space into natural habitat, this would increase usable habitat for insects by more than 4 million acres. Converting lawns into natural habitat is relatively easy, and if preexisting turf grass is needed to be removed beforehand, this can be done with a sod cutter or through solarization before seeding. Fallen leaves, twigs, and fruit in this space should be left in place, and vegetation should be minimally trimmed or not trimmed at all, as many insects depend on new growth and complex plant structure. A model effort is the “Thousands of Gardens – Thousands of Species” project in Germany, funded by 2.5 million euros from the German Federal Ministry for the Environment (18).

2. Grow native plants.

Although there are exceptions, increasing evidence shows that growing native plants provides more benefits to native insects, on average, than growing nonnative ornamental species. Native insects have tight ecological relationships with native plants that have been shared for millions of years. Many different kinds of insects rely on these plants as a food source or nesting sites. These insects are in turn prey for birds and other wildlife, thus native plants indirectly attract many vertebrates. For example, almost all songbirds (∼96%) feed insects to their young (19), and declines in suburban backyard birds have been linked to an increased number of nonnative plants (20).

3. Reduce pesticide and herbicide use.

Pesticides often harm nontarget, natural insect populations (reviewed in 5, 7), whereas reduction of their use fosters beneficial arthropods (e.g., 21). Pesticides have been found far from their application source (22) and, in some regions, are more prevalent in urban streams than in those near agricultural lands (23). Many pesticides are applied for cosmetic purposes, that is, aimed only at improving the appearance of nonagricultural green spaces such as lawns, gardens, or parks. Reduction or elimination of cosmetic pesticide use, already legislatively mandated in Nova Scotia and Ontario (24), could greatly benefit both terrestrial and aquatic insect communities.

4. Limit use of exterior lighting.

Since the 1990s, nighttime light pollution has increased sharply, even doubling in some of the world’s most biodiverse areas (27, 28). The majority of nocturnal insects are attracted to artificial lights, and these lights are powerful sensory traps that can indirectly kill insects via exhaustion or result in predation before sunrise (29). In Europe, nocturnal moths are declining more quickly than moths and butterflies that fly during the day, and this trend is likely attributable to light pollution (30). Artificial light has also been shown to reduce reproductive success in fireflies because these insects use light to attract mates (31). To reduce harm to insects, people should turn off unneeded lights, dim necessary light sources, use motion-activated lighting, shield bulbs, and switch to bulbs that produce amber- or red-colored light, which produce wavelengths that are less attractive to insects (32). UV-blacklight “bug zappers,” with a purported function to attract pests such as biting flies, mainly kill harmless, nontarget insects (33). Insect populations will benefit from conservation efforts to protect dark night skies.

*Insect key: Examples of insects that are beneficial to humans (AJ), and examples of amazing things that insects do (KT). A, Pollinator: Honey bee (Apis mellifera). B, Bumble bee (Bombus sp.). C, Decomposer: Dung beetle (Scarabaeidae: Scarabaeinae). D, Biocontrol: Ladybird beetle (Harmonia sp.). E, Ecosystem service: Ants (Formicidae). F, Silk production: Silk moth (Bombyx mori). G, Research: Fruit fly (Drosophila melanogaster). H, Vaccine development, including coronavirus: Alfalfa looper moth (Autographa californica). I, Dye production: Cochineal scale insect (Dactylopius coccus). J, Environmental assessment: Stonefly (Plecoptera). K, Visual systems: Dragonflies (e.g., Neurothemis sp.) have near 360° vision. L, Visual defense: Hawkmoth caterpillars (Hemeroplanes triptolemus) scare predators by flipping over and resembling a snake. M,Immunity and symbiosis: Parasitic wasps (e.g., Aleiodes indiscretus) subdue their host with a virus. N, Acoustic defense: Tiger moths (Bertholdia trigona) use ultrasound to jam bat sonar. O, Biomechanics: Water striders (e.g., Gerridae) walk on water. P, Agriculture: Leaf cutter ants (Atta sp.) farm fungi. Q, Chemical defense: Bombardier beetles (Brachinus sp.) blast boiling benzoquinones at predators. R, Migration: Monarch butterflies (Danaus plexippus) migrate thousands of kilometers. S, Longevity: Periodical cicadas (e.g., Magicicada septemdecim) live for nearly two decades. T, Visual mimicry and luring: Firefly (Photinus pyralis) females mimic other firefly light flash signals to lure mate-seeking males and consume them alive. See SI Appendix for further information about each insect. Image credits: Fig. 1A: Michael J. Raupp (photographer); Fig. 1B: Flickr/James Johnstone, licensed under CC BY 2.0; Fig. 1C: L.E.R.; Fig. 1D: Flickr/John Spooner, licensed under CC BY-NC 2.0; Fig. 1E: iNaturalist/Jakob Fahr, licensed under CC BY-NC 4.0; Fig. 1F: L.E.R.; Fig. 1G: iNaturalist/alexis_orion, licensed under CC BY 4.0; Fig. 1H: iNaturalist/Anita Sprungk, licensed under CC BY-NC 4.0; Fig. 1I: Wikimedia Commons/Peggy Greb, licensed under CC BY 3.0; Fig. 1J: Flickr/USFWS Mountain-Prairie, licensed under CC BY 2.0; Fig. 1K: L.E.R.; Fig. 1L: André Victor Lucci Frietas (photographer); Fig. 1M: Wikimedia Commons/USDA; Fig. 1N: Aaron J. Corcoran (photographer); Fig. 1O: Flickr/Brad Smith, licensed under CC BY-NC 2.0; Fig. 1P: L.E.R.; Fig. 1Q: Flickr/Katja Schulz, licensed under CC BY 2.0; Fig. 1R: Jeffrey Gage (photographer); Fig. 1S: Michael J. Raupp (photographer); and Fig. 1T: Flickr/James Jordan, licensed under CC BY-ND 2.0.

**Opinion: Eight simple actions that individuals can take to save insects from global declines. Akito Kawahara, Lawrence E. Reeves, Jesse R. Barber, and Scott H. Black. PNAS January 12, 2021 118 (2) e2002547117 https://doi.org/10.1073/pnas.2002547117

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