This was a sad year to be an amateur naturalist at my house. Native bee and butterfly populations were puny and late to appear, and it was rare to see bats lurching through the evening sky. The insect decline I had read about in Germany and Puerto Rico, suggesting a 60 percent drop in the world’s insects, was showing itself in my garden.
Chances are good that our familiar garden ecosystems are changing, functioning in new ways with a different set of players. For example, despite fewer native bees, moths and butterflies in my garden, invasive cabbage white butterflies were in good supply. And whatever is bothering my native bees seems to have had no impact on squash bugs and Japanese beetles. In terms of surviving whatever is causing insect decline, durable pests of food crops may have an edge.
Causes of Insect Decline
It is almost certain that heavy pesticide use contributes to insect losses, but pesticides cannot be logically blamed for insect decline in the tropical rain forests of Peru and Puerto Rico, and not in nature preserves in western Germany, and not where I live on the edge of a heavily forested National Park. It is also a weak explanation for the disappearance of insects from a trout stream in rural Pennsylvania, where habitat loss may have played the biggest role.
Similarly, light pollution may explain the disappearance of some species, but in a remote part of Australia? Another possible explanation that has been woefully understudied is “electrosmog,” or the ecological effects of electro-magnetic signals from telecommunications towers and wireless devices. Working for the British non-profit buglife.org, an international consortium of biologists and physicists recently reviewed all of the known science on the effects of electromagnetic radiation on plants, insects, and animals. Their list of unknowns (research gaps) was very long indeed, with few questions answered. Until we have those answers, electrosmog must stay on the list of possible contributory factors to insect decline, especially for bees.
Which brings us to climate change, which has many parts. Rising carbon dioxide levels may make plants work harder, requiring more nitrogen. Trees and other plants may change their carbon/nitrogen balance, resulting in leaves that are less nutritious to the insects that eat them. Atmospheric methane could be a factor, too, so these and other climate change details may explain insect decline affecting the entire planet.
How Gardeners Can Fight Insect Decline
As organic gardeners, we can step up our efforts to help our gardens function as insect conservatories by growing more flowers for bees and other flying insects, and providing mulch or other cover for ground-dwelling species. This summer when I took down my sweetcorn, I piled the stalks on a vacant bed to provide stable habitat for ground beetles and earthworms. In a few weeks, I will cover other beds with deep mulches of leaves. Now more than ever, it’s time to mulch like you never mulched before.
If we must choose who to save, let’s start by growing more plants to attract pollinators and other beneficial insects. Watch for changes in your garden’s insect ecosystem, and do what you can to make life more comfortable for surviving species. This year I saw fewer ladybirds in my garden, but there were plenty of hoverflies – another major aphid predator that thrives in gardens rich with flowers. Growing more native plants with small flowers is a guaranteed way to keep them happy.
Put more thought into enhancing your garden’s value as an insect sanctuary. You might make an insect hotel so solitary bees, wasps and beetles will have a safe place to live season after season. Providing food and habitat for insects really can help, as many American gardeners saw this summer with monarch butterflies. Milkweed planted by thousands of gardeners over the last few years has helped North American monarch butterflies make a comeback, which would never have happened without human help.
As a favour to fireflies and moths, regard outdoor lighting as a source of pollution, and turn off lights at night. And make sure to report any bugs you see to The Big Bug Hunt to help monitor populations of pests and beneficial insects across the world.