Dramatic Worldwide Declines in Insects

Figure 4 from Lister & Garcia 2018 PNAS 115 (44) E10397-E10406 comparing the biomass of insects captured in ground and canopy traps at the same sites in Puerto Rico 45 years apart.

This week’s paper is on a topic so upsetting that I have been avoiding writing about it. Dave Goulson has published an essay this week in Current Biology entitled “The insect apocalypse, and why it matters”. Goulson is a Professor at the University of Sussex in England who researches bumblebee ecology, and whose popular science books “A Sting in the Tale” and “A Buzz in the Meadow” are wonderful reads that I highly recommend. In his essay this week Goulson reviews the literature on widespread declines in insects. In the 2000’s people anecdotally began noting that car windshields needed to be cleaned of dead insects much less often than they used to. These anecdotes have become known as the “windshield phenomenon” and have sparked interest in finding real data on insect numbers to determine what types of declines may be occurring. The problem is, that unlike birds or mammals, there are not a lot of long-term study systems set up to monitor insect populations across decades. In 2017, data from one of these few long-term study systems was published. It showed that numbers of insects collected in traps in 63 protected areas in Germany had declined 75% from 1989 - 2016. 75%!! That is a lot. Another study last year by Lister & Garcia (see above figure) showed even more dramatic declines in the rainforests of Puerto Rico, of between 75 and 98% depending on the type of sampling. The study from Puerto Rico showed associated declines in the birds, lizards, and frogs that eat insects. As Goulson covers in his review, it is most likely a combination of factors driving these declines, including pesticide usage, climate change, habitat loss, and the introduction of insect diseases and parasites. It should not be a surprise to anyone that the widespread use of pesticides is causing widespread insect declines, that has been, after all, the goal. But it must be noted that the declines are happening beyond agricultural areas where pesticides are being applied, such as the Puerto Rican rainforests in Lister & Garcia (2018). Lister & Garcia (2018) attribute the declines at their study sites to the 2 degree celsius increase in temperature that has occurred over the study period due to human fossil fuel usage worldwide.

These insect declines are terrifying. Insects are the food for most non-human animals on the planet. The animals that don’t eat insects eat other animals (which eat insects) or they eat plants. But insects are required to pollinate 87% of all plants and 75% of our crops. In addition, insects are critical to decomposition. They break down the food waste, the leaf litter, the dead animals, and lots and lots and lots of poop. I have a little baby, and my concerns are not only about the ecological collapse that we are likely to see in his lifetime due to climate change and these insect declines, but that he will not have the joys of watching wild animals in nature that I have had. To quote Goulson:

“Is this the future we would wish for our children, one in which they will never see a monarch butterfly flying overhead, where there are no wildflowers, and where the sound of birdsong and the buzz of insects is replaced by the monotonous drone of robot pollinators? They may be free from malaria, but they will have paid a high price. Once again I am valuing nature for what it does for us humans. There is one final argument, an unselfish one at last. Do not the rest of the organisms on our planet have as much right to be here as we do?”

So what can you do?

1. Get rid of your lawn! In a recent interview May Berenbaum from the University of Illinois suggested this as one of the first things you can do (plus its easy! you actually have to do less). Stop mowing and raking. Let the weeds grow up. Mowing once a year in early October or so will keep the trees down and maintain flowering plant habitat for pollinators and the leaf-litter creates important habitat for insects in your yard.

2. Stop using pesticides, especially ones that include the active ingredients Clothianidin, Imidacloprid, Thiacloprid and Thiamethoxam. These are neonicitinoid pesticides that extensive research has shown have detrimental effects on bees. Many of them are banned in Europe but still legal in the US.

3. Plant native plants. If the thought of an overgrown yard is filling you with anxiety, think instead (or as well) about intentionally planting beneficial plants. The Xerces Society has native plant lists for plants that benefit pollinators suited to your particular region (for example here is the one for my area in Maine). Xerces has worked with Ernst Seeds to create mixes for your region.