Insect Populations Decline In Number And Diversity
Thirteen years ago I went and sat in a field full of Common Milkweed (Asclepias syriaca). The photographs I took of insects visiting the fragrant blossoms ended up being the subject of my first children’s book, Milkweed Visitors. The number and diversity of invertebrates in that patch of milkweed was astounding. Over a decade later I find milkweed flowers alarmingly free of insect visitors. I first noticed this several years ago, and unfortunately the trend has continued. An occasional honey bee or bumblebee, perhaps a swallowtail butterfly or a red milkweed beetle or two can be seen, but nowhere near the number or variety of insects that you found just a few years ago.
Recent studies show that insect populations are declining dramatically not only in milkweed patches, and not only in North America, but in many parts of the world. A global index for invertebrate abundance showed a 45 percent decline over the last four decades. (Yale School of Forestry and Environmental Studies). Researchers say various factors, from the rampant use of pesticides (in particular, neonicotinoids), the spread of monoculture crops such as corn and soybeans, urbanization, and habitat destruction contribute to this decline.
This phenomenon affects everything from pollination to the documented decline in bird populations that feed on flying insects. However, thus far, only the decline of honey bee populations has received widespread public attention, in large measure because of their vital role in pollinating food crops. The rest of the insect world has been widely ignored. Insects play a major role not only in pollination but as predators of insect pests and as food for birds, amphibians and bats. Who knows how many plant species live in symbiotic relationships with highly specialized insects.
Given the importance of insects for agriculture, biodiversity and the health of ecosystems, one hopes that studies regarding the decline of insects will increase in the near future. We can all contribute to a greater understanding of what is happening by participating in “citizen science” projects which undertake monitoring of specific insect species. A list of such projects and how to get involved can be found at https://xerces.org/citizen-science/.
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