Insect populations declining, threatening “catastrophic collapse”

A new global scientific review has found alarming declines across insect populations. The review’s authors have concluded the current rates of decline could end in “a catastrophic collapse of nature’s ecosystems.”

The study found more than 40% of insect species were in decline and a third of the total species are endangered. The total mass of insects is shrinking by 2.5% a year.

Insects are the largest group of animals on earth with more than 900,000 recorded species but their population numbers are falling the quickest.

Insects are a vital part of the ecosystem

The importance of insects to the broader ecosystem is immense. They act as food for other animals in many instances and are also important as pollinators, distributors and recyclers of nutrients.

The loss of insects would lead to what has been termed a “bottom-up trophic cascade”, which would see the impact of the insect collapse cause extinctions higher up the food chain. Further, the deficit of insects would have disastrous consequences for clean water and air.

The study, published in Biological Conservation, involved a comprehensive review of 73 historical reports on insect numbers across the planet and sought to identify the reasons behind the decline.

Climate change and pollution have contributed to the decline in insect numbers

It forecasts a calamitous 40% extinction of existing insect species which will occur “over the next few decades”.

Insect types which have already seen major decline include dung beetles, Odonata (dragonflies), Plecoptera (stoneflies), Trichoptera (caddisflies) and Ephemeroptera (mayflies).

The decline of insect populations has been occurring for at least 100 years, but seems to have accelerated recently. It has been driven by a number of factors including the loss of habitat due to increased urbanisation and the spread of agriculture, rising pollution levels, biological factors and climate change.

The study’s authors advocate a major reduction in pesticide usage to slow or mitigate the loss of insects. The review suggests more sustainable practices need to be used in place of these pest control substances to the ecosystem services provided by insects. Concerted efforts to clean polluted bodies of water should also be made a priority, the authors argue.

Last year’s report from the United Nations’ climate change body, the Intergovernmental Panel on Climate Change, warned that there would be serious loss of natural ecosystems, among other consequences, by 2040 if radical changes to policy and industry are not made.

Header image credit: Ron Whitaker

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