My chronic worry about bugs disappearing is no longer merely anecdotal.

A study published last month of insect population research states unequivocally that “the demise of major insect taxa … (has) attained alarming proportions globally over the last two decades.” At the current rates of decline, the study says, 40 percent of the Earth’s insect species could go extinct in the next few decades.

Here are some examples of the losses documented:

• Over the past 40 years, 41 percent of the Earth’s insect species have declined in population.

• A study found a 76 percent decline in flying-insect biomass in some of Germany’s protected areas between 1989 and 2016.

• A study in Puerto Rico’s rain forests found arthropod biomass losses of 78 to 98 percent over a 36-year period.

• Studies of 67 butterfly species in California imply that since 1997, 23 percent of them are disappearing. Another study published too late to be included in the review study found that California’s monarch butterfly population in 2018 declined nearly 86 percent compared to 2017; the state’s monarch population has declined 97 percent since the 1980s.

• Studies of eight bumblebee species in 382 locations in the U.S. found that four of the species had declined up to 96 percent in the last 30 years, and their geographic range was reduced between 23 and 87 percent.

• North American species of ladybugs have declined sharply since 1986. “At least two previously common species … have since become very rare or entirely disappeared from the north-eastern USA,” the study says.

A damselfly in the Unity park in 2011. Fifteen percent of dragonfly and damselfly species in North America are thought to be threatened. Photo by Dana Wilde

• The study estimates 15 percent of dragonfly and damselfly species are threatened in North America. In Japan, populations of 57 (out of 200 identified) species are declining; 19 are endangered.

• Studies have found sharp declines in ground beetle populations in the Netherlands, Belgium, Luxembourg, Denmark, the United Kingdom and New Zealand since the 1950s.

• To be clear, not all insect populations are declining. Some are holding steady, and a few insect species are growing. But overall, insects are having survival problems on Earth.
You might be thinking: Fewer bugs, so what? Fewer nuisances.

But reality is a lot larger than your own backyard, and more complicated. Here are some examples of the effects of insect declines:

• Many insects, especially bees, pollinate flowering plants, including food crops. Declines in pollinating insect populations will likely lead to declines in agricultural production — food shortages.

• Many insects such as ground beetles play a role in decomposing wood and recycling nutrients needed to keep plants, and the animal life that depends on them, growing. If saproxylic ground beetles died out in Northern Europe, for example, forests would deteriorate, and the lives of all the creatures living there would be disrupted or threatened, including humans.

• Insects control other insect pests. Dragonflies and damselflies, for example, control mosquitoes and insects that damage crops such as rice.

• Insects are food for larger animals, such as moles, porcupines, lizards, frogs, bats, birds and fish. As insects die out, other animals will start to starve. Eventually the whole food chain will collapse. It’s already happening in Puerto Rico’s rain forest. Our place at the top of the chain means we have the farthest to fall, when you think about it. All 7 billion of us live in ecosystems that depend on insects.

What is killing the insects? The answer is: us. The major factors are:

• Habitat loss. Deforestation and especially agricultural expansion and intensification change the landscape, forcing many species of bugs to vacate their natural ranges, or die. Some of the sharpest declines in U.S. bee populations have been recorded in regions dominated by intensive agriculture.

• Pollution. The use of chemical fertilizers and pesticides in large-scale agriculture is wiping out insects in whole regions. The study says, “In aquatic environments, the evidence points to pollution as the main driver of the declines and extinctions recorded so far.”

• Biological factors. The introduction of insects and other kinds of predators for purposes of controlling pests has caused unintended ecological disruptions leading to insect population declines. These practices have been refined in recent years and have less negative impact than they did earlier.

• Climate change. As air and water temperature rises, some species expand into areas they’ve never lived in before and displace native species; this is believed to be what’s happened to ladybugs in the Northeast. Global warming is “certainly” responsible for reducing the ranges of dragonflies, bumblebees and stoneflies, the report says. The explosion of disease-carrying tick populations in the Northeast is another effect of warming. And just to be clear, human activities that generate gigatons of carbon dioxide are driving climate change. There is less doubt about this than there is about next week’s weather forecast.

Earth’s ecosystems are facing catastrophe, the study says. “We are witnessing the largest extinction event on Earth since the late Permian and Cretaceous periods,” 250 million and 65 million years ago, respectively.

Is there any hope? The answer is: yes, if humans make changes. “Habitat restoration, coupled with a drastic reduction in agro-chemical inputs and agricultural ‘redesign,’ is probably the most effective way to stop further declines,” the study says.

We have less than 100 years to figure this out.

 

Dana Wilde lives in Troy. You can contact him at [email protected] His recent book is “Summer to Fall: Notes and Numina from the Maine Woods.” Backyard Naturalist appears the second and fourth Thursdays each month.


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