Apr 21, 2022 - Science

Climate change and intense farming may be devastating some insect populations

Illustration of a monarch butterfly with a question mark pattern on its wings.

Illustration: Aïda Amer/Axios

As the sheer number and types of insects living on Earth's land decreases, scientists are beginning to determine the impacts of habitat loss, climate change and other threats on insect populations worldwide.

What's new: The combined consequences of climate change and high-intensity agriculture may be driving declines in insects — on average by 49% in some of the most impacted places, according to a study published this week in Nature.

Why it matters: Insects that pollinate crops, cycle nutrients into soil, and eat pests are linchpins in the ecosystems that produce food. A finer picture of the global insect decline — which species are affected and where — could help to better inform international agreements to protect biodiversity.

Details: Charlotte Outhwaite, a research associate at University College London, and her colleagues found a 27% drop in the number of insect species in places experiencing the highest temperature increases and where one crop is grown or large amounts of pesticides are used. (Agriculture and other changes in land use can alter the microclimate in an area.)

  • But in farmland near natural habitats, the reductions in insect biodiversity were less dramatic, even if those places experienced climate warming.
  • That's consistent globally, Outhwaite says, adding it will "hopefully be applicable in most contexts" and could "provide alternative resources to help protect insect biodiversity in the future when it is likely further warming will occur."

Insects in heavily farmed regions of the tropics were particularly hard hit, based on data collected in a 20-year period for nearly 17,900 species of beetles, flies, butterflies, bees and other insects from more than 6,000 places around the world, the researchers found.

  • Tropical insects evolved in a narrow temperature range, and it is possible they are already living close to their climate limits, Outhwaite says, adding that because there is less data from tropical regions, the impact there is likely even worse.
  • What's next: The researchers plan to analyze the data to try to understand how different types of insects are faring, she says.

The big picture: Studies have pointed to massive losses of insects — but not everywhere and not among every species of insect.

  • The abundance of some insects — for example, some arthropod species in the Arctic and freshwater insects— and the range of others, including some butterfly species in Europe and mosquitoes —haven't changed or have increased as the climate, people, and how they use land and water shifts.
  • A study published this week found warmer spring temperatures in the U.S. Rocky Mountains are associated with an increase in smaller bees and a decrease in bumblebees and other larger species, which could reorder bee communities that are crucial for pollination, the Guardian reports.

Between the lines: That suggests some good news for the world's insects, but the metrics of abundance and species richness (the number of species) that are commonly used to assess biodiversity may be masking the nuances of what is happening, Nature's Gayathri Vaidyanathan wrote last year.

  • For example, a study of Arctic arthropods found their total abundance dropped gradually from 1996 to 2014 before sharply increasing.
  • But when researchers looked at the diversity of insect families, they found those increases appeared to be driven by a small number of types of insects.
  • Another challenge is that data skews toward North America and Europe though some global-scale datasets are becoming available, Outhwaite says.

"There are definitely instances where insects are at risk and are declining," she says. But, "whether it is as dire as some say, we don’t have enough data to say one way or another."

What to watch: As better datasets and finer details emerge, they will inform conservation efforts through the United Nations' lesser-known agreements on biodiversity and land use.

  • The draft framework for the 2022 UN Biodiversity Conference (COP15) that will take place this year, includes protecting 30% of land and seas around the world and reducing the rate of extinctions by 90% by 2050.
  • The International Indigenous Forum on Biodiversity (IIFB) is urging the framework reflect Indigenous peoples' knowledge and role in conservation.
  • Governments will also convene in Côte d’Ivoire in about two weeks for the UN conference on the future of land management, which Outhwaite's study indicates has a strong impact on insect biodiversity.

The bottom line: "There is a global mosaic of national responsibility versus global level targets," says Brent Loken, global food lead scientist at the World Wildlife Fund. "It's a puzzle we have to piece together."

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