Multiple Studies Show Rapid Decline In Terrestrial Insects In Brazil; Aquatic Counts OK For Now
In 1978, when he moved to his current home on the rural outskirts of Campinas, Brazil, Thomas Lewinsohn, a professor of ecology at Campinas University, routinely encountered a “rewarding assortment of insects” at night, he writes in a new paper in Biology Letters. Today, Campinas, 100 kilometers (60 miles) from São Paulo, is a booming urban and suburban agglomeration of more than 3 million people. Conversely, in the 40-plus years since his arrival, Lewinsohn reports insect populations have “plummeted.” The scientist has failed to see many species, including plume moths and flat-faced longhorn beetles, in 15 years.
Lewinsohn’s story isn’t unique; it echoes anecdotal evidence offered up by entomologists, ecologists and nature lovers around the world. But the story of the great insect dying, which burst into media headlines in 2018 with apocalyptic screams and backlash claims of overhyping, has also seen the publication of numerous studies worldwide. However, that attention has always suffered from an obvious gap: a dearth of news and research from the tropics.
Unidentified insect in the Santarém region, Brazilian Amazon. Insects provide invaluable ecological services: pollinating, spreading plant seeds, enriching soils with their waste, and serving as food for animals further up the food chain. Their loss could undermine whole ecosystems. Image by Filipe França.
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Lewinsohn and his colleagues examined 75 projects tracking insects in Brazil. In all, 17 studies showed declines in terrestrial insect abundance, while only three showed a population rise. Eleven studies found declines in diversity, while one showed rising insect diversity. On average, these terrestrial studies covered 22 years of tracking. “Overall, global studies are seeing a decline in insects, and the study we’ve done is further evidence of the trend,” says co-author Kayna Agostini from the Federal University of São Carlos.
The results for aquatic insects were far different. Just two studies showed declining abundance, with two showing rising abundance. Three studies found declining diversity against four showing rising diversity. Most of the studies evaluated, however, found a stable trend for aquatic insects in abundance and diversity.
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https://news.mongabay.com/2022/10/trouble-in-the-tropics-the-terrestrial-insects-of-brazil-are-in-decline/