Studies: Insect populations suffering death by 1,000 cuts, say scientists

The Guardian: Insect populations suffering death by 1,000 cuts, say scientists. ‘Frightening’ global decline is ‘tearing apart tapestry of life’, with climate crisis a critical concern.

The 12 new studies are published in the journal Proceedings of the National Academy of Sciences. “Nature is under siege [and] most biologists agree that the world has entered its sixth mass extinction event,” concludes the lead analysis in the package. “Insects are suffering from ‘death by a thousand cuts’ [and] severe insect declines can potentially have global ecological and economic consequences.”

One of the studies identifies an increasingly erratic climate as the overarching reason for region-wide losses of moths and other insects in the forests of north-western Costa Rica since 1978. This could be a “harbinger of the broader fate of Earth’s tropical forests”, said Wagner.

However, another study contradicts a 2018 report of a 98% collapse in insects in a Puerto Rican forest. The new paper says “abundances are not generally declining” and that changes in populations are driven by the impacts of hurricanes and not climate change.

Another of the papers sets out actions that can protect insects. Individuals can rewild their gardens, cut pesticide use and limit outdoor lighting, it said, while countries must reduce the impacts of farming.

The biggest systematic assessment of global insect abundances to date, published in April 2020, showed a drop of almost 25% in the last 30 years, with accelerating declines in Europe. It indicated terrestrial insects were declining at close to 1% a year. The previous largest assessment, based on 73 studies, led the researchers to warn of “catastrophic consequences for the survival of mankind” if insect losses were not halted.

Other PNAS papers found both declines and rises. Butterfly numbers have fallen by 50% since 1976 in the UK and by 50% since 1990 in the Netherlands, according to one. It also showed the ranges of butterflies began shrinking long ago, dropping by 80% between 1890 and 1940. However, a study of moths showed zero or only modest long-term decreases over the past two decades in Ecuador and Arizona, US.

Another paper in the series, co-authored by Wagner, concluded: “To mitigate the effects of the sixth mass extinction event that we have caused, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice, that empowers the less wealthy people and nations of the world, where the vast majority of us live.”

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