Insect populations are suffering “deaths from thousands of layoffs,” many of them falling at a “frightening” rate that “breaks the tapestry of life,” according to scientists behind a new body of research.
Insects face a number of overlapping threats, including the destruction of wildlife for agriculture, urbanization, pesticides and light pollution. Population collapses have been reported in places dominated by human activities, such as Germany, but there is little data outside Europe and North America, especially in the wild tropical regions, where most insects live.
Scientists are particularly concerned that the climate crisis could cause serious damage in the tropics. But while much more data is needed, researchers say enough is already known for emergency action.
Insects are the most diverse and numerous animals on Earth, with millions of species more than 1
Studies show that the situation is complex, with some insect populations increasing, such as those whose range is expanding as global warming limits cold winter temperatures, and others recovering from low levels as pollution in water bodies decreases.
The good news is that the increased profile of insect decline over the past two years has prompted government action in some places, scientists said, while a “phenomenal” number of civilian scientists are helping the huge challenge of studying these little creatures.
The 12 new studies are published in the Proceedings of the National Academy of Sciences. “Nature is under siege [and] most biologists agree that the world has entered its sixth mass extinction, ”concludes the lead analysis in the package. “Insects suffer from” death from thousands of cuts ” [and] severe insect decline could potentially have global environmental and economic consequences. “
Professor David Wagner of the University of Connecticut in the United States, the lead author of the analysis, said that the abundance of many insect populations is declining by 1-2% per year, which should not be seen as small: “You have to lose 10-20 % of their animals for a decade and it’s just absolutely scary. You are tearing the tapestry of life. ”
Wagner said most of the reasons for the decline in insects are well known. “But there’s a really big uncertainty, and that’s climate change – that’s what really scares me the most.” He said that increased climate variability could be “an engine [insect] disappearing at a speed we have never seen before. “
“Insects are really susceptible to drought because they all have a surface and no volume,” Wagner said. “Things like dragonflies and dams can dry to death in an hour in really low humidity.”
One study identifies an increasingly volatile climate as the main cause of moth and other insect losses throughout the region of forests in northwestern Costa Rica since 1978. This may be “a harbinger of the wider fate of Earth’s rainforests.” “Wagner said.
However, another study contradicts a 2018 report of a 98% insect collapse in a Puerto Rican forest. The new document says that “abundance does not usually decrease” and that population changes are due to the effects of hurricanes, not climate change. Brad Lister, who led the study in 2018, said he was not convinced by the work, but would conduct his own analysis of the data used and pass the conclusion to the editors of PNAS.
Wagner said the increased public attention has prompted some action, such as an EU initiative to protect pollinators, a € 118 million (£ 106 million) pledge to protect insects in Germany and $ 25 million in Sweden.
Another document sets out actions that can protect insects. People can rebuild their gardens, reduce pesticide use and limit outdoor lighting, he said, while countries need to reduce the impact of agriculture. All groups can help change attitudes toward insects by communicating that they are key components of the living world.
The largest systematic estimate of global insect abundance to date, published in April 2020, shows a decline of almost 25% in the last 30 years, with an accelerating decline in Europe. This shows that terrestrial insects are declining by nearly 1% per year. The previous highest estimate, based on 73 studies, prompted researchers to warn of “catastrophic consequences for human survival” if insect losses are not stopped. It estimates the rate of decline at 2.5% per year.
Other PNAS documents reveal both declines and increases. The number of butterflies has dropped by 50% since 1976 in the UK and by 50% since 1990 in the Netherlands, according to one. It also shows that butterfly ranges began to shrink long ago, declining by 80% between 1890 and 1940. However, a study of moths showed zero or only moderate long-term reductions over the last two decades in Ecuador and Arizona, USA.
“The most important thing we learn [from these new studies] is the complexity behind reducing insects. No quick fix will solve this problem, “said Roel van Klink of the German Center for Integrative Biodiversity Research.. “There are certainly places where the abundance of insects is declining sharply, but not everywhere. This is a cause for hope because it can help us understand what we can do to help them. They can bounce very quickly when conditions improve. “
Wagner said: “We know that nature is under siege and we know we have a responsibility – we don’t really need much more data to start changing what we do. It is unscrupulous what can happen if we do not start paying attention and do not change the way we consume. “
Another article in the series, co-authored by Wagner, concludes: “To mitigate the effects of the sixth mass extinction event we have caused, we will need the following: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice, enabling less affluent people and nations in the world where most of us live. ”