According to the scientists behind a new study, insect populations ‘died’ a thousand times, while many fell at ‘alarming’ rates and ‘tore up the tapestry of life’.
The insects face several, overlapping threats, including the destruction of wild habitats for farming, urbanization, pesticides and light pollution. Population spills have been recorded in places where human activities predominate, such as in Germany, but there is little data from outside Europe and North America and in particular from wild, tropical regions where most insects live.
The scientists are particularly concerned that the climate crisis could cause serious damage in the tropics. But although much more data is needed, the researchers say there is already enough to act urgently.
Insects are by far the most varied and abundant animals on earth, with millions of species weighing 17 times more than humans. It is essential for the ecosystems on which mankind depends, pollinates plants, provides food for other beings and recycles the waste of nature.
The studies show that the situation is complicated, with some insect populations increasing, such as those whose distribution expands as global heat curbs the cold winter temperatures, and others recover from a low level as pollution in water bodies is reduced.
The good news is that the increased profile of insects has declined in the past two years, prompting government action in some places, the scientists said, while a “phenomenal” number of scientists are helping with the big challenge of studying these little creatures.
The 12 new studies are published in the journal Proceedings of the National Academy of Sciences. ‘Nature is besieged [and] most biologists agree that the world has entered its sixth mass extinction event, ”concludes the main analysis in the package. “Insects suffer from ‘death by a thousand cuts’ [and] severe insect decline could potentially have global ecological and economic consequences. ”
Prof David Wagner of the University of Connecticut in the USA, lead author of the analysis, said that the prevalence of many insect populations decreases by 1-2% per year, a rate that should not be considered small: ‘You are 10-20% of your animals lose in a single decade and that is absolutely frightening. You tear apart the tapestry of life. ‘
Wagner said most causes of insect decline are known. “But there’s one big unknown, and that’s climate change – that’s what scares me the most.” He said that increased climate change could be ‘managed’ [insect] extinctions at a rate we have not seen before ”.
“Insects are really susceptible to drought because they are all surface and have no volume,” Wagner said. “Things like dragonflies and dam flies can dry out in an hour with very low humidity.”
One of the studies identified an increasingly volatile climate as the overriding reason for the loss of moths and other insects in the region since 1978 in the northwestern part of Costa Rica. , says Wagner.
However, another study contradicts a 2018 report of a 98% collapse in insects in a Puerto Rican forest. The new article states that ‘abundance is generally not declining’ and that the changes in the population are being driven by the effects of hurricanes and not by climate change. Brad Lister, who led the 2018 study, said he was not convinced of the work, but that he would do his own analysis of the data used and present the conclusion to the PNAS editors.
Wagner said greater public attention had prompted some action, such as an EU initiative to protect pollinators, a pledge of € 118 million (£ 106 million) for insect conservation in Germany and $ 25 million in Sweden.
In another of the articles, actions that can protect insects are outlined. Individuals can rebuild their gardens, reduce pesticide use and limit outdoor lighting, while lands should reduce the impact of farming. All groups can help change attitudes towards insects by indicating that they are important components of the living world.
The largest systematic evaluation of the global insect stock so far, published in April 2020, has shown a decline of almost 25% over the past thirty years, with accelerating declines in Europe. This indicated that rural insects are declining by almost 1% per year. The previous largest assessment, based on 73 studies, led researchers to warn of “catastrophic consequences for the survival of mankind” if insect losses are not halted. It estimated the decline rate at 2.5% per annum.
Other PNAS papers found both declines and increases. According to one, butterfly numbers have dropped by 50% in the United Kingdom since 1976 and by 50% in the Netherlands since 1990. It also showed that the butterfly series began to shrink long ago and fell by 80% between 1890 and 1940. However, a study of moths has shown zero or only moderate decline over the past two decades in Ecuador and Arizona, USA.
‘The most important thing we learn [from these new studies] is the complexity behind insect declines. No single quick fix will solve this problem, ”said Roel van Klink of the German Center for Integrative Biodiversity Research.. ‘There are definitely places where the insect clouds are declining sharply, but not everywhere. This is a reason for hope because it can help us understand what we can do to help them. They can bounce back really fast if conditions improve. ”
Wagner said: ‘We know that nature is under siege and we know that we are responsible for it. We do not really need to have more data to be able to change what we do. It is unscrupulous what can happen if we do not pay attention and change our way of consuming. ”
Another article in the series, co-authored by Wagner, concluded: “To mitigate the effects of the sixth mass extinction event we have caused, the following is needed: a stable (and almost certainly lower) human population, sustainable levels of consumption and social justice, which empowers the less wealthy people and nations of the world, where the vast majority of us live. ”