The world's insects are pushing for extinction, threatening a "catastrophic collapse of nature's ecosystems," according to the first global scientific review.
More than 40% of insect species are declining and one third is endangered, the analysis says. The extinction rate is eight times higher than in mammals, birds and reptiles. The total mass of insects, according to the best data available, drops by a proud 2.5% per year, suggesting that they could disappear within a century.
The planet is at the beginning of a sixth mass extinction in its history, with major losses already reported in larger animals, which are easier to study. But insects are by far the most diverse and richest animals, outnumbering humanity 17-fold. The researchers are "essential" for the proper functioning of all ecosystems as food for other creatures, pollinators and nutrient recyclers.
In Germany and Puerto Rico a collapse of the insect population has been reported recently, but the review clearly shows that the crisis is global. The researchers presented their conclusions for a peer-reviewed paper in an unusually powerful manner: "The [insect] Trends confirm that the sixth major extinction has major implications [on] Life forms on our planet.
"If we do not change our way of producing food, insects as a whole will be threatened with extinction in a few decades," they write. "The impact this will have on the planet's ecosystems is catastrophic, to say the least."
According to the analysis published in the journal Biological Conservation, intensive agriculture is the main reason for the decline, especially the heavy use of pesticides. Urbanization and climate change are also important factors.
"If the loss of insect species can not be stopped, it will have catastrophic consequences for both the planet's ecosystems and human survival," said Francisco Sánchez-Bayo of the University of Sydney, Australia, who reviewed Kris Wyckhuys at the China Academy of Agricultural Sciences in Beijing.
The annual loss rate of 2.5% over the past 25 to 30 years is "shocking," Sánchez-Bayo told the Guardian: "It's very fast, in 10 years you have a quarter less, in 50 years, only the Half left and in 100 years you have none. "
One of the biggest effects of insect loss concerns the many birds, reptiles, amphibians and fish that eat insects. "When this food source is taken away, all these animals starve to death," he said. Such cascade effects have already been observed in Puerto Rico, where a recent study found a 98% decrease in soil insects over 35 years.
In the new analysis, the 73 best studies were selected to determine the decline in insects. Butterflies and moths are among the most affected. For example, between 2000 and 2009, the number of common butterflies in England fell by 58% on arable land. The United Kingdom has the largest overall decline in insects, although this is probably due to more intense investigation than in most areas.
Bees were also severely affected. Only half of the bumblebee species found in Oklahoma, USA, in 1949 were present in 2013. The number of honeybee colonies in the US in 1947 was 6 million, but since then 3.5 million have been lost.
There are more than 350,000 species of beetles, many of which are believed to have decreased, especially dung beetles. But there are also big gaps in knowledge, about which many flies, ants, aphids, shield bugs and crickets are hardly known. Experts say there is no reason to believe that they are better off than the species studied.
A small number of adaptive species are increasing, but not nearly enough to outweigh the large losses. "There are always some species that use the vacuum left over from the extinction of other species," said Sanchez-Bayo. In the US, common Eastern bumblebee is increasing due to its tolerance to pesticides.
Most of the studies studied were conducted in Western Europe and the US, with some reaching from Australia via China and Brazil to South Africa, but very few in others.
"The main cause of the decline is agricultural intensification," said Sánchez-Bayo. "That means removing all the trees and shrubs that normally surround the fields. So there are simple, bare fields that are treated with synthetic fertilizers and pesticides. "He said that the demise of insects began at the beginning of the 20th century, accelerated in the 50s and 60s, and reached in the last two decades "Alarming proportions".
He believes that new classes of insecticides introduced over the last 20 years, including neonicotinoids and fipronil, have been particularly harmful as they are routinely used and remain in the environment: "They sterilize the soil and kill all the maggots." Nature reserves nearby; The 75% insect losses recorded in Germany were located in protected areas.
The world needs to change the way it produces food, Sánchez-Bayo said. He noted that organic farmers had more insects and that occasional pesticide use in the past has not resulted in the decline seen in recent decades. "Intensive agriculture on an industrial scale is the one that kills ecosystems," he said.
In the tropics, where industrial agriculture often does not exist, it is believed that rising temperatures due to climate change have a significant impact on the decline. The local species have adapted to very stable conditions and can hardly change, as in Puerto Rico.
Sánchez-Bayo said the unusually strong language used in the review was not alarming. "We really wanted to wake people up," the reviewers and the editor agreed. "Considering that 80% of insect biomass has disappeared in 25 to 30 years, this is a big problem."
Other scientists agree that it is clear that insect losses are now a serious global problem. "The evidence points in the same direction," said Professor Dave Goulson of the University of Sussex in the UK. "It should be of great concern to all of us, because insects are at the heart of every food web, pollinating the vast majority of plant species, keeping the soil healthy, recycling nutrients, fighting pests, and more. You love or loathe, we humans can not survive without insects. "
Matt Shardlow of Buglife said: "It is sobering to see this evidence demonstrating the miserable state of global insect populations. It is becoming increasingly apparent that the ecology of the planet is breaking and it is necessary to make intensive and global efforts to stop and reverse these terrible trends. "In his opinion, the report over-emphasizes the role of pesticides and undermines global warming, although other factors have not been studied. Factors such as light pollution could prove significant.
Prof. Paul Ehrlich of Stanford University in the US saw insects disappear first-hand while working on checkerspot butterflies in the Jasper Ridge Reservation in Stanford. He first studied it in 1960, but all had disappeared in the year 2000, mainly due to climate change.
Honestly, the review praised the words, "It's extraordinary to have gone through all these studies and to analyze them as well as they did." He said that the particularly sharp drops in aquatic insects were striking. "But they do not mention that overpopulation and overconsumption of people drive things [eradicating insects]including climate change, "he said.
Sánchez-Bayo said he recently saw an insect bug himself. A family vacation that was recently undertaken with a 700-kilometer drive through rural Australia did not even require the windshield to be cleaned, he said. "Years ago, you had to do that all the time."