The world’s insect populations could disappear in the next century, triggering a “catastrophic collapse of nature’s ecosystems”, according to a first-ever global scientific review that points to climate change as one of the main threats to species that are a foundation of the Earth’s food chains and ecosystems.
The analysis “says intensive agriculture is the main driver of the declines, particularly the heavy use of pesticides,” The Guardian reports. “Urbanization and climate change are also significant factors.”
With more than 40% of insect species declining and one-third endangered, “the rate of extinction is eight times faster than that of mammals, birds, and reptiles,” the article adds. “The total mass of insects is falling by a precipitous 2.5% a year” over the last 25 to 30 years.
“It is very rapid. In 10 years you will have a quarter less, in 50 years only half left and in 100 years you will have none,” said Francisco Sánchez-Bayo of the University of Sydney, Australia, co-author of the paper in the journal Biological Conservation. “If insect species losses cannot be halted, this will have catastrophic consequences for both the planet’s ecosystems and for the survival of mankind.”
“Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades,” write Sánchez-Bayo and co-author Kris Wyckhuys of the China Academy of Agricultural Sciences. “The repercussions this will have for the planet’s ecosystems are catastrophic to say the least.”
Those repercussions are already visible in Puerto Rico, where the population of ground insects has fallen 98% in 35 years, with dire results for the birds, reptiles, amphibians, and fish that eat them. “If this food source is taken away, all these animals starve to death,” Sánchez-Bayo told The Guardian.
The analysis, which brought together the results of 73 past studies, found butterflies and moths among the species facing the sharpest declines—including a 58% drop in butterfly species on farmed land in the UK between 2000 and 2009. Bee species in Oklahoma declined by half between 1949 and 2013, and the U.S. as a whole is down from six million honeybee colonies in 1947 to 2.5 million today.
“There are more than 350,000 species of beetle and many are thought to have declined, especially dung beetles,” The Guardian states. “But there are also big gaps in knowledge, with very little known about many flies, ants, aphids, shield bugs, and crickets. Experts say there is no reason to think they are faring any better than the studied species.”
The small number of adaptable species that are increasing in number are “not nearly enough to outweigh the big losses.”
Sánchez-Bayo cited agricultural intensification, particularly the introduction of new classes of insecticides over the last 20 years, as the main cause of the decline. But most of the studies included in the analysis were from western Europe and the United States. “In the tropics, where industrial agriculture is often not yet present, the rising temperatures due to climate change are thought to be a significant factor in the decline,” The Guardian states. “The species there have adapted to very stable conditions and have little ability to change, as seen in Puerto Rico.”
The Guardian says the published paper used unusually strong language, but Sánchez-Bayo maintained there was nothing alarmist about it. “We wanted to really wake people up,” he explained, and the reviewers and editor at Biological Conservation agreed. “When you consider 80% of biomass of insects has disappeared in 25 to 30 years, it is a big concern.”