Entering the 6th Global Extinction Stage: Insect populations suffering death by 1,000 cuts

At a time when the global population has grown from one million to 7.8 billion people during the last 10,000 years, most biologists agree that the world has entered the sixth mass extinction, the first since the end of the Cretaceous period 66 million years ago, When more than 80% of all species perished, including non-flying dinosaurs.

Mass extinction and acute shortage

Scientists have information about the shrinking sizes and ranges of the organisms that are being studied further. Terrestrial vertebrate numbers have decreased by a third, and many mammals have experienced a decrease in range by at least 80% over the past century.

An assessment conducted in 2019 indicates that half of all amphibians are at risk, with 2.5% of them being extinct recently.

Bird numbers across North America have decreased by 2.9 billion since 1970. As for coral reefs, the situation could not be more serious. A 2020 United Nations report estimated that more than a million species are at risk of extinction over the next few decades.

As for the entomologist, although a series of reports have drawn attention to declines in their abundance, biomass, species richness, and ranges sizes, there is insufficient information available to estimate their levels of decreases.

New research to study insects

To make up for this deficiency, 11 new research papers were published in the American journal PNAS on January 12th. The papers aimed to identify the deterioration of insects from a geographical, environmental and social perspective, as well as assess the main threats, and delve into how the general population is perceived. 

The main analysis, which is added to 11 other studies, concludes that insects are seriously dying, and that this steep decline in insect populations could have global environmental and economic consequences.

Insects are by far the most diverse and abundant organisms on Earth, with millions of species in them and 17 times the weight of all humans.

They are essential for the ecosystems humankind depends on, such as pollinating plants, providing food for other animals and recycling nature’s waste.

Although insects face multiple and overlapping threats, including the destruction of wild habitats for agriculture, urbanization, pesticides and light pollution, scientists are particularly concerned that the climate crisis could cause massive damage in the tropics.

Although more data is needed to clarify matters, the researchers believe that enough information is already known to take urgent action to protect the insect world.

Professor David Wagner of the University of Connecticut in the United States, the lead author of the analysis, says: “The number of insects is decreasing by 1-2% annually, which is not considered small, because this is very scary that it is tearing apart the fabric of life.”

“Insects are really vulnerable to drought,” Wagner says. “They are a surface area that has no volume.” Thus insects such as dragonflies and damselflies can dry up to death within an hour when the humidity is too low.

Very accelerated decline

The largest systematic assessment of global insect abundance to date, published in April 2020, showed a decrease of nearly 25% in the past 30 years, and indicated that terrestrial insects are declining by nearly 1% annually.

The researchers – who made the largest previous assessment published a year ago, which was based on 73 studies – also warned of “catastrophic consequences for the survival of the human race” if the insect losses were not stopped. This assessment had estimated the rate of decline at 2.5% annually.

As for the 11 papers published in PNAS, some decreases and increases in insect numbers are estimated, with the number of butterflies falling by 50% since 1976 in the United Kingdom and by 50% since 1990 in the Netherlands.

It also showed that butterfly ranges began to shrink long ago, declining by 80% between 1890 and 1940.

However, another study found that moths showed a slight decline over the past two decades in Ecuador and Arizona, in the United States.

“The most important thing to learn from these new studies is the complexity behind insect decline, and there is no single quick solution to this problem,” says Roel van Klink of the German Center for Integrative Biodiversity Research.

Sources: https://www.pnas.org/content/118/2/e

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