Extreme El Niños Linked to Insect Decline in the Amazon: Study
Sun, April 11, 2021

Extreme El Niños Linked to Insect Decline in the Amazon: Study



Scientists estimated that there are millions of insect species living on Earth — and the majority of them have yet to be discovered or collected. Many of us probably see them as pests that only cause disease or compete for human agricultural products. While some insects do this, they represent only a small fraction of the world’s insect population. In reality, most insects are beneficial to humans and the environment. Without them, our planet wouldn’t function as it does.


The Decline of Insect Populations

However, just like other species, insects are also at risk of climate change. A 2019 study published in the journal Biological Conservation revealed that the rate of insect extinction is eight times faster than that of mammals, birds, and reptiles. More than 40% of insect species are declining and a third are endangered. The findings suggest that they could vanish within a century, with the total mass of insects falling by a precipitous 2.5% a year. 

“Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades. The repercussions this will have for the planet’s ecosystems are catastrophic, to say the least,” the researchers said. 

According to The Guardian, a British daily newspaper, Francisco Sánchez-Bayo from the University of Sydney, Australia said that the main cause of the decline is agricultural intensification. Previous studies show that the demise of insects started at the dawn of the 20th century, accelerated during the 1950s and 1960s, and reached “alarming proportions” over the last two decades. Sánchez-Bayo added that a 2.5% rate of annual loss over the last 25-30 years is “shocking.”

“If insect species losses cannot be halted, this will have catastrophic consequences for both the planet’s ecosystems and for the survival of mankind,” Sánchez-Bayo said. 



One of the biggest impacts of insect loss is on the many birds, reptiles, amphibians, and fish that eat insects. Unfortunately, these effects are now being seen in Puerto Rico. A 2019 study revealed a 98% fall in ground insects over 35 years, while 80% had vanished in the leafy canopy. The researchers said that the insect population in the country had collapsed.

“It was just astonishing. Before, both the sticky ground plates and canopy plates would be covered with insects. You’d be there for hours picking them off the plates at night. But now the plates would come down after 12 hours in the tropical forest with a couple of lonely insects trapped or none at all,” author Brad Lister said. 

The findings also revealed data on animals that feed on bugs. Frogs and birds have declined simultaneously by about 50% to 65%, respectively. The Puerto Rican tody, for instance, dropped by 90%. “We are essentially destroying the very life support systems that allow us to sustain our existence on the planet, along with all the other life on the planet,” Lister said.



Insect Populations in the Amazon

The Amazon rainforest, one of the most biodiverse regions on the planet, is home to about 30 million species. Every year, around 10,000 new species of insects are discovered, mostly around the Amazon River basin. Scientists said that they are mostly found in the canopy of the Amazon and live side-by-side with the wildlife, and have done for over 100 million years.

The Amazon is the perfect place for insects to live because of its warm and stable climate. They maintain the incredible biodiversity and plant life in the rainforest. Their role is extremely significant, such that life in the forest wouldn't exist if not for them. However, they are also at risk of being extinct. 

A recent study published in Biotropica examined the impacts of stronger El Niños and human activity on dung beetles populations, revealing how insect populations are in terrible danger. The findings revealed that intense droughts and wildfires during the last El Niño climate phenomenon led to beetle numbers falling by more than half. Knowing the status of Amazonian dung beetles is important because those population drops show how changes in climate can interact with other drivers to impact ecosystem functioning and services.

“If we knew more about the direct or indirect effects of the observed dung beetle declines on other organisms, we could get a better handle on the cascading effects of these losses. The story may appear grimmer if this was revealed. But that gets at another conversation on the need for long-term research on insects and species interactions in the tropics,” Danielle Salcido, a Ph.D. student at the University of Nevada, said. 

According to Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, the researchers examined more than 14,000 dung beetles from 98 species across 30 forest plots in the Brazilian state of Pará, within the Amazon. The data was gathered using several surveys conducted between 2010 and 2017. The numbers of dung beetles, which are important indicator insects used to gauge the overall health of an ecosystem, plummeted to around 3,700 in 2016 from 8,000 beetles in 2010. In 2017, they found just 2,600 beetles.



The decline was driven by human-induced fires in the Amazon and El Niño-intensified drought and human activities. According to Mongabay, a nonprofit provider of conservation and environmental science news, forests burned during the El Niño lost 64% of the dung beetle species while those affected only by drought showed an average decline of 20%. The increasing frequency and intensity of droughts in the Amazon are caused by climate change, which makes fires more likely to spread. 

“Dung beetle species richness, abundance, biomass, compositional similarity to pre‐El Niño condition, and rates of dung removal and seed dispersal declined after the 2015–16 El Niño, but the greatest immediate losses were observed within fire‐affected forests,” the study found.

In a statement, the researchers said that the findings of the study provide important insights into how human activities and climate extremes can act together and affect tropical forest biodiversity and ecosystem functioning. “The loss of these hardworking beetles could indicate a wider problem that many mammals living in the forest may have also succumbed to the drought and fires,” they said.