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Insects touch nearly every corner of life on this planet, filling endless functional roles and providing services too vast to name — and they are disappearing. According to the largest study of insect populations to date, published in the journal Science, insect populations on land are decreasing by 0.92% per year. This number may seem small, but it amounts to 24% fewer insects in 30 years and 50% fewer in 75 years, a significant decline.

This study comes on the heels of scientists’ warning to humanity on insect extinctions, in which 30 scientists from around the world express their deep concerns about global insect declines and warn that we are pushing many ecosystems beyond the point of recovery. Insects, they assert, provide irreplaceable services, and urgent action must be taken to save both ecosystems and humanity.

“Insect declines happen in a quiet way and we don’t take notice from one year to the next,” Roel van Klink, first author of the Science study and a scientist at the German Centre for Integrative Biodiversity Research (iDiv) and Leipzig University, said in a statement.

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“It’s like going back to the place where you grew up. It’s only because you haven’t been there for years that you suddenly realize how much has changed, and all too often not for the better.”

While the year-to-year decline of insect populations on land may be largely imperceptible, people have noted that fewer bugs appear to be splattered on their windshields now, compared to a few decades ago. This anecdotal observation, dubbed the “windscreen phenomenon,” was investigated by citizen science insect research in the U.K. The survey used a standardized grid placed over license plates to record the number of bugs being squashed. The survey found that, indeed, 50% fewer insects were squashed on the license plates of cars in 2019 than in 2004.

Where have all the insects gone?

Yet while land-dwelling insect populations dwindle, the numbers of insects that live their lives (or part of them) in freshwater habitats are on the rise by about 1.08% per year. The trend is strongest in the Western U.S. and in Northern Europe, where scientists believe clean water initiatives and anti-pollution legislation over the past 50 years may be responsible for the positive trends.

“Insect populations are like logs of wood that are pushed under water,” van Klink said. “They want to come up, while we keep pushing them further down. But we can reduce the pressure so they can rise again. The freshwater insects have shown us this is possible.”

The study, which analyzed 1,676 sites around the world, revealed that despite overall trends on land and in the water, local trends were highly variable. In general, insects fared better in areas least impacted by humans.

One limitation of the meta-analysis, the researchers note, is that most of the data came from temperate North America and Europe. Overall trends were highly influenced by strong North American trends. Another weakness of the study is that highly disturbed sites were underrepresented. Over a third of the data came from protected sites. Other recent studies have found insects declining at rates of 3% to 6% per year.

Although the authors were unable to say exactly why these trends, both positive and negative, have emerged, they did find an association between insect declines and habitat loss, particularly through urbanization.

In the Mongabay investigative series “The Great Insect Dying,” most of the 24 entomologists interviewed pointed to habitat loss (especially due to the expansion of agribusiness), pesticide use, and climate change as the major causes of global insect declines. Invasive species, overexploitation, industrial pollution, agricultural runoff, and the dramatic loss of food plants for insects have also been cited as reasons for insect declines.

“We’ve seen so much decline, including on many protected sites. But we’ve also observed some sites where butterflies are continuing to do well,” said Ann Swengel, a co-author of the Science study. Swengel has studied butterflies in the U.S. for 34 years and stresses the complexity of these findings as well as what they mean for effective conservation management.

“It takes lots of years and lots of data to understand both the failures and the successes, species by species and site by site. A lot is beyond the control of any one person, but the choices we each make in each individual site really do matter.”

This article was originally published on Mongabay, written by Liz Kimbrough, and is republished here as part of an editorial partnership with Earth.Org. 

A study has found that hotter and drier El Niño events are impacting biodiversity in the Amazon rainforest, causing the collapse of insect populations, specifically dung beetles, an important ‘indicator species’ used to gauge the health of a larger ecosystem. 

The study, published in the journal, Biotropica, led by scientists from Brazil, New Zealand and the United Kingdom, reveals that the dung beetle numbers in the Brazilian state of Para fell by half after the 2015-2016 El Niño event. 

The team scouted for the insects in 30 forested areas spread across Para, from 2010 to 2017. They counted more than 14 000 dung beetles and monitored their effectiveness in maneuvering dung and the amount of seed they were dispersing. 

The researchers recorded 8 000 beetles across their plots in the first year of their study. However, after the devastating El Niño event in 2016 that charred 7.4 million acres of forest in the Amazon, this number reduced to just 3 700 beetles. As of 2017, their numbers dropped even further to a mere 2 600. The researchers also observed that the population of these insects was smaller in areas impacted by wildfires as compared to those that experienced only drought.

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The dung beetles, with their matte-finished black backs, are responsible for collecting animal faeces in the Amazon rainforest. They play a crucial role in increasing the organic content of the soil by burying the collected dung in burrows. As a result, the soil underneath aerates leading to higher water holding capacities and increase in the nutritious value of the soil. 

Dr Felipe Franca, an ecologist at Lancaster University and Embrapa Amazonia Oriental in Brazil and lead researcher of the study explains that the findings provide “important insights into how human activities [agriculture & deforestation] and climate extremes can act together and affect tropical forest biodiversity and ecosystem functioning.”

He adds, “Dung beetles depend on mammal’s poo for nesting and feeding, therefore declines in beetles are likely associated with the loss of mammals due to that El Niño drought and fires.”

The available research indicates that as the planet has warmed due to human activities, the insect populations have declined globally, not just in the Amazon. Hence, early intervention by concerned authorities will play a crucial role in protecting the important players of our ecosystem from extinction.

This discovery echoes similar research conducted on the global insect population collapse. Data gathered since the 1960s suggests that beetles, mayflies, dragonflies and other creatures that spend a good part of their lives in water have increased about 11% per decade, while land-dwelling insects have shrunk by about 9% per decade.

A study of global insect populations has revealed that 40% of the world’s insect species are threatened with extinction. This revelation is alarming, spelling an uncertain future at best and a major ecosystem collapse at worst. 

Insect Populations Decline

Insecticides and habitat loss are two major causes of dwindling insect numbers around the world. A habitat’s transformation- or destruction- completely uproots the ecosystems existing there, which is devastating for many organisms. Intensive agriculture has caused much of the current habitat loss, emphasising the need for sustainable farming methods. Monoculture farming creates vast fields of singular crops, which is convenient for farming productivity, but not for plants, which may get eaten in larger quantities by plant-eating insects that favour the singular crops.

These fields envelop previously thriving land and take the place of natural structures like trees and rivers. Organisms like mosquitoes are less likely to exist and reproduce in areas without bodies of water; three must occur in standing water sources of the four lifecycle stages they experience. Aquatic insects will disappear completely; dragonflies and caddisflies have already seen considerable losses. Those that manage to find viable bodies of water must contend with pollution and oxygen loss as a result of synthetic fertilisers.

According to the study, the species most threatened are Lepidoptera, an order of insects that includes butterflies, Hymenoptera, an order that includes bees, as well as dung beetles.

Studies of insect declines are notoriously limited, however, according to the United Nations Environment Programme, most studies focus on the US and Europe, with little information on other territories. Very few studies have tracked insect biomass over the long term. It’s also difficult to gauge the types of insects that are disappearing- much more information exists about bees and butterflies than ants, for example. Despite these limitations, it’s clear that numerous environments are facing an alarming number of insect disappearances.

The Ramifications of the Loss of Insect Populations

Insects do a lot of heavy lifting to keep the world’s ecosystems afloat. Professor Dave Goulson from the University of Sussex notes that insects perform vital roles such as pollination, seed dispersal, and nutrient recycling. They are also food for numerous larger animals, including birds, bats, fish, amphibians, and lizards’. If one section of the food chain disappears in a given area, the entire system could collapse.

Flying insects in Germany have diminished by more than 75% in under 30 years. Researchers used Malaise traps to record the biomass of flying arthropods in protected areas and found that both endangered and safe species- such as wild bees and moths- have experienced a significant drop in numbers. Fewer bugs will cause a decline in the creatures that consume them, signaling major biodiversity loss.

Flowers and plants will experience lower pollination rates from a lack of pollinators, while invasive organisms will drive out native insects. For example, in South Africa, the introduction of aquatic predators like rainbow trout has crowded out Ecchlorolestes peringueyi, a rare species of dragonfly. The planting of exotic trees along riverbanks has further diminished the diversity of dragonfly species. As foreign animals adapt to a new environment, they often bring a cascade of adverse effects for the native ones. The invasive species may prey on the native ones and further their shrinking numbers, or they can bring more invaders, turning the ecosystem on its head. 

New plants can spring up when native bugs aren’t there to eat them. A study of invasive plants revealed that they have a reducing effects of 56% on animal abundance, diversity, fitness, and ecosystem function across different ecosystems, animal classes, and feeding types with no increasing effects. 

What We Can Do

Insect-saving initiatives exist across the world for bees, butterflies, and numerous other affected creatures. Homes can be made more insect-friendly by creating pollination gardens or establishing ponds for aquatic bugs. Agrochemicals like pesticides or synthetic fertilisers should be avoided. The innards of a dead tree can serve as bee habitats; on a community level, parks and gardens should be advocated for. 

Governments can help prevent insect decline as well. In Germany, a €100 million project to help protect native insects is underway, with a quarter of the money earmarked for research and monitoring. Much of the rest will go toward protecting insect habitats, decreasing disruptive light pollution, and phasing out the use of the world’s most popular weedkiller, glyphosate- better known as Roundup- which often kills the native plants that insects need for survival. The United Nations has also called on governments around the world to stop biodiversity loss by protecting critical habitats and restoring damaged ecosystems.

Practical countermeasures can halt an insect extinction before it’s too late. All ecosystems should be preserved and protected to avoid collapses of those that rely on each other for survival. 

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