Scientists reveal the causes behind the global crash in insects

By Alice Clifford via SWNS

The reasons behind a "global crash" in insect numbers have been revealed by scientists.

The drop has a huge knock-on effect on pollination and also on animals that feed off insects.

Study author Dr. Florian Menzel from the Institute of Organismic and Molecular Evolution at Johannes Gutenberg University of Mainz, Germany, said: "Generally speaking, a decline in insect diversity threatens the stability of ecosystems.

"Fewer species means that there are fewer insects capable of pollinating plants and keeping pests in check.

"And, of course, this also means that there is less food available for insect-eating birds and other animals.

"Their continued existence can thus be placed at risk due to the decline in insect numbers."

A 2019 review found that populations of 41 percent of insect species are in decline globally, with one-third being threatened by extinction.

It estimates that the total mass of insects is dropping by 2.5 percent each year.

Now a new study blames the rise of agriculture, building development, climate change and the spread of invasive animals for causing the decline.

And ecosystems already deteriorated by humans thanks to trade and tourism are more susceptible to climate change.

With rising temperatures, insects are forced away from their natural habitats, putting them at risk.

Insects that have specialized to specific habitats are most at risk as they are more vulnerable to changes.

Also, invasive species can establish themselves easier in habitats damaged by human land use and displace native species.

With the drop in insects, these invasive species can thrive and increase, reducing insect diversity.

This has been seen in Brazil, where there has been an invasion of non-native insect- eating fishes that has caused a major decline in freshwater insects.

Dr. Menzel said: "In view of the results available to us, we learned that not just land-use intensification, global warming, and the escalating dispersal of invasive species are the main drivers of the global disappearance of insects, but also that these drivers interact with each other.”

Not only does each specific animal suffer, elements of their habitat have also started to wane as a consequence.

The loss of bumblebee diversity has led to a decline in plants that rely on certain bumblebee species for pollination.

Dr. Menzel added: "It looks as if it is the specialized insect species that suffer most, while the more generalized species tend to survive.

“This is why we are now finding more insects capable of living nearly anywhere while those species that need specific habitats are on the wane.”

The researchers promote a particular approach for future research into insect decline.

Standardized techniques should be employed to monitor insect diversity across many habitats and countries.

They also propose the creation of a network of interconnected nature reserves so that species can move from one habitat to another.

If this was in place, less heat-tolerant insects would be able to migrate from areas where global warming is causing temperatures to rise to higher elevations or cooler regions.

They also suggest measures are needed to reduce the spread of invasive animal and plant species through globalized trade and tourism.

Dr. Menzel said: "This is another problem that has become extremely serious in the last decades."

"As evidence of an ongoing global crash in insect populations increased over the last few years, we decided it was time to publish this study.

“Our aim was not to document insect population declines but to better understand their causes and consequences."

The study was published in the journal Biology Letters.