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Global insect population decline may lead to pest plagues

Populations of cockroaches and houseflies are thriving because many of their natural enemies are disappearing
by TR Pakistan

A scientific review of insect populations has found that 40 percent of insect species are declining around the globe. The review is based on 73 studies that have been published over the past 13 years.

Bees, ants and beetles have been found to be declining eight times faster than mammals, birds or reptiles. Agricultural practices, insecticide use and climate change were found to be the main factors leading to these changes.

“The main factor is the loss of habitat, due to agricultural practices, urbanization and deforestation,” said the study’s lead author Dr Francisco Sánchez-Bayo, from the University of Sydney.

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“Second is the increasing use of fertilisers and pesticides in agriculture worldwide and contamination with chemical pollutants of all kinds. Thirdly, we have biological factors, such as invasive species and pathogens; and fourthly, we have climate change, particularly in tropical areas where it is known to have a big impact,” he added.

The study also brought attention to the rapid decline of flying insects in Germany and the massive drop in size of insect populations in the tropical forests of Puerto Rico, which has been linked to rising temperatures.

“It’s not just about bees, or even about pollination and feeding ourselves — the declines also include dung beetles that recycle waste and insects like dragonflies that start life in rivers and ponds,” said Matt Shardlow from UK campaigners Buglife. “It is becoming increasingly obvious our planet’s ecology is breaking and there is a need for an intense and global effort to halt and reverse these dreadful trends. Allowing the slow eradication of insect life to continue is not a rational option.”

Some less savoury species however, such as houseflies and cockroaches, were found to be thriving.

“Fast-breeding pest insects will probably thrive because of the warmer conditions, because many of their natural enemies, which breed more slowly, will disappear, ” said Professor Dave Goulson from the University of Sussex, who was not involved in the review. “It’s quite plausible that we might end up with plagues of small numbers of pest insects, but we will lose all the wonderful ones that we want, like bees and hoverflies and butterflies and dung beetles that do a great job of disposing of animal waste.”