Dramatic rates of decline could lead to over 40 per cent of insect species becoming extinct in the next few decades, That’s the alarming conclusion of a comprehensive global review of 73 long-term scientific surveys of insects published this month by Francisco Sanchez-Bayo and Kris Wyckhuys in the journal Biological Conservation.
In terrestrial ecosystems, butterflies, moths, bees and dung beetles are the worst affected groups. In addition, four major groups of aquatic insects are also imperilled, having already lost a considerable proportion of species. The worst affected taxa were not restricted to specialists that occupy particular ecological niches, but also included many common generalists.
At the same time, the review found that a small number of highly adaptable generalist species are increasing as they fill the ecological niches vacated by declining species.
According to the review, habitat loss is the single largest driver of the declines. This stems from the conversion of land to intensive agriculture and urbanisation. Next up is pollution, mainly that by synthetic pesticides and fertilisers from farming. Invasive species, parasites and diseases are also playing a role. Climate change was also identified as an important driver, particularly in tropical regions.
It should be noted that while the review is presented as a global study, the vast majority of the 73 studies reviewed were from Europe and the US. This is due those regions having the most comprehensive historical records and a lack of long-term insect abundance studies for much of the rest of the world. For example, for the entire continents of South America and Africa the reviewers could find just one relevant study from Brazil and one from South Africa. This means that for huge parts of the planet we know very little about how insects are faring.
“The repercussions this will have for the planet’s ecosystems are catastrophic to say the least, as insects are at the base of many of the world’s ecosystems,” says the paper, by Francisco Sanchez-Bayo at the University of Sydney, Australia, and Kris Wyckhuys at the China Academy of Agricultural Sciences in Beijing. Because insects play crucial roles in ecosystems, declining insect populations around the world has catastrophic repercussions for plants, birds, fish, small mammals, and indeed all of life on earth, including ourselves.
To reverse the declines and safeguard the vital ecosystem services provided by insects, the authors advocate substituting current intensive agricultural practices with more sustainable, ecologically based practices as a matter of urgency. Ultimately the size of the human population and the resources we use determine how much wildlife will be lost. Protecting habitats is incredibly important, as is reducing the impact of farming, and tackling climate change.
Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232: 8-27.