By Adam Bakewell, Co-host of Generic Drift
Last week, insects took the news by swarm. A new review including studies from around the globe, published in Biological Conservation, finds that over 40% of insect species are declining and could be threatened with extinction. For the last 400 million years, insects have provided the foundations for entire ecosystems as consumers, the consumed, pollinators, and waste nutrient recyclers. Now they’re disappearing from habitats eight times faster than mammals and birds, and to lose them could trigger a catastrophic collapse in the world’s ecosystems.
The review brings together the findings of insect surveys from the 1830s right up until 2016, from around the world (but mostly Europe and the USA). Dung beetles, bees, moths, butterflies and ladybirds have all been hit particularly hard by the advancing of Earth’s sixth mass extinction - and the trends from the aquatic insect data paint an even worse picture. What’s to blame? Us, of course.
Specifically; feeding 7.7 billion humans is taking its toll. Intensive agriculture is highlighted in many of the studies as driving insect declines, and 12% of the world’s surface is currently used for agricultural crops. Throughout the last century, expansion of agricultural land on an industrial scale has altered landscapes beyond recognition. Where once diverse grassland and forest habitats supported insect communities, genetically-uniform monocultures now dominate much of the Earth’s surface. We modify the hydrology of landscapes to improve irrigation and drainage, altering habitats away from the fields. We use synthetic fertilisers to squeeze every bit of productivity out of the soil for human ends, polluting waterways in the process. And when a species does attempt to make the best out of this new landscape, we (for the most part) poison it.
We’ve simplified our landscapes to facilitate their management, but as we lose diversity in plants in search of the perfect field of wheat, we lose it at other levels within the system too. Without the intricacies of diverse floral architecture, we lose the species adapted to pollinate them. We lose the species that feed on these plants, and in turn the species (whether they be other insects or not) that feed on the consumers, and the species that feed on the waste of the consumers further up the food-chain. Urbanisation can similarly deplete biodiversity, though the authors of the review say this may be partially offset by urban parks and gardens acting as sources of novel habitats (because we like pretty flowers from across the world).
In their coverage, BBC News chose to focus on the consequences of declining insect populations. In the article they mention some of the tremendous services which insects provide: providing food, pollinating most of the worlds crops, replenishing soils and regulating the number of pests. But the headline, and the message for much of the article, is “Global insect decline may see ‘plague of pests’”.
This isn’t in fact what the paper was about, but the reasoning is fairly robust. Some insects don’t seem to mind what we’re doing to the planet, houseflies and some human-associated cockroaches for instance. Without the species that have evolved as their enemies out in nature, and with temperatures increasing through climate change allowing them to breed faster, a small number of insect species may overwhelmingly benefit from the changes of the Anthropocene. To focus on this as a negative is missing the point somewhat though. After each of the five preceding mass extinctions came a great genesis, where species adapted to fit into newly available niches. Of course, the scale of the loss of insect diversity is alarming, and we should do everything that we can to preserve the diversity that we have – but complaining that there’s now too many isn’t the way to go about it, or to engage the public about it. Those few success stories are probably the future of insects, and they shouldn’t be maligned.
Sánchez-Bayo, F. & K. A. G. Wyckhuys, 2019. Worldwide decline of entomofauna: A review of its drivers. Biological Conservation 232 8-27.
McGrath, M., 2019. Global insect decline may see ‘plague of pests’. BBC News. https://www.bbc.co.uk/news/science-environment-47198576 (Accessed 18 ii 2019).