Insects: a barometer for environmental health - National Insect Week

Max Anderson is a PhD student at the University of Sussex. His research has been focussed on understanding the impacts of livestock farming systems on wildlife, with a particular focus on bats and their invertebrate prey.

Max Anderson (Twitter: @maxando)

In every nook and cranny of our planet, there are hidden worlds where insects work tirelessly, day and night to pollinate crops, improve soil quality, maintain and create sustainable and healthy ecosystems – all for free!

Insects are the most abundant animals on earth, and are estimated to make up around 90% of all animal species. They play an integral role in the survival of humans by providing a range of beneficial services including pollination of crops, pest suppression and recycling of organic matter. Insects are very sensitive to changes in the environment, and there are growing concerns about the global state of insects, with declines in many species being reported. Habitat loss has played a significant role in the declines of some insects, particularly for some specialist species, which require very specific conditions within habitats in order to survive.

Beetles (Coleoptera) are the largest order of insects, with over 350,000 described species worldwide, which makes up around 25% of all known species. In the UK alone, there are over 4000 species, which occupy a wide range of habitats. Within agricultural ecosystems, dung beetles play an crucial role in sustainability, maintaining healthy soils by recycling nutrients from animal dung, reducing greenhouse gas emissions and dispersing seeds. The burial of dung also supresses parasites, which ultimately reduces the need to treat livestock with antiparasitics. An assessment of the services provided by dung beetles estimated that they save the UK’s cattle farming industry £347 million per year (Benyon et al. 2015). Worryingly, over 50% of the UK’s 60 dung beetle species are listed as being threatened to some degree (Lane and Mann, 2016)

As well as being reliant on livestock and grassland habitats, some dung beetles also depend on the dung of native, wild mammals in a range of other habitats. In addition to the ecosystem services provided by dung beetles, they are also an important source of food for many mammal species. Adult beetles are a crucial component of the diet for serotines, noctules and particularly for juvenile greater horseshoe bats, while many species of small terrestrial mammals will feed on beetle larvae.

The next largest order of insects are Lepidoptera, which includes butterflies and moths. In the UK, there are around 60 species of butterfly and 2,500 species of moth, both of which contribute significantly towards pollination of wild plants and crops. Moths are largely nocturnal, and compared to butterflies, there is far less known about the extent of pollination services provided by them. Adult moths make up a considerable proportion of the diet for many bat species including long-eared bats, greater horseshoe bat and barbastelle. Also, the pupae and larvae of moths are consumed by shrews, mice and other small terrestrial mammals. Given their sensitivity to changes in the environment, moths are a valuable group of indicator species for environmental health. Long-term trends in the abundance of moths in Britain have shown that many species are declining (Fox et al. 2021). These declines have been strongly linked to habitat loss and reduced connectivity of suitable habitats, and like their bat predators, they can be negatively impacted by artificial light at night.

Managing our gardens, parks, farms and urban areas to benefit insects on a local and landscape scale is vitally important. This will not only allow us to reap the rewards from the astounding services provided by these animals, but it is also vital for maintaining and improving the status of some of our most threatened native, wild mammals.

References:

Beynon, S.A., Wainwright, W.A. and Christie, M., 2015. The application of an ecosystem services framework to estimate the economic value of dung beetles to the UK cattle industry. Ecological Entomology, 40, pp.124-135.

Fox R, Dennis EB, Harrower CA, Blumgart D, Bell JR, Cook P, Davis AM, Evans-Hill LJ, Haynes F, Hill D, Isaac NJB, Parsons MS, Pocock MJO, Prescott T, Randle Z, Shortall CR, Tordoff GM, Tuson D, Bourn NAD (2021) The State of Britain’s Larger Moths 2021. Butterfly Conservation, Rothamsted Research and UK Centre for Ecology & Hydrology, Wareham

Lane, S. A. & Mann, D. J. 2016. A review of the status of the beetles of Great Britain: The stag beetles, dor beetles, dung beetles, chafers and their allies-Lucanidae, Geotrupidae, Trogidae and Scarabaeidae, Natural England.

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