Written by: Georgia Kahan
Insects seem to get the short end of the stick when it comes to conservation. They’re hardly the most charismatic creatures and there’s probably a reason why the iconic World Wildlife Fund logo is the cute and cuddly panda bear rather than, say, a fly. But conservation isn’t about what pulls on your heartstrings, it’s central to the way we live. Now you might say that you don’t mind that there aren’t as many midges anymore, but you might think differently when you discover that the whole chocolate industry depends on them.1 Given that insects play an important part of the world’s ecosystem (decomposition, pollination, position in food webs etc.)2 we really should be worried if they’re at risk. So, when headlines such as “insect apocalypse”3 or “insectageddon”4 appeared earlier this year, it undoubtedly raised some alarm.
The study that these stories were referring to was a global scientific review on the population of insects. Its researchers conducted a meta-analysis, meaning that they didn’t count the bugs themselves but analysed a lot of studies from people who did. They claimed that the mass of insects is falling by 2.5% a year and 41% of species are threatened with extinction.5
It’s not perfect though. For starters, the studies included in the meta-analysis were selected through a database using the search terms “insect”, “decline” and “survey”,5 meaning that any that discovered an overall increase in insects were excluded. So there was a bias in the analysis from the get-go. Even once the studies were chosen they weren’t entirely representative for a so-called “global study”. Of the 73 studies, 60 examined insects in North America and Europe,5 which makes extrapolating globally a bit tricky.6
And how about that 2.5% decline? Turns out that figure only came from three studies: Germany, UK and Puerto Rico.5 One problem with these is that the insect population is measured using biomass, rather than actually counting the number of individuals. It’s a good rough estimate of numbers but not great for determining the actual composition of the community because it doesn’t account for changes in mass due to different species or life stages.7
The methodology of the three studies is sketchy too. Of particular concern is the Puerto Rico study which only measured insect population in two periods over 30 years apart8 so it’s hard to conclude that this snapshot is representative of the population overtime.
Although current data on insect populations may be too piecemeal to warrant such hyperbolic claims, this isn’t to say that insect decline isn’t a real problem. In New Zealand the main cause is said to be habitat destruction and introduced predators.9 943 species of our terrestrial invertebrates are classified as threatened and there’s evidence they’re dropping in numbers.10 In fact, you may have recently heard about an endemic beetle that’s now tragically a goner.11 What’s just as worrying should be New Zealand’s lack of good data in this area,10 which is characteristic of a worldwide problem. So while we wait for science to catch up with the media that reports on it, next time you take a bite of chocolate, spare a thought for the insects.
1 Osterloff, E. (2018, May 14th). Flies are saving your chocolate cravings. Retrieved March 2019, from Natural History Museum: http://www.nhm.ac.uk/discover/flies-are-saving-your-chocolate-cravings.html
2 Weisser, W. W., & Siemann, E. (2013). Insects and ecosystem function. Springer Science & Business Media.
3 Yong, E. (2019, 19 February). Is the Insect Apocalypse Really Upon Us? Retrieved March 2019, from The Atlantic: https://www.theatlantic.com/science/archive/2019/02/insect-apocalypse-really-upon-us/583018/
4 Palmer, S. (2019, Feburary 12th). Insectageddon: New Zealanders have ‘two weeks of life’ after insect apocalypse – expert. Retrieved March 2019 from Newhub: https://www.newshub.co.nz/home/new-zealand/2019/02/insectageddon-new-zealanders-have-two-weeks-of-life-after-insect-apocalypse-expert.html
5 Sánchez-Bayo, F., & Wyckhuys, K. A. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8-27.
6 Albers, C. (2019, March 2nd). Insectageddon. More or Less: Behind the Stats. (A. Ruth, Interviewer, & D. Graham, Producer). Retrieved March 2019 from BBC: https://www.bbc.co.uk/programmes/p072c44x
7 Weir, J. (2019, March 2nd). Insectaggedon. More or Less: Behind the Stats. (R. Alexander, Interviewer, & D. Graham, Producer). Retrieved March 2019 from BBC: https://www.bbc.co.uk/programmes/p072c44x
8 Lister, B. C., & Garcia, A. (n.d.). Climate-driven declines in arthropod abundance restructure a rainforest food web. Proceedings of the National Academy of Sciences, 115(44), E10397-E10406.
9 McGuinness, C. A. (2007). Carabid beetle (Coleoptera: Carabidae) conservation in New Zealand. Journal of Insect Conservation, 11(1), 31-41.
10 Hitchmough, R., Bull, L., & Cromarty, P. (2005). New Zealand threat classification system lists. Department of Conservation. Wellington: Science & Technical Publishing.
11 Hancock, F. (2019, February 13). Hello cows, bye-bye rare beetle. Retrieved March 2019, from Newsroom: https://www.newsroom.co.nz/2019/02/12/440614/hello-cows-bye-bye-rare-beetle