Bioabundance and Biodiversity: Why focusing on extinction could overlook bigger problems

The loss of plants, animals and other organisms with which we share our planet is quite rightly a hot topic. Preventing extinction is often the main driver of conservation policy and funding.

There are plenty of initiatives to save threatened species, and why not? Trying to save an endangered species is not only morally right but it makes a compelling story. The public and major funding bodies love funding projects to save individual species, particularly if they are charismatic ones such as water voles, hedgehogs, curlews or swifts. Projects to prevent or reverse species extinctions have been a core part of Gloucestershire Wildlife Trust’s work for nearly 60 years and we are proud that we have helped to save species such as the large blue butterfly (Phengaris arion). But, species specific programmes focus on a minuscule percentage of our biodiversity, so are we missing an important part of the bigger picture by focusing so much on the loss of individual species? 

The Earth is now within a sixth mass extinction event, the like of which has not been seen since dinosaurs were wiped out 65 million years ago. Scientific data shows that the number of species going extinct is now 1000 times higher than natural rates over the last 10 million years [1] with an estimated 1 million species facing extinction within decades [2].  This is serious stuff, but closer examination reveals that even the accelerated level only equates to 0.1 extinctions per million species per year and the UK extinction rate is 1-5% species per 100 years [3]. This doesn’t mean that we shouldn’t be concerned that human activity is irrefutably driving the mass extinction of life on Earth, but even at these vastly accelerated rates extinction remains rare and other aspects of biodiversity loss may be just as important.  

At this point, it is probably worth a whistle-stop look at what biodiversity is. Biological diversity (biodiversity) is the variability of life. It can be measured in many different ways, but at basic level it comes down to four components [4] 

  1. The number of different species (species richness) 

  1. Abundance (population sizes) 

  1. Phylogeny (genetic differences) 

  1. Function (the range of roles provided in an ecosystem) 

By focusing conservation efforts on biodiversity loss and preventing the extinction of specific species, we risk overlooking three of the four components of biodiversity. No doubt preventing species extinctions has a knock-on benefit for abundance, phylogeny and function, but what are the pitfalls of this approach? This is perhaps best explained by the long-term study of airborne insects on nature reserves in Germany, which recorded a 76% decline in biomass (a measure of abundance) between 1990 and 2011 [5]. Such a decline is likely to be devastating for an ecosystem considering the wide range of vital functions performed by insects, such as pollination, nutrient cycling and their importance as food for other species.  

The German study recorded a huge, ongoing and rapid decline in biodiversity, including both common and rare species. However, had the study focused on extinction and species richness rather than abundance the decline would have appeared less severe, as many of the species were still present just in lower numbers.  Herein lies the issue, focusing on species richness and preventing extinction can vastly underplay the scale of loss and the amount of damage that is being done to our ecosystems.  It also tempts us to focus efforts on firefighting interventions that save a small number of species rather than tackle the more difficult job of restoring ecosystems for all species.  

We are increasingly hearing from people who have lived in Gloucestershire all their lives and are devastated by declines in the abundance of common species. We hear stories of hedgerows and fields that were once ‘alive with hundreds of butterflies’ but now harbor just a handful in the peak of summer. People who used to find clouds of moths around their lightbulbs in the evening if a window was left open, now rarely see a moth. Unless you have the time to read lots of scientific research, it’s easy to not realise just how much has been lost, and therefore, you accept what you see as normal. There is a term to describe this, it is called ‘shifting baseline syndrome’ and it’s one of the biggest obstacles to widespread and urgent action for wildlife [6]. To put it simply, too many people feel they still see a lot of wildlife but don’t realise that they are seeing small remnants of what we once had, as a result there is a lack of urgency for action.  

Tackling biodiversity loss is a challenge not unlike that faced by the NHS. In a world of limited resources, how do you balance your efforts between treating those who are sick and stopping more people getting sick? It’s easier to install homes for hedgehogs than tackle the real challenges, which is the fragmentation and degradation of their habitat and the loss of abundance of insect prey. Why? Because that means fundamentally rethinking how we garden, how we build houses and roads and how we produce our food. Focusing on quick fixes for single species can give the impression that we are overachieving and doing a better job of saving wildlife than we actually are.  

Extinctions are rare (albeit increasing) and saving one charismatic species can take attention and resources away from addressing more fundamental aspects of biodiversity declines, such as the widespread loss of abundance. This is particularly pertinent as the charismatic species we tend to focus on saving are rarely the most important species for maintaining healthy functioning ecosystems. Re-focusing our efforts on reducing declines in abundance, functioning and genetic diversity forces us to think about restoring ecosystems on large scale, which ultimately will reduce extinctions as well. 

Taking an ecosystem approach means managing nature reserves as part of a connected landscape of habitats rather than as an isolated site where we focus on a small number of charismatic species This will ensure that we do not fall into the trap of ‘gardening’ nature reserves to achieve the maximum number of species in that space, when the nature reserve is likely to be too small to support sustainable long-term populations of those species. It will also make sure that we do not overlook species which form a significant part of bio abundance, such as soil fungi, bryophytes and the lesser known invertebrates, which are under-recorded but typically form a significant proportion of the bio abundance and are vital to a healthy ecosystem To do this we will  need the support and understanding of people who love wildlife and love our nature reserves as we shift our approach to reserve management.    

Declines in abundance are the starting point for extinction, so much like the NHS perhaps we should re-balance our efforts between saving threatened species and tackling the difficult but vital system changes that will stop species getting to that state in the first place. 

 

[1]J. M. De Vos, L. N. Joppa, J. L. Gittleman, P. R. Stephens, and S. L. Pimm, “Estimating the normal background rate of species extinction,” Conserv. Biol., vol. 29, no. 2, pp. 452–462, 2015. 

[2]M. Fischer et al., “IPBES: Summary for policymakers of the regional assessment report on biodiversity and ecosystem services for Europe and Central Asia of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.,” 2018, pp. 1–48. 

[3]C. Hambler, P. . Henderson, and M. R. Speighta, “Extinction rates, extinction-prone habitats, and indicator groups in Britain and at larger scales,” Biol. Conserv., vol. 44, no. 2, pp. 713–721. 

[4]S. M. Scheiner, E. Kosman, S. J. Presley, and M. R. Willig, “The components of biodiversity, with a particular focus on phylogenetic information,” Ecol. Evol., vol. 7, no. 16, pp. 6444–6454, 2017. 

[5]C. A. Hallmann et al., “More than 75 percent decline over 27 years in total flying insect biomass in protected areas,” PLoS One, vol. 12, no. 10, 2017. 

[6]S. Masashi and G. K. J, “Shifting baseline syndrome: causes, consequences, and implications,” Front. Ecol. Environ., vol. 16, no. 4, pp. 222–230, 2018.