Biodiversity is too simple
This term from the field of ecology has become very popular for biological sustainability, and with good reason. Biodiversity implies the presence of many different species in a given area. The benefit of a biodiverse site is that it is more resilient to external change. Some might even refer to it as ‘healthy’ or ‘successful’, however these are mainly anthropomorphic interpretations of ecology. An ecosystem is not something that can be successful: it simply is. Success implies a purpose, however ‘purpose’ does not really exist in ecosystems. It is important to keep this in mind to understand the use and misuse of the concept of biodiversity.
In this blog I hope to convey its merits and its flaws. But mostly I wish to impart how ecological sustainability requires another perspective on life.
Our skewed perspective on life
This image, taken from the Active8-Planet newsletter, shows a typical representation of biodiversity. We see a variety of animals, mostly mammals, some plants and one arthropod. Pretty diverse right? Sure, from a human perspective this is the diversity we encounter consciously in our daily life. But it is not even close to representing the actual diversity of life on earth.
In the image above you can see a visual interpretation of the actual worldwide biodiversity in the animal kingdom. It shows that mammals and birds are only a very small part of the world’s ecosystem. Arthropods and fish have a much bigger presence! And this image is not representing numbers of individuals. You probably know that we are easily outnumbered by the number of ants living under our house. But this picture shows biomass! The sheer volume of arthropods on our planet outshines our presence almost 20 times. Also note that this is only the animals. If we take all living organisms into account (a.k.a. life), such as fungi, plants and bacteria, we get this (less pretty, but very accurate) picture.
Graphic representation of the global biomass distribution by taxa. Source: ‘The biomass distribution on Earth’ by Bar-On, Yinon M. et al. (2018)
In the graphic above you can see that the animals we see as symbols of biodiversity make up only a fraction of life on earth. The majority are by far plants, and next up we have bacteria and fungi. Even this group called archaea (cousins of bacteria, which most of you probably never heard of) have a bigger, more voluminous presence on our planet than all animals combined. Significantly. Interestingly, this distribution is not something that has changed much over time. Sadly, not many people are considering plants, bacteria or fungi when measuring biodiversity, even though their vast presence on our planet has an immense impact on our climate.
Less is more, smaller is bigger
Some ecosystems have been existing steadily for hundreds of thousands of years with a very low biodiversity of, say, 2 to 3 multicellular species. Examples of these sustainable low biodiversity ecosystems can be found in deserts or in extremely acidic lakes. Striving for more biodiversity in such sites could actually make these ecosystems less sustainable.
Indeed, biodiversity could indicate a higher resilience against external or internal stressors, however this is not always the case. Neither is the lack of change necessarily beneficial or more sustainable than certain fluctuations. The changing tide, for example, creates an environment of high biodiversity. If the tides would stop (I don’t know, maybe somebody blows up the moon), the sudden stability of the seawater would disrupt many lifecycles and cause massive extinction in marine life (not to mention the catastrophic effect of no more moon, but that’s another topic).
Note also the addition of the word ‘multicellular’ to the species count. Unfortunately in our strive for biodiversity we tend to focus on species we can see, or in worse cases, species we find useful. This forgoes the essential ecosystem functions of microbes. Though many of them are hard to eradicate (though we do like to try), forgetting about these microbes in our biodiversity ambition could create areas where they cannot thrive and therefore cause the collapse of the entire ecosystem. Also, since biodiversity tends to work with counting species, microbes can really throw off the count! They tend to be present in very high numbers, and possibly coexisting with thousands of different species, but still be invisible to the naked eye. In some cases their presence is negligible and in others they are essential. Once again proving that biodiversity is not a synonym for a sustainable ecosystem.
Let us embrace our flaws
So no, biodiversity is not in and of itself a useful goal to tally our biological sustainability. Does this mean we should ignore biodiversity? No. In many cases aiming for biodiversity has created more sustainable ecosystems. It is however not a one-size-fits-all solution. Ecosystems do not adhere to our human centric view of ‘healthy’ or ‘successful’. Each ecosystem is unique, has its own needs and many to us invisible and wholly important species working together, or destroying one another in harmony. My advice? Sustainability in ecosystems can be reached by giving it space and trusting nature to do what it does best. Most of these systems are simply beyond our understanding, but luckily they do not need us to understand in order to exist.
Photo by James Wheeler on Unsplash
