by Justin N. Marleau
As the intensity and destructiveness of human activities increased over the course of the twentieth century, biologists began to worry about the loss of species, of genetic variation and of ecosystems. The maintenance of the variety of life required an overarching concept that could link such vastly different elements under one umbrella. In 1986, the term ‘biodiversity’ was coined and defined at a National Academy of Science (USA) meeting, and quickly spread throughout both the scientific and policy world. In 1992, the Convention on Biological Diversity established a legal definition of biodiversity, which is “the variability among living organisms from all sources […] includes diversity within species, between species and ecosystems”.
However, ‘biodiversity’ is falling out of favour. Mentions about biodiversity in the media have held steady for the past thirty years, despite growing awareness of a possible ‘sixth extinction’ event. Such a disconnect between the term and the loss of life led The Guardian to update to its style guide to drop the use of ‘biodiversity’ in favour of ‘wildlife’ in order to emphasize that “the subject involves living things”. It is striking that a term used to describe the variety of life on the planet could be viewed as one not involving living things, yet here we are.
From Legagneux, P., Casajus, N., Cazelles, K., Chevallier, C., Chevrinais, M., Guéry, L., … & Ropars, P. (2018). Our house is burning: discrepancy in climate change vs. biodiversity coverage in the media as compared to scientific literature. Frontiers in Ecology and Evolution, 5, 175.
What happened? Some insights can best be gleamed by considering conceptual, sociological and philosophical foundations of the biodiversity concept. While many practicing biologists and biological societies subscribe to the all-encompassing definitions of biodiversity, there are difficulties with its use. For example, does an exotic species contribute to local biodiversity? Some biologists say yes, others say no.
The vagueness in the concept of biodiversity is grounds for concern in the field of conservation and in management. For example, definitions of ‘biodiversity’ commonly include ‘ecosystems’. However, ecosystems are strongly identified with inorganic properties and conditions, such that there is a conflation between the organic and inorganic. There are also issues with defining ecosystem boundaries. One way to avoid this issue is to drop ‘ecosystems’ entirely from the definition.
There are also issues with the normative values that are associated with the concept. Biodiversity is commonly viewed as a ‘good’ in itself or as something that provides goods and services (i.e. biodiversity leads to ecosystem functioning which leads to ecosystem services which leads to human well-being). However, if the biodiversity is due to non-native species, then there is great uncertainty about its value. Furthermore, is it ‘good’ to generate diversity through genetic engineering? Perhaps we need to ‘scientize’ biodiversity or make it strictly normative to make it useful.
But perhaps such half measures are insufficient. Carlos Santana (not that Carlos Santana, this Carlos Santana) has argued that as a scientific concept, ‘biodiversity’ is a failure. Scientists do not measure ‘biodiversity’, but rather measure species richness or allele frequencies. Furthermore, ‘biodiversity’ is not something that can explain the lack of fluctuations in biomass overtime, but only acts as a proxy for the specific causal mechanism. The main complaint is that ‘biodiversity’ is an amalgam of uncorrelated concepts and should be replaced by more specific concepts.
Looking at this landscape of opinions and arguments, it is clear that ‘biodiversity’ requires some trimming to be useful. There is very little reason to explicitly incorporate ecosystems in the definition when we draw hard distinctions in our work (i.e. biodiversity-ecosystem function research should just be ‘biodiversity function’ if we accepted the broad definition). Such a biotic definition, while not fully measurable in most cases, would at least alleviate confusion in the press and public about what it refers to.
The normative aspects of the biodiversity concept are more difficult to address. Focusing on the positive outcomes of biodiversity and/or its value in itself is important for conservation biology and ecology. However, these components are not necessary to those simply interested in patterns and processes in ecological systems. Perhaps it can be useful in these cases to be explicit and refer to the ‘value of biodiversity’ rather than ‘biodiversity’ per se, since much scientific work is agnostic on the particular value of biodiversity in a given system of study.
Despite these caveats, biodiversity is an important, unifying concept in our lexicon. We should not give it up for ‘wildlife’ or other terms that limit the scope of our interests excessively. There is a definite need to make ‘biodiversity’ more understandable to the public and the popular press, which requires us to make the definition more intelligible. In my view, the best way forward is to focus on the ‘variety of living things’ and move away from including non-biotic parts into such an already broad concept. This change, at least, answers the objections of the press about biodiversity not referring to living things.
Justin Marleau is a research associate at McGill University who develops mathematical models and theoretical concepts for ecological and evolutionary problems. His current projects include modelling the evolutionary rescue and ecological sorting within perturbed aquatic metacommunities at the Large Experimental Array of Ponds and extending meta-ecosystem theory to include non-resource aspects of matter. He has also worked as a college professor and a federal government science policy analyst.
Visit Justin’s website or follow him on twitter @jnmarleau