While philosophers have spend centuries pondering the question of “Why is there something and not nothing”, a biologist is more likely to ask “Why is there so damn much of everything?”.
Global biodiversity is estimated at approximately 8.7 million eukaryotic species, while more than 85% have so far remained undescribed¹. Most of this diversity is found in the tropics, of which Panama serves as a good example – in Barro Colorado Island the 50 ha plot alone harbors a greater diversity of tree species than Western Europe; likewise, 120 species of bats have been recorded in Panama, compared to 45 in Europe. Diversity of the physical landscape, energy input and water availability have generally been considered as conducive to greater biological diversity, while interactions between species further drive diversification (e.g. the “race of arms” between toxic plant species and specialized herbivores.).
A systems perspective on diversity
But is biological diversity merely a function of geophysical diversity? Is it just the result of continued evolution? Looking at the biosphere from a complex systems point of view, there is no particular reason that diversity should be ever increasing or stabilizing at a high level. Greater structural diversity of the physical landscape may favor biological diversity but it doesn’t necessarily has to. One could imagine a complex landscape dominated by just a few very dominant species. Why haven’t we ended up with systems that consist of lower biological diversity?
The very fact that such a great variety of species exists on the planet – and that species diversity has been high for millions of years – suggests that biological diversity is not only a byproduct of evolution or the necessary result of a diverse physical landscape but as a fundamental feature which allows complex ecological systems (and the whole biosphere) to persist over time, and which allows these systems to adapt to change. Functionally redundant species usually respond differently to change (be it sudden or slow) – some might become threatened, others might strive – thereby providing an insurance against loss of ecological function. And if conditions change sufficiently that new niche space is created, an already diverse set of species will provide enough “raw material” to make use of it. In this sense, the diversity of a complex system is linked to redundancy, adaptation and resilience of the whole system – and systems which do not possess these qualities will eventually collapse. So far, the global biosphere has not collapsed but rather increased in complexity, and it might eventually survive us.
Diversity and natural resource management
What does this view on biodiversity imply for managing environmental systems? Because of redundancy and insurance effects, we might not experience immediate loss of function for a given ecological system if we reduce its diversity. However, we are likely to limit the system’s capacity to adapt and thereby its capacity to sustain its functions over time. Dealing with diversity requires experience over generations and is often associated with a set of social rules and norms that are sufficiently diverse themselves. The agroforestry systems of the Maya exemplify this. In these forest gardens – which probably date back to pre-Mayan civilizations – more than 350 species of plants have been recorded, of which the vast majority has been utilized by humans for a variety of different needs (food, clothing, medicine, etc.)². Keeping this kind of system intact requires skill and knowledge, which can also be passed on in the form spiritual tradition. During the Spanish conquest, settlers tended to simplify these systems – e.g. turning them into pasture – as they didn’t possess the necessary skills to make use of the forest gardens and simplification was a way to make them controllable.
Unfortunately, simplification of ecological systems ha been the rule rather than the exception for the last hundred years. This “command and control” paradigm is actually far more likely to create environmental problems than solving them³. It might therefore be the right time to promote and learn from ecological and social diversity, not only in conservation areas but especially in the context of multiple-use landscapes.
1: Mora, C. et al., 2011. How many species are there on earth and in the ocean? G. M. Mace, ed. PLoS Biology, 9(8), p.e1001127.
2: A., F., 2008. Dominant plants of the maya forest and gardens of El Pilar: implications for paleoenvironmental reconstructions. J.Ethnobiol., 28(2), pp.179–199.
3: Holling, C.S. & Meffe, G.K., 1996. Command and control and the pathology of natural resource management. Conservation biology, 10(2), pp.328–337.