Why (I think) biodiversity matters
This topic is a source of much debate over at Jen Marohasy's blog. The following is my reply, which I've decided to re-post in full here.
Louis asks what is biodiversity? In my view, it’s simply an extension of genetic diversity (and epigenetic diversity, but I won’t go into that as it complicates things a little). Within a species there is often, though not always, genetic variation (i.e. different forms or alleles of the same genes). Whether you take a cubic metre of soil, a paddock, the Great Barrier Reef, of the earth in its entirety, you get a series of genetic interactions mediated by direct or indirect interactions at the organism level. So even though genes encoded by the DNA of different organisms never come into direct contact, genes are changed by the evolutionary pressures resulting from interactions between organisms.
When it comes to pathogen-host interactions, the gene-for-gene hypothesis is fairly well accepted (it’s worth googling). In my view, there’s no reason to limit this hypothesis to pathogen-host interactions as it works equally well with all interactions, whether they be mutually beneficial, predator/prey etc.
So how does this explain why biodiversity is important?
Firstly, look at why genetic diversity is important to a species. When an organism’s environment is unchanging it’s actually not that important. But when an organism’s environment is variable, genetic diversity allows the species as a whole to cope with change, though individuals with the ‘wrong’ genes loose out. If this concept is extended to all species, biodiversity makes the Earth’s biological systems as a whole more robust.
If climate change, for example, knocks out one species of nitrifying bacteria, bacterial genetic diversity will hopefully allow another species to fill its place and keep the nitrogen cycle going happily on its way. Reduce the amount of diversity and you reduce the amount of raw material you have available to compensate for change, to act as a buffer as it were.
Talk of previous mass extinctions as normal is not helpful from a human viewpoint. A collapse of the nitrogen or carbon cycles, for example, would be catastrophic. The reason why this is unlikely to happen is that there is plenty of natural redundancy built in to the system. The redundancy comes from biodiversity, which is really genetic diversity, and genetic diversity is self-promoted by interactions with genetically diverse organisms (and diverse non-organic environments).
By artificially reducing both genetic and non-organic environmental diversity, we are making adaptation in a changing world more difficult. Instead of small, gradual changes to the environment, you get sudden lurches to extremes as the natural buffering capacity is no longer sufficient. This isn’t a good thing for human civilization or the large cuddly, furry animals we hold near-and-dear.
Louis asks what is biodiversity? In my view, it’s simply an extension of genetic diversity (and epigenetic diversity, but I won’t go into that as it complicates things a little). Within a species there is often, though not always, genetic variation (i.e. different forms or alleles of the same genes). Whether you take a cubic metre of soil, a paddock, the Great Barrier Reef, of the earth in its entirety, you get a series of genetic interactions mediated by direct or indirect interactions at the organism level. So even though genes encoded by the DNA of different organisms never come into direct contact, genes are changed by the evolutionary pressures resulting from interactions between organisms.
When it comes to pathogen-host interactions, the gene-for-gene hypothesis is fairly well accepted (it’s worth googling). In my view, there’s no reason to limit this hypothesis to pathogen-host interactions as it works equally well with all interactions, whether they be mutually beneficial, predator/prey etc.
So how does this explain why biodiversity is important?
Firstly, look at why genetic diversity is important to a species. When an organism’s environment is unchanging it’s actually not that important. But when an organism’s environment is variable, genetic diversity allows the species as a whole to cope with change, though individuals with the ‘wrong’ genes loose out. If this concept is extended to all species, biodiversity makes the Earth’s biological systems as a whole more robust.
If climate change, for example, knocks out one species of nitrifying bacteria, bacterial genetic diversity will hopefully allow another species to fill its place and keep the nitrogen cycle going happily on its way. Reduce the amount of diversity and you reduce the amount of raw material you have available to compensate for change, to act as a buffer as it were.
Talk of previous mass extinctions as normal is not helpful from a human viewpoint. A collapse of the nitrogen or carbon cycles, for example, would be catastrophic. The reason why this is unlikely to happen is that there is plenty of natural redundancy built in to the system. The redundancy comes from biodiversity, which is really genetic diversity, and genetic diversity is self-promoted by interactions with genetically diverse organisms (and diverse non-organic environments).
By artificially reducing both genetic and non-organic environmental diversity, we are making adaptation in a changing world more difficult. Instead of small, gradual changes to the environment, you get sudden lurches to extremes as the natural buffering capacity is no longer sufficient. This isn’t a good thing for human civilization or the large cuddly, furry animals we hold near-and-dear.
posted by Green Scientist at 6:00 pm
