Written by Claire’s been reading. And I for one don’t envy her. Of a 119-page document (one of many), a single figure she quoted jumped out as rather surprising for me; and, given a single sentence can provoke so much subsequent analysis, I fear for what the remaining 118.9 pages may contain.
The particular statistic mentioned was that when a habitat’s size is increased by a factor of ten, the number of species only doubles. I’m not sure of the wider context in which this was stated – and in particular whether it was presented as a problem – but it immediately implies a number of things as far as I can tell:
1. Species density is non-linear. That is to say that the number of species found per unit of land area is not linearly correlated. The following chart based on the quoted statistic shows this more clearly (assuming a starting point of 100 species in 100 units of land area):
2. As land area decreases, the number of species decreases (tending towards zero) but at a much slower rate. This implies that you’ll run out of land leaving some species with no habitat (but still present).
3. As land area increases, the number of species increases (tending towards infinity) but at a much slower rate. This implies (given a finite maximum land area on our planet) that there is a finite maximum number of species the earth can accomodate.
4. The non-linear relationship implies some kind of ‘compression’. That is to say, as land area is reduced by 90%, the species density (note not population density) is reduced by only 50%. This equates to an increase in the number of species per land-area-unit of 500%.
5. This increase of 500% implies an inherent change to inter-species relationships; specifically the food chain (to me at any rate). After all, as you crush competing species together with ever-increased resource shortages – living space, food resources, etc. – it makes sense that competition will increase correspondingly. Dramatic changes to environmental or inter-species relationships are – under Punctuated Equilibrium Darwinism – believed to be a key driver for an increase in the rate of evolution.
6. An increase in the rate of evolution should be measurable, primarily by intra-species variations.
This last one is particularly interesting to me. If punctuated equilibrium were true, and we would see an increased rate of evolution in habitats under threat (and assuming the rate of evolution were fast enough to cope with the rate of habitat destruction), then is habitat destruction implicitly bad? Is it true to say that evolution is inherently positive, given its definition being ‘survival of the fittest’?
And, what of the inverse? The above supposition would suggest that given an abundance of available habitat and resources, the rate of evolution would slow down. Is that inherently bad?
I don’t know the answers, or even whether inferences drawn from theories like PED are necessarily valid. But like I say, I don’t envy Claire the work she has ahead – just the subject matter 
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