Jeff Sachs on biodiversity

His new book Common Wealth devotes an entire chapter to this important topic.  Sachs writes:

The main lesson of ecology is the interconnectedness of the various parts of an ecosystem and the dangers of abrupt, nonlinear, and even catastrophic changes caused by modest forcings…It is a basic finding that biological diversity increases the productivity and resilience of ecosystems.  With more species filling more niches in a given location, a biodiverse ecosystem is better buffered against external shocks in is more adept at cycling nutrients, capturing solar radiation, utilizing water resources, and preventing the takeover of the system by single predators, weeds, or pathogens.  In other words, preserving biodiversity helps to preserve all aspects of ecosystem functions.  Removing one or more species from an ecosystem, for example, by selective harvesting of trees or fish or hunted animals, can lead to a cascade of ecological changes with large, adverse, and nonlinear effects on the functioning of the ecosystem.

Now, loyal MR readers may remember that I am genuinely uncertain how much we should worry about the loss of biodiversity.  I do know the following:

1. Many smart people who know much more science than I do are very worried about the loss of biodiversity.

2. Given that the human population has ballooned for the foreseeable future, massive losses in biodiversity are inevitable.  The question is how bad the marginal losses will be, if we do not adapt policy accordingly.

3. If I had to conduct a debate and argue that the marginal loss of biodiversity was going to be a tragedy for human beings (obviously, I can see the loss to animals, and yes I do count that for something), I would not do very well.  Yes Yana’s children won’t eat tuna and then I would sputter something about carbon and nitrogen cycles.

So OK readers, help me out.  I’ve read Sachs’s passage and I don’t think I disagree with any of the claims in it.  But I still cannot articulate to a skeptic exactly what marginal disaster will come if we do not take drastic action to preserve biodiversity.

Please use the comments to set me straight.  What exactly will go wrong?  And do not compare seven billion humans to pristine nature.  Compare seven billion humans with bad biodiversity policy to, say, five billion humans with a pretty good biodiversity policy.  What exactly is the difference?  What are these costs as a percentage of gdp? 

Please be as specific as possible; I genuinely would like to learn more.


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