Se vogliamo che tutto rimanga come è, bisogna che tutto cambi!
If we want things to stay as they are, everything must change!
"There are very strong indications that the current rate of species extinctions far exceeds anything in the fossil record."
This is from Magurran and Dornelas, writing in Phil Trans Royal Society, the PNAS of the old world.
Joe Romm has more. You can accuse Joe of overstating his case sometimes, but "far exceeds anything in the fossil record" is something that is really, really, really hard to exaggerate.
The scary assertion is referenced back to The Future of Biological Diversity in a Crowded World by Robert May (2002).
He shows this graph of the great extinctions of the past:
and claims
"There are very strong indications that the current rate of species extinctions far exceeds anything in the fossil record."
This is from Magurran and Dornelas, writing in Phil Trans Royal Society, the PNAS of the old world.
Joe Romm has more. You can accuse Joe of overstating his case sometimes, but "far exceeds anything in the fossil record" is something that is really, really, really hard to exaggerate.
The scary assertion is referenced back to The Future of Biological Diversity in a Crowded World by Robert May (2002).
He shows this graph of the great extinctions of the past:
and claims
recent extinction rates in well-documented groups haveMay makes three cases for conservation:
run one hundred to one thousand times faster than the
average background rates
Such figures correspond to likely extinction rates of a
factor of ten thousand, give or take at most an order of
magnitude, above background, over the next century or
so. This represents a sixth great wave of extinction, fully
comparable with the Big Five mass extinctions of the
geological past
A narrowly utilitarian argumentYet he admits that these arguments may not be seen as compelling. Personally, I find the highlighted text dispositive. Anyone who has read Lovelock's Gaia books will understand that at least conceivably we may breaking things which we may never have the capacity to fix.
One argument for the preservation of biological diversity
is narrowly utilitarian. It correctly emphasizes the benefits
already derived from natural products, as foods,
medicines, and so on. Currently, 25% of the drugs on the
shelves in the pharmacy derive from a mere 120 species
of plants. But, throughout the world, the traditional
medicines of native peoples make use of around 25,000
species of plants (about 10% of the total number of plant
species); we have much to learn. More generally, as our
understanding of the natural world advances, both at the
level of new species and at the level of the molecular
machinery from which all organisms are self-assembled,
the planet’s genetic diversity is increasingly the raw stuff
from which our future can be constructed. It seems a pity
to be burning the books before we can read them, and
before we can create wealth from the recipes on their
pages.
A broadly utilitarian argument
Another class of arguments is more diffusely utilitarian.
The interactions between biological and physical processes
created and maintain the earth’s biosphere as a
place where life can flourish. With impending changes in
climate caused by the increasing scale of human activity,
we should be worried about reductions in biological
diversity, at least until we understand its role in maintaining
the planet’s life-support systems. The first rule of
intelligent tinkering is to keep all the pieces.
An ethical argument
For me, however, a third class of argument is the most
compelling. It is clearly set out by the UK Government in
This Common Inheritance22. It is ‘the ethical imperative
of stewardship . . . we have a moral duty to look after our
planet and hand it on in good order to future generations’.
Truly horribly frightening, to me at least. The first "narrow utility" argument and its reference to native peoples using ~1/10 of all plant species reminds me of E.O. Wilson's book Biodiversity. He pointed out that when that book was written marine biologists had no idea to the nearest order of magnitude how many species of bacterium there were in the oceans. On top of that, we're forever discovering new plant species, some even very close to home (Wollemia nobilis <3 hours drive from Sydney for example). And yet we're wiping this stuff out faster than any time since the last great extinction, mostly often without knowing what we're wiping out and frequently wiping out stuff we've only just found, let alone knowing sufficient about it to discover what it does.
ReplyDeleteTo me the biodiversity argument is primarily aesthetic. There's something profoundly ugly and unsettling in causing an environmental disturbance that will last for millions of years, a disturbance that makes climate change effects of ten thousand years seem like an eyeblink.
ReplyDeleteWe should choose not to create a mass extinction, simply because we don't want it.
The case for being in the 6th great extinction is way older than Magurran & Dornelas or Robert May's book. E.O. Wilson said the same thing in his book Diversity of Life (1999) . . .and I'm sure that wasn't the first time it had been proposed, either.
ReplyDeleteBrian, well put. To me it's all three propositions together... which somehow amount to more than the sum of their parts.
ReplyDelete@ mt - I've just rediscovered my Blogger login details, which accounts for my recent spate of posts on your blog. If my posts on the various biodiversity topics you've raised seem a bit Negative Nellie, I apologise. It's just that in the midst of the (relatively) high profile coverage of climate change, the urgency of the biodiversity crisis (that's been going on for decades) is mostly getting lost. I'm not saying the coverage that climate change gets is undeserved, but that the continuing and increasingly rapid loss of species, communities and entire ecosystems seems (to me) to deserve a much higher profile than it now gets.
And I'm really really really worried about this, so thanks for the opportunity to comment.
This comment has been removed by a blog administrator.
ReplyDelete@Luddite,
ReplyDeleteMy wife and I just submitted a manuscript last week on the topic of climate change and biodiversity conservation. Maybe a few months from now I can point you to a published version. :)
Stephen -- I think Stuart Pimm was the first to write about the 6th mass extinction. This should be searchable.
ReplyDeleteI like the ethical argument best (although all three could make claims to being 'ethical'). My version goes something like this: bodies are survival machines (sensu Dawkins) built for the preservation of genes. It's genetic diversity that represents the real inherent value in the world (it strives to replicate itself, so it must value itself). Notwithstanding some additional value for the inherent value resulting from self awareness, the evolutionary legacy and genetic heritage of life on Earth is distributed in a clustered manner that roughly reaches most urgently to distant, least redundant branches of the tree of life. The longer the branches some action breaks, the more that action is to be avoided.
I've never dug into this, but there is a bit of a bias in terms of identifying species today versus in the paleontological record. Uh, isn't there? I don't doubt that we're in a mass extinction; I'm just wondering how 'they' compare rate of loss of fossil species to rate of loss of present day species when lots of today's species are not easily identifiable without a fresh specimen. Examples? How about snails that are identified largely on the basis of their genitalia (which do not fossilize well)? Thanks for letting me know.
ReplyDelete@SteveL:
ReplyDeleteExtinction data from the fossil record is usually tracked by following appearances and disappearances of higher-level taxa - that's what Raup and Sepkowski did, as I recall, and their data set was, further, restricted to marine invertebrates, at least for their first study back in the 80s. So extinction rates in the palaeontological record are actually underestimated. As long as there was a single species in a family left alive, that family wasn't extinct, even if all of the rest of the species in it had all died one rainy night.
Palaeo-species are even more difficult to diagnose than modern species, and they are frequently described on the basis of small samples from single localities, so an extinction curve based upon palaeo-species data would have an awful lot of noise in it.
The fact that we can draw these curves, and replicate them, and that the mass-extinction signal still comes through so clearly, indicate that these were real events.
More on modern species later, if I get the chance.
Thanks for bring this to peoples' attention Michael. Am not 100% sure, but I believe the last sentence of the highlighted text is attributed to Aldo Leopold, one of America's greatest ecologist/conservationists.
ReplyDeleteThings such as Arctic Marine Mammals (polar bears, seals, walrus, whales, and every critter that needs sea ice) may be gone, and we just have not admitted it. I.e., the graph understates the situation.
ReplyDeleteSome more detail on comparing modern faunal die-offs with palaeofaunal die-offs...
ReplyDeleteModern species can be quite hard to distinguish except on chromosomal or genetic grounds, true enough - actually a lot of what's said about the modern extinction crisis is based upon data that differ for different taxa.
It's pretty obvious that a lot of the vertebrates are in trouble, especially the big ones - estimates of something like one-third the world's amphibian species on the way down the chute are based upon reasonably rigorous census data of described species with known ranges - things like that. And it's going to vary from place to place - Madagascar, for instance, appears to have a whole lot of very highly localized endemic amphibian species - easy to keep track of, and easily expunged by someone clearcutting a few square kilometres of forest, say.
For a lot of the smaller stuff, it's estimates based upon habitat change data, which is reasonably hard - but the species/area relationship, or something like it, will be used here to give us estimates of what the species diversity for a particular area was like before it was disturbed (cleared, mined, what have you); what it's like after the disturbance can be checked by field work, and it's usually a lot easier than it would have been before the disturbance, as there will be far fewer species to census.
So yes, we can get a far more precise estimate of what's happening in the modern world than we could from the fossil record. But they both suggest that there are periods when biodiversity goes into free-fall, and that this is one of them.
Hope that you'll excuse the soap-boxing, mt.
Lars,
ReplyDeleteThanks for your comment. I should have remembered this stuff from some of the work I have read on island biogeography, but that was a long time ago in a land far, far, away.
Oh no... I can hear the pathological sceptics sharpening their pencils already...
ReplyDeleteR. norvegicus -
ReplyDeleteGlad that it was of some use.