Biodiversity loss: as serious a threat as most other fears.
I’ve been harping about overpopulation for some time now. Fortunately, there are major efforts around the world to reduce fertility levels to more sustainable values. But are they being implemented fast enough?
Of course, I don’t forget the additional (derivative?) concerns about inadvertent climate modification (including global warming) and its effects on ecosystems as well as people. We cannot neglect the role of what are called “nature’s services,” which depend upon maintaining biodiversity. [Do a Google search on “Nature’s services” for numerous links to information on that topic.]
Now, thanks to Joe Bish at Population Media Center, comes this pair of interesting articles on diversity loss:
Impacts of biodiversity loss rival those of climate change and pollution by Emmett Duffy on May 2, 2012 in SeaMonster – Ocean science, sports, and discovery
The first article repeats noted ecologist E. O. Wilson’s claim that “we are now, or soon will be, in the grip of earth’s sixth mass extinction of species” caused mostly by humanity. See: http://www.dailygalaxy.com/my_weblog/2008/02/the-6th-great-m.html
The first article then reviews the scientific study on which the thesis is based:
“That is the message from our new analysis, published online today in Nature.
“For the first time we’ve been able to compare–directly, quantitatively, and rigorously–the impacts of losing wild species to the effects of all the other human-caused environmental changes on the productivity and functioning of ecosystems and their ability to continue providing for us.
“The time is ripe because two decades of research have now shown pretty conclusively that more biologically diverse ecosystems are generally more productive, as John previously highlighted here. And that means that ongoing extinctions of species caused by habitat loss, overharvesting, and a slew of other environmental changes might well stuff up nature’s ability to provide things we need and want. Like food, clean water, and a stable climate. But so far it’s been unclear how such biodiversity losses stack up against other big environmental changes.
“Now we can answer that question with some confidence.
“Our team combed the scientific literature for rigorous peer-reviewed experiments that measured impacts of various global environmental stressors on plant productivity and decomposition, two processes that are fundamental to support of food webs, habitat structure, and carbon cycling in ecosystems. We then compared those effects with impacts of changing diversity, drawn from a growing database of of experiments that manipulated the number of species and examined the impact on ecosystem processes. By tallying up results from all these studies, we could compare how important losing species is relative to various other environmental changes in affecting ecosystem productivity and decomposition.”
Click on the link above for the remainder of the article, or the link to the article in Nature for the more scientific perspective.
The second article bills the Nature article as the scientific response to a meeting a year and a half ago of some of the world’s top authorities on the consequences of species loss which took place at the National Center for Ecological Analysis and Synthesis. (At NCEAS, scientists conduct collaborative research on major fundamental and applied problems in ecology.) At that meeting, Brad Cardinale asked, “So, where does diversity loss rank? As important as climate change? Rampant nutrient runoff from agriculture? I mean, come on, how important is it, really?”
None of those present at the meeting knew the answer. Now they do. At least that’s the claim of the authors of the Nature article. Their conclusion is that species loss matters quite a bit, as much as many of the other major drivers of environmental change. The remainder of this second article describes how 15 years of work has gone into divining the consequences of species loss. One thing they have found:
“Losing species, at the bare minimum, reduces the ability of fields of plants or algae to most efficiently turn sunlight and nutrients into new production. Losing some of the myriad of species responsible for munching their way through dead detrital material will slow that whole process down. More questions remain, but diversity loss seems to be altering a wide variety of ecosystem properties.”
The group “sat down, rolled up our digital sleeves, and got to work. Led by the ever steady Dave Hooper and always insightful Carol Adair, we began to dig into the literature – to see what information was out there about the impacts of these different forms of environmental change. We were armed with the hugely revised and updated version of Brad [Cardinale’s] monster database.”
They struggled to find some commonality amongst the various studies that had been performed, a way to synthesize that information in a way that might be able to answer the primary question. They hit upon a strategy, after a whole lot of arguing “as only scientists can when they want to get something dead-on right” and working toward the answer. In the end, “the solution ended up being delightfully elegant.”
They struggled with a variety of visualizations and finally noticed that, following initial species losses, no big deal, but “as you start losing more and more, the problem of species loss starts to compound. Like the interest rate from hell, more species lost means exponentially more plant production lost.” But there were questions, so they tried to deal with them using more analysis and different ways of looking at the data. And they found some additional studies that confirmed the trends they were uncovering.
The author of the article, Jarrett E.K. Byrnes, concluded:
“Overall, we felt like this told a pretty tight story. Sure, as we came up with question after question, we accumulated a lot of figures and explanatory materials that made their way into the supplementary material, but the big story was pretty clear and compelling. In working group meeting 3, we really shaped this sucker, and then bounced revisions back and forth, wrenching the text back and forth. I’ve never been part of such a large collaboration (save for our earlier first paper), so it was an inspiring process to see big ideas hashed out, thrown aside, revised, and made into clearer cleanly crafted pieces all on the screen of my word processor.
“I’m pretty psyched that the paper is now out, and I hope you all enjoy it as well. There’s more to come from the working group, so stay tuned!” – Jarrett E.K. Byrnes
It is interesting to me whether such “nonlinear”* environmental responses to change, which we see in global warming effects**, are more widespread. Finding additional positive nonlinearities (amplifications of effects over time) and negative ones (self-correcting or self-diminishing effects) would seem to be of very high priority in the scientific as well as the political communities.
* When you double something and the response is twice as large, that is a linear response. When the initial quantity is changed by some amount but the response change is proportionately greater, such as 130% greater, 200% greater, or even 500% greater, that is called a nonlinear response because when the response is plotted versus the stimulus (the dependent variable) the curve is not a straight line, but rises faster than a straight line would.
** Reductions in arctic sea ice in summer, greatly increase the solar absorptance of the ocean, adding to heating effects, which accelerates the warming and melting of the sea ice.