Earlier this month, research came to light suggesting that the Permian-Triassic extinction- the greatest mass extinction in the history of the planet- was most likely caused by a population explosion of methane-producing bacteria (aka methanogens), probably caused by the large amount of nickel released by the massive eruption of the Siberian traps. These bacteria spewed out enough methane to wreck the climate and disrupt the carbon cycle.
This isn’t the only incident of microbial alteration of the Earth’s climate. The Huronian glaciation– one of the longest and most severe ice ages known- was probably caused, at least in part, by the rapid addition of oxygen to the Earth’s atmosphere by the evolution of bacteria capable of oxygenic photosynthesis. The O2 oxidized the methane, reducing the greenhouse effect of the Earth’s atmosphere, and leading to extensive glaciation.
This is of interest to astrobiologists, of course- if the evolution of life is potentially hampered by these kinds of events frequently, that may be the reason complex life seems to be so rare in our galaxy- but I think it also has relevance for environmental thought and philosophy. Specifically, we may need to rethink the Gaia hypothesis.
The Gaia hypothesis comes in several different flavors, but the gist of its primary suppositions is that 1) the biosphere of a planet has a significant influence on its geochemical conditions (atmospheric composition, erosional processes, mineral formation, etc) and 2) this combination of biosphere and geosphere tends towards homeostasis. Supposition 1 is not in question, and is in fact well known by astrobiologists- if the planet you’re looking at has an atmosphere that’s not in chemical equilibrium (say, has oxygen and methane at the same time), then there’s probably something interesting going on there. Supposition 2, on the other hand, is, at least in my opinion, looking kind of shaky.
After all, microbes have completely disrupted this homeostasis at least twice, and in the case of the Huronian glaciation, we’re very lucky that life survived at all. The biosphere does not appear to be anchored to any one particular equilibrium state. Peter Ward went as far as to coin the Medea hypothesis– the idea that the biosphere is actually self-destructive- but I think that’s a bit much (if nothing else, it seems a bit to teleological).
The problem is that many environmentalist still ascribe to the idea of Gaia (in some cases, thinking of the biosphere in terms of an actual, conscious entity, which even James Lovelock, the theory’s creator, vehemently denied; part of this, no doubt, is from the difficulty people have grasping the idea of emergent complexity). In some respects, it’s simply an extension of the idea of ecosystems as being self-regulating and in equilibrium to the global scale- but, unfortunately, that idea is flawed, as well. The bottom line is that, because of Gaia, many environmentalists seem to hold dearly to the idea that nature “knows what it’s doing,” and that we can trust the biosphere to be in an optimal state (as long as we don’t disturb it). But the fact of the matter is, that doesn’t appear to be the case- humans, it seems, are not unique in our reckless disruption of our planet’s climate and habitability.
We do, however, have the dubious honor of being the first species to do so knowingly.
This is probably a topic deserving of its own post, but, in short, I really think William McDonough was on to something in The Upcycle when he pointed out that too much environmentalist practice was framed in the context of doing “Less Bad”- and that this creates a goal (zero disruption to the environment) that is ultimately unreachable (you can only approach it asymptotically). This idea is indeed rife, especially in some of the older generation activists (AKA the aging hippies); the worst (or best) example of this tendency I’ve seen was a commenter on grist.org who opined that the ultimate goal of humanity should be evolving into non-corporeal forms, so that way we could ensure that our presence would in no way harm the environment. With friends like these…