Friday, June 08, 2012

Periodizing the Anthropocene

There's a very important new paper out in Nature entitled "Approaching a state shift in the Earth's biosphere." Executive summary:
Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence. The plausibility of a planetary-scale ‘tipping point’ highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions. It is also necessary to address root causes of how humans are forcing biological changes.
Let's summarize this further: humans are producing a "sledgehammer effect" on the global ecosystem, overdrawing on a variety of "ecosystem services," and unless humanity changes the way it interacts with the environment in a radical way, we're looking at an ecological catastrophe of a scale that may well compare with the dinosaur-extinction event.

There's already an excited conversation taking place about this. For samples, check out Forbes, Wired, and Slate.

My own view on the "anthropocene" debate is that, seen in geological-ecological timescales, the phenomenon we've become acutely conscious of over the past couple of decades and which usually gets labelled "climate change" didn't actually begin with industrial revolution 250 years ago. Rather, it began 40,000 years ago, when humans arrived in Australia, initiating the ongoing process of mass mega-fauna extinctions. This phenomenon continued with the arrival of humans in the Americas, about 15,000 years ago, which also resulted in the loss of many of the continents' large beasts.  Agriculture begins around 10,000 years ago, and what's happened since then forms a single continuous process of progressive human "commandeering" (to use this paper's term) of the planet's resources.

Scientists usually treat the die-offs at the start of the Holocene as conceptually and processually separate from the current round of post-industrial die-offs, but I think it's better to regard them as one macro-process.  I suspect that the reason we treat these as separate historical episodes is partly because we still fetishize the historical significance of industrialization, and partly because we narcissistically think that human consciousness (and hence intent) is a biologically unique category.

Yes, industrialization enormously accelerated the continuous process of resource commandeering, but human population has been increasing more or less non-stop for 74,000 years (since the Toba Eruption [update: of which more below]), and ecosystemic resource appropriation by humans has been continuously increasing in parallel. Industrialization allowed for an increase in the pace of this commandeering, but did not a change the motive or direction, all of which has been trending for millennia toward global-scale ecosystem disruption. Even without global warming, the human impact on the global ecosystem would/will eventually be total. (The idea that humans would completely harness all of Earth's resources was explicitly blueprinted back in the 1960s by Konstantinos Doxiadis, published as Ecumenopolis: The Inevitable City of the Future — the most totalizing vision of modernization ever produced.) 

What has further accelerated the threat of planetary-scale ecosystemic "state shift" is an inadvertent byproduct of industrialization, namely the carbonization of the atmosphere and the oceans, which is now a second planetary-scale anthropogenic forcing mechanism. In geological terms, however, this distinction between direct and intentional commandeering of resources and indirect changes caused by atmospheric carbonization is overdrawn: it's all part of a single integrated process of anthropogenic ecosystemic transformation — two phases of a single historical episode.

(We don't have the evidence, but there's no reason not to believe that other episodes of global-scale "state shift," such as the K/T extinction event or the Cambrian explosion, didn't also proceed through various "phases" in which the central dynamic driver changed — for example, the initial shift may have been some alteration in atmospheric chemistry, but then as it unfolded, it killed or generated species, which then became direct drivers of change in their own right. None of that makes it hard for us to see these historical process as singular.)

Because we narcissistic humans like to believe human intelligence is some unique and privileged biological feature, we insist on distinguishing between the direct and intentional commandeering of resources (killing or domesticating megafauna, plowing the Great Plains, etc.) and the unintentional byproducts of our actions, like atmospheric carbonization. That distinction isn't particularly meaningful at an ecological level, however.

In sum, I believe that some Archimedean intellect millions of years from now is likely to regard the shift to the Anthropocene as a single process that unfolded over eighty millennia, beginning with the Toba Eruption, and culminating in the complete melting of the polar ice caps around the year 4000. How many humans will be around by then to see that world is anyone's guess….

Update: The Toba Eruption is hypothesized to have reduced the human population to as few as 10,000, isolated in a couple of tropical refugia. This population bottleneck may well have created the conditions for an extremely harsh "survival of the fittest" moment. Although anatomically modern humans predate the Toba Eruption by 100,000 years, this winnowing effect of the Toba bottleneck may well have selected for physically indistinct byt psychologically or socially crucial traits for surviving amid climatic chaos. Interestingly, geological events — asteroids and mass volcanic eruptions — are hypothesized to be the root cause of all the other big die-offs. If the Toba Hypothesis is correct (it's highly controversial) it would suggest that the Anthropocene is just another example of the same sorts of shift, which would seriously downgrade the somewhat exalted role that we humans cast ourselves in when we deem ourselves to be the fundamental driver of the historic shift. In fact, our own "peak humanity" moment is perhaps best seen as a mere epiphenomenon of deep geological processes.


Noah Raford said...

To summarize even more, we're screwed?

Nils said...

Well, I'd be a little more precise, Noah. For all that we love to believe that our higher consciousness makes us unique and special, that is not subject to the same rules as other species, humans in fact behave like all other creatures: we will munch and sleep our way to the Malthusian limit. We're correctly in the middle of a one-time harvesting of fossilized sunlight which has allowed the usual operation of Malthusian limits to be temporarily suspended, but once the hydrocarbons are used up....

The interesting issue, to me, is what form the Malthusian limits will take, longer term (barring thermonuclear annihilation, which is of course still a possibility). One model is to achieve an "equilibrium state" - that is, a more or less stable population. Many species largely achieve this within climatically stable contexts. Another model, however, is "oscillating explosions"; where a population booms and busts repeatedly. All the examples I know of for this are insects, but perhaps we humans will do something similar.

Anonymous said...

I'm sorry but the idea that humans only arrived in the America's 15K is extremely unlikely.

lft said...

Constantinos Doxiadis is indeed an interesting case: the totalizing vision of Ecumenopolis embodied both dreamworlds (entopia) and catastrophes (dystopia) of the "inevitable" future. Would his proclaimed guidelines have helped or was it already "late" for action? Arguably, the 1960s witnessed a phenomenological social shift yet with ambiguous results.

Nils said...

To "Anonymous" -- the date of first arrival of humans in the Americas is a hotly contested subject. There is unambiguous archaeological evidence that humans were extensively distributed around North America by ~11K BP (Clovis culture). Genetic evidence pushes things back a bit further to "about 15K years ago" (give or take 1500 years).

Here's a Nature article from last month that provides the summary of current thinking:

Money quote:
"The [DNA] results effectively rule out the possibility that humans came to North America as early as 40,000 years ago — a date based on equivocal evidence from archaeological sites in the eastern United States. The finding also argues against the idea that people used boats before the thaw to go around the glaciers and come down the coast. Instead, the DNA evidence supports the consensus that people didn't migrate into the Americas — whether by boat or over land — until the end of the last glacial maximum, 16,500 years ago at most."

gundaricus said...

"We don't have the evidence, but there's no reason not to be believe"

Such lines of reasoning make clear to me that this is a non-argument wrapped up as a case.

Nils said...

@gundaricus - it's more like a statement of a hypothesis and an acknowledgement that we don't have sufficient data to validate it, but that it conforms with existing data.

My main point in that aside is that what we call extinction "events" are more properly conceived as "processes" that, were one to live through them, would be seen to have a variety of phases and steps. This is a commonplace historiographical insight, in situations where the historical record is rich, but is not as usually applied to pre-historic situations, in which the data record is sparse.