Some ecologists are arguing that humans and alien species have been churning up ecosystems far more intensively, and for far longer, than we assume:
We like to think that most nature was pristine and largely untouched until recent times. But two major studies in recent weeks say we are deluded. In one, Erle Ellis, a geographer at the University of Maryland Baltimore County, and colleagues have calculated that at least a fifth of the land across most of the world had been transformed by humans as early as 5,000 years ago — a proportion that past studies of historical land use had assumed was only reached in the past 100 years or so.
The human footprint was huge from the day, perhaps 60,000 years ago, when we began burning grasslands and forests for hunting, according to the Ellis study. It extended further with swidden “slash-and-burn” agriculture, and became more intense when farmers began to domesticate animals and plow the land.
And if that is right we should change the way we think about stewardship:
Far from reaching some equilibrium state with niches filled, ecosystems have always been in a constant state of flux, says Stephen Jackson, of the Southwest Climate Science Center in Arizona, in Novel Ecosystems. “Change, including rapid and disruptive change, is a natural feature of the world.” Humans may have dramatically speeded that up, but novelty is the norm.
In that light, we need to look afresh at conservation priorities. Novel ecosystems cannot be dismissed as degraded versions of proper ecosystems, nor can alien species be demonized simply for not belonging. If novelty and change is the norm, Hobbs and colleagues ask, does it make sense for the growing business of ecosystem restoration to try and recreate static historic ecosystems? By doing that, you are not creating a functioning ecosystem; you are creating a museum exhibit that will require constant attention if it is to survive.
Ecosystems can be hardy, and no doubt have always been in a state of flux and evolution. The big issue now is that humans are turbo-charging the rate of change. And that will be a severe test of how fast ecosystems and the species within them can adapt. No doubt some will, but it could get ugly.