The Global Human Footprint Is Running Out of Globe

The physical, geographical impact of humans on global ecosystems—what's known as the human footprint—has grown more slowly than Earth's human population, finds a study published this week in Nature Communications. That is, as more humans are added to the planet, the rate of increase of those humans' impact on the planet in terms of land use has not kept pace. The implication is that on a per-person average, humans are leaving a smaller ecological imprint now than they had been previously.

The human footprint generally refers to land taken up by humans for urbanization and agricultural purposes. It was first measured on a global scale in the 1990s, but has apparently not been updated since then. To this end, ecosystems researcher Oscar Venter and colleagues set about creating an updated footprint measurement using existing data on built surfaces, roads, crop and pasture land, nighttime lights, and human population density.

What they found was a footprint increase of about 9 percent between 1992 and 2009. This is in contrast to an increase in the human population on planet Earth of about 23 percent. That's a fairly dramatic improvement, but we also don't have any data to about how this relationship has changed through other periods in history.

"The primary aims of this study are to update the original human footprint map to provide a contemporary view of human pressures, and to create the first temporally consistent maps of the human footprint, such that patterns of change over time can be analysed," Venter and co. write.

It's tempting to interpret these findings as, well, good, but if we ditch the headline for a minute, we're left with the fact that the global human footprint is increasing really fast. The overall growth rate is tempered in wealthier nations and those with relatively little corruption, but in many locales with threatened ecosystems—particularly those in tropical regions featuring high levels of biodiversity—it's increasing at rates beyond 20 percent. That's pretty dire.

Adding to the gloom is another statistic (or another face to the same statistic). While in 1993, 27 percent of Earth still had no measureable human footprint, that figure has declined to just over 9 percent. It's not terribly hard to imagine a future point in which this measurement won't have meaning at all: It will all be footprint.

So what's left? Well, it's not exactly prime real estate. Most of the remaining land is desert and tundra, with some slices of boreal forestland and remote jungle. The really good stuff is long gone.

"Some of the hardest decisions about protecting natural landscapes must be taken within the planet's most biologically valuable regions," the authors conclude. "While remote sensing has estimated biodiversity hotspots to have around 15 percent natural vegetation remaining, our results suggest that opportunities for conservation may be much constrained, with only 3 percent of these areas currently free of human pressures. This result indicates that maintaining biodiversity will require extensive restoration to remove and mitigate existing pressures."

You can see in the map above where things have actually gotten better footprint-wise. The study notes that these areas also happen to be net exporters of agricultural and forestry products. In other words, they're not simply outsourcing their footprint. That's something.

We might be encouraged by the assumption that as the rest of the world catches up to the first-world, the deepest red areas on the map will likewise turn green. It's a hell of an assumption, unfortunately. We don't really know how much footprint-increase got the developed world to where it is today. One might reasonably assume that most of the current footprint, that 90ish percent of stepped upon land, bore the weight of Western industrialization and the accompanying population explosion. If land consumption is at all analogous to fossil fuel consumption, then I'm not sure how we could think otherwise.