In your opinion, what’s the most significant and certain global trend that is not on conservation’s radar, but should be? The coming phosphate scarcity? The gradual deterioration of the world’s soils? Or perhaps the smartphone revolution that we have failed to harness in support of conservation?

Here’s my candidate: the demographic statistic called potential support ratio (PSR), which measures the ratio of a) the number of people ages 15 to 64 in a given population to b) the number of people age 65 or over in that population. Currently, the global PSR is 8.4, but it is expected to fall to 2.5 by 2050 and to 1.2 in 2100. Remarkably, there is very little uncertainty surrounding this prediction — the 80% prediction intervals are 2.2 to 2.8 for 2050, and 0.7 to 1.8 for 2100. Moreover, the trend cuts across virtually all countries, developing and developed.

PSR is meant, of course, to measure a society’s ratio of productive workers to retirees. But why should conservationists start thinking about a world that will be at least three times older than it is now (as measured by PSR) in less than 40 years? Because, in that future world, the most profound national issues will be healthcare and social services, as well as providing infrastructure and cities that serve an aging population. Just as we now couch conservation in terms of today’s global challenges (food, energy and water), in 2050 we will need to couch conservation in terms of that era’s global challenges — one of which will be an unprecedentedly older population.

One advantage of an aging population is that people over age 60 tend to drive less, fly less, consume less and consequently tread less heavily on the planet — all trends that point toward lower greenhouse gas emissions. But what other features of an aging population can we take advantage of in service of conservation, and what type of conservation will an aging population most care about?

Two things strike me. First, we will need to switch our conservation stories from what I would call “nature adventures” (swimming with the sharks, hiking across rugged and dangerous landscapes) to “walks in nature.” We would shift our emphasis from conservation in far away and exotic locations to conservation in our own backyards.

Second, the elderly are uniquely susceptible to heat stress, and therefore anything conservation can offer to urban design that would reduce temperature spikes in cities will be a boon to an aging population. Thus, tree-lined streets, expansive urban parks and restored urban streams and rivers will be the hallmarks of cities that appeal to an older population. I have not been able to find data on this — but I hypothesize (based on my parents’ behavior as they aged) that the elderly will favor cities designed for walking (as opposed to driving). In Europe, where populations are older, modal splits of transportation to work heavily favor walking, cycling and public transportation, whereas U.S. cities favor cars. Peter Calthorpe gave a talk last year at the California Academy of Sciences in which he said that 52% of Swedes walk and bike to work, as opposed to 11% in the United States. The difference is cultural, but it is also driven by the demands of demographics.

So maybe this aging world will be a blessing for nature. I can imagine a world where greenhouse gas emissions have fallen substantially due to changes in individual behavior, a world with greener and more walkable cities containing restored nature and urban parks, and a world where conservation is embraced as a global ethic thanks to the wisdom of elders. But conservation had better start preparing now for that embrace and not simply assume that it will happen because we deserve it. If we don’t cultivate 20- somethings to have an affinity for nature now, they won’t suddenly be receptive to it (or us) when they’re 60-somethings in 2050.

By Peter Kareiva, chief scientist, The Nature Conservancy

Image credit: montuschi/Flickr

Reference
Raftery, A. E. et al. 2102. Bayesian probabilistic population projections for all countries. PNAS online Early Edition.