Today is the 38th Earth Day. It’s hard to escape the conclusion that we haven’t made nearly as much progress as those celebrating the first one in 1970 would have hoped. How will we save nature from the onslaught of our own appetites and fecundity? Nearly every week there is some new round of disturbing news about environmental deterioration. Big swaths of rain forest are going up in smoke every day, the great giants of the sea are being hunted out, the remaining patches of wild nature are giving way to cultivated land and homes and shopping malls at a steady rate. The prospects for conservation seem grimmer than ever. One could be forgiven for feeling, in dark moments, that all hope is lost.
But perhaps we have been approaching conservation in the wrong way. Or, more accurately, perhaps we are being too narrow-minded about how to conserve species. Maybe there are tools in the arsenal that we haven’t yet learned how to use.
This, in a nutshell, is the argument of “Win-Win Ecology” by Michael Rosenzweig, Professor of Ecology and Evolutionary Biology at the University of Arizona. Rosenzweig’s argument, which may sound radical and even heretical, is that our only hope for saving a substantial fraction of earth’s biodiversity is not (only) to set aside parks and preserves, but to adapt our own civilization fundamentally to accommodate the rest of creation. To learn to live with each other.
Rosenzweig distinguishes three approaches to conservation, which can be summarized as the three Rs:
Reservation ecology is the historical approach: set aside (usually small) plots of land that retain some semblance of pristine natural habitat and wildlife, and keep people out, or at least keep them from doing anything in there.
Restoration ecology seeks to remedy some of the damage we’ve already done by replanting native trees or seagrasses, introducing controlled fires into natural areas adapted to fire, and generally trying to take degraded land and recreate what we know or think was the original natural habitat.
Reconciliation ecology is the new one (so I’m a little behind the curve here — the book appeared in 2003. But it’s still new relative to the other two R’s), the idea that Rosenzweig focuses on:
“It is the science of inventing, establishing, and maintaining new habitats to conserve species diversity in places where people live, work, or play . . . I am talking about creating self-supporting populations of species on our land. It will take a lot of work. But imagine the result: a vast area of diverse anthropogenic habitats that meet nature halfway instead of trampling her underfoot. Although these habitats would not be ideally suited to wild things, they would provide enough support to allow them to adapt to us. They would give natural selection the time and space in which to work, and thus could save the overwhelming majority of today’s species.”
Whether or not you’re willing to swallow the last sentence (I’m not at all sure that I am), I think he’s on to something. There are several elements to the agument:
First, the basic premise is indisputable. We, the single species Homo sapiens, now appropriate a majority of this planet’s resources — land, water, biological production — for our own use. The human population is still growing and is variously projected to stabilize at something very roughly around twice the present population of ~6.5 billion. Before that happens, we can expect a large fraction of the world’s poor to increase substantially their standard of living, which is good, and concomitantly their per capita impacts on the world’s environment, which is less good. All this is background to the important point that: “pristine” natural habitats will inevitably become a tiny fraction of the earth’s surface. This is not a pessimistic rant, it is a simple fact that follows from everything we know about the way humans and their societies work.
The second point of the argument is also indisputable. Over a century of research in ecological science has established the pattern, so consistent that it can be considered a law of nature, that the number of species in a region increases with area of the region. For example, the figure at right shows the number of species of birds (squares) and reptiles (circles) on Caribbean islands of different sizes. A tenfold increase in habitat area results in very roughly doubling the number of species. The flip side of this law is that, as area of natural habitat decreases, as is happening worldwide through human impacts, species are lost through extinction until diversity reaches the level that can be supported by the size of the habitat fragment. The upshot is that: by themselves, the small fragments of natural habitat that we preserve can support only a small fraction of earth’s biodiversity. It is simple mathematics. Depending on how one estimates the slope of the species-area relation, and the proportion of earth’s habitat likely to be conserved in wild form, Rosenzweig estimates that somewhere between 44 and 87% of species will be lost. And that is just the first-stage extinctions, that is, those lost because the habitat areas are not large enough to support viable populations. Then comes the long, drawn-out second stage, in which the remaining habitat fragments continue to lose species as accidents (hurricanes, disease epidemics, cold winters) snuff out the small populations surviving in them.
Are you depressed yet? Well, here is where the new idea comes in. Since reservation of natural habitats cannot BY ITSELF save a substantial fraction of the earth’s biodiversity, we need a complementary approach: reconciliation ecology. We need to take advantage of the huge matrix of habitat that humans have appropriated for our own use, and engineer it so that it accomodates other species. That is, we need to reconcile our needs with those of the rest of life.
Several happy accidents suggest that this is not impossible. One of the world’s largest colonies of Mexican free-tailed bats — over a million and a half — roosts under the Congress Avenue bridge in Austin Texas, where their nightly emergence (left) is a major tourist attraction. Nearly ten percent of the world’s population of endangered American Crocodiles live in the cooling canals of the Turkey Point power plant in South Florida. Who would’ve thunk it? Neither of these places was designed for wildlife, of course. But if we did design our human habitats to accommodate other species, think what we might accomplish. For example, “green roofs” on urban buildings not only soothe the soul, they help filter storm runoff, and they provide habitat for plants, birds, and insects that might otherwise disappear from the city. And there is something equally important. As Rosenzweig emphasizes, a major indirect benefit of such an approach would be another kind of reconciliation:
“It promises to reduce the endless bickering and legal wrangling that characterize environmental issues today. We are all human beings. We share a stake in the world we are building. No one wants it to be sterile and lonely. And no one wants us to destroy our technology and reduce our future to the harsh, subsistence-level lives led by our Stone-Age forbears. Reconciliation ecology recognizes these simple truths and unites us in our common goals.”
(The photo shows the Severn Savings Bank headquarters in Annapolis, Maryland, USA, with its green roof. The building captures and treats stormwater where it falls.)