A postcard, issued from 1930 to 1945, depicting the man-made Rainbow Bridge at Yellowstone National Park,
Creative Commons courtesy Boston Public Library A postcard, issued from 1930 to 1945, depicting the man-made Rainbow Bridge at Yellowstone National Park,

In his polemical 1968 treatise "The Tragedy of the Commons," biologist Garrett Hardin concluded that there is no technical solution for the overuse of natural resources. He uses the metaphor of a pasture, arguing that each herdsman would simply try to maximize personal gain by increasing his herd numbers beyond what is sustainable. In Half-Earth: Our Planet's Fight for Life (Liveright, 2016), out next month, contemporary biologist and Pulitzer Prize winner Edward O. Wilson takes a different tact, making a case for setting aside half the planet as a wildlife preserve to prevent the mass extinction of non-human life. Building on a premise he had earlier proposed in The Future of Life (Knopf Doubleday, 2002), Wilson finds good company among other biodiversity-loss journalists, including fellow Pulitzer Prize winner Elizabeth Kolbert, author of Field Notes from a Catastrophe (Bloomsbury, 2006) and The Sixth Extinction: An Unnatural History (Henry Holt, 2014).

Compared to Hardin's pasture, Wilson's reserve presents an even greater challenge to humanity's resource-hoarding tendencies. If the former illustrates the problem of sustainable collective resource management, the latter presents the difficulty of establishing a territory that is off-limits to human influence. Wilson’s approach raises two questions. First, is such a massive reserve even possible? And, second, what implications does it have for design and planning?

Where the Wild Things Are—And Where They're Not
To evaluate Wilson's Half-Earth proposal, we first need to understand the scope of the current situation. Wilson bases his argument on the idea that the amount of suitable habitat left to a species is crucial to that species’ survival. Scientists have calculated the relationship between changes to habitat area and the number of surviving species—the species–area relationship—to be inversely proportional. When 90 percent of a natural habitat is eradicated, scientists found, about half of its existing species will eventually disappear. (This equation refers to the number of unique species, not populations of individual organisms.) Although the remaining species may eke out a sustainable existence, Wilson explains in his forthcoming text, “if 10 percent of the remaining natural habitat were then also removed—a team of lumbermen might do it in a month—most or all of the surviving resident species would disappear." The Half-Earth mega-reserve would protect roughly 85 percent of the remaining species, when calculating with a median value of the fourth root, or more if endangered species “hot spots” are included in this area, Wilson writes.

"If [Hardin's pasture] illustrates the problem of sustainable collective resource management, [Wilson's reserve] presents the difficulty of establishing a territory that is off-limits to human influence."

Current protected wild lands cover approximately 15 percent of land and inland marine areas and 3 percent of the oceans, according to the United Nations Environment Programme publication “Protected Planet Report 2014,” which is based on data from the World Database on Protected Areas. In theory, if all non-protected areas were degraded, only 62 percent of land species and 4 percent of marine species would remain. Even if the Convention on Biological Diversity (CBD) 2020 preservation targets of 17 percent land and inland marine along with 10 percent coastal and marine regions are achieved, these areas would protect only 64 percent and 56 percent of remaining planetary species, respectively. And in the United States, home to the world’s first national park—Yellowstone National Park, established in 1872—the now nearly 110 million acres of protected wilderness would safeguard only 44 percent of Earth’s land-based species.

Selecting Strategies for Land Use
Humanity is only driving up the rate of species extinction, which is estimated today to be at least 1,000-times higher than in pre-human eras. So, what land-use strategies could we adopt to slow our progress? One method is to preserve the remaining undeveloped and ecologically valuable territories. This would require a piecemeal effort, given that few expansive uninhabited areas remain on the globe. As a result, the Half-Earth method doesn’t mean dividing the planet into large tracts based on hemispheres, continents, or even nation-states but instead involves the incremental purchase and supervision of wild lands by public, private, indigenous, and combined governance structures. This residual approach is relatively easy for planners and developers to appreciate, as it typically involves the sequestration of areas still considered wild, or at least underdeveloped.

"It’s hard to argue that a complex network of reclaimed wild lands will remain truly wild, for these territories will require extensive human oversight to counter the unrelenting perils of HIPPO."

The problem with this strategy is that it results in a patchwork of small, disconnected territories not conducive to many species’ migratory or mobility needs. For this reason, conservationists call for wild connections to be made between these bits and pieces of the natural world. “I see a chain of uninterrupted corridors forming, with twists and turns, some of them opening up to become wide enough to accommodate national biodiversity parks, a new kind of park that won’t let species vanish,” Wilson told Smithsonian Magazine in 2014. The problem with creating such expanses of wilderness is that they often physically conflict with established human transportation networks. The Seattle-based Wildlands Network seeks to address this by building wildlife overpasses and underpasses above and below highways and railways. The organization is working to reestablish four wildlife corridors in the United States—one spanning each coast, one across the North American forest roof, and one from Baja California to Alaska. Such a herculean project must overcome the challenges of established land ownership and a society that is largely apathetic to such an agenda.

Challenges to Keeping the Wild Lands Wild
Even if sufficiently broad and interconnected wildlife thoroughfares can be stitched within a considerably Anthropocene terrain, other challenges remain. Conservationists employ the acronym HIPPO—habitat distribution, invasive species, pollution, human over-population, and over-harvesting by hunting and fishing—to summarize the list of human-influenced biodiversity threats. Some of these dangers are minimized in protected areas, but threats such as invasive species and pollution are harder to control. In Rambunctious Garden: Saving Nature in a Post-Wild World (Bloomsbury, 2011), author Emma Marris argues for a re-conceptualization of wilderness based on the omnipresent influence of human societies, and describes the “novel ecosystems” that occur at the intersections between human and natural ecologies as realms of fertile opportunity. Wilson is not enamored with such a view, which he describes as representing a “new conservation” philosophy, and declares such a perspective to be an “assault on wilderness.” Still, it’s hard to argue that a complex network of reclaimed wild lands will remain truly wild, for these territories will require extensive human oversight to counter the unrelenting perils of HIPPO.

In this way, the Half-Earth manifesto fuses with the "Tragedy of the Commons," and an elaborate super-reserve for the biological kingdom substitutes for Hardin’s pasture. Only, here, such a resource is decidedly not for human consumption and, by definition, reduces the overall area that may be used by people. As a result, we face an unsettling question: If we agree with Hardin’s mistrust of society to make decisions that benefit the common good, can we imagine humanity making an even greater commitment to aid other species—even in the name of avoiding a biological cataclysm?