What did happen? As of 2013, the International Union for the Conservation of Nature (IUCN) lists 709 known species as having gone extinct since 1500. A study published in Science in July 2014 reported that among terrestrial vertebrates, 322 species have become extinct since 1500. That being noted, the IUCN Red List records 6,451 species as endangered and 4,286 as critically endangered. Species are considered to be endangered if, among other findings, they number fewer than 2,500 mature individuals, their habitat encompasses fewer than 5,000 square kilometers, and/or their population size has been reduced by more than 70 percent over the last ten years or three generations, whichever is the longer. They are deemed critically endangered if they number fewer than 250 mature individuals, their range is less than 100 square kilometers, and/or their population has been reduced by more than 90 percent over the last ten years or three generations, whichever is longer.
In September 2014, the World Wildlife Fund published its Living Planet Index 2014 report, which alarmingly calculates that the Earth is home to about half the number of vertebrates (mammals, birds, reptiles, amphibians, fish) that it hosted in 1970. Let’s be clear: The report is not saying that half of vertebrate species have gone extinct, but that the overall number of wild vertebrates have declined by half. The trend is calculated using a complicated system for weighting the declines in various vertebrate species populations. The report also finds that 37 percent of the population declines result from direct exploitation (for example, overfishing and hunting); 31.4 and 13.4 percent are from habitat degradation and destruction (for example, cutting down tropical forests).
In an effort to deal with the threat of species extinction, in 1973 the United States adopted the Endangered Species Act, with the goal being to prevent the extermination of native species. The United States is home to approximately 200,000 species. In 2014, there were 1,529 domestic and 625 foreign species listed as either endangered or threatened under the Endangered Species Act.
A 2004 report by the Center for Biological Diversity lists 108 species as having gone extinct since the adoption of the Endangered Species Act. The researchers found that while 23 species became extinct after they were placed on the endangered species list, 85 species that died off never made it onto the list. The CBD list of US extinctions underlines the reality that most extinctions occur on oceanic islands—for example, Hawaii, Guam, and Puerto Rico—and in freshwater streams. The relatively small size and isolation of islands and freshwater streams render their endemic species especially vulnerable to being wiped out. In addition, lots of island species have lost their wariness of predators and consequently are devastated when mainland carnivores and omnivores such as rats and pigs are introduced. As a result, most of the species listed as going extinct in the CBD report were island endemics or denizens of freshwater streams (mostly mollusks). Interestingly, the 2004 CBD report lists the giant Palouse earthworm as having been extinct since 1978. The good news is that it was rediscovered in 2008 and was found to be so abundant that the US Fish and Wildlife Service declined in 2011 to list it as endangered.
Still, humanity is quite capable of wiping out species. Just as the last ice age was ending, our hunter-gatherer ancestors spread across the world, killing off megafaunal populations already stressed by climate change. Some 178 mammal species weighing more than a hundred pounds disappeared, drastically reducing the total mammalian biomass of the planet. For example, after humans arrived in North America, more than thirty different groups of large mammals, including horses, camels, mammoths, and mastodons, disappeared. In South America, 100 percent of mammals weighing more than a ton, including ground sloths, armadillo-like glyptodonts and rhinoceros-like toxodons, and 80 percent of those weighing more than a hundred pounds went extinct. Total mammalian biomass did not recover until just before the Industrial Revolution, when the post-ice-age losses were finally offset by the collective weight of the populations of humans and our domesticated animals. A 2013 study estimates that Polynesian wayfarers caused the extinction of 1,300 species of birds as they colonized the isolated islands of the Pacific Ocean. The arrival of Europeans killed off an additional 40 Pacific island bird species.
As we’ve seen from the IUCN list, biologists are not actually counting the number of species that are going extinct. As the example of the giant Palouse earthworm shows, it is really difficult to be sure when the last individuals of a species die off. So how do biologists come up with their shocking estimates of the number of species that they believe are likely to go extinct before the end of this century?
Calculating Extinctions
For the most part, the dire extinction estimates cited earlier are based on computer model calculations using the species-area-curve relationship derived from the theory of island biogeography. In the 1960s, Harvard University biologists E. O. Wilson and Robert MacArthur devised that theory, which basically predicts that the bigger the island, the more species it can support. This relationship is captured in the species-area curve. As Wilson explained it, in general if an ecosystem is reduced by 90 percent, the number of different species it can sustain is cut by 50 percent. For example, the Ehrlichs simplistically extrapolated from this crude species-area-curve relationship to make their wrong prediction back in 1975 that half of all tropical species would be extinct by 2000.
More recent research is questioning the calculations made on the basis of the species-area-curve relationship. For example, in a 2011 article in Nature, “Species-Area Relationships Always Overestimate Extinction Rates from Habitat Loss,” researchers concluded that “extinctions caused by habitat loss require greater loss of habitat than previously thought” and that reliance on the species-area curve overestimates species loss by as much as 160 percent.
The IPCC’s 2014 Adaptation report notes: “Models project that the risk of species extinctions will increase in the future due to climate change, but there is low agreement concerning the fraction of species at increased risk, the regional and taxonomic focus for such extinctions and the timeframe over which extinctions could occur.” That is to say, the computer models that researchers use to try to estimate the effects of climate change on species don’t agree on how many species are at risk, where they are at risk, which species are at risk, and how long it would take before species went extinct. As a result, the report finds that “model-based estimates of the fraction of species at substantially increased risk of extinction due to 21st century climate change range from below 1% to above 50% of species in the groups that have been studied.” Another interesting observation in that report is that “evidence from the paleontological record indicating very low extinction rates over the last several hundred thousand years of substantial natural fluctuations in climate—with a few notable exceptions such as large land animal extinctions during the Holocene—has led to concern that forecasts of very high extinction rates due entirely to climate change may be overestimated.” Furthermore, the Adaptation report notes, “The limited number of studies that have directly compared land use and climate change drivers have concluded that projected land use change will continue to be a more important driver of extinction risk throughout the 21st century.” In other words, the biggest peril faced by species is not climate change but how human beings use and alter landscapes.
Since how people use land and water is the critical factor in protecting species from extinction, looking to the future there is good news with regard to strongly positive trends in population, farmland, urbanization, protected areas, and wealth. As we’ve seen in earlier chapters, human population will most likely peak in this century and begin to fall. Second, average wealth will also increase substantially, which will generate more demand for environmental quality, including the expansion and protection of wild areas.
Expanding Protected Land and Seascapes
In fact, the expansion of protected areas is already happening at a remarkably fast pace. The World Bank notes that protected areas have nearly doubled from 8.5 percent in 1990 to 14.3 percent in 2012 of the w
orld’s total land area. That’s an area twice the size of the entire United States. Marine protected areas have increased from 4.7 percent of territorial waters in 1990 to 10 percent in 2012. Under the Convention on Biological Diversity, governments of the world have committed to protecting 17 percent of terrestrial and inland water areas and 10 percent of coastal and marine areas by 2020.
Additionally, forests covered 41.6 million square kilometers (16 million square miles) of the globe in 1990, falling to 40.2 million square kilometers (15.5 million square miles) in 2011, about one-third of the world’s land area. The encouraging news is that the annual global deforestation rate decelerated from an average of 0.18 percent in during the 1990s to an average of 0.11 percent in the last decade.
Still Time Enough to Save Ocean Biodiversity
A January 2015 article in Science by a team of researchers led by University of California at Santa Barbara ecologist Douglas McCauley seeks to analyze what is happening to marine biodiversity. The good news is that extinctions in the seas appear to have been much rarer than on land. For example, while the IUCN reports that 514 terrestrial animal species have gone extinct since 1500, only 15 marine species have. These include the great auk, Steller’s sea cow, and the Caribbean monk seal.
Nevertheless human pressure, especially overfishing, has dramatically reduced the numbers and ranges of many marine species. The study notes, “Aggregated population trend data suggest that in the last four decades, marine vertebrates (fish, seabirds, sea turtles and marine mammals) have declined in abundance by on average 22%. Marine fishes have declined in aggregate by 38%, and certain baleen whales by 80% to 90%.” Scripps Institution of Oceanography researcher Jeremy Jackson reported in 2008 that the populations of large open ocean predators such as tuna and sharks have been reduced by 90 percent, oysters by 91 percent, and North Atlantic cod by 96 percent. Nevertheless, as the Science article points out, “Marine defaunation, however, has not caused many global extinctions of large-bodied species. Most large-bodied marine animal species still exist somewhere in the ocean.”
The chief cause for declining marine populations is overfishing, but habitat degradation could play a bigger role over the course of this century if global warming and ocean acidification continue apace. To rein in excessive exploitation of wild marine populations, the authors recommend among other policies the adoption of incentive-based fisheries. One of the main ways to achieve this is to close open-access fisheries by privatizing them. A 2008 study in Science found that implementing such a policy “halts, and even reverses, the global trend toward widespread collapse.”
McCauley and his colleagues observe, “Wildlife populations in the oceans have been badly damaged by human activity. Nevertheless, marine fauna generally are in better condition than terrestrial fauna: Fewer marine animal extinctions have occurred; many geographic ranges have shrunk less; and numerous ocean ecosystems remain more wild than terrestrial ecosystems.” As a result, the researchers conclude that while the need for action is urgent, there is still time to rescue and restore the biodiversity of the oceans.
Cities Spare Nature
Another extremely positive megatrend with regard to protecting and restoring nature is urbanization. In his 2010 article “How Slums Can Save the Planet,” prominent environmental thinker Stewart Brand cited architect Peter Calthorpe’s 1985 assertion that “[t]he city is the most environmentally benign form of human settlement. Each city dweller consumes less land, less energy, less water, and produces less pollution than his counterpart in settlements of lower densities.” By 2010, the majority of people lived in cities for the first time in history. Demographers expect that 80 percent of people will live in urban areas by 2050 or so. Setting aside the demographic fact that people who live in cities have fewer children, what this trend means is that a lot fewer people will be living on the landscape in the future. Today, about half of the world’s population of 7.2 billion people lives in rural areas. Assuming that world population grows to 9 billion by 2050 and that 80 percent do live in cities, that would mean that only 1.8 billion would be on the landscape, as compared to 3.6 billion today. If world population tops out at 8 billion, then only 1.6 billion people would live in the countryside—2 billion fewer people than live there now.
In The Communist Manifesto, Karl Marx asserted that bourgeois capitalism fueled the growth of cities and “thus rescued a considerable part of the population from the idiocy of rural life.” History has shown that people prefer the opportunities and excitement of city life to rural “idiocy.” And the former country dwellers are voting massively in favor of urban living with their feet. Some 60 million people are leaving the countryside to move into cities annually. While some portion may be pushed by war or drought or poverty into cities, most people today are pulled in by the prospect of reinventing themselves, escaping from the narrow strictures of family, class, and community, and a shot at really making it.
As humanity has urbanized, people have become ever less subject to nature’s vagaries. For instance, a globally interconnected world made possible by the transportation networks between cities means that a crop failure in one place can be overcome by food imports from areas with bumper crops. Similarly, resources of all types can be shifted quickly to ameliorate human emergencies caused by the random acts of a brutal insensate nature.
Today cities occupy just 2 percent of the earth’s surface, but that will likely grow to 3 percent over the next half century. Oddly, environmentalist gadfly Jeremy Rifkin has proclaimed, “In the next phase of human history, we will need to find a way to reintegrate ourselves into the rest of the living Earth if we are to preserve our own species and conserve the planet for our fellow creatures.” Actually, he’s got it completely backward. Humanity must not reintegrate into nature—in that way lies disaster for humanity and nature. Instead we must make ourselves even more autonomous than we already are from her.
Peak Farmland
Considering that agriculture is the most expansive and intensive way in which people transform natural landscapes, the really good news is that the amount of land globally devoted to food production may be falling as population growth slows and agricultural productivity increases. “We believe that projecting conservative values for population, affluence, consumers, and technology shows humanity peaking in the use of farmland,” conclude Jesse Ausubel, the director of the Program for the Human Environment at Rockefeller University, and his colleagues in their 2013 article “Peak Farmland and the Prospect for Land Sparing.” They add, “Global arable land and permanent crops spanned 1,371 million hectares in 1961 and 1,533 million hectares in 2009, and we project a return to 1,385 million hectares in 2060.” As a result of these trends, humanity will likely restore at least 146 million hectares, an area two and a half times that of France or the size of ten Iowas, and possibly much more land. “Another 50 years from now, the Green Revolution may be recalled not only for the global diffusion of high-yield cultivation practices for many crops, but as the herald of peak farmland and the restoration of vast acreages of Nature,” write the researchers. “Now we are confident that we stand on the peak of cropland use, gazing at a wide expanse of land that will be spared for Nature.”
The Return of the Forests?
As a consequence of peak farmland, the forests that harbor many species are regrowing around the world. This was confirmed by researchers in a 2006 article on forest trends in the Proceedings of the National Academy of Sciences that found that “[a]mong 50 nations with extensive forests reported in the Food and Agriculture Organization’s comprehensive Global Forest Resources Assessment 2005, no nation where annual per capita gross domestic product exceeded $4,600 had a negative rate of growing stock change.” Consider, for example, that between 1960 and 2000, India added 15 million hectares to its forests, an area larger than the state of Iowa. In fact, leaving aside Brazil and Indonesia, forests around the world have increased by about 2 percent since 1990, according to researchers at Resources for the Future.
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br /> In 2014, the Food and Agriculture Organization (FAO) reported somewhat less rosy trends with regard to global forest cover. Based on analyzing satellite imagery, the FAO’s Global Forest Resources Assessment team concluded that the total forest area in 2010 was 3.89 billion hectares (15 million square miles), which is around 30 percent of the global land area. Between 1990 and 2010, there was a net reduction in the global forest area of around 5.3 million hectares (20,000 square miles) per year. Net deforestation amounted to roughly 106 million hectares (400,000 square miles), an area more than double the size of California. The FAO reports that the extent of boreal, temperate, and subtropical forest area over the past twenty years has largely remained steady and most of the forestland cover reduction occurred in tropical forests.
A February 2015 study also using satellite imagery published in Geophysical Research Letters by University of Maryland researchers reported similar but accelerated trends for net tropical deforestation. They looked at trends in thirty-four countries that account for 80 percent of tropical forestlands. During the 1990–2000 period the annual net forest loss was 4 million hectares (15,000 square miles) per year. During the 2000–2010 period, the net forest loss rose to 6.5 million hectares (25,000 square miles) per year. The net tropical deforestation in the past twenty years amounts to about 105 million hectares (400,000 square miles).
The End of Doom Page 28