There is every sign that humanity has entrained a sixth great extinction episode in the history of life on Earth. Species are disappearing at dozens of times the “background” rate—the average rate that has prevailed during geological periods outside of previous mass extinctions. The diversity of populations, essential for the delivery of crucial ecosystem services, is being lost even faster. These losses are mostly irreversible, and in aggregate they threaten to unravel the very fabric of civilization.
Yet most people are unaware of the peril. They don’t realize that populations of animals, plants and microbes are essential to the functioning and overall stability of our life-support systems. Among ecosystem services they provide, interacting organisms stabilize climate and reduce human vulnerability to extreme weather events (floods, droughts, destructive storms) and even tsunamis. They help prevent soil erosion and recycle essential nutrients, thus preserving the productivity of farmland and forests. They help control potential pests of crops, carriers of diseases, and supply free pollination services. And they supply wild food from both land and sea.
Still less do people grasp the causes of the decay of biodiversity, even though they have long been well known to science.(1) The most obvious immediate factor in causing extinctions is the destruction of habitats. For instance, it is estimated that roughly half of Earth’s wetlands have been lost since 1900, while forest area has been approximately halved in the past 300 years.(2) All living beings are attuned to living in certain conditions, as any child who drops a bowl with a goldfish in it quickly discovers. The relationships often are very tight indeed: many butterflies can live only where certain kinds of plants grow for their caterpillars to eat; most plants need specific conditions of temperature and moisture and soils with certain chemical and physical characteristics. When its habitat is destroyed or greatly altered, a population of organisms can migrate to another place with suitable habitat, evolve to fit into new conditions, or—most often—go extinct. Survival depends on a variety of factors such as ability to travel and rapidity of reproduction (time between generations). With human-caused habitat modification, displaced organisms often have nowhere to go, as remaining suitable habitat may be beyond barriers or already occupied. Human-caused changes are often too quick and too extensive for a successful evolutionary response.
“Human beings are great habitat wreckers, but they sometimes also exterminate populations and species while leaving their habitats more or less intact.”
“Habitat destruction” generally raises visions of bulldozers filling in a wetland or chainsaws putting finish to a tropical rainforest. There’s all too much of that. But a lot of habitat mayhem is much more subtle. Climate change destroys habitats for many creatures. Populations of butterflies that our group studied on Stanford campus were extirpated partly by climate change, but it took detailed statistical analyses to show it. There were no piles of dead butterfly bodies as evidence. Habitats also can be altered dramatically by the injection of chemical pollutants, including endocrine-disrupting compounds (EDCs), which can have more damaging effects at extremely low concentrations than at high concentrations. Signs symptomatic of EDC pollution affecting wild organisms are becoming increasingly worrying. Fertilizer runoff destroys the freshwater habitats of many species by encouraging the overgrowth of algae, which suffocates fish, shellfish and other creatures in a process called eutrophication. In some cases, invasions of exotic organisms can fatally change a habitat when they eat or out-compete the previous occupants. The introduction of rats, dogs and pigs played major roles in the prehistoric extermination of as many as 2,000 species of birds, mostly flightless rails, on Pacific islands.(3) In Hawaii, the presence of the new animals destroyed the habitat for dozens of bird species and introduced mosquitoes that carried a disease that decimated others.
Human beings are great habitat wreckers, but they sometimes also exterminate populations and species while leaving their habitats more or less intact. One reason for this kind of anthropogenic mayhem is overharvesting. Many kinds of oceanic fishes and some whales are notoriously threatened by overfishing, as are many animals in poor countries that are harvested for “bush meat.” In this, as in many cases of environmental destruction, historically rich countries have led the way. A classic case is that of the passenger pigeon, whose flocks in eastern North America once numbered in billions. Market hunting for the succulent squabs (young pigeons) for the table and even for use as targets in shooting galleries did them in around the end of the 19th century. The American bison lost most of its gigantic populations to hunting for hides and tongues around the same time; unlike the passenger pigeon, some remnant bison populations survive. Many populations of black rhinos and tigers have plummeted or disappeared because of demand for some of their body parts in folk medicine in Asia, especially as aphrodisiacs. Viagra may prove a boon for the survival of remnant groups of these animals! Some species of cacti have suffered population extinctions because of “cactus rustling”. That is the illegal collection of cacti, especially from the Chihuahuan desert of the southwestern USA and northern Mexico, for use as ornamentals in landscaping. Saguaro and barrel cacti are especially desired and so especially threatened.
Of course, direct endangering is not limited to animals and plants that people wish to use—it also happens to those considered to be pests or enemies. Prairie dogs, once a major feature of landscapes in the western United States, are keystone species critical to the health of some ecosystems because they are important prey for various predators and because of their important effects on the soil. Sadly, they have largely been reduced to remnant populations. Their persecution can be traced in part to damage they can do in agricultural areas (they clear vegetation around their burrows), but perhaps more to the myth that horses can break their legs in prairie dog holes. Wolf populations in North America have suffered greatly because of the threat they represent to domestic livestock, and the largely imaginary threat to people (attacks are extremely rare; dogs are much more dangerous). Wolf management is a complex issue of trying to balance the esthetic and ecosystem benefits of wolves against the economic damage ranchers can suffer. Tiger management can present even more problems in India, where the big predators sometimes develop a taste for human flesh.
This brings us to the question of the ultimate drivers of extinction. Wolves and tigers pose no problem at all when they do not mix with people. Paul remembers well a day in 1951 when he was camped in a swampy area on the south shore of the Great Slave Lake in northern Canada. He was awakened by a splashing sound and peered out of his tent. Two big wolves were trotting toward his tent. About ten feet away they stopped, gazed in astonishment at the tent and the human head, and loped off; a thrill for Paul, a shock for the wolves. A rare contact at a time and place when both species were scarce and conflicts were few.
But fewer and fewer areas of Earth remain where contact with people can be easily avoided by other animals. There are now almost three times as many people as there were in 1951, some 15 times as many as in 1651. There is no question whatsoever that the escalating global extinction crisis is partly the result of the population explosion of Homo sapiens. But it is not only the increase in human numbers that has so decimated biodiversity, it is also the result of the escalating demands each person, on average, has made on the environment.(4) Growing per capita consumption has contributed almost as much to the problem as population growth. In the end, aggregate consumption, the product of human numbers and each person’s consumption, is the ultimate cause of habitat destruction and direct endangering—modulated by the technologies and socio-political arrangements made to service the consumption, including, in part, how “green” it is.
Much could be done to help conserve biodiversity and ecosystem services. Many steps, such as the establishment of reserves and laws to protect endangered species, have long been in place. But populations and species continue to disappear. A fundamental change in human culture seems required to prevent the loss of those elements of natural capital(5,6) from causing a collapse of civilization. The idea that growth of material output can and will be a permanent feature of civilization is really an artifact of the past two centuries or so, as exploiting the bonanza of fossil fuels allowed Homo sapiens to speed cultural and environmental change to a level that it became easily perceptible by individuals—something the agricultural revolution of 100 centuries ago failed to do. But long-term economic growth as imagined by most economists is biophysically impossible. Simple mathematics shows that a “long” history of exponential growth (in this case just ~250 years out of millions) does not imply that a long future of such growth is possible.(7) Whenever people talk as if a 3.5 per cent annual growth would be a desirable global goal, you know they don’t comprehend that this means, ceteris paribus, doubling the impact of humanity on its life-support systems in just 20 years, and multiplying it more than 30-fold in a century. Since, at today’s level of assault, those systems are rapidly deteriorating, with billions of people malnourished, climate disaster looming, a wild scramble for the last resources launched,(8) and more billions still “scheduled” to augment the human population, the notion that the problem can be solved by further economic growth is insane. Growth is not the cure, it is the disease.
So the first big cultural change that is needed is to transform the recently dominant view of overall growth of the economy, to change the focus to needed growth among the poor to be compensated by required shrinkage among the rich. We’ll not dodge a central issue: if we’re going to rescue civilization, some redistribution will be necessary. As we pointed out 40 years ago, the rich countries are overdeveloped, and seemingly universal development goals are environmentally lethal.(9) Then we called the cure “semi-development” of poor countries balanced by “de-development” of the rich. More recently, we have used different words, calling for “rescaling” the human enterprise.(10)
The second needed cultural change is to end a more recent widespread myth—that the world can be satisfactorily run by free markets. It can’t. In economic lingo, all externalities (unintended side effects of market transactions) can’t be internalized. In some circumstances, properly regulated markets can do an excellent job of allocating resources. But markets can’t foresee the consequences of climate disruption or the release of EDCs, think about modernizing infrastructure or institutions, or encourage the building of social capital. Markets can’t consider the needs of societies as a whole or those of future generations. In short, markets can’t plan.
Changing the norms represented by growthmania and unnatural marketophilia will not be easy, but that may well be necessary before proper policies to protect biodiversity can be implemented. Leading such a change in norms is a major challenge for IHDP. Helping to meet that challenge is the nascent Millennium Alliance for Humanity and the Biosphere, the MAHB (“mob”—mahb.stanford.edu). The MAHB is a global initiative aspiring to catalyze a network for fundamental social change. One way is by bringing interdisciplinary research on Foresight Intelligence, the art of “future friendly” individual, social and political decision-making, to civil society activists and think tanks. To complement the research component of the MAHB, it is building a cyberhub for progressive civil society networks seeking to reverse environmental and social trends threatening humanity. The hub’s mission is to transform knowledge and insight into action. Populated by existing civil society groups, the hub will be fueled by “MAHB knowledge nodes”, in a network of scholars and social thinkers committed to closing the puzzling gap between our understanding of the effects of environmental degradation and our ability to act in ways that will reverse current trends.
This sort of concerted effort seems to be required to catalyze the necessary transformation, but it would have little hope of success unless it can connect with a top-down effort working for the same goals. At the moment, hope for this seems forlorn. The United States government is not providing leadership—it is largely in the hands of the economically and environmentally clueless. Only if a citizen-based movement can generate the political clout to change that, might the probability of success significantly increase. Political power now rests heavily with the plutocracy, especially the fossil-fuel industries, whose business plan, to burn the known reserves of fossil fuels, could be described as “a plan to destroy the world”. In that other key nation, China, the national leadership is much better informed environmentally, but mid-level governmental growthmania and corruption make it difficult for them to make real progress.(11) While civil society in the USA is an uncoordinated shambles, in China it is just being born. The situation is hardly better in less powerful nations, with exceptions like Bhutan and Costa Rica, which can at most serve as good examples.
So what needs be done to try to save biodiversity? Obviously the stop-gap measures, inadequate as they are, must be continued to slow the decay of our life-support systems as much as possible until the needed cultural evolution can occur. And the wide variety of steps necessary to achieve a reorientation of society must be implemented as soon as possible. Long-term changes involve educating the entire public on at least the most basic elements of how the world works. That means introducing environmental science throughout school curricula and being sure that no one graduates from a university not knowing the significance of, for instance, the second law of thermodynamics, externalities, exponential growth, and ecosystem services. This is supremely important for individuals training to become social scientists, who would then (like the few pioneering heroes of today) hopefully be competent to consider the biophysical constraints under which social systems must operate. Such training is especially needed in the largely failed discipline of macroeconomics, suffering not just from unnatural marketophilia but also from planning phobia and utter neglect of natural capital.
But we cannot wait for the educational system to change gradually, because what happens in the next two decades will be critical. That’s where public education, social media, civil society, IHDP and the MAHB must come in. Whether the trajectory of society can be changed toward preservation of biodiversity and sustainability in time remains to be seen. If it is not, nature will change it for us in, from a human viewpoint, a much less desirable direction.
Note: The authors would like to thank Larry Goulder for his comments on this article.
REFERENCES
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ABOUT THE AUTHORS
Paul R. Ehrlich is presently Bing Professor of Population Studies and President of the Center for Conservation Biology, Department of Biology,
Stanford University, where his research focuses on Population Biology.
Anne H. Ehrlich is a senior research scientist and policy director of the Center for Conservation Biology at Stanford University. Besides her
research in ecology and population biology, she has taught and written extensively on issues of public concern such as population growth,
environmental protection, and environmental consequences of nuclear war.
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