Kenneth J. Strom
Global human population growth is placing stresses on wildlife species and habitats, which challenges efforts to maintain Earth’s biodiversity. It is the purpose of this analysis to summarize what is currently understood about human population growth and its impacts on wildlife populations in order to better inform efforts to take direct action to prevent or mitigate those impacts. A review of recent findings about the population-environment nexus and the experience of the National Audubon Society in addressing population issues serves as the basis for this analysis.
During the twentieth century human population exhibited an unprecedented scale of growth, nearly quadrupling in just one century to over 6 billion people. At the current annual growth rate of approximately 1.4%, our population could double again by the middle of this century. Of particular concern to the fate of the rest of Earth’s species is the fact that the human populations inhabiting most of the 25 recognized global biodiversity hotspots are both denser and growing faster than the world average.1
Human populations can cause the extinction of other species through a number of mechanisms, including hunting and deliberate extermination, habitat degradation or destruction, and introduction of exotic species, each of which tends to be aggravated by growth in human numbers.2 Birds are particularly sensitive to these impacts, and recent trends in their numbers are indicative of the pressures created by human population growth. Fully half the species migrating between the United States and Latin America have experienced significant declines in recent years, while Latin America’s human population more than doubled in only 30 years. This extremely rapid rate of growth overwhelms the developing economies of the region, leading nations to exploit their natural wealth to try to solve their economic and social problems. The migratory birds are also impacted by population growth in the United States, the third most populous nation on Earth, where growth-driven habitat fragmentation contributes to their declining numbers.3
In response to a concerted international effort to address the causes of rapid human population growth, the global rate of growth has been declining in recent years. One dramatic example of this decline is Mexico, where the fertility rate has dropped to less than half of what it was in 1970. The experience of the last 30 years demonstrates that five factors are generally present in countries which experience significant declines in fertility rates: improved status for women, improved employment opportunities for women, better education for girls and women, reduced infant mortality rates, and increased access to modern means of contraception.3
Because continuing growth of the human population can undermine progress made on every other front in the protection and restoration of populations of wild species, it is clear that any successful effort to improve the global environment must be accompanied by direct action to address our own species’ population growth. Zoo veterinarians and other zoo professionals are in a uniquely influential position to address this issue. Their credibility as scientifically grounded conservators of wild species lends weight to their arguments when they educate the public or advocate to decision makers and the media on behalf of policies that will address population growth while also improving the lives of people and the survival of wildlife species around the world.
1. Cincotta RP, Engelman R. 2000. Nature’s Place: Human Population and the Future of Biological Diversity. Washington, DC; Population Action International: 80 pp.
2. Harrison P, Pearce F. 2000. AAAS Atlas of Population & Environment. Berkeley, CA; Univ. of Calif. Press: 204 pp.
3. Strom K. 1998. Population and Habitat in the New Millennium. Boulder, CO; National Audubon Society: 37 pp.