Our species is threatening the existence of thousands of others in 25 biological hotspots around the world. According to a new study by Population Action International (PAI), Nature's Place: Human Population and the Future of Biological Diversity, more than 1.1 billion people are living within the 25 areas that are at once the richest in species diversity and the most environmentally threatened.
Census data from countries around the world were used to determine the population density and projected population growth in each of 25 biologically rich hotspots and three major tropical wilderness areas. Together, the hotspots contain more than 60 percent of the world's plant and animal species within just 1.4 percent of the planet's land surface.
Human population density levels and growth rates in the hotspots significantly exceed the world average. In 19 of the 25 hotspots, population is growing faster than in the world as a whole. In 16 of 25, population densities are at or above the average density of the planet. Today, each hotspot retains no more than 25 percent of its original natural vegetation.
The report finds that the human population of six billion combined with human demand for natural resources, waste disposal methods, and concentration in hotspot regions underlies and fuels the more direct causes of recent and current plant and animal extinctions. These extinctions are proceeding at least 1,000 times faster today than in the pre-human past, PAI notes, and this rate is expected to accelerate in the 21st century.
PAI's findings are consistent with the beliefs of many scientists. A 1998 Harris poll found that almost 70 percent of biologists polled believe that a mass extinction is already underway, and that one fifth of all living species could disappear within the next 30 years.
Extinction caused by humans is not new. Between 50,000 and 10,000 years ago, as early populations of humans expanded across the continents, more than 200 species of large animals disappeared forever. Then, between 1,500 and 500 years ago, as human populations reached the farthest oceanic islands, over 1,000 species of island birds went extinct.
Today's wave of extinctions, however, is even more extensive, the report continues.
It is fundamentally different from its two predecessors in ways that relate strongly to the pervasiveness and size of today's human population.
For the first time, human activities are affecting species of all types and habits, at all points of the globe, and pushing many toward extinction, PAI finds. Habitat loss alone could drive at least half of all living species to extinction, the report says.
Other agents of human caused extinction, including pollution, overhunting, overfishing and introduction of exotic species into weakened ecosystems could cause the loss of even more species.
More than 75 million people, or about 1.3 percent of the world's population, now live within the three major tropical wilderness areas, Upper Amazonia and Guyana Shield, the Congo Basin, and New Guinea and the Melanesian Islands. Population growth in these regions averages about 3.1 percent per year, more than twice the world's average population growth rate. The result is rapid deforestation and increased hunting of native species.
PAI notes some reasons for hope. Population experts say human fertility'measured as the number of children born by each woman'is declining in most regions. Women are choosing to have fewer children, and to have them later in life. Human population is expected to stabilize in this century.
PAI recommends three major initiatives to remedy the situation: