CONTENTS
- The Earth and Its People
- Pollution and Health Risks
- Feeding a Future World
- Freshwater: Lifeblood of the Planet
- Oceans in Decline
- Forests: The Earth's Lungs
- Endangered Biodiversity
- Toward a Livable Future
HIGHLIGHTS
- Can development be sustained?
- Scientists point to environmental distress syndrome
- Cities grow ever larger
- Global temperatures rising
- Are we setting the stage for our own extinction?
- World population must stabilize
Population Reports is published by the Population Information Program, Center for Communication Programs, The Johns Hopkins School of Public Health, 111 Market Place, Suite 310, Baltimore, Maryland 21202-4012, USA
Fall 2000
Series M, Number 15
Special Topics
Population Pressures on Biodiversity
Population pressures have played a major role in the loss of biological resources (9). Human activities have accelerated the normal pace of species extinction—that is, the pace that could be expected without the influence of humanity—by some 1,000 to 10,000 times, depending on the specific species (141, 246).
In a study of 50 countries in Asia and Africa from 1980 to 1990, the United Nations Population Fund (UNFPA) found that the loss of natural habitat was greatest in areas of high population density and least in low-density areas. In the 10 countries that had lost the most habitat (averaging 85%), the average population density was close to 200 people per square kilometer. In the 10 countries that had lost the least amount of habitat (averaging 41%), the average population density was just 29 people per square kilometer (95).
Other researchers have reached similar conclusions (9, 43, 179). One estimate is that three-quarters of human-induced pressures on mammal species, and nearly two-thirds of such pressures on bird species, are the result of fragmentation and destruction of their habitats, as people use more land for agriculture, industry, roads, and other purposes (43).
Human migration and trade have posed other problems for biodiversity, as people have introduced many nonnative species to areas, such as Hawaii, whose fragile habitats cannot cope with them (19, 108). For example, the Black Sea's fauna have been nearly exterminated not only by overfishing and pollution, but also by the accidental introduction of a comb jelly fish from the North Atlantic, a species that now comprises about 95% of the Black Sea's biomass (19, 153). In the US the introduction of nonnative species has been implicated in close to 70% of all freshwater fish extinction (216).
 Lauren Goodsmith |
A nurse tends medicinal plants. About 40% of modern drugs come from the wild. Biodiversity also is key to agriculture, as constant infusions of new genes are crucial to improving staple food crops. |
Biodiversity Hotspots
Biodiversity hotspots are areas that contain a superabundance of plant and animal species but are threatened by human activities. Norman Myers coined the term "hotspots" in 1988, initially listing 10 tropical rainforests (161). He later expanded the number of hotspots to 18, and then to 25. Collectively, hotspots contain slightly more than half of all terrestrial species on just 2% of the world's land area. Most hotspots are substantially endangered already, having lost three-quarters of their total original vegetation (155, 164).
So far, all hotspots identified are on land (270). Many hotspots remain to be assessed and identified in marine areas, especially coral reefs, which are thought to contain more than a million species living on less than 1% of the earth's surface (103, 270).
Of the world's 25 terrestrial hotspots, 9 are in tropical rainforests, 5 include both wet and dry tropical forests, and another 5 consist of temperate Mediterranean-type ecosystems. In addition, three include tropical rainforest, dry forest, and arid systems; another is a mosaic of dry forest and savannah; while another is temperate forest and steppe; and the last is an arid region. An estimated 75% of all terrestrial animal species considered endangered or threatened live within these 25 hotspots (155) (see map).
The poor state of most biodiversity hotspots results directly from population growth and migration into these areas. A study by PAI found that by 1995 around 1.1 billion people, or 20% of the global population, were living within the 25 hotspots. Moreover, the average annual population growth rate in these areas was 1.8%, substantially higher than the 1.4% global rate and even above the average for developing countries, at 1.6%. PAI concluded that "human-induced environmental changes" will continue to put pressure on hotspots and, therefore, that conserving biodiversity requires paying close attention to population trends (35, 36).
What Can Be Done?
Scientists point to three actions in particular that could help protect biodiversity--and might even help ensure that human life on earth itself does not become extinct (9, 141, 163, 216) (see sidebar, Five Extinctions and Counting).
Protect hotspots. As more organizations focus on protecting hotspots, the species within them might stand a better chance of survival. In 1989 Conservation International and the MacArthur Foundation became the first organizations to adopt the concept of biodiversity hotspots as a guiding principle for investments in environmental conservation (155). As new hotspots in marine areas are identified and added to the 25 currently identified terrestrial hotspots, protection should be extended to them, as well (270).
Safeguard protected natural areas from development. Over the past two decades population pressures and a shortage of arable land have forced some 200 million landless peasants out of traditional farming areas and onto protected land rich in biodiversity. These "shifted cultivators," as Myers has termed them, have little choice but to exploit the animal and plant species in these "biological oases" (164). To protect these natural areas, more must be done to help farmers settle on productive land, while stemming the future flow of population into protected natural areas.
Implement the Convention on Biological Diversity. This Convention, which was opened for signature at the Earth Summit in Rio, took force in December 1993 and so far has been ratified by 175 countries. The Convention has three major objectives: conserving biodiversity, ensuring its sustainable use, and guaranteeing the fair and equitable sharing of its benefits.
The US has rejected this third objective, as currently worded, largely because of the influence of the pharmaceutical industry. As a result, the US has not ratified the Convention and is unlikely to help implement it until agreement can be reached on how to compensate the US pharmaceutical industry for its bio-prospecting costs (6). Nevertheless, the Convention can be a major force for conservation, and the 175 countries that have ratified can do more to achieve its goals.
