The core threat to biodiversity on the planet, and therefore a threat to human w
The core threat to biodiversity on the planet, and therefore a threat to human welfare, is the combination of human population growth and the resources used by that population. The human population requires resources to survive and grow, and many of those resources are being removed unsustainably from the environment. The three greatest proximate threats to biodiversity are habitat loss, overharvesting, and the introduction of exotic species. The first two directly result from human population growth and resource use. The third results from increased mobility and trade. A fourth major cause of extinction, anthropogenic (human-caused) climate change, has not yet had a large impact, but it is predicted to become significant during this century. Global climate change is also a consequence of the human population’s need for energy and the use of fossil fuels to meet those needs (Figure 1). Environmental issues, such as toxic pollution, have specific targeted effects on species but are not generally seen as threats at the magnitude of the others.
Habitat Loss
Humans rely on technology to modify their environment and make it habitable. Other species cannot do this. Remove the entire habitat, and the species will become extinct unless they are among the few species that do well in human-built environments. Human destruction of habitats (habitat generally refers to the part of the ecosystem required by a particular species) accelerated in the latter half of the twentieth century.
Consider the exceptional biodiversity of Sumatra: it is home to one species of orangutan, a species of critically endangered elephant, and the Sumatran tiger, but half of Sumatra’s forest is now gone. The neighboring island of Borneo, home to other orangutan species, has lost a similar forest area. Forest loss continues in protected areas of Borneo. The orangutan in Borneo is listed as endangered by the International Union for Conservation of Nature (IUCN). Still, it is simply the most visible of thousands of species that will not survive the disappearance of the forests of Borneo. The forests are removed for timber and to plant palm oil plantations (Figure 2). Palm oil is used in many products, including food products, cosmetics, and biodiesel in Europe. A 5-year estimate of global forest cover loss from 2000 to 2005 was 3.1%. Much loss (2.4%) occurred in the tropics, where forest loss is primarily from timber extraction. These losses certainly also represent the extinction of species unique to those areas.
Most consumers do not imagine their home improvement products might contribute to habitat loss and extinction of species. Yet the market for illegally harvested tropical timber is huge, and the wood products often find themselves in building supply stores in the United States. One estimate is that up to 10% of the imported timber in the United States, the world’s largest consumer of wood products, is illegally logged. In 2006, this amounted to $3.6 billion in wood products.