Scientists worry that rapid population growth will overstress the earth's natural resources and crowd out undomesticated plant and animal species. All people want to be fed, clothed, housed, and have access to clean water. To meet these desires, water, land, forests, and other natural resources must be exploited to some degree. As population increases, more resources are needed to meet basic desires. More forest must be chopped down to provide wood for housing and fuel.
More cleared land is needed for agriculture and development.
All of these resources are finite. At the same time as people consume these resources, they produce waste that is put back into the air, land, and water. The greater amount of waste from larger populations puts more stress on ecosystems. Even if markets function with perfect efficiency, and the best technology is always used, it will take more resources to support a larger population than a smaller one, and the environmental costs of doing so will be probably be higher as well. It is true that the highest population growth rates are found in developing countries.