The primary source of environmental degradation in the US is corporate waste and pollution, not increased population. Destructive agricultural and industrial practices, such as flood irrigation, unnecessary pesticide and chemical use, strip mining, timber clear cutting, toxic dumping and wasteful energy use on the part of corporations have a much greater negative impact on our environment than growth in population. Resource depletion cannot be viewed in terms of sheer population numbers.
Some people consume far more than others.
Developing countries that have traditionally had very low resource consumption such as China, Mexico, and Angola are now the target of a corporate media blitz designed to boost consumption. Halting the export of wasteful Western consumerism will do far more to save the environment than focusing on population growth. Lines drawn on the map for political reasons such as the border around the US have nothing to do with natural systems, the resources available within those systems, and the rate of resource consumption that will maintain ecological balance. Many population control advocates tend to focus on birth rates in the last few decades, a very short period in the history of the world, during which birth rates for people of color have exceeded those of white people. Today, people of Asian and African descent account for 71.2 percent of the world's population, less than in 1650.