There are numerous problems with the environment today. Problems that are in dire need of attention. However, what needs to be acknowledged is that the vast majority of these problems cannot be corrected in the long run without first dealing with the problem of overpopulation.
When people think of population, they're most likely to think of swarms of people. Overpopulation is not population density, but rather the number of people in an area relative to its resources and the capacity of the environment to sustain human activities. Even more important than the number of people are the resources consumed by each person, and the damage done by technologies used to supply them.
As the population of the United States recently surpassed 300,000,000, many people are still incapable of sensing the problem of overpopulation. They point to the fact that there is enough wide open space available to hold numerous times the present population. But what they don't realize is that most of the open space that they are talking about is not inhabitable.
Sure there are other countries that have many more people per square mile than the United States. But these countries are either third world countries that use just a small percentage of the natural resources that we do, or else they rely on other countries to supply them with natural resources. Overpopulation is when the number of people can not be permanently maintained without depleting resources and without degrading the environment and the people's standard of living. Because we are rapidly using up resources around the world, virtually all nations are overpopulated.