The general idea that Thomas Robert Malthus had; population needs to be regulated to a "sustainable" level.
In the 60's through 80's, the Earth's population skyrocketed, causing many to think there would be no food left in coming years.
Many Neo-Malthusians believed that natural checks on population like hunger was good for our world, but not the global crisis that was forseen.
The world came up with the green movement, trying to balance our resources.
Malthus believed that "self control" or abstinence, was the best method of birth control.
This line of thought has been transferred to todays Neo- Malthusians. The idea of birth control is one of wealth in many communities, considering some couples cannot buy it.
Neo Malthusianism was and is controversial because of how much the rich liked it. The rich wanted to keep the population of the commoners in check, so to keep their own property.
Many believe that the world, and humans, will change so that our growing population is not a problem. Most of these people live by this and are active in womens rights, green movements, or food supply programs. Others believe that control of our own population will benefit us. The simplest way given by Malthusians is to use birth control.