What world leaders are doing about it depends on which world leaders you're talking about. Many world leaders ignore population concerns because they don't care, or because they are afraid to step on people's reproductive rights. Some world leaders actually have an underpopulation problem to worry about; many parts of Russia and Europe have shrinking populations due to many people electing to have only one kid, or no kids at all. But for leaders for whom overpopulation is a pressing problem, some have taken measures to prevent it: China is famous for its "one child" policy permitting only one or two children to each family, and some parts of India have experimented with incentives like paying poor women to undergo sterilization surgery when they decide they don't want any more kids.
I'd advise you not to panic yet. Our technology is improving at an impressive rate; we have more clean energy, better food-growing capabilities, and a better understanding of ecology than ever. There are still a lot of problems, sure. But many people are working to make things better, and how many people the planet can support is partially a function of how efficiently and wisely we use our resources. It could conceivably hold many more people than we have now if we had highly efficient ways of producing and using food, and of living without destroying the environment around us.
Lastly, I need to say that if the world were to end in 2012 or anytime soon--which I find unlikely--it would be much more likely to be a completely natural disaster than a human-made one. There are a large number of natural disasters that could topple our civilization at any given time--supervolcanoes, massive earthquakes, asteroid impacts, etc.--but all of those tend to happen only once in tens or hundreds of thousands of years, and all of them are things that are not influenced by human activity.
If the 2012 doomsday really happen, Humans will learn a lesson that they will never forget so they won't overpopulate the earth again.
Or there are many things because it overpopulated the earth? or other
Humans don't change their ways until they are placed under extreme circumstances,such as extinction, when we are facing the end of our race we will find a solution one way or another, we are very resource full. And China was doing something about it, until they stopped caring.
And our population will be the least of our problems. A huge crisis will come up, ex: ice age, since were burning so much fossil fuels we are increasing the rate in which the next ice age is approaching, the ice age is natures way of making sure earth doesn't burn up and that everything is balanced out, but after that happens i guarantee humanity will change their ways. They just have to find out what the consequences for their mistakes are.
i leave it up to natural disasters to keep the course of the population intact. i do not believe the end of the world is coming because i don't this that will come until around the 40th century.
i also believe that between the year 2012 and 2020 that there will be 2 more major earthquakes another major hurricane and i believe that the Yellowstone volcano will erupt which will indeed set back the population. i do not believe that the volcano will erupt the way scientist think it will erupt. i don't even think it would wipe out all of america but it will definitly destroy a substantial amount
Most of your rant is off-topic for Astronomy and Space, and the Mayans didn't really make any 2012 doomsday predictions. I have an anxiety disorder too, but I don't believe everything I read on conspiracy sites. Stop reading those sites if they upset you and try listening to scientists who know what they're talking about. Overpopulation and scarcity of resources are very real concerns, but they have nothing to do with the crackpot 2012 theories.
World leaders are old, they don't care about the furture, they're be dead.