There is an interesting debate in "The Economist" on whether there are too many people on planet Earth.
My perspective: All of the current crises (financial, economic, energy, climate change, food, water) are, in essence, expressions of the excessive population of the world, which will only grow worse as the 9.2 billion population figure is reached.
In some cases (food, energy, climate change) the connection is rather obvious. Prices are rising as demand outstrips supply. Greenhouse gas emissions are increasing as the population produces and consumes more and more. Other asset bubbles (housing, financial assets) are also related to the growing pull of demand.
It was appropriate that one of President Obama's first actions was to overturn Bush's ban on funding and promoting population control activities. But, as others have noted (for example, an article in Newsweek last week), perhaps it is too late to revert global warming.