The past week saw the human population reach the 7 billion mark (or, perhaps not yet as Robert Mackey of the NY Times blogs). In the wake of this milestone there has been substantial activity on the internet and international newswires to mark its passing. The Guardian visualizes how future population trajectories will look like in different countries around the world by 2010, while the BBC has a neat little tool that allows you to calculate how much the world's population has changed since ones birth.

There has been two main takes on the passing of the 7 billion mark - either that its a sign of coming increased pressure on the Earth system, or that population per se is not the key issues to be tackled. A very good resource on the complex issues regarding the population growth topic is the National Geographic website.

The under-secretary general of the United Nations and executive director of the UN Population Fund, Babatunde Osotimehin, writes that reaching this number should act as a stark reminder that there is still much work to do to on sexual and reproductive health if we are to meet the millennium development goals by 2015.

In slight contrast, an interesting piece by Juliette Jowit argues that its not the growing number of people on the planet that should be worrying us, but rather the way a minority of humans use the Earth's resources (IIASA makes a similar argument):

"For environmentalists, talk of too many people is a dangerous distraction for campaigners and consumers, too many of whom will find it a convenient excuse to ignore the more pressing need for changes to what and how we spend our growing riches."

This is supported by recent empirical studies that shows how the richer a country is, the more environmental damage it does (seriously damaging the popular idea of the Kuznets curve - that environmental degradation plateaus or decreases past a certain threshold of per capita wealth).

Surely the constantly growing human populace will bring with it great challenges, such as how to feed the planet. But at the same time, it brings with it an increase in opportunities to make a difference. One of my personal favorite sites, discovered by researching for this post, is the 7 billion actions site:

"A world of 7 billion people poses many challenges – and countless opportunities to make a positive difference. 7 Billion Actions, established by the United Nations Population Fund, inspires change that will make a difference by highlighting positive action by individuals and organizations around the world."