Today approximately 44 percent of the world’s 7.2 billion people are under 24 years old – and 26 percent are under 14. Of those 7.2 billion people, a staggering 82 percent live in less developed regions of the world – primarily sub-Saharan Africa and Asia. Currently, the global median age is 29.2 years old, a sharp contrast to Europe, for example, where the median age is 41.

October 31, 2011, was notable not only for the annual ritual of candy and costumes, but also for its designation by the United Nations as the date when global population reached seven billion. Although just an estimate – demographers are not able to count individuals in real time on such a large scale – the event was an important opportunity to present population trends to the media and public dialogue. Several babies born that day were named the “seven billionth;” in Russia, where various incentives have been implemented to try to boost an ultra-low fertility rate, Vladimir Putin visited a maternity ward to greet one of them.

The original version of this article, by Carl Haub, appeared on Demographics Revealed.

There has been quite a bit made in the media and in blogs about low birth rates in industrialized countries. Quite correctly, many people (and countries!) are concerned that unprecedented aging and a dearth of younger people are leading to serious pressure on national budgets from a rising burden of support for the elderly because of  a declining group of tax-paying workers. But the situation is far from equal everywhere, and less is written about that.

Friction between Japan and China in the East China Sea has escalated this year to the point where jets on both sides have been scrambled and Chinese military vessels have locked their fire control radar onto their Japanese counterparts multiple times. The source of this tension is the Senkaku (as they are known in Japan) or Diaoyu (if you’re in China) Islands – specifically, who owns them.

When Superstorm Sandy slammed into the U.S. East Coast last October, it was the latest in a series of “teachable moments” about our growing vulnerability to climate change.

2012 witnessed a remarkable number and extremity of environmental conditions, from Hurricane Sandy and the U.S. drought to wildfires in Siberia and drought-driven blackouts in India. Arctic sea ice melted to its furthest extent in recent history. The energy landscape continued to change as well, from the launch of the U.S. Navy’s Great Green Fleet to the first liquefied natural gas shipments across the Arctic. As President Obama clearly stated in his second inaugural address, climate change is heightening both our risks and the need to respond, but tying together all of these issues is a highly complex endeavor.

The original version of this article, by Christina Larson, appeared on Yale Environment 360.

Bouncing along bad roads in a jeep through central Mongolia, with bright blue skies and high clouds overhead, we drive for miles through a treeless landscape, passing only dry grasslands dotted with cattle and white yurts. But as we head north – myself, two U.S. scientists, and one Mongolian forestry expert – we begin to notice Siberian pine and larch growing on the northern slopes of rolling hills, but not the southern slopes, and at some elevations, but not others. In water-scarce Mongolia, as my travel companion Neil Pederson of Columbia University’s Lamont-Doherty Earth Observatory explained, the precarious growth of trees is limited by temperature and moisture availability; small variations – northern slopes are slightly cooler and wetter – can make all the difference.