Although you cannot read the articles online without a subscription to the magazine, I strongly encourage you to pick up a copy at your library. The Sciencemag.org website does include a nice seven-minute video providing an overview of the world's population issues, and the introduction to the special issue lays out the problem:
Today these demographic patterns spark concerns, not of a single explosion, but of “cluster bombs” in rapidly growing countries such as Nigeria and Pakistan, which are hobbled by poor governance and limited schooling capacity and already have huge numbers of poorly educated young adults without job prospects.
Debate continues over how best to address these and other problems and over whether rapid population growth is best dealt with by expanding family planning programs or implementing policies that will improve livelihoods and increase the education of girls and young women—or both. Still, many experts remain optimistic that with the right mix of policies, countries can harness the opportunities for economic growth and development offered by a young and educated workforce, congregating in dense, networked urban environments.
The [special issue] contains News stories by Science's staff and research assessments by leading experts, enhanced online with videos and dynamic graphics, explores these issues, many of which continue to split demographers.