Monday marks World Population Day, as the UN Population Fund says the world's population may reach 7 billion by the end of October.

This year's event will serve as a call to governments, organizations and communities to understand population issues worldwide and spearhead action. The UN Population Fund estimates that people's average age around the world has been raised by more than 20 years.

The world now sees a population increase of nearly 80 million every year, most of which comes from under-developed countries. As a result, issues such as the gap between rich and poor, food safety and resource shortages are becoming more challenging.