Population as a global issue
According to the United Nations, the world's population passed 7 billion on 31 October 2011. How many people there are, how many children they have, how long they live, and where and how they live all affect almost every part of the planet. That includes land, oceans, fisheries, forests, wildlife, grasslands, rivers and lakes, groundwater, air quality and climate.
This is why many geographers rank population growth among the most important issues facing humanity. People disagree about it, though. Some argue the world is overpopulated and that growth must be slowed. Others say more people is not automatically a problem.
A 2011 estimate suggested that if every person on Earth stood shoulder to shoulder, the whole world population would fit inside the area of Los Angeles.
The planet is not short of space. The debate is about where people live and how they use resources.
Demographers use a set of tools to describe population: maps of where people live, rates that measure births and deaths, graphs of growth, and population pyramids. Each one shows a pattern. Learning to read them carefully comes before explaining why the patterns exist.
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