Sometime today [October 31, 2011], the human population of the world reached 7 billion, according to the United Nations.
Whether the date is precisely accurate or only a reasonably close estimate, give or take a few days, is not the point. What matters is that, for the first time in human history, 7 billion people are now living on Earth and competing for essential resources—and we’re not ready for them, let alone for the billions of others who will soon be joining them.
Population Growth Has Been Accelerating for Centuries
The details of different population timelines and forecasts may vary slightly, but all clearly show that global human population growth has been accelerating rapidly over the past two centuries and is on track to continue increasing throughout the 21st century.
It took thousands of years, from the dawn of human history until 1804, for the human population to reach 1 billion worldwide. Yet it took only a little more than a century for the population to double to 2 billion in 1927, and less than 50 years for the global population to double again to 4 billion in 1975.
Global Population Still Growing Fast
Even with declining birth rates in many developed countries, the UN estimates that by 2050 global population will end up somewhere between 8 billion and 11 billion, and could reach 15 billion by the end of this century. At its current rate of growth, by 2030 humans will need a second planet the size of Earth—and with the same amount of natural resources—to satisfy their need for food, water and energy, and to handle their accumulated waste, according to a September 2011 calculation by the Global Footprint Network .
Here are just a few ways that the growing population will affect the planet and the people who live here:
Water Scarcity
By 2025, 1.8 billion people will be living in countries with water scarcity, and two-thirds of those will be living in conditions of severe water stress. People are using groundwater faster than it can be naturally replenished.
“We cannot talk about water without also understanding the enormously important role of population dynamics and population growth,” said Peter Gleick, a MacArthur Fellow who is also co-founder and president of the Pacific Institute for Studies in Development, Environment, and Security in Oakland, California.
Food Shortages
Population growth has forced more than 20 countries with scarce water and/or too little agricultural land to import grain, making them vulnerable to volatile food prices in the international market. To meet the future demands of a growing population, we must double world food supplies by 2050, possibly sooner, while reducing our impact on the environment.
Dwindling Forests
The growing demand for energy has led to significant deforestation worldwide. More than two billion people depend on wood for cooking and heating, particularly in developing countries. Projects in countries such as Indonesia, Nepal, and Uganda are fighting deforestation by providing alternative energy and incomes that don’t depend on clearing forest land for subsistence agriculture, along with health and family planning services to control population growth.
Decreasing Biodiversity
Population density is connected to the loss of biodiversity in many regions. Data from the Apache Highlands along the U.S.-Mexico border indicate that biodiversity tends to drop off at population densities of more than 10 people per square kilometer, according to research by Richard Gorenflo at Pennsylvania State University.
Climate Change
Determining how evolving demographic trends will affect the global climate is complex at best. Aging populations in industrialized nations could reduce carbon emissions long-term, while the growth of cities in developing countries could increase emissions. Overall, “slowing population growth by 2050 would meet 16 percent to 29 percent of the reductions in carbon emissions necessary to avoid dangerous climate change,” according to Brian O'Neill of the National Center for Atmospheric Research.