World Population Projected to Cross 11 Billion Threshold in 2100

By Sophie Simon and Brian Kateman

On a Tuesday in September of 1999, the number of people living on Earth hit 6 billion. In 2011, the U.N. announced that the world population had reached 7 billion. This year’s new projections for future population growth are higher than previously expected.

Last month, on June 13, 2013, the U.N. released new estimates based on statistical analysis at the University of Washington indicating that the world population could reach nearly 11 billion people by 2100. This number represents a significant increase from the previous 2011 projection of 10.1 billion – a difference of 800 million people.

According to Adrian Raftery, a Professor of Statistics and Sociology at the University of Washington, the projected rise is mostly attributed to fertility rates in Africa. Because birth rates have not dropped as quickly as expected, researchers’ long-term population predictions are altered. Consequentially, the continent’s current population of 1.1 billion is forecasted to reach 4.2 billion by 2100, nearly quadrupling its size.

The 2013 projection modifies previous numbers — thanks to improved fertility forecasting methods, updated U.N. population data, and finer-tuned statistics to anticipate life expectancies. While Europe’s population may decline slightly due to fertility below replacement level, longer life expectancies may cause subtle increases in populations in other nations across the globe. Nowhere, however, do population shifts compare to the drastic fourfold increase projected for the African continent.

Raftery also mentions the absence of discussion on the increasing world population, an issue with no expiration date that has been overshadowed by other critical global matters such as poverty and climate. However, it is important to recognize the incontestable ties between such concerns and the pressures of an expanding population.

A greater number of people create greater challenges for the future, when rapid population growth brings concern for the social and environmental consequences. The massive surge in population will be most prominent in ballooning mega-cities, whose swelling occupancies will exacerbate environmental problems and overcrowding.

Joel E. Cohen, population biologist at Columbia University, expressed urgency when the population hit the 7 billion mark in 2011: “Today’s as good a day as any to be aware of the problems of the world’s population and to begin to take action to solve them.” Now, in 2013, scientists and researchers in various fields are searching for solutions to slow population growth and develop sustainable cities that can better support large populations.

A century ago, there were fewer than 20 cities of one million or more people. Today, there are 450. Such cities that cover less than 5 percent of the Earth’s land surface leave a disproportionately hefty environmental impression. Urban sprawl is requiring the ongoing construction of cities that are both resource-intensive, and not thoughtfully adapted to local climates.

According to scientists, over 70 percent of carbon dioxide emissions today can be attributed to city needs. Urban CO2 emissions increased from 15 billion metric tonnes to 25 billion metric tonnes from 1990 to 2010, and forecasts project that number to increase to 36.5 billion by 2030. Participants in the “Planet Under Pressure” conference held in London in 2012 advocate re-engineering cities to make them more energy efficient. Fundamentals from trash to transportation need to be rethought through the lens of global sustainability in burgeoning urban centers. Across the globe, projects and initiatives are springing up to address the challenges of growing cities.

Columbia University’s Millennium Cities Initiative, founded by Jeffrey Sachs, Director of the Earth Institute, Professor of Sustainable Development, and Professor of Health Policy and Management, is a project that aims to help expanding cities in sub-Saharan Africa become viable and sustainable. As the population of Africa continues to inflate, sub-Saharan Africa’s urban population is projected to double between now and 2030. The burden created by urban crowding necessitates a reconsideration of how the basic infrastructures of schools, health facilities, water, waste disposal, and energy systems are provided.

Projects like Millennium Cities hope to alleviate many of the pressures that crowded cities place on infrastructure, public services, and the environment. In the long term, experts are also searching for means to slow population growth and decrease the birth-rate. While fertility rates globally are, in fact, declining, many scientists and experts propose that structural changes can play a role in how much and where our population shifts.

“What will happen to the world population is not carved in stone,” said Cohen, “but is subject to influence by how much we invest today in family planning programs, education and the status of women, and alleviation of poverty. Nobody knows when or at what number the human population will peak because it depends on what we and future people decide to do to improve human well-being.”

Sophie Simon is an Intern at the Earth Institute Center for Environmental Sustainability. She is studying Geography and Human Rights at Macaulay Honors College at Hunter College.

Brian Kateman is the Assistant Program Manager at the Earth Institute Center for Environmental Sustainability. He is studying Conservation Biology at the Ecology, Evolution, and Environmental Biology Department.

— Interested in learning more? Join EICES in class or online to examine issues concerning the growing population and climate change as part of the Earth Institute’s Executive Education Certificate in Conservation and Environmental Sustainability. Contact Brian Kateman, Assistant Program Manager of Education Programs, at bk2460@columbia or 212-854-0350 for more information.