What many of us really worry about is that there will be a crash landing.
California has 157 endangered or threatened species, looming water shortages, eight of the 10 most air-polluted cities in the country and 725 metric tons of trash washing up on its coast each year. California also has 38 million people, up 10% in the last decade, including 10 million immigrants. They own 32 million registered vehicles and 14 million houses. By 2050, projections show 51 million people living in the state, more than twice as many as in 1980.
In the public arena, almost no one connects these plainly visible dots.
For various reasons, linking the world’s rapid population growth to its deepening environmental crisis, including climate change, is politically taboo. In the United States, Europe and Japan, there has been public hand wringing over falling birthrates and government policies to encourage childbearing.
But those declining birthrates mask explosive growth elsewhere in the world. In less than a lifetime, the world population has tripled, to 7.1+ billion, and continues to climb by more than 1.5 million people a week.
A consensus statement issued by scientists at Stanford University and signed by more than 1,000 scientists warned, “Earth is reaching a tipping point.” An array of events under way—including what scientists have identified as the sixth mass extinction in the earth’s 540 million-year history—suggest that human activity already exceeds Earth’s capacity.
Climate change is but one of many signs of environmental stress. “The big connector is how many people are on Earth,” said Anthony Barnosky, a UC Berkeley integrative biologist. The world population is expected to reach 9.6 billion by mid-century. The addition alone will be greater than the global population of 1950. “The combination of climate change and 9 billion people to me is one that is just fraught with potential catastrophes,” said John Harte, a UC Berkeley ecosystem scientist.
The United States is expected to grow from 313 million people to 400 million. Economies have expanded many times faster, vastly increasing consumption of goods and services in rich and developing countries.
“We’re changing the ability of the planet to provide food and water,” Harte said.
Even scientists who doubt ecological collapse, such as Michele Marvier, chair of environmental studies at Santa Clara University, acknowledge, “humans dominate every flux and cycle of the planet’s ecology and geochemistry.”
Plummeting fertility rates, from 4.9 births per woman in the 1960s to the current 2.6, led to the belief that worries about population were overblown. The drop surprised demographers. Half the world—including Japan and Western Europe but also China, Vietnam, Brazil and other emerging economies—is below the 2.1 fertility rate needed for zero growth. The United States, the world’s third-largest country behind China and India, and the only rich country still growing rapidly, recently saw its birth rate fall to 1.9. [US growth is mainly due to high levels of immigration.]
But population momentum ensures that absolute numbers will keep rising for decades despite falling birth rates. That’s because the exponential growth that took just 12 years to add the last billion in 2011—and will take just 14 more years to add the next billion—means growth is building from a large base of children and teenagers, many intering their child-bearing years.
Falling birth rates have lulled people into complacency, said Joseph Speidel, a professor at UCSF’s Bixby Center on Global Reproductive Health. “The annual increment is rising quite dramatically,” he said. “We are still adding about 84 million people a year to the planet.”
More than 40% of the world’s 208 million pregnancies each year are unplanned, according to the Guttmacher Institute, a family planning research group. Half of U.S. pregnancies, about 3 million a year, are unintended, according to the National Campaign to Prevent Teen and Unplanned Pregnancy, a Washington advocacy group. About half of them end in abortion.
Across cultures, from Iran to Thailand to California, voluntary access to contraception has slashed fertility rates, Speidel said. But discussion of population growth remains taboo in the US. “Many young people on university campuses have been taught over the past 15 years that the connection between population growth and the environment is not an acceptable subject for discussion,” said Martha Campbell, director of International Population Dialogue at UC Berkeley’s School of Public Health, in a recent essay. Campbell argued that voluntary contraception is not coercive, but blocking women from controlling how many children they have is coercive. When given a chance, she said, women across cultures choose to provide a better life for fewer children.
The Guttmacher Institute said it would cost an extra $4.1 billion a year, little more than a rounding error in the $3.8 trillion U.S. budget, to provide birth control to all 222 million women in the world who want to limit their pregnancies but lack access to contraception.
“What many of us really worry about is that there will be this crash landing, from a planet with 9 billion, rapidly down to 5 or so,” said ecologist Harte. “The landing will result from methods of population reduction that none of us want to see, like famine, disease and war,” he added. “I don’t think anybody has described a workable trajectory that gets us up to 9 and then softly back down to 5.”
Sources for statistics: United Nations; Stuart Basten, Wolfgang Lutz, Sergei Scherbov, “Very long range global population scenarios to 2300 and the implications of sustained low fertility” in Demographic Research, Vol. 28, Article 39, May 30.
Carolyn Lochhead is the Washington correspondent for the San Francisco Chronicle. This article first appeared September 2, 2013, see: <http://www.sfgate.com/science/article/Population-growth-increases-climate-fear-4781833.php>.