Still, like Goodall, other scientists, advocacy groups and lawmakers argue that slowing population growth could be key to fighting climate change.
The United Nations Population Fund's 2009 annual report links slower population growth to reduced greenhouse-gas emissions.
"The whole world has been talking about carbon credits, carbon trading and emissions targets. But not enough has been said about the people whose activities contribute to those emissions," the report says. "Unless climate policies take people into account, they will fail to mitigate climate change or to shield vulnerable populations from the potentially disastrous impacts."
In December, more than 60 members of Congress, citing in part the need to address climate concerns, urged the Obama administration to improve financing for family planning efforts in a letter to Peter Orszag, director of the Office of Management and Budget.
A report in September from the London School of Economics found that contraception is almost five times cheaper than conventional green technologies such as windmills or solar panels at combating climate change. It cites U.N. estimates that 40% of pregnancies worldwide are unintended.
"Stabilizing population levels has always been essential ecologically, and this study shows it's economically sensible, too," said Roger Martin, chair of the Optimum Population Trust, which commissioned the report.
The non-profit Trust, of which Jane Goodall is a patron, campaigns for family planning, sex education and women's rights. It advocates that couples voluntarily "stop at two."#