12/21/2012 11:46 am ET Updated Feb 19, 2013

Leaving a Green Legacy Depends on Our Actions Today

December is an excellent time to ponder the past year - what we've accomplished, and what we didn't quite finish. But frankly, I've always found the future to be way more interesting. The past is done and gone. The future's an open book, just waiting to be written.

What will our story be? When people in the future look back, what will they say about us? I hope they'll be able to say we did our best to leave them a planet they can thrive on, but at the rate we're going, that's certainly not assured.

As we head into 2013, we face big environmental challenges that are hundreds of years in the making. Many of them could take hundreds more years to make right. If we want to leave Earth in good shape for our great-grandchildren, we'd better start now.

One of the ways we can leave a better planet for everyone is to slow down population growth. Don't get me wrong: Population growth is not solely to blame for our environmental problems - not by a long shot. But population growth makes many of them worse - and makes solutions that much harder to achieve.

Climate change is the granddaddy of them all, and as our world population has surpassed 7 billion, our carbon emissions have grown, too. According to a 2005 study by the London School of Economics, every one of us in highly developed nations could reduce our carbon footprint by 40 percent over 40 years, and the savings would be canceled out by population growth alone. And that doesn't even count what we all hope happens - that the developing world rises from poverty and begins to enjoy some of the creature comforts we all take for granted.

Deforestation is another environmental challenge closely tied to climate change and population growth. Philip M. Fearnside of the National Institute for Amazon Research put it simply: "More population leads to more deforestation." He should know: The institute is based in Manaus, one of the fastest-growing cities in Brazil. While the average Brazilian woman has 1.86 children, rates in the Amazon are significantly higher, at 2.42. As land is cleared for building, agriculture and resource extraction, carbon is released. In fact, few human activities release more greenhouse-gas emissions than does deforestation in the Amazon.

Food security is another environmental and humanitarian challenge in 2013 and beyond. Water resources have grown scarce in many areas thanks in part to drought. Meanwhile, the miraculous growth of agriculture productivity - the "green revolution" - has slowed, and some experts think we could be headed toward "peak fertilizer," a time when the amount of agricultural chemicals we're currently using can no longer be sustained. It's estimated that we'll need to increase food production 70 percent to adequately feed everyone in 2050 - a tall order.

According to the United Nations, we could have anywhere from 9 billion to 10.6 billion people on Earth by then. Meanwhile, 222 million women in developing nations want to end or delay childbearing but don't have access to contraception. Half of pregnancies in the United States are unplanned. Ensuring that every woman around the world is able to avoid pregnancy when she wants to is an important step toward slowing population growth, reducing environmental pressures and providing a bright future for everyone. An American investment of $1 billion annually in international family planning - our fair share of meeting this unmet need - would help ensure that bright future.

The kind of world we can expect in 2013 and far beyond depends on the decisions we make today. One of those decisions needs to be support for voluntary family planning programs if we're going to leave a green legacy for our grandchildren. That's a new year's resolution we should all be making.

John Seager is President of Population Connection, the nation's largest grassroots population organization. The organization's website is