Barbara Kingsolver's latest book, Animal, Vegetable, Miracle, tells the story of how she and her family lived for a year eating only food they grew themselves or that they purchased from local food-growers.

She was generous enough to take time from her book tour to answer our questions on the importance of keeping in mind that we are what we eat.

Why is buying and eating locally-grown food important?

The shorter the distance between your meal and its point of origin, the more you can know about it. Certain systems of oversight are meant to help you untangle the great unknowns of a complex system: "organically grown," for example, guarantees that a food item was produced without toxic chemicals. But it still may have accrued the same fuel costs of processing and long-distance transport as the conventional counterpart. And if there's profit to be made, corporate agriculture will be involved, with the likely agenda of watering down all standards.

"Locally grown," by contrast, is a designation that's incorruptible. Buying food from growers at small markets or through Community Supported Agriculture (CSAs) is really the only way for most of us to step away from a disordered food system. Food from your neighborhood will likely be whole, unprocessed vegetables, fruits, or animal products grown on small, diversified farms by growers committed to the health of their land. The food is good for you, and the money you spend on it stays in your community, helping to keep those nearby green spaces intact and strengthening your local food economy.

Environmental Defense is working to reform the nation's farm policies, which historically have helped agribusiness rather than family-run farms. What can individuals do to help keep farmers on the land?

We can start by thinking about farmers every time we eat. Our food, however it may have been altered in the interim, was grown somewhere, by someone. Who was it? How did that person use the land? How much of my food dollar went to a farmer, to help support sustainable choices? On average, 85 cents of every food dollar goes to the processors, packagers, advertisers and oil companies who profit handsomely from our lack of regard for soil, water, climate and the future. Farmers have no choice but to respond to consumer demand. They can only grow what we will buy.

Food policy is made, not born. It's not "natural" that organic and whole foods cost more than tallow-fried junk. We choose that through our tacit approval of the Farm Bill that defines food and nutrition policy in this country. We've elected to subsidize corporate commodity farms while leaving small, diversified fruit and vegetable farmers on their own, trying to compete. For organic farmers it's even worse – we make them pay for their own inspection and oversight. If we'd like to flip this over and subsidize healthy rather than unhealthy foods, we can call our legislators and start talking. This is a good time to do it, because the Farm Bill is being renegotiated at this moment.

The experiment chronicled in your book was a major family commitment. Did it change you as a family? How?

Commitment is exactly the right word for it, and that's what made the project valuable to us. For years we had been thinking about the food industry and our part in it. We tried to make choices that were better for the environment and our farmers – but mostly when those choices were pretty easy.

When we made a formal commitment to ourselves (and the world, via a book contract) to spend one year eating only fruits, vegetables, and animal products that were produced locally, it felt something like a marriage ceremony. It pushed us toward a fuller engagement with a way of life we really knew we wanted. It moved us to get to the farmers' market even on Saturday mornings when we didn't exactly feel like it. It helped us pass up the Peruvian asparagus and Bolivian bananas, concentrating instead on whatever wonderful things were coming into season in our own county. We learned to start with incredibly fresh ingredients and cook with the seasons. We learned to sleuth out local products at our supermarket, where we found organic dairy products, cider vinegar, and many other wonderful things produced here in our region. We spent more time as a family in the kitchen, and in the garden. Hoeing weeds is good exercise; inventing recipes is both scientifically and artistically creative; these things added up to time well spent. Our formal year-of-local has ended, but we're still eating locally because we enjoy it. We occasionally buy transported foods (usually something from the ocean) but we now consider that a splurge rather than a daily entitlement.

When my kids are my age, everything about food will be different except for one thing: they will still have to eat. The fuel-intensive food industry of the present, which has come to seem normal to us in recent decades, will become impossible. When people look back on this era, it will surely seem grotesquely indulgent. The next generation will have to return in some way to more local and sustainable food economies. I'm happy to participate in this part of my kids' education, giving them a genuine understanding of food processes. What could be more important?

You're a long-time supporter of Environmental Defense. Is there a particular message you would like to give our audience of online members and activists?

Your members already know, as I do, that Environmental Defense is an effective force for steering this country's environmental policies into a cleaner future. I can only offer individual encouragement, and the promise that small changes in our lives, multiplied by thousands, add up to a revolution. We can't wait for radical conservation measures to be imposed on us by our government – that takes a courage that our political system probably can never muster, no matter who's in charge. The way to look at it, I think, is that WE are in charge, individually and collectively. By proving to myself that my family can learn to live well with less, drastically reducing our food-miles and our carbon footprint, I'm giving myself the courage to require more responsibility from myself, my fellow citizens, and our government.

Thanks so much for your time.

Thank you and thanks to all the other Environmental Defense supporters out there

Looking for more environmentally themed books? Check out the Environmental Defense summer reading list.

Our guest blogger, Sheryl Canter, is an Online Writer and Editorial Manager at Environmental Defense.

If you have a garden, you know the climate is warming. In temperate zones, the last frost in spring comes earlier, and the first frost in fall comes later. The longer growing season may allow you to grow vegetables you never could grow before. But you also may have noticed your weeds are more aggressive, insect pests are more of a problem, and pollen plagues you all summer long. You're not imagining things!

For over 40 years, gardeners have relied on the USDA Plant Hardiness Zone Map as a guide to what they can grow in their area. But the USDA zone map hasn't been updated since 1990, and gardeners have seen detectable shifts since that time.

In 2003, the American Horticultural Society (AHS) updated the zone map with a grant from the USDA, and published a draft of the new map [PDF] in The American Gardener. Based on temperature information from July 1986 to March 2002, the map showed widespread warming, with zones edging northward.

The USDA rejected the new map without explaining why, and said they would update it themselves. Four years have passed and still they have not released a new map. But the National Arbor Day Foundation has just released one, current for 2006. Like the 1990 and 2003 maps, the Arbor Day map is based on 15 years of data. The changes between 1990 and 2006 are dramatic; the U.S. is clearly getting warmer.

Global warming is caused by elevated concentrations of greenhouse gases in the atmosphere - notably carbon dioxide (CO2). Plants use sunlight, water, and CO2 to synthesize the glucose they need to grow - a process called photosynthesis. Thus when CO2 concentrations in the atmosphere increase, it acts as a fertilizer, accelerating plant growth. This may sound good at first, but there's more to the story.

CO2 fertilization affects different plants to different degrees. As Duke University biologists discovered, one plant that loves additional CO2 is poison ivy [PDF]. With increased CO2, poison ivy grows 2.5 times faster, and produces a more potent version of the rash-causing chemical urushiol. Other types of woody vines also grow much faster with higher levels of CO2 - fast enough to strangle and topple trees.

Accelerated plant growth has some other bad side effects. One is increased pollen production, creating misery for asthma and allergy sufferers. A Harvard study [PDF] showed that elevated CO2 concentrations caused up to a 55 percent increase in ragweed pollen production.

Another consequence is that high levels of CO2, while increasing crop yields, decrease the plants' nutritional value. Obviously this is bad for humans eating the plants, but it's also bad for humans growing them. Insects eat dramatically more plant matter when the plants are less nutritious (and ironically, can still starve to death from poor nutrition). Farmers using more pesticides to control infestations will increase pollution in rivers and streams.

So the next time you hear people arguing that global warming will be good for gardeners and farmers, set them straight!