Just Asking...David Tilman

What does President Obama have to do in, say, his first year, to show you, as an ecologist, that he’s committed to dealing with this challenge?
Conserving energy often saves money, but it often takes capital. So I would like to see the administration outline the major ways that are cost-effective for us to reduce greenhouse gases. And that has to do with energy efficiency in vehicles and buildings. In this country, we use twice as much energy in buildings as we do in cars. Our buildings are massively energy inefficient. The heating systems most of us have in our homes are old and outdated. Windows aren’t very good. Insulation isn’t good. Refrigerators are very inefficient. We now have technology that can cut that energy way down.

Nothing crazy, like a ban on front lawns or something.
Nothing crazy.

The situation is playing to Obama’s strengths in some ways—just communicating.
There are many times when politicians, because they’ve interacted with scientists and others, know more about a situation than most citizens do. But it’s very hard for them to do something about it because the public doesn’t understand the issue. Someone like Barack Obama, who is so good at communicating, has a chance to exert significant leadership on climate change and other environmental issues.

Will he be able to explain what negative carbon-dioxide sequestration means?
Well, I hope he can. When you burn something like alcohol or synthetic gasoline made from switchgrass or prairie grass, it’s recycled carbon dioxide. No increase in the air.

So the plant actually consumes the carbon dioxide. How is that different from burning fossil fuels?
Well, you’re burning carbon that was stored in the earth and you’re now putting it into the atmosphere. Fossil fuels cause greenhouse gases in the air to go up and up and up. If you have renewable fuels, it doesn’t go up at all anymore. We discovered that when you have these worn-out agricultural soils and you plant a mixture of prairie plants on them, not only will these plants remove carbon dioxide that is above ground, they’ll also put some of that into their roots below ground, and those roots get shed every year rebuilding carbon back up in the soil. [At Cedar Creek] we had more than a ton of carbon dioxide taken out of the atmosphere and stored in an acre of soil as dead organic matter every year. It went up by about a ton per acre, year after year after year. When you make a fuel with that biomass, the above-ground biomass becomes the fuel. The stuff building up in the soil restores it back to what it was before farming, and over the whole life cycle, carbon dioxide is removed from the air. It goes into the field, into the soil, and is stored and stays there as organic matter year after year. That means that these fields are carbon negative. At the end of making and burning this fuel, you have less greenhouse gas at the end than you did in the beginning because it’s being stored in that soil.

Whether it’s our electorate or what’s put on our table, diversity has a lot of cachet right now.
It’s interesting—as best we understand it, three and a half billion years ago there was no life on earth. Then there were some very primitive single-cell organisms, and those things have diversified through time. Now we have 3 million or maybe 10 million—we’re not sure—plants and animals and microbes living here. We now understand what those reasons are. Species on earth exist with each other basically because they do different jobs. When you have many species living together, that system as a whole actually functions better. It’s like having an economy—you want to diversify your portfolio. You actually get better long-term returns with diversification than you would if you bought any single stock on its own and just sold it.

We were addicted to monocultures for so long: White people are awesome. Corn is awesome. Ford and Chevy are awesome. How did this shift to diversity happen?
I’m not a social scientist, but it’s one of my untested hypotheses that some of our greatness as a nation is a result of accepting many, many different people with different backgrounds who have different ways of thinking. And we’ve let those with new ideas sort of invade our society and let those ideas grow and spread. So in many ways our long-term culture has been one of embracing diversity and using it—using intellectual diversity, using cultural diversity, taking the best part of one culture and the best part of another, and making a new culture. That’s really how diversity works in nature. There’s this competitive interaction. Things that do better when it’s hot take over when it’s hot, and when it’s cold, something else takes over. And in total, that system functions better.