The world is gathered in Copenhagen in an effort to reach an agreement to slow global warming. Elinor Ostrom, winner of this year's Nobel prize for economics, spoke with Spiegel Online about shared ownership, local action and why we can't sit around waiting for politicians to act.

SPIEGEL ONLINE: The Copenhagen summit is about setting new global rules for how we treat the Earth. But are people willing to change their personal lives accordingly?

Elinor Ostrom: Under the right circumstances, people are willing to accept additional efforts and costs. It all depends on trust in the fact that others will also act. Humans have the capacity to engage and see that their own long-term future is harmed if they don't change their lifestyles. Under the right circumstances they understand: It's not me against you. It's all of us against ourselves, if we don't act. So trust really is the most important resource.

SPIEGEL ONLINE: How can we generate enough trust so that we all act in concert?

Ostrom: Rules set from the top are not enough. Successful communities often have a few common design principles - monitoring and sanctioning of the participants, for example. They also have conflict resolution mechanisms in place and the people have some authority to make their own rules. Under those circumstances humans can develop some trust in each other - faith that if they take a costly action that benefits everybody in the long run, others will also invest.

SPIEGEL ONLINE: Why is it less effective if governments establish strict rules from the top down?

Ostrom: Because people will not identify with it. My research has shown that forests managed by local communities are in a far better state than state-run parks, where locals feel left out and officials can be bribed. Let us imagine, we live in a village and have all agreed that none of us is going to be in the forest on Saturday or Sunday, so that we can give the forest time to recreate. If I then see you in the forest when you're not supposed to be, I will probably yell at you. If only the state is in charge, I will just walk on past.

SPIEGEL ONLINE: In your research, you focused on local and regional levels. What makes you think that your solutions would work for the entire planet as well?

Ostrom: Indeed, the global scale is a challenge. Building that kind of knowledge between the different parties is tricky. We need our global leaders to take some of the decisions on a very big level. Here at the summit, those guys are talking to each other and gaining some trust because they meet face to face. But then they go home - and that's when the real action starts.

SPIEGEL ONLINE: Can money help to build trust between developing nations and industrialized nations?

Ostrom: Maybe, and it is hard to see a climate deal without serious financial commitments. But at the same time, I am very worried and nervous about corruption. If we pour money into a country in which the corruption level is very high, we would be kidding ourselves not to think that some of it will end up in the wrong pockets. At first, a lot of the proposals on the table sound great. But four to six years later, you have a lot of politicians who have money in Swiss bank accounts. What we need are tight rules and controls to ensure that the billions that might be put on the table here are used correctly.

SPIEGEL ONLINE: In other words, an anti-corruption task force - like the one that exists in Indonesia - might be the best environmental protection agency?