Trees are worth more dead than alive on the international market — a stark economic fact that has undermined countless programmes to protect rainforests over the years. It is a lesson that should not be forgotten as the international community explores ways to reduce global-warming emissions from deforestation. Conventional programmes involving incentives, laws and enforcement may prove useful, or even necessary — as highlighted by Brazil's approach to the issue (see page 134) — but to solve the problem completely, the international community will need to design a better market that recognizes the value of standing trees, forests and the less tangible services they provide. Integrating deforestation into international carbon markets, the most notable of which is the European emission-trading scheme, is a good place to start.

In this context, the European Commission's recent proposal to bar deforestation credits from the next phase of trading is a disappointment. The commission's fear is that cheap deforestation credits will suddenly soak up all of the money for reducing emissions (see Nature 452, 8–9; 2008). If ending deforestation quickly is indeed the cheapest way of reducing emissions, it is not clear why this should be a problem. But in truth, a great deal has to be accomplished before any market scheme will be viable.

Global warming has given the world the opportunity to build a more comprehensive and inclusive economic model.

In recent years, for example, scientists have greatly improved their models for estimating the most critical number for deforestation: the amount of carbon released into the atmosphere when a given plot of land is razed. This information can now be extracted fairly accurately from satellite images. But to do that consistently, on a global scale, rainforest nations will need to train people and develop a standing infrastructure for monitoring. This will not be cheap — and is another area in which conventional government-run programmes might be needed. The scientific community can play a direct role as well, by helping to get these programmes up and running.

Access to information will be critical. A few satellites can cover the entire globe, but there needs to be a system in place to ensure their images are readily available to everyone who needs them. Brazil has set an important precedent by making its Earth-observation data available, and the rest of the world should follow suit. This is more than a matter of common courtesy. It will foster the kinds of checks and balances and independent analysis that must necessarily underpin a viable carbon market.

And the international community needs to start thinking about the next step: how to encourage good forest stewardship. As it stands, nations such as India and Costa Rica are in the odd position of receiving little or no benefit from a market in carbon credits precisely because they have been able to control deforestation. And if illegal deforestation were to come to a halt, then those nations benefiting from the carbon market would see that source of income dry up, creating the same pressures that caused the problem in the first place.

True, dealing with standing forests will be tricky; no one wants to create a permanent welfare programme for the tropics. Nevertheless it is vital that the issue is tackled. This is essentially what the delegates agreed to do last December at the United Nations climate-change conference in Bali, and their decision was a wise one. As long as the international community is playing with the architecture of a carbon economy, it should explore new and creative ways to build in 'ecosystem services' such as biodiversity and coastal protection. Bear in mind that the alternative to putting an economic value on these intangibles is implicitly to set their value at zero.

One of the oddly positive effects of global warming is that it has given the world the opportunity to build a more comprehensive and inclusive economic model by forcing all of us to grapple with our impact on the natural environment. We are entering a phase in which new ideas can be developed, tested, refined and rejected as necessary. If we find just one that can beat the conventional economic measure of gross domestic product, and can quantify some of the basic services provided by rainforests and other natural ecosystems, it will more than pay for itself.