Just two years ago, forest lined most of the dirt road from this jungle town westward to the Andean foothills. As paving of the Interoceanic Highway from the Brazilian border to the Pacific coast nears completion, however, cattle pastures and gold mines have advanced in lockstep with the road graders.

Such trends pose a stern test for Reducing Emissions from Deforestation and Forest Degradation (Redd), a concept aimed at allowing industrialized countries to meet greenhouse-gas emissions targets in part by funding forest protection in developing nations.

With deforestation the cause of 17% of the world’s greenhouse gas emissions—more than those of the globe’s entire transport sector—Redd is expected to be a high-profile topic at the upcoming United Nations climate conference in Copenhagen. (See Centerpiece—this issue.)

For many forest advocates, Redd represents a way of tapping the emerging world market for carbon offsets to create a strong economic incentive for woodland conservation. Indeed, Peru’s environment ministry and green groups see compensation for avoided deforestation as the greatest hope for the country’s rainforest. “There has got to be some other financial force coming into the tropics than mining, logging and cattle,” says Gregory Asner, a Carnegie Institution for Science researcher who is based at Stanford University. “Redd represents an alternative.”

But the plan to turn forest conservation into income could be torpedoed by competing forces—particularly in this region by miners who blast away with high-pressure hoses in search of gold. Another threat is climate change itself, which could compromise the ability of the region’s forests to store carbon.

For avoided-deforestation efforts, this adds up to twin challenges—ensuring powerful economic incentives are brought to bear while at the same time developing reliable ways to measure and monitor forest-based carbon stocks.

Southeastern Peru’s Madre de Dios department has become a laboratory for efforts on both fronts. For instance, Asner is testing new satellite and aerial technology to make monitoring faster, more accurate and cheaper.

To date, the difficulty and cost of monitoring tropical carbon stocks have been an obstacle. Some companies have embraced voluntary carbon offsets, but many are reluctant to pursue Redd without reliable ways to measure carbon in the forest and to monitor deforestation.

Aerial measurement

Asner says that by combining satellite images with three-dimensional, laser-generated aerial images, his team can calculate carbon stocks remotely with the same precision as can be achieved in the field—and at a fraction of the cost. In one afternoon, a technician sitting at a desk in Lima could produce an up-to-date image of the pilot area in Madre de Dios—some 4.3 million hectares (10.63 million acres)—at a cost of about 10 cents a hectare, he says.

From the air, Peru’s Amazonian lowlands resemble a mottled green carpet adorned with snaking brown rivers and comma-shaped lagoons. Beneath the canopy, however, are dozens of forest types, from upland terra firme woodlands to palm swamps. They have different characteristics and store different amounts of carbon. Carried by plane 2,500 meters (8,200 feet) above the forest, Asner’s Light Detection and Ranging (Lidar) system shoots laser beams at the trees below. The result is a three-dimensional image of the forest’s biomass. Because about 48% of biomass is carbon, that allows Asner to calculate the forest’s carbon stocks.

“These forests have, on average, 140 tons of carbon per hectare,” Asner says of Madre de Dios. He can calculate the amount to within 20 tons per hectare. While that may still seem like a wide margin of error, other systems have an uncertainty level of 100% or more, he says.

Bamboo stores less carbon than a tree. But in the lowlands, carbon storage also depends on soil type and fertility, nutrient levels, frequency of inundation and human disturbance.

Asner found higher carbon stocks in forests that get enough seasonal flooding to wash nutrients into the zone, and lower levels in forests growing over more recent river meanders, where more severe inundation uproots trees.

Comparing Lidar images to satellite images enables Asner and Peruvian technicians to calculate biomass more precisely. They confirm their figures with on-the-ground spot checks of field plots. By making the software available for free and providing training, Asner hopes to develop an accurate, standardized system for use across the tropics. His next step will be to use Lidar to gather chemical data from trees so he can map species along with carbon stocks.

Subtler impacts

Monitoring must detect more than clear cuts. While selective logging causes less concentrated impacts than clear cutting, Asner says, the impacts add up. His data show that in tropical forests, selective cutting affects areas 20 times larger than clear cuts. And for every tree felled through selective logging, he says, 10 to 30 more fall due to the opening of access roads and damage during logging operations. Says Asner: “Selective logging “is better than [clear-cutting], but only if you do it well.”

Global warming itself could compound the problem. “Climate change might trump all the issues,” says Foster Brown, a scientist with the Woods Hole Research Center who studies land-use change in Acre, Brazil. “The range of plausible impacts [from climate change] is great enough to be of concern, and that is beyond the control of planners in the Amazon.”

Climate models predict warmer, drier areas along the base of the Andes south of the equator—right where Peru hopes to offer forests for carbon offsets. Says Asner: “We have really scary evidence that these forests can’t persist under a warm climate.”

In Madre de Dios, alluvial-gold mining poses a particularly urgent problem. Environmental groups are devising a plan by which Redd will be used to persuade local landowners to protect their forested property. But miners worry about being forced out, and have threatened to lead regional strikes.

Whether initiatives such as Redd could create truly competitive incentives at the local level remains a question mark for many.

“[Redd] shows potential on the carbon-emitter side of the equation,” Asner says. “The hard question is: can you bring it into a region and offset the desire to do mining?”