More than half of the carbon stored in forests around the globe is found in tropical forests. When they are destroyed, the carbon can escape into the atmosphere in the form of the greenhouse gas carbon dioxide, accelerating climate change as a result. For several years, with its REDD program, the United Nations has been attempting to implement various measures to protect the valuable tropical forests. However, hardly any of them work in practice.
The REDD program describes a total of five measures that are intended to preserve the tropical forests as valuable carbon sinks. We recently examined the measure “sustainable forest management,” which involves making more room for the crowns of so-called future crop trees by felling less-valuable tress in their immediate vicinity.
Doing so allows future crop trees to grow better, and this in turn means that they can remove more CO2 from the atmosphere and store it in their wood. Once the trees have reached a certain height, they are felled and used to make durable wooden products, in which the carbon remains stored. This is an established forest management method in Central Europe.
However, in the tropics the practice is problematic, as our latest findings show.
Over a period of four years, we mapped a total of 100 hectares of forest in Belize, Guyana, Surinam and Trinidad. To do so, we measured every one of the more than 80,000 trees in the area, compiling a veritable treasure trove of data that’s likely the only one of its kind.
Some of the regions we surveyed were extremely difficult to access. In such cases, someone familiar with the area usually led the way with a machete and forged a path through the dense forest – and we followed behind in single file. Among other things, we recorded the species, girth, height and coordinates of each tree. We then used this information to calculate the biomass and, from it, the amount of carbon stored in the wood.
As a rule, in tropical forests there are only a few tree species that can be marketed, and which are therefore worth felling. On average, only one or two trees per hectare are suitable for commercial use. To support these final crop trees, for every tree I had to clear up to four weaker trees, as our data shows.
Does this allow the final crop tree to grow so well that it stores more carbon and therefore more than compensates for the carbon loss due to the felled trees? We have calculated that we would have to wait over 130 years for this to be the case – an unrealistic timespan.
Forest management that is harmful in three ways
Harvesting trees in tropical forests is a fundamentally sensitive issue. Every metric ton of biomass that is intentionally harvested produces a further metric ton of lost biomass, which then lies in the forest unused: a dramatic balance sheet. These crop losses arise, e.g., as a result of clearing transport paths, or by adjacent trees that are knocked down during felling. In the areas we studied, we showed that “sustainable forest management,” in other words, the release of final crop trees, could more than double such losses.
But how can a measure that is essentially harmful end up in a rain forest protection program? Apparently, here a method that is suitable in Europe has been adopted for the tropics without examining the long-term growth dynamics involved.
This measure, however, is harmful in three ways. Any intervention in an untouched forest impacts the overall species diversity. At the same time, releasing individual trees is expensive, and is not commercially profitable. Furthermore, such measures don’t help the climate, because they don’t lead to increased carbon binding.
The balance is sobering. Last year we determined that compensation payments – another measure that the REDD program plans to implement – can also be counterproductive. To put it bluntly, countries that have long protected their forests are disadvantaged, while those that have destroyed their forests are rewarded if they slightly reduce the amount trees they fell.
Europe partly responsible for the destruction
This measure financially rewards countries if they clear less of their rainforests. However, the countries must prove how much forest they have saved. Especially for those countries that already protect their forests, delivering the proof is an extensive and therefore expensive process, since minor changes are more difficult to measure; often the compensation payments don’t cover the costs. At the same time, payments for preserving the forest as a whole are too low – selling timber, or clearing the forest and using the land for agriculture, are much more financially lucrative.
For the future of REDD, I advocate tightening the measures based on scientific consulting. The program has raised international awareness for the fact that rainforest protection is climate protection – and that is a positive development.
Basically, we need mechanisms that target the causes of rainforest destruction. 80 percent of deforestation in the tropics is the result of conversion into farmland, half by subsistence farmers and half by agribusiness.
Energy crops like sugar cane and oil palms, for example, are industrially cultivated, even though they’re not particularly efficient. Large areas are used for feed crops such as soybeans, which are needed for meat production. This meat is then imported by countries in the European Union. Here the initiative “deforestation-free supply chains” is a possible first step forward, since, through their consumer behavior, EU citizens are responsible for roughly ten percent of tropical forest destruction worldwide.
Michael Köhl is a Professor of Forestry and an expert on tropical forests. He conducts research at the Center for Earth System Research and Sustainability (CEN), and at Universität Hamburg’s Cluster of Excellence for climate research, Climate, Climatic Change, and Society (CLICCS).