From 2016 to 2019, the team led by Prof. Dr. Michael Kohl of the University of Hamburg has collected a globally unique treasure trove of data in South America (Guyana and Suriname), Central America (Belize) and the Caribbean (Trinidad). With the help of students and local partner institutions, all trees on a total of 100 hectares of forest were recorded; a total of 80.000 pieces.
In view of the extreme diversity of species in tropical forests, species identification alone was sometimes only possible with the aid of laboratory tests. In addition, Prof. Kohl measured trunk diameters and coordinates of all trees, estimated their age and the amount of carbon they sequestered.
There are only one or two commercially viable trees per hectare of forest in the tropics. Other woods emit unpleasant odors, for example, dog urine among others. Or they have such short fibers that boards made from them break very quickly.
The study showed, for example, that forests have not recovered twenty years after they were first used, as was generally assumed.
Huge areas of forest are cut down every year in the tropics. Animals and plants lose their habitat, climate-damaging greenhouse gases are produced. Tropical forest specialist Prof. Dr. Michael Kohl has studied established protection measures – and helped develop more efficient ones.
Mr. Kohl, since 2005, the United Nations has been bundling its extensive measures for tropical forest protection under the name REDD+. Two out of five approaches have put you under the microscope. What conclusions have you come to?
Unfortunately, the analyzed measures do not produce the desired effects. Last year, we examined the release of so-called future trees, which is recommended as a measure for sustainable forest management and for increasing the carbon storage of forests. The growth of these future trees is to be encouraged by cutting down neighboring trees. In Europe, this is a common method in forest management. In tropical forests, on the other hand, it has a negative impact, as felling leads to high carbon losses and affects animal and plant habitats. The measure does nothing for climate protection, i.e. the actual goal, as we have calculated.
How would that have worked?
Plants protect the climate by sequestering carbon. The future trees should sequester a particularly large amount of carbon through their increased growth – more than if they were allowed to grow together with neighboring trees with which they compete for light and growing space. Apart from the negative side effects mentioned above, however, this calculation does not add up. It takes 130 years for there to be a positive effect on the carbon balance of the forest. This is a time span we can’t keep track of. We do not know what will happen to the climate and tropical forests by then. It would therefore be better not to interfere with the natural forest structure.
What about the second measure you examined in the REDD+ program?
We have also analyzed the impact of financial compensation for countries that want to cut down less rainforest in the future. Countries must demonstrate that they will destroy less forest than in previous years. However, this penalizes countries that have long protected their forests and favors countries that have deforested large areas recently. In addition, such a proof for the countries is complex and expensive. Often, compensation payments are not enough to offset the cost of capturing the altered carbon stocks.
Are no more effective instruments?
But. Sometimes very small, practical measures can help. For example, we studied local sawmills and found that they can only process 30 percent of a tree into lumber due to outdated technology – as opposed to 80 percent of a tree that is processed in sawmills in Germany. So more than two-thirds of the tropical forest giants cut end up as unused sawdust. If the local sawmills were better equipped, the felled trees could be much better utilized. As a result, the mostly poor countries of origin would have to cut down fewer trees and could afford more forest protection.
Relatively new is the approach to certify supply chains. My team at the Institute of Wood Science at the University of Hamburg has collaborated on a new ISO/DIN standard. This measure is aimed at us as consumers in Europe. After all, destroyed tropical forests are in many products we buy. For example, they contain palm oil from plantations that have been established on cleared forest land.
Is the deforestation-free supply chain standard already in use?
It is still relatively new. But it is already being discussed intensively at the EU level. And a few days ago, even a major discount grocer announced plans to ensure deforestation-free supply chains by 2025. I hope that many more companies will follow.
Michael Kohl is Professor of World Forestry at the Institute of Wood Sciences at the University of Excellence in Hamburg, Germany.