How much carbon dioxide can the earth’s forests draw from the atmosphere and at what price? Researchers have now investigated this using model calculations. According to this, the costs for afforestation and the like rise exponentially with higher CO2 reductions. According to the model, savings of 0.6 gigatons of CO2 per year would cost two billion dollars annually by 2055. On the other hand, if trees were to pull ten times the amount of CO2 out of the atmosphere, 393 billion dollars would be due. According to the study, the best cost-benefit ratio is the conservation of tropical rainforests.
Forests play an important role in efforts to meet internationally agreed climate targets. Year after year, the trees bind large amounts of the greenhouse gas CO2 and thus mitigate climate change. Numerous projects are therefore committed to the reforestation and replanting of forests in different parts of the world and are committed to the conservation of tropical rainforests. While several studies have examined the effectiveness of the individual measures, there has so far been little focus on the expected costs. A team led by Kemen Austin from RTI International in North Carolina has now dealt with this.
Incentives for sustainable forest management
For their calculations, the researchers used an existing model for global forest management and modified it so that they could use it to assess the effects and costs of various conservation, afforestation and management measures. “The global forestry sector can make a really significant contribution to achieving global climate goals,” says Austin colleague Justin Baker. “The physical potential is there, but when we look at the economic costs, they are not linear. That means that the more we want to reduce emissions, the more expensive it will be. ”For the scenario by 2055, forests could contribute ten percent of the total reduction required, provided they pull six gigatons of CO2 from the atmosphere every year. The researchers estimate the costs for this at 393 billion dollars per year.
This money should be used, for example, to set financial incentives for landowners and states to bind as much additional CO2 as possible in tree populations through sustainable forest management. For each tonne of CO2 that is drawn from the atmosphere in this way, the researchers have calculated an amount of 5 to 100 dollars and analyzed the effects on CO2 reduction in each case. In the most expensive scenario with the highest CO2 reduction, in which, in addition to conservation measures, the planting of trees and sustainable forest management also play a major role, the researchers even come to the cost of 281 dollars per ton of CO2. According to the researchers’ recommendation, CO2 prices should rise year after year, but they must be carefully balanced: First of all, they should promote the preservation of tropical rainforests in particular, as these make by far the largest contribution to binding CO2. If you prevent them from disappearing, that alone provides 30 to 54 percent of the potential CO2 reductions through forests.
International interactions
In contrast, the replanting of large forest monocultures should be financially less attractive. Because such intensive use is not only less sensible with regard to the climate, it also endangers natural ecosystems. In scenarios with high costs and high savings, such measures can still make a contribution, but in the opinion of the scientists they should not be the top priority.
In their model, the researchers also take into account that conservation efforts in one part of the world have an impact on other regions. For example, if the tropical rainforests are cut down to a lesser extent, this leads to rising timber prices and makes tree felling in other areas more attractive. This reduces the overall effect of the measure. In the model calculation, this leads to higher costs for the desired effects. However, from the researchers’ point of view, such cross-border interactions do not pose a problem. If the CO2 prices also rise, this in turn motivates to manage forests in a particularly sustainable manner, so that the removal of wood and new planting are balanced.
Just part of the puzzle
“To avoid the dangerous effects of climate change, it will be necessary to protect, rebuild and sustainably manage the world’s forests,” says Austin. “So far there has been little research into the costs of mitigating climate change through forests. A better understanding of costs will help us prioritize certain resources and develop more efficient mitigation strategies. “
In view of the fact that, even in the most expensive scenario, trees only contribute around ten percent of the total required reduction in emissions, the researchers also point out the importance of other measures, such as renewable energies that do not produce greenhouse gas emissions. “From this point of view, one should devote about a third of the effort to the forests and two thirds to other things – reducing coal, investing in solar energy, converting to electric mobility,” says Sohngen. “That’s what needs to be done if you want to make the overall mitigation as inexpensive as possible.”
Source: Kemen Austin (RTI International) et al., Nature Communications, doi: 10.1038 / s41467-020-19578-z