Large-scale afforestation and reforestation can brake climate change
The Paris Agreement calls on us to limit global warming to 1.5 degrees Celsius above pre-industrial levels. To reach this goal, we need to reduce CO₂ emissions and remove existing CO₂ from the atmosphere. A team led by CDRterra scientists Yiannis Moustakis and Julia Pongratz has now demonstrated that large-scale afforestation/reforestation (AR) can make an important contribution to such efforts. Simulations by the researchers show that AR could reduce peak and end-of-century temperature and shorten the period during which global temperature exceeds the 1.5-degree target, The results are published in the journal Nature Communications.
AR is currently the most commonly used method of removing carbon dioxide from the atmosphere. “Overall, the international community has already announced ambitious AR goals of up to 490 million hectares by 2060, and this figure is likely to increase even further as more countries present their long-term plans. We wanted to find out how strongly these measures can influence the climate,” reports Moustakis. “Investigating their effects in detail requires the use of cutting-edge models which can represent an interactive carbon cycle that takes into account various processes and feedbacks.”
Modeling with more than 1,200 scenarios
The CDRterra-researchers employed an unprecedented number of more than 1,200 scenarios from Integrated Assessment Models (IAMs) – models that link climate policies with future energy, economic, and land use pathways – as well as restoration priority maps and biodiversity data to develop an ambitious AR scenario. In this way, the scientists were able to take technical and economic challenges into account, while also considering the impact on biodiversity and land availability in the countries.
Based on this, the researchers developed a scenario that foresees 595 million hectares (Mha) of afforested/reforested land by 2060 and 935 Mha by 2100. “This is definitely an ambitious scenario, and one could of course question the feasibility of such ambitious efforts. However, this is not arbitrarily chosen. We tried to develop a scenario that is rather in the range of country peldges globally, extend it to the end of the century, and constrain its spatial and temporal features by technoeconomic considerations, while minimizing the impact on biodiversity. ,” highlights Moustakis.
Next, the scientists analyzed this AR scenario with the Earth System Model of the Max Planck Institute for Meteorology in Hamburg, It models e the effects of afforestation/reforestation on the climate. The simulations used an overshoot scenario. It is a climate scenario where the emission trajectory is such that average global temperature goes beyond the 1.5°C target before falling back below this level around the end of the century. “As delays in drastic climate action persist, such scenarios are becoming increasingly probable,” emphasizes Moustakis.
Average temperature falls, overshoot duration shortens
The results of the simulations demonstrate that ambitious AR measures could substantially influence the climate. Specifically, AR could reduce global peak temperature at mid-century by 0.08°C, while lowering end-of-century temperature by 0.2°C compared to a scenario without AR. In addition, the measures could shorten the time during which global temperature overshoots the 1.5-degree target by 13 years. The footprint of AR on global temperature becomes evident already by 2052.
Another important finding of the simulations is that the feedbacks of AR do not outweigh their positive effects. This is significant because AR not only has effects on carbon sequestration, but also changes physical properties of the Earth’s surface, the evaporation of water and uch as the albedo – the ability of the Earth’s surface to reflect sunlight. This can lead to slight warming in some regions. But the study reveals, the cooling effect of CO₂ absorption predominates, as the local warming caused by AR is not strong enough to cancel out the cooling effect.
“These results show that global AR can in fact make an important contribution to mitigating climate change, when applied at the large sale,” explains Moustakis. “But it is not a panacea and must be viewed in a more comprehensive framework that takes socioeconomic trade-offs equally into account. Planting a forest could create jobs, revenue, and promote ecosystem services, but it could also deprive people’s livelihood, exacerbate poverty, financially or physically displace people, and disturb local food networks.”
Publication:
Yiannis Moustakis, Tobias Nützel, Hao-WeiWey, Wenkai Bao, Julia Pongratz: Temperature overshoot responses to ambitious forestation in an Earth System Model. Nature Communications 2024.
https://www.nature.com/articles/s41467-024-52508-x
Yiannis Moustakis, Julia Pongratz, Hao-WeiWey und Wenkai Bao are part of the CDRterra-consortium CDRSynTra.
Tobias Nützel does research for the CDRterra-consortium STEPSEC.
