Large-scale afforestation and reforestation can halt global warming

The Paris Agreement calls for limiting global warming to 1.5°C above pre-industrial levels. To achieve this goal, we need to reduce CO₂ emissions and remove existing CO₂ from the atmosphere.

A team led by LMU scientists Yanis Moustakis and Julia Pongratz has demonstrated that large-scale afforestation/reforestation (AR) can make an important contribution to such efforts. As reported in the journal Nature Communications, simulations by the researchers show that AR could reduce peak and end-of-the-century temperatures and shorten the period during which global temperatures exceed the 1.5°C goal. are.

AR is currently the most frequently deployed method of removing carbon dioxide from the atmosphere. “Overall, the international community has already announced ambitious AR targets of up to 490 million hectares by 2060, and this number is likely to increase further as more countries present long-term plans. “We wanted to know how powerful these measures are in their impact on the climate,” Moustakis says.

“To investigate its effects in detail, we need to use state-of-the-art models that can represent an interactive carbon cycle that takes into account a variety of processes and feedbacks.”

Modeling with over 1,200 scenarios

Researchers analyzed an unprecedented number of more than 1,200 scenarios from the Integrated Assessment Model (IAM), a model that links climate policy with future energy, economic, and land-use pathways, as well as recovery priority maps and biodiversity data. We used this to develop an ambitious AR scenario. . In this way, scientists were able to consider technical and economic challenges while taking into account the impact on each country’s biodiversity and land availability.

Based on this, the researchers created a scenario that predicts 595 million hectares (Mha) of afforestation/reforestation by 2060 to 935 million hectares (Mha) by 2100. .

“This is undoubtedly an ambitious scenario, and of course some may question the feasibility of such an ambitious undertaking.However, this was not chosen arbitrarily. Rather, it sought to extend it to all countries around the world, within the limits of national commitments, while minimizing its impact on biodiversity and limiting its spatial and temporal characteristics through techno-economic considerations. ” emphasizes Moustakis.

The scientists then analyzed this AR scenario using the Max Planck Institute for Meteorology’s Earth System Model. This model can simulate the impact of afforestation/reforestation on climate. The simulations used an overshoot scenario, a climate scenario in which the global average temperature exceeds the target of 1.5°C and falls below this level around the end of the century.

“Such a scenario is becoming increasingly likely as fundamental climate action continues to be delayed,” Moustakis explains.

Lower average temperature and shorter overshoot period

Simulation results show that ambitious AR measures can have significant climate impacts. Specifically, AR could reduce mid-century global peak temperatures by 0.08 °C and end-of-century temperatures by 0.2 °C compared to the no-AR scenario. Furthermore, this measure could shorten the period during which global temperatures exceed the target of 1.5 degrees Celsius by 13 years. The impact of AR on global temperature will already be evident by 2052.

Another important finding of the simulation is that the side effects of AR on the climate do not outweigh the positive effects of CO2 uptake. AR not only affects carbon sequestration but also changes the physical properties of the Earth’s surface, such as albedo. The ability of the Earth’s surface to reflect sunlight, and the evaporation of water. This could lead to warming in some areas. However, as studies have shown, the local warming caused by AR is not strong enough to counteract the cooling effect, so the cooling effect from CO2 absorption dominates.

“These results show that global AR can make an important contribution to climate change mitigation if it is indeed applied at scale,” Moustakis says. “However, it is not a panacea and needs to be thought of in a more comprehensive framework that takes into account socio-economic trade-offs as well.

“Forest planting has the potential to generate jobs and income and promote ecosystem services, but it also deprives people of their livelihoods, exacerbates poverty, displaces people economically or physically, and disrupts local food networks. It can be confusing.”