labs_title

Caldeira Lab Research:Land Plants, Carbon, and Climate

Past land use decisions have increased mitigation potential of reforestation

Julia Pongratz, C. Reick, T. Raddatz, K. Caldeira, and M. Claussen

In this study, we find that the farmers' choice in the past to use relatively productive and snow-free land increases the potential of future reforestation to mitigate global warming.


Pongratz, J., C. Reick, T. Raddatz, K. Caldeira, and M. Claussen (2011), Past land use decisions have increased mitigation potential of reforestation, Geophys. Res. Lett., doi:10.1029/2011GL047848

Radiative forcing (RF) caused by historical deforestation: The negative RF (cooling effect) of an increase in surface reflectivity has been overwhelmed in most agriculturally important regions by the positive RF (warming effect) of CO2 emissions, increasing their potential to counteract global warming when reversed to their natural forested state.

Abstract

Anthropogenic land cover change (ALCC) influences global mean temperatures via counteracting effects: CO2 emissions contribute to global warming, while biogeophysical effects, in particular the increase in surface albedo, often impose a cooling influence. Previous studies of idealized, large‐scale deforestation found that albedo cooling dominates over CO2 warming in boreal regions, indicating that boreal reforestation is not an effective mitigation tool. Here we show the importance of past land use decisions in influencing the mitigation potential of reforestation on these lands. In our simulations, CO2 warming dominates over albedo cooling because past land use decisions resulted in the use of the most productive land with larger carbon stocks and less snow than on average. As a result past land use decisions extended CO2 dominance to most agriculturally important regions in the world, suggesting that in most places reversion of past land cover change could contribute to climate change mitigation. While the relative magnitude of CO2 and albedo effects remains uncertain, the historical land use pattern is found to be biased towards stronger CO2 and weaker albedo effects as compared to idealized large‐scale deforestation.

 

Video of Julia Pongratz discussing the paper

Link to Press Release