Regrowing forests can sequester CO2 and offset the loss carbon to land-use change
Through practices such as forest clearance and cropland cultivation, humans have altered 42-68% of the Earth’s surface and added over a hundred billion tones of carbon dioxide (CO2) to the atmosphere. Elena Shevliakova and colleagues of Cooperative Institute for Climate Studies (CICS) at Princeton University and at NOAA used a new land model LM3V to provide the global estimate of how much of the CO2 emitted from land has been offset by forest regrowth. They used four different scenarios, and found that even extensive human interference caused the net loss of only 1.1-1.3 billion tones of carbon per year in the 1990s – about half of previous estimates. One factor that may explain this is the 0.35-0.6 billion tones of carbon per year absorbed by plants growing back after disturbance, mostly in tropical forests.
The new land model LM3V is developed in collaboration with the scientists from Geophysical Fluid Dynamics Laboratory (GFDL) and is a component of the GFDL Earth System Models (ESMs). ESMs will be used in the next, 5th assessment of Intergovernmental Panel on Climate Change (IPCC) to explore interactions between carbon cycle, climate change, and land cover changes. LM3V is specifically designed to address the consequences of human activities including cropland and pasture dynamics, shifting cultivation, logging, fire, and resulting patterns of secondary regrowth.
The smaller magnitude of the land-use source relative to previous estimates implies a smaller magnitude of the “missing sink”, that
scientists have been seeking to help them balance the global carbon budget. LM3V provides GFDL ESMS with modeling capabilities to explore the consequences of land-use/land-management changes and its implications for climate in the past and under future scenarios.
Shevliakova, Elena, S W Pacala, S Malyshev, P C D Milly, and Lori T Sentman, et al., June 2009: Carbon cycling under 300 years of land use change: Importance of the secondary vegetation sink. Global Biogeochemical Cycles, 23, GB2022, doi:10.1029/2007GB003176.
Click here to access the manuscript.