Huge Uncertainty in the Carbon Outcomes of Common Land-use Transitions

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By Global Change Biology | 31 July 2012 | 99

Land-use changes, including deforestation, are important sources of carbon emissions linked to global climate change. However, a new study challenges key policy assumptions. The study reports that it remains virtually impossible to anticipate how many common land-use transitions affect carbon stocks, based on existing data.  This includes agricultural shifts, suggesting that efforts to replace slash-and-burn agriculture with other farming systems may not always reduce emissions.

The study was first published in the journal Global Change Biology on July 26th, 2012.

The article reviewed more than 250 studies of different land-use types from across Southeast Asia in order to identify trends in the likely carbon outcomes of land-use transitions.

Lead author, National University of Singapore Assoc. Prof. Alan Ziegler, was “surprised by the gross uncertainty for changes not involving mature forests.  It is clear that deforestation results in emissions, but we know very little about the carbon outcomes of many other common land-use transitions. This should alarm policy makers interested in climate change mitigation”.             

Policies to reduce forest-based carbon emissions and enhance forest carbon stocks to help mitigate climate change (known as REDD+ policies) are currently under development across the tropics.

In many countries, REDD+ efforts target slash-and-burn farming.  Slash-and-burn farming, also known as swidden agriculture, involves using fire to help clear vegetation for cultivation, often for subsistence or small-scale agriculture.  Although farming practices vary widely, swidden is a conspicuous cause of land-use change and point of carbon emissions.  In an effort to reduce emissions, many REDD+ policies propose to transition small farmers towards other types of agriculture, including sedentary agriculture, agroforestry and plantation agriculture.