finding 13.3 : key-message-13-3

The current rate of terrestrial wetland loss is much less than historical rates (about 0.06% of the wetland area from 2004 to 2009) with restoration and creation nearly offsetting losses of natural wetlands. Although area losses are nearly offset, there is considerable uncertainty about the functional equivalence of disturbed, created, and restored wetlands when comparing them to undisturbed natural wetlands. Correspondingly, there remains considerable uncertainty about the effects of disturbance regimes on carbon stocks and greenhouse gas (GHG) fluxes. For this reason, studies and monitoring systems are needed that compare carbon pools, rates of carbon accumulation, and GHG fluxes across disturbance gradients, including restored and created wetlands. Those studies will produce data that are needed for model applications (high confidence, likely).

This finding is from chapter 13 of Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report.

Description of evidence base: The evidence for Key Finding 3 is from updated published literature for the United States and Mexico (Casasola 2008; Landgrave and Moreno-Casasola 2012; USFWS 2011) and the same data reported in SOCCR1 (CCSP 2007) for Canada. The amount of wetlands being restored is also a function of recent literature estimates (e.g., Dahl 2011). Disturbance also needs to be considered in the context of changes to carbon cycling processes.

New information and remaining uncertainties: Where wetlands are mapped well, the area of wetland loss is very certain. Some areas not mapped well, such as remote locations in Alaska, generally are not under threat from development, but changes in climatic conditions threatened the boreal region more than temperate and tropical regions. However, the opposite is true for areas under development in Mexico. The amount of area being restored is also not tracked very well, especially when restoration fails. Crossing the gradient from disturbed to restored and/or created wetlands, there exists considerable uncertainty about the level of functions that those wetlands provide.

Assessment of confidence based on evidence: There is high confidence that systems for reporting wetland losses and gains are accurate in the United States, but periodic inventories in other countries are lacking. Also, tracking the amount of wetlands that have been disturbed in some way is very difficult.

This finding was derived from figure P.2: P.2. Likelihood and Confidence Evaluation

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