U.S. land management can contribute 1.2 Pg CO ₂ e year ⁻¹ of greenhouse gas mitigation, 76% of which costs USD 50 Mg CO ₂ e ⁻¹ or less.

Peatlands comprise a globally important carbon pool whose input–output budgets may be significantly altered by climate change. To experimentally determine the sensitivity of the carbon stored in peatlands to climate change, we constructed a mesocosm facility with 54 peat monoliths from a bog and fen in northern Minnesota, USA. These mesocosms were subjected to nine combinations of heat and water‐table levels over eight years. Bog mesocosms initially accumulated soil carbon, with greater gains in wetter mesocosms, but after three years no further water‐table effects occurred. In contrast, fen mesocosms lost or had no change in soil carbon, with the greatest losses in drier and warmer mesocosms. Changes in soil‐carbon storage resulted in concomitant changes in water‐table depth, so that water‐table depths were similar to those in the natural source sites by the end of the experiment regardless of the initial treatment. These results were primarily due to water‐table effects onSphagnummoss production in the bog mesocosms and to a more complicated suite of warming and water‐table effects on production and decomposition in the fen mesocosms. We show that different kinds of peatlands will rapidly gain or lose carbon following hydrological disturbance until they return to their characteristic (“equilibrium”) water‐table levels. Our results illustrate the potential for a rapid homeostatic response of these ecosystems to future climate change at small spatial scales. Climate change will likely also interact with other carbon cycle–hydrological feedbacks at the scale of the entire peatland over longer time frames and larger spatial scales.

Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions.