Carbon Sequestration by Wetlands: A Critical Review of Enhancement Measures for Climate Change Mitigation
Wetlands are among the most important ecosystems in the response strategy to climate change, through carbon sequestration (CS). Nevertheless, their current CS potential is declining due to human disturbance, with further decrease expected under global population growth and climate change scenarios. Literature has documented various measures that seek to enhance CS by wetlands and therefore enable these ecosystems remain vital in global carbon (C) balance and climate change mitigation. The objective of this review is to critically analyse these measures with respect to their feasibility and impact on wetland functioning, both in ecological and socio-economic perspectives. In doing this, we strive to address the concerns of wetland scientists, managers and other stakeholders pertaining CS by wetlands. Findings indicate that CS can be enhanced through both non-manipulative and manipulative measures. Non-manipulative measures aim at enhancing CS by increasing wetlands' spatial extent, while manipulative ones aim at altering characteristics of certain wetland components that influence CS. Their overall target is to increase organic matter input, apportion C to longer-lived pools, and increase residence times of C pools. Based on the identified research gaps, we recommend that CS actions for wetlands should prioritize conservation of existing natural wetlands. Additional measures should consider associated risks such as those on wetland flora and fauna, soil and hydrological regimes, and competing services. We further believe that successful implementation of non-manipulative measures for CS will require attachment of economic incentives that are not only foreseeable, but also adequate to match returns from competing land uses.