The cost-effective mitigation of climate change through nature-based carbon dioxide removal strategies has gained substantial policy attention. Inland and coastal wetlands (specifically boreal, temperate and tropical peatlands; tundra; floodplains; freshwater marshes; saltmarshes; and mangroves) are among the most efficient natural long-term carbon sinks. Yet, they also release methane (CH 4 ) that can offset the carbon they sequester. Here, we conducted a meta-analysis on wetland carbon dynamics to (i) determine their impact on climate using different metrics and time horizons, (ii) investigate the cost-effectiveness of wetland restoration for climate change mitigation, and (iii) discuss their suitability for inclusion in climate policy as negative emission technologies. Depending on metrics, a wetland can simultaneously be a net carbon sink (i.e. boreal and temperate peatlands net ecosystem carbon budget = −28.1 ± 19.13 gC m −2 y −1 ) but have a net warming effect on climate at the 100 years time-scale (i.e. boreal and temperate peatland sustained global warming potential = 298.2 ± 100.6 gCO 2 eq −1 m −2 y −1 ). This situation creates ambivalence regarding the effect of wetlands on global temperature. Moreover, our review reveals high heterogeneity among the (limited number of) studies that document wetland carbon budgets. We demonstrate that most coastal and inland wetlands have a net cooling effect as of today. This is explained by the limited CH 4 emissions that undisturbed coastal wetlands produce, and the long-term carbon sequestration performed by older inland wetlands as opposed to the short lifetime of CH 4 in the atmosphere. Analysis of wetland restoration costs relative to the amount of carbon they can sequester revealed that restoration is more cost-effective in coastal wetlands such as mangroves (US$1800 ton C −1 ) compared with inland wetlands (US$4200–49 200 ton C −1 ). We advise that for inland wetlands, priority should be given to conservation rather than restoration; while for coastal wetlands, both conservation and restoration may be effective techniques for climate change mitigation.

Sawfish are among the world's most threatened and understudied marine fishes. There are few studies on sawfish from outside Australian and USA waters ‐ a significant knowledge gap considering their circumtropical distribution and migratory nature. This paper presents the first assessment of sawfish exploitation and status in Bangladesh: a country that is subject to extensive fishing efforts, and home to the largest mangrove forest on Earth – an ecosystem that provides critical nursery habitat for juvenile sawfish. A countrywide rapid assessment was undertaken between December 2011 and November 2012, using an interdisciplinary methodology. Fish landing stations, dry fish markets, and fishing villages were visited and a sawfish medicine maker was found and interviewed. In addition, interviews with national specialists at academic and fisheries institutions were undertaken. In total, 203 questionnaire surveys were conducted with fishers and traders in order to understand the extent of decline, potential drivers of declines, and local perceptions and uses of sawfish. Eighteen rostra were documented from museum archives and private collections, and unpublished data were sourced. Two sawfish species, Pristis pristis and Anoxypristis cuspidata were confirmed to be present in Bangladesh. General population declines were revealed. The average annual sawfish encounter rate (observations and catches) declined from 3.7 individuals using lifetime recall data (~22‐year), to 1.5 using 5‐year recall data, and further to 0.7 using 1‐year recall data. The consensus from social research methods was that sawfish were caught as bycatch, with drift gill nets being cited as the most damaging gear type. Every respondent perceived sawfish as a useful animal – typically for medicinal or cultural values. Conservation measures are proposed, including a local education and outreach programme to seek behavioural changes – primarily to release live sawfish. Copyright © 2014 John Wiley & Sons, Ltd.

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Many drivers of mangrove forest loss operate over large scales and are most effectively addressed by policy interventions. However, conflicting or unclear policy objectives exist at multiple tiers of government, resulting in contradictory management decisions. To address this, we considered four approaches that are being used increasingly or could be deployed in Southeast Asia to ensure sustainable livelihoods and biodiversity conservation. First, a stronger incorporation of mangroves into marine protected areas (that currently focus largely on reefs and fisheries) could resolve some policy conflicts and ensure that mangroves do not fall through a policy gap. Second, examples of community and government comanagement exist, but achieving comanagement at scale will be important in reconciling stakeholders and addressing conflicting policy objectives. Third, private-sector initiatives could protect mangroves through existing and novel mechanisms in degraded areas and areas under future threat. Finally, payments for ecosystem services (PES) hold great promise for mangrove conservation, with carbon PES schemes (known as blue carbon) attracting attention. Although barriers remain to the implementation of PES, the potential to implement them at multiple scales exists. Closing the gap between mangrove conservation policies and action is crucial to the improved protection and management of this imperiled coastal ecosystem and to the livelihoods that depend on them.

Mangrove forests hold some of the highest densities of carbon recorded in any ecosystem, but have experienced widespread deforestation through conversion to aquaculture and agriculture. Alongside deforestation, mangroves have shown simultaneous natural expansion in some parts of the world, and considerable investments have been made into restoration programmes. Here we estimate net changes in the global mangrove carbon stock due to land cover change between 1996 and 2016, using data on mangrove deforestation and forestation, and proportional changes in carbon stock during processes of mangrove loss and gain. The global mangrove carbon stock declined by 158.4 Mt (95% CI = −156.8-525.9 Mt); a reduction of 1.8% of the stock present in 1996. Efforts to conserve and restore mangroves appear to have had some success, and-along with natural forestation-have contributed to relatively low net losses of mangrove carbon stocks over two decades.

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