Thinning practices in rehabilitated mangroves: Opportunity to synergize climate change mitigation and adaptation

Mangrove trees act important roles in the coastal ecosystems, protecting community against high-tide and\ud storms, controlling land erosion and providing fish breeding ground. In the last few decades, the massive area has\ud devastated due to commercial shrimp and fish ponds development. To rehabilitate the coastal ecosystems, some\ud mangrove has been planted with spacing distances of 1x1 m with minimal forest management. Those dense-spaced\ud stands enhanced light competitions and inhibit growth. These poor quality and immature stands that reach an early\ud climax in 10-15 years were observed in two adjacent sites near Nam Dinh and Thanh Hoa in northern Vietnam, where\ud Kandelia candel were planted. To cultivate the resurgent stands and increase their growth, thinning mangrove is\ud essential. Stand densities of the mangrove trees with and without the thinning practice were 17,800 and 5,200 trees ha-1,\ud respectively. Their potential of the maximum above-ground biomass were 303 and 239 Mg ha-1, respectively. However,\ud quality of the single tree was largely different whether or not thinning practice is conducted, as the thinned one of 46 kg\ud tree-1 was about three times higher than the non-thinned of 17 kg tree-1. The thinning practice enhances stand biomass\ud growth with improved growth condition in the forest, which advances carbon sequestration for the climate change\ud mitigation. The cultivated trees also ensure the climate change adaptation of coastal protection, fishery products and\ud bio-diversity. Synergizing mitigation and adaptation strategies with the mangrove thinning would enhance the benefits\ud for coastal communities most vulnerable to climate change

Greenhouse gas emission factors associated with rewetting of organic soils

Drained organic soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils may reduce GHG emissions and could also create suitable conditions for return of the carbon (C) sink function characteristic of undrained organic soils. In this article we expand on the work relating to rewetted organic soils that was carried out for the 2014 Intergovernmental Panel on Climate Change (IPCC) Wetlands Supplement. We describe the methods and scientific approach used to derive the Tier 1 emission factors (the rate of emission per unit of activity) for the full suite of GHG and waterborne C fluxes associated with rewetting of organic soils. We recorded a total of 352 GHG and waterborne annual flux data points from an extensive literature search and these were disaggregated by flux type (i.e. CO2, CH4, N2O and DOC), climate zone and nutrient status. Our results showed fundamental differences between the GHG dynamics of drained and rewetted organic soils and, based on the 100 year global warming potential of each gas, indicated that rewetting of drained organic soils leads to: net annual removals of CO2 in the majority of organic soil classes; an increase in annual CH4 emissions; a decrease in N2O and DOC losses; and a lowering of net GHG emissions. Data published since the Wetlands Supplement (n = 58) generally support our derivations. Significant data gaps exist, particularly with regard to tropical organic soils, DOC and N2O. We propose that the uncertainty associated with our derivations could be significantly reduced by the development of country specific emission factors that could in turn be disaggregated by factors such as vegetation composition, water table level, time since rewetting and previous land use history

A cost-efficient method to assess carbon stocks in tropical peat soil

Estimation of belowground carbon stocks in tropical wetland forests requires funding for laboratory analyses and suitable facilities, which are often lacking in developing nations where most tropical wetlands are found. It is therefore beneficial to develop simple analytical tools to assist belowground carbon estimation where financial and technical limitations are common. Here we use published and original data to describe soil carbon density (kgC m<sup>−3</sup>; C<sub>d</sub>) as a function of bulk density (gC cm<sup>−3</sup>; <i>B</i><sub>d</sub>), which can be used to rapidly estimate belowground carbon storage using <i>B</i><sub>d</sub> measurements only. Predicted carbon densities and stocks are compared with those obtained from direct carbon analysis for ten peat swamp forest stands in three national parks of Indonesia. Analysis of soil carbon density and bulk density from the literature indicated a strong linear relationship (C<sub>d</sub> = <i>B</i><sub>d</sub> × 495.14 + 5.41, <i>R</i><sup>2</sup> = 0.93, <i>n</i> = 151) for soils with organic C content > 40%. As organic C content decreases, the relationship between C<sub>d</sub> and <i>B</i><sub>d</sub> becomes less predictable as soil texture becomes an important determinant of C<sub>d</sub>. The equation predicted belowground C stocks to within 0.92% to 9.57% of observed values. Average bulk density of collected peat samples was 0.127 g cm<sup>−3</sup>, which is in the upper range of previous reports for Southeast Asian peatlands. When original data were included, the revised equation C<sub>d</sub> = <i>B</i><sub>d</sub> × 468.76 + 5.82, with <i>R</i><sup>2</sup> = 0.95 and <i>n</i> = 712, was slightly below the lower 95% confidence interval of the original equation, and tended to decrease C<sub>d</sub> estimates. We recommend this last equation for a rapid estimation of soil C stocks for well-developed peat soils where C content > 40%

Integrating climate change mitigation and adaptation in agriculture and forestry: opportunities and trade-offs

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.International audienceAlthough many activities can jointly contribute to the climate change strategies of adaptation and mitigation, climate policies have generally treated these strategies separately. In recent years, there has been a growing interest shown by practitioners in agriculture, forestry, and landscape management in the links between the two strategies. This review explores the opportunities and trade-offs when managing landscapes for both climate change mitigation and adaptation; different conceptua-lizations of the links between adaptation and mitigation are highlighted. Under a first conceptualization of 'joint outcomes,' several reviewed studies analyze how activities without climatic objectives deliver joint adaptation and mitigation outcomes. In a second conceptualization of 'unintended side effects,' the focus is on how activities aimed at only one climate objective—either adaptation or mitigation—can deliver outcomes for the other objective. A third conceptualization of 'joint objectives' highlights that associating both adaptation and mitigation objectives in a climate-related activity can influence its outcomes because of multiple possible interactions. The review reveals a diversity of reasons for mainstreaming adaptation and mitigation separately or jointly in landscape management. The three broad conceptualizations of the links between adaptation and mitigation suggest different implications for climate policy mainstreaming and integration

Mangrove blue carbon stocks and dynamics are controlled by hydrogeomorphic settings and land-use change.

Globally, carbon-rich mangrove forests are deforested and degraded due to land-use and land-cover change (LULCC). The impact of mangrove deforestation on carbon emissions has been reported on a global scale; however, uncertainty remains at subnational scales due to geographical variability and field data limitations. We present an assessment of blue carbon storage at five mangrove sites across West Papua Province, Indonesia, a region that supports 10% of the world's mangrove area. The sites are representative of contrasting hydrogeomorphic settings and also capture change over a 25-years LULCC chronosequence. Field-based assessments were conducted across 255 plots covering undisturbed and LULCC-affected mangroves (0-, 5-, 10-, 15- and 25-year-old post-harvest or regenerating forests as well as 15-year-old aquaculture ponds). Undisturbed mangroves stored total ecosystem carbon stocks of 182-2,730 (mean ± SD: 1,087 ± 584) Mg C/ha, with the large variation driven by hydrogeomorphic settings. The highest carbon stocks were found in estuarine interior (EI) mangroves, followed by open coast interior, open coast fringe and EI forests. Forest harvesting did not significantly affect soil carbon stocks, despite an elevated dead wood density relative to undisturbed forests, but it did remove nearly all live biomass. Aquaculture conversion removed 60% of soil carbon stock and 85% of live biomass carbon stock, relative to reference sites. By contrast, mangroves left to regenerate for more than 25 years reached the same level of biomass carbon compared to undisturbed forests, with annual biomass accumulation rates of 3.6 ± 1.1 Mg C ha-1  year-1 . This study shows that hydrogeomorphic setting controls natural dynamics of mangrove blue carbon stocks, while long-term land-use changes affect carbon loss and gain to a substantial degree. Therefore, current land-based climate policies must incorporate landscape and land-use characteristics, and their related carbon management consequences, for more effective emissions reduction targets and restoration outcomes

Author Correction: The future of Blue Carbon science.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Landscapes in transition: an analysis of sustainable policy initiatives and emerging corporate commitments in the palm oil industry

The recent Southeast Asian haze crisis has generated intense public scrutiny over the rate, methods and types of landscape change in the tropics. Debate has centred on the environmental impacts of large-scale agricultural expansion, particularly the associated loss of high carbon stock forest and forests of high conservation value. Focusing on palm oil—a versatile food crop and source of bioenergy—this paper analyses national, international and corporate policy initiatives in order to clarify the current and future direction of oil palm expansion in Malaysia and Indonesia. The policies of ‘zero burn’, ‘no deforestation’ and ‘no planting on peatlands’ are given particular emphasis in the paper. The landscape implications of corporate commitments are analysed to determine the amount of land, land types and geographies that could be affected in the future. The paper concludes by identifying key questions related to the further study of sustainable land use policy and practice