The impact of changes in management, climate and sea level on blue carbon and greenhouse gas emissions in coastal wetlands

沿海湿地提供许多关键的生态系统服务，包括风暴潮保护、渔业生产、改善水质和碳固存，并且可能是地球上减缓全球变暖最有效的生态系统之一。蓝色碳是指被海洋和沿海生态系统捕获和储存的有机碳，特别是被海草草甸、潮汐沼泽和红树林[1]等植被覆盖的沿海生态系统捕获和储存的有机碳。全球盐沼土壤表层的平均碳储量约为255毫克/公顷(范围为16-623毫克/公顷)[2]。与陆地生态系统不同，沿海土壤中储存的碳可能非常广泛，并会被困住很长一段时间(数百年到数千年)，从而产生非常大的碳储量。在蓝碳系统中，土壤被水饱和，使其处于厌氧状态(低氧到无氧)，并能以较高的速度垂直生长，导致碳随着时间的推移而不断积累[3]。随着时间的推移，沿海湿地在碳固存方面的重要作用日益得到认可，当退化时，它们可能成为温室气体、二氧化碳、甲烷和一氧化二氮的来源[4]。由于甲烷和一氧化二氮的全球变暖潜力在100年内分别是二氧化碳的25倍和310倍，因此将这些气体的排放列为未来气候变化的风险是很重要的。在盐沼中，温室气体的释放可能是显著的，因为盐沼经历了土壤水盐度的降低、土壤氧气有效性的变化以及人为养分负荷的增加[4]。(2017)[5]确定沿海湿地恢复和保护是以前考虑的缓解选项中的一个缺口，并估计这些选项具有1-2 pg/年的二氧化碳当量的全球气候变化缓解潜力。这高于任何农业或草原选项的估计潜力，与恢复和保护泥炭地的综合潜在影响相当。为了准确预测未来管理和气候变化对碳储存和温室气体排放的影响，需要动态的、基于过程的模拟模型，但针对泥炭地[6]已经开发了这样的模型，而针对沿海湿地的基于过程的模型是缺失的；拟议的PHD将解决这一缺口。通过对沿海湿地中的碳封存进行模拟，我们可以更有效地确定减少温室气体排放和增加土壤碳储量的选项，从而产生高影响产出和迫切需要的信息，以支持改善沿海湿地保护和恢复的政策。这项研究将在新成立的“苏格兰蓝碳论坛”(SBCF)的框架下进行，该论坛为支持模型验证和影响的政府数据和政策提供了一个渠道。

Coastal wetlands provide numerous critical ecosystem services, including storm surge protection, fisheries production, improvement of water quality, and carbon sequestration, and are potentially one of the most effective ecosystems on the planet for slowing global warming. Blue Carbon refers to organic carbon that is captured and stored by the oceans and coastal ecosystems, particularly by vegetated coastal ecosystems: seagrass meadows, tidal marshes, and mangrove forests [1]. The global average carbon storage in the top metre of salt marsh soils is approximately 255 Mg/ha (with a range of 16-623 Mg/ha) [2].Unlike terrestrial ecosystems, carbon sequestered in coastal soils can be extensive and remain trapped for very long periods of time (centuries to millennia), resulting in very large carbon stocks. In blue carbon systems, the soil is saturated with water keeping it in an anaerobic state (low to no oxygen), and can accrete vertically at high rates, resulting in continuous build-up of carbon over time [3].Increasingly, coastal wetlands are being recognized for their important role in carbon sequestration and, when degraded, their potential to become sources of the greenhouse gases, carbon dioxide, methane and nitrous oxide [4]. Because methane and nitrous oxide have global warming potentials that are, respectively, 25 and 310 times greater than carbon dioxide over 100 years, it is important to include the release of these gases as presenting a risk for future climate change. Release of greenhouse gases can be significant in salt marshes that experience reduced soil water salinities, changes in soil oxygen availability, and increases in anthropogenic nutrient loading [4].Griscom et al. (2017) [5] identified coastal wetland restoration and protection as a gap in mitigation options previously considered and estimated that these options have a global climate change mitigation potential in carbon dioxide equivalents of 1-2 Pg/y. This is higher than the estimated potential of any agricultural or grassland options, and comparable to the combined potential impact of restoration and protection of peatlands. Dynamic, process-based simulation models are needed to accurately predict the impacts of future changes in management and climate on carbon storage and greenhouse gas emissions, but whereas models have been developed to do this for peatlands [6], process-based models for coastal wetlands are missing; it is this gap that the proposed PhD will address.By modelling the carbon sequestered in coastal wetlands, we can more effectively identify options to reduce greenhouse gas emissions and increase soil carbon stocks, so producing high impact outputs and much needed information to support improved policies on the protection and restoration of coastal wetlands. This research will be under the framework of the newly established "Scottish Blue Carbon Forum" (SBCF) providing a conduit to governmental data and policy in support of model validation and impact.