Identifying potential tipping points in the benefits derived from the UK's land ecosystems

我们的研究旨在确定，由于气候变化、土地利用变化、政策变化及其相互作用，英国土地生态系统给我们带来的好处——包括提供食物、娱乐价值、水质、自然防洪和温室气体储存——是否会在本世纪超过“临界点”。这里，我们将“临界点”定义为生态系统所带来的巨大而持续的变化。因此，这可能是由于生态系统驱动因素的一个临界点——这里是气候变化、土地利用变化或政策变化——或者可能是由于生态系统本身的一个临界点，这样即使驱动因素的一个小变化也会引发利益流的一个大变化。我们的目标是了解哪些临界点可能发生，并预测它们何时可能发生，以及它们在地理上可能出现的位置。为了评估这一点，我们将使用一组三个最先进的模型，并结合临界点检测的数学方法。这三个模型将以前所未有的空间分辨率捕捉英国土地生态系统的功能、从中产生的效益，以及它们如何受到气候变化、土地利用变化和政策变化的影响。其中两个模型——“JULES”和“LPX”——通过生态系统捕获水和碳的循环，包括植被的变化。我们将利用它们来探索碳储存、温室气体通量和淡水服务的潜在临界点，包括自然防洪——这是由高地泥炭地和低地洪泛平原的储水提供的。我们还将研究一项预测，即由于气候变化，地毯式沼泽和它们所储存的大量碳正面临消失的威胁。由此产生的理解将用于更新第三个模型——称为“TIM”（综合模型）——它将我们关于生态系统过程的自然科学知识与关于农民和林农在气候或政策变化时如何改变土地利用的经济理解结合起来。由于英国75%的土地是某种形式的管理农业用地，因此了解对人类土地利用的影响至关重要。我们将在其他模型的基础上改进TIM中碳储量和温室气体通量的表示，并纳入自然洪水保护的表示。我们还将用新的、高分辨率的气候变化预测来驱动该模型，并使用TIM来研究土地使用者将如何应对全国不同地区的气候变化。我们检测临界点的方法将应用于三个模型的输出，以检查在英国未来气候的不同情景下临界点发生的位置和类型。由于TIM被用于英国国家生态系统评估及其后续工作，这将为政策建议提供直接反馈，特别是通过英国政府的“自然资本委员会”。TIM的“引爆点启用”版本将用于重新审视现有的气候变化和政策情景，以了解结果和相应的建议如何改变。该项目的主要成果将是首次对英国土地生态系统服务带来的潜在利益临界点进行综合分析，同时对用于量化和评估英国生态系统存量和利益流以及评估政策选择的既定框架（TIM）进行重要改进。

Our research aims to identify whether the benefits flowing to us from the UK's land ecosystems - including the provision of food, recreational value, water quality, natural flood protection, and greenhouse gas storage - could pass 'tipping points' this century as a result of climate change, land-use change, policy change and their interaction. Here we take a 'tipping point' to mean a large and persistent change in the benefits flowing from an ecosystem. As such it could be due to a tipping point in the drivers of an ecosystem - here climate change, land-use change, or policy change - or it could be due to a tipping point within the ecosystem itself such that even a small change in its drivers triggers a large change in the flow of benefits. Our aim is to understand which of these kinds of tipping points could occur and predict when they might occur and where they might arise geographically. To assess this we will use a set of three state-of-the-art models combined with mathematical methods of tipping point detection. The three models will capture (at unprecedented spatial resolution) the functioning of the UK's land ecosystems, the benefits flowing from them, and how they are affected by climate change, land-use change and policy change. Two of these models - called 'JULES' and 'LPX' - capture the cycling of water and carbon through ecosystems, including changes in vegetation. We will use them to explore potential tipping points in carbon storage, greenhouse gas fluxes, and freshwater services, including natural flood protection - which is provided by water storage in upland peatlands and lowland flood plains. We will also examine the prediction that blanket bogs, and the large stores of carbon they hold, are threatened to disappear due to climate change. The resulting understanding will be used to update the third model - called 'TIM' (the integrated model) - which brings together our natural science knowledge of ecosystem processes with economic understanding of how farmers and foresters change their use of the land when climate or policy changes. As 75% of the UK is some form of managed agricultural land, this understanding of the influences upon human land-use is crucial. We will improve the representation of carbon stocks and greenhouse gas fluxes in TIM, based on the other models, and include a representation of natural flood protection. We will also drive the model with new, high resolution climate change projections and use TIM to examine how land users will respond to climate change across different areas of the country. Our methods for detecting tipping point will be applied to the output of the three models to examine where and what type of tipping points occur under different scenarios for the future of the UK climate. As TIM is used in the UK National Ecosystem Assessment and its follow-on this will provide a direct feed-through to policy advice, especially via the UK government's 'Natural Capital Committee'. The 'tipping point enabled' version of TIM will be used to revisit existing climate change and policy scenarios to see how the results and corresponding advice are altered.The main outcomes of the project will be the first integrated analysis of potential tipping points in the benefits flowing from UK land ecosystem services, together with important improvements to the established framework (TIM) used for quantifying and evaluating UK ecosystem stocks and benefit flows, and assessing policy options.