Editing IPCC:AR6/WGII/Chapter-18 (section)

==== 18.3.1.3 Land, Oceans and Ecosystems ====

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Land, oceans and terrestrial ecosystems are in transition globally, with anthropogenic factors including climate change being a major driving force ( ''very high confidence'' ) ( [[#IPBES--2019|IPBES, 2019]] ) (Box 6). Seventy-five percent of the land surface has been significantly altered, 66% of the ocean area is experiencing increasing cumulative impacts and over 85% of wetland areas have been lost ( [[#IPBES--2019|IPBES, 2019]] ). Since 1970, only four out of eighteen recognised ecosystem services assessed have improved in their functioning: agricultural production, fish harvest, bioenergy production and material harvests. The other 14 ecosystem services have declined ( [[#IPBES--2019|IPBES, 2019]] ), raising concerns about the capacity of ecosystems and their services to support sustainable and CRD.

Given the pressures on land, oceans and ecosystems, enhancing resilience to climate change and other pressures of human development is a core priority of transition in these systems. Yet there are a few recorded initiatives that provide evidence of successful improvement in ecosystem resilience ( ''high agreement'' , ''limited evidence'' ). Similarly, although there is significant evidence that a broad range of adaptation initiatives have been pursued across global regions and sectors, including a rapid expansion of nature- or ecosystem-based solutions ( [[#Mainali--2020|Mainali et al., 2020]] ), there is ''limited evidence'' of how these planned climate adaptation efforts have contributed to enhanced ecosystem resilience. Additional research is necessary to evaluate these efforts in terms of their performance and also to identify mechanisms for scaling them up in different contexts. As an example, Paik et al. ( [[#Paik--2020|Paik et al., 2020]] ) record the increased diffusion of salt tolerant rice varieties in the Mekong River Delta, which is at risk of sea level rise and an associated saline intrusion. This is a low-cost adaption to saline ingress, that increases food productivity and reduces the risk of outmigration for this vulnerable agricultural region.

Evidence of the interactions between ecosystems and resilience come from a range of sources including both regional and sectoral examples (Box 18.2; Tables 18.7–18.8. For example, regional examples suggest that the use of land to produce biofuels could increase the resilience of production systems and address mitigation needs (Box 2.2). Nevertheless, the potential of bioenergy with carbon capture and storage (BECCS) to induce maladaptation needs deeper analysis ( [[#Hoegh-Guldberg--2019|Hoegh-Guldberg et al., 2019]] ). Climate Smart Forestry (CSF) in Europe provides an example of the use of sustainable forest management to unlock the EU’s forest sector potential ( [[#Nabuurs--2017|Nabuurs et al., 2017]] ). This is in response to diverse climate impacts ranging from pressure on spruce stocks in Norway and the Baltics, on regional biodiversity in the Mediterranean region, and the opportunity to use afforestation and reforestation to store carbon in forests ( [[#Nabuurs--2019|Nabuurs et al., 2019]] ). CSF considers the full value chain from forest to wood products and energy and uses a wide range of measures to provide positive incentives to firmly integrate climate objectives into the forestry sector. CSF has three main objectives; (i) reducing and/or removing greenhouse gas emissions; (ii) adapting and building forest resilience to climate change; and (iii) sustainably increasing forest productivity and incomes ( [[#Verkerk--2020|Verkerk et al., 2020]] ).

Other solutions focus on specific subsectors. Mutually supportive climate and land policies have the potential to save resources, amplify social resilience, support ecological restoration, and foster engagement and collaboration between multiple stakeholders (IPCC, 2019 f, C.1). Land-based solutions can combat desertification in specific contexts: water harvesting and micro-irrigation, restoring degraded lands using drought-resilient ecologically appropriate plants, agroforestry and other agroecological and ecosystem-based adaptation practices (IPCC, 2019 f, B.4.1). Reducing dust, sandstorms and sand dune movement can lessen the negative effects of wind erosion and improve air quality and health. Depending on water availability and soil conditions, afforestation, tree planting and ecosystem restoration programmes using native and other climate-resilient tree species with low water needs, can reduce sand storms, avert wind erosion and contribute to carbon sinks, while improving micro-climates, soil nutrients and water retention (IPCC, 2019 f, B.4.2).

Coastal blue carbon ecosystems, such as mangroves, salt marshes and seagrasses, can help reduce the risks and impacts of climate change, with multiple co-benefits. Over 150 countries contain at least one of these coastal blue carbon ecosystems and over 70 contain all three. Successful implementation of measures of carbon storage in coastal ecosystems could assist several countries in achieving a balance between emissions and removal of greenhouse gases. Carbon storage in marine habitats can be up to 1,000 tC ha –1 , higher than most terrestrial ecosystems. Conservation of these habitats would also sustain a wide range of ecosystem services, assist with climate adaptation by improving critical habitats for biodiversity, enhance local fishery production and protect coastal communities from sea level rise (SLR) and storm events ( [[#IPCC--2019b|IPCC, 2019b]] ). Ecosystem-based adaptation is a cost-effective coastal protection tool that can have many co-benefits, including supporting livelihoods, contributing to carbon sequestration and the provision of a range of other valuable ecosystem services ( [[#IPCC--2019b|IPCC, 2019b]] ).

Diversification of food systems is another component of land, ocean and ecosystem transitions that are consistent with CRD. Balanced diets, featuring plant-based foods such as those based on coarse grains, legumes, fruits and vegetables, nuts and seeds, and animal-sourced food produced in a resilient, sustainable and low-greenhouse gas (GHG) emission manner, are major opportunities for adaptation and mitigation and improving human health. By 2050, dietary changes could free several million km 2 of land and provide a mitigation potential of 0.7–8.0 Gt CO 2 -eq yr -1 , relative to Business-As-Usual projections.

For coastal systems, many frameworks for climate resilience and adaptation have been developed since the AR5 ( [[#Hoegh-Guldberg--2014|Hoegh-Guldberg et al., 2014]] ; [[#Settele--2014|Settele et al., 2014]] ) with substantial variations in approach between and within countries and across development status. Few studies have assessed the success of implementing these frameworks owing to the time-lag between implementation, monitoring, evaluation and reporting ( [[#IPCC--2019g|IPCC, 2019g]] ). As an example, the Nature-Based Climate Solutions for Oceans initiative has the potential to restore, protect and manage coastal and marine ecosystems, adapt to climate change, improve coastal resilience, and enhance their ability to sequester and store carbon ( [[#Hoegh-Guldberg--2019|Hoegh-Guldberg et al., 2019]] ).

Polar regions will be profoundly different in the future. The degree and nature of that difference will depend strongly on the rate and magnitude of global climate change, which will influence adaptation responses regionally and worldwide. Future climate-induced changes in the polar oceans, sea ice, snow and permafrost will drive habitat and biome shifts, with associated changes in the ranges and abundance of ecologically important species ( [[#IPCC--2019g|IPCC, 2019g]] ). Innovative tools and practices in polar resource management and planning show strong potential in improving society’s capacity to respond to climate change. Networks of protected areas, participatory scenario analysis, decision support systems and community-based ecological monitoring that draws on local and Indigenous knowledge and self-assessments of community resilience contribute to strategic plans for sustaining biodiversity and limit risk to human livelihoods and well-being. Experimenting, assessing and continually refining practices while strengthening links with decision making has the potential to ready society for the expected and unexpected impacts of climate change ( [[#IPCC--2019g|IPCC, 2019g]] ).

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