Editing IPCC:AR6/SROCC/SPM (section)

==== Projected Risks for Ecosystems ====

'''B.4 Future land cryosphere changes will continue to alter terrestrial and freshwater ecosystems in high mountain and polar regions with major shifts in species distributions resulting in changes in ecosystem structure and functioning, and eventual loss of globally unique biodiversity (medium confidence). Wildfire is projected to increase significantly for the rest of this century across most tundra and boreal regions, and also in some mountain regions (medium confidence). {2.3.3, Box 3.4, 3.4.3}''' ''''''

B.4.1 [[File:4d299f9da92412c8279a7422468e6e12 SPM-Icon-xooo.png]] In high mountain regions, further upslope migration by lower-elevation species, range contractions, and increased mortality will lead to population declines of many alpine species, especially glacier- or snow-dependent species (high confidence), with local and eventual global species loss (medium confidence). The persistence of alpine species and sustaining ecosystem services depends on appropriate conservation and adaptation measures (high confidence). {2.3.3} ''''''

B.4.2 [[File:219efacb8ac4464b2e76514065b22cc7 SPM-Icon-oxoo.png]] On Arctic land, a loss of globally unique biodiversity is projected as limited refugia exist for some High-Arctic species and hence they are outcompeted by more temperate species (medium confidence). Woody shrubs and trees are projected to expand to cover 24–52% of Arctic tundra by 2050 (medium confidence). The boreal forest is projected to expand at its northern edge, while diminishing at its southern edge where it is replaced by lower biomass woodland/shrublands (medium confidence). {3.4.3, Box 3.4}

B.4.3 [[File:7dd9d5f1c0e829eec2bf341c5154813e SPM-Icon-xxoo.png]] Permafrost thaw and decrease in snow will affect Arctic and mountain hydrology and wildfire, with impacts on vegetation and wildlife (medium confidence). About 20% of Arctic land permafrost is vulnerable to abrupt permafrost thaw and ground subsidence, which is projected to increase small lake area by over 50% by 2100 for RCP8.5 (medium confidence). Even as the overall regional water cycle is projected to intensify, including increased precipitation, evapotranspiration, and river discharge to the Arctic Ocean, decreases in snow and permafrost may lead to soil drying with consequences for ecosystem productivity and disturbances (medium confidence). Wildfire is projected to increase for the rest of this century across most tundra and boreal regions, and also in some mountain regions, while interactions between climate and shifting vegetation will influence future fire intensity and frequency (medium confidence). {2.3.3, 3.4.1, 3.4.2, 3.4.3, SPM B.1}

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'''B.5. A decrease in global biomass of marine animal communities, their production, and fisheries catch potential, and a shift in species composition are projected over the 21st century in ocean ecosystems from the surface to the deep seafloor under all emission scenarios ( ''medium confidence'' ). The rate and magnitude of decline are projected to be highest in the tropics ( ''high confidence'' ), whereas impacts remain diverse in polar regions ( ''medium confidence'' ) and increase for high emission scenarios. Ocean acidification ( ''medium confidence'' ), oxygen loss ( ''medium confidence'' ) and reduced sea ice extent ( ''medium confidence'' ) as well as non-climatic human activities ( ''medium confidence'' ) have the potential to exacerbate these warming-induced ecosystem impacts. {3.2.3, 3.3.3, 5.2.2, 5.2.3, 5.2.4, 5.4.1, Figure SPM.3}'''

'''B.5.1''' [[File:37d9ca019c63e0a7a080aaca0b2016e4 SPM-Icon-oxox.png]] Projected ocean warming and changes in net primary production alter biomass, production and community structure of marine ecosystems. The global-scale biomass of marine animals across the foodweb is projected to decrease by 15.0 ± 5.9% ( ''very likely'' range) and the maximum catch potential of fisheries by 20.5–24.1% by the end of the 21st century relative to 1986–2005 under RCP8.5 ( ''medium confidence'' ). These changes are projected to be ''very likely'' three to four times larger under RCP8.5 than RCP2.6. {3.2.3, 3.3.3, 5.2.2, 5.2.3, 5.4.1, Figure SPM.3}

'''B.5.2''' [[File:37d9ca019c63e0a7a080aaca0b2016e4 SPM-Icon-oxox.png]] Under enhanced stratification reduced nutrient supply is projected to cause tropical ocean net primary production to decline by 7–16% ( ''very likely'' range) for RCP8.5 by 2081–2100 ( ''medium confidence'' ). In tropical regions, marine animal biomass and production are projected to decrease more than the global average under all emissions scenarios in the 21st century ( ''high confidence'' ). Warming and sea ice changes are projected to increase marine net primary production in the Arctic ( ''medium confidence'' ) and around Antarctica ( ''low confidence'' ), modified by changing nutrient supply due to shifts in upwelling and stratification. Globally, the sinking flux of organic matter from the upper ocean is projected to decrease, linked largely due to changes in net primary production ( ''high confidence'' ). As a result, 95% or more of the deep sea (3000–6000 m depth) seafloor area and cold-water coral ecosystems are projected to experience declines in benthic biomass under RCP8.5 ( ''medium confidence'' ). {3.2.3, 5.2.2. 5.2.4, Figure SPM.1}

'''B.5.3''' [[File:37d9ca019c63e0a7a080aaca0b2016e4 SPM-Icon-oxox.png]] Warming, ocean acidification, reduced seasonal sea ice extent and continued loss of multi-year sea ice are projected to impact polar marine ecosystems through direct and indirect effects on habitats, populations and their viability ( ''medium confidence'' ). The geographical range of Arctic marine species, including marine mammals, birds and fish is projected to contract, while the range of some sub-Arctic fish communities is projected to expand, further increasing pressure on high-Arctic species ( ''medium confidence'' ). In the Southern Ocean, the habitat of Antarctic krill, a key prey species for penguins, seals and whales, is projected to contract southwards under both RCP2.6 and RCP8.5 ( ''medium confidence'' ). {3.2.2, 3.2.3, 5.2.3}

'''B.5.4''' [[File:aa4c791c8b6f965d8de1653e5ac59fbc SPM-Icon-ooox.png]] Ocean warming, oxygen loss, acidification and a decrease in flux of organic carbon from the surface to the deep ocean are projected to harm habitat-forming cold-water corals, which support high biodiversity, partly through decreased calcification, increased dissolution of skeletons, and bioerosion ( ''medium confidence'' ). Vulnerability and risks are highest where and when temperature and oxygen conditions both reach values outside species’ tolerance ranges ( ''medium confidence'' ). {Box 5.2, Figure SPM.3}

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'''Figure SPM.3 | Projected changes, impacts and risks for ocean regions and ecosystems. (a) depth integrated net primary production (NPP from CMIP5), (b) total animal biomass (depth integrated, including fishes and invertebrates from FISHMIP), (c) maximum fisheries catch potential and (d) impacts and risks for coastal and open ocean ecosystems. The three left panels represent […]'''
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[[File:b47d229351c0bccdc6b8379dd3db9458 SROCC_SPM3d_Final_RGB.jpg]]

Figure SPM.3 | Projected changes, impacts and risks for ocean regions and ecosystems. (a) depth integrated net primary production (NPP from CMIP5 <sup>[[#fn:27|27]]</sup> ), (b) total animal biomass (depth integrated, including fishes and invertebrates from FISHMIP <sup>[[#fn:28|28]]</sup> ), (c) maximum fisheries catch potential and (d) impacts and risks for coastal and open ocean ecosystems. The three left panels represent the simulated (a,b) and observed (c) mean values for the recent past (1986–2005), the middle and right panels represent projected changes (%) by 2081–2100 relative to recent past under low (RCP2.6) and high (RCP8.5) greenhouse gas emissions scenario {Box SPM.1}, respectively. Total animal biomass in the recent past (b, left panel) represents the projected total animal biomass by each spatial pixel relative to the global average. (c) *Average observed fisheries catch in the recent past (based on data from the Sea Around Us global fisheries database); projected changes in maximum fisheries catch potential in shelf seas are based on the average outputs from two fisheries and marine ecosystem models. To indicate areas of model inconsistency, shaded areas represent regions where models disagree in the direction of change for more than: (a) and (b) 3 out of 10 model projections, and (c) one out of two models. Although unshaded, the projected change in the Arctic and Antarctic regions in (b) total animal biomass and (c) fisheries catch potential have low confidence due to uncertainties associated with modelling multiple interacting drivers and ecosystem responses. Projections presented in (b) and (c) are driven by changes in ocean physical and biogeochemical conditions e.g., temperature, oxygen level, and net primary production projected from CMIP5 Earth system models. **The epipelagic refers to the uppermost part of the ocean with depth &lt;200 m from the surface where there is enough sunlight to allow photosynthesis. (d) Assessment of risks for coastal and open ocean ecosystems based on observed and projected climate impacts on ecosystem structure, functioning and biodiversity. Impacts and risks are shown in relation to changes in Global Mean Surface Temperature (GMST) relative to pre-industrial level. Since assessments of risks and impacts are based on global mean Sea Surface Temperature (SST), the corresponding SST levels are shown <sup>[[#fn:29|29]]</sup> . The assessment of risk transitions is described in Chapter 5 Sections 5.2, 5.3, 5.2.5 and 5.3.7 and Supplementary Materials SM5.3, Table SM5.6, Table SM5.8 and other parts of the underlying report. The figure indicates assessed risks at approximate warming levels and increasing climate-related hazards in the ocean: ocean warming, acidification, deoxygenation, increased density stratification, changes in carbon fluxes, sea level rise, and increased frequency and/or intensity of extreme events. The assessment considers the natural adaptive capacity of the ecosystems, their exposure and vulnerability. Impact and risk levels do not consider risk reduction strategies such as human interventions, or future changes in non-climatic drivers. Risks for ecosystems were assessed by considering biological, biogeochemical, geomorphological and physical aspects. Higher risks associated with compound effects of climate hazards include habitat and biodiversity loss, changes in species composition and distribution ranges, and impacts/risks on ecosystem structure and functioning, including changes in animal/plant biomass and density, productivity, carbon fluxes, and sediment transport. As part of the assessment, literature was compiled and data extracted into a summary table. A multi-round expert elicitation process was undertaken with independent evaluation of threshold judgement, and a final consensus discussion. Further information on methods and underlying literature can be found in Chapter 5, Sections 5.2 and 5.3 and Supplementary Material. {3.2.3, 3.2.4, 5.2, 5.3, 5.2.5, 5.3.7, SM5.6, SM5.8, Figure 5.16, Cross Chapter Box 1 in Chapter 1 Table CCB1}

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'''B.6. Risks of severe impacts on biodiversity, structure and function of coastal ecosystems are projected to be higher for elevated temperatures under high compared to low emissions scenarios in the 21st century and beyond. Projected ecosystem responses include losses of species habitat and diversity, and degradation of ecosystem functions. The capacity of organisms and ecosystems to adjust and adapt is higher at lower emissions scenarios ( ''high confidence'' ). For sensitive ecosystems such as seagrass meadows and kelp forests, high risks are projected if global warming exceeds 2°C above pre-industrial temperature, combined with other climate-related hazards ( ''high confidence'' ). Warm-water corals are at high risk already and are projected to transition to very high risk even if global warming is limited to 1.5°C ( ''very high confidence'' ). {4.3.3, 5.3, 5.5, Figure SPM.3}'''

'''B.6.1''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] All coastal ecosystems assessed are projected to face increasing risk level, from moderate to high risk under RCP2.6 to high to very high risk under RCP8.5 by 2100. Intertidal rocky shore ecosystems are projected to be at very high risk by 2100 under RCP8.5 ( ''medium confidence'' ) due to exposure to warming, especially during marine heatwaves, as well as to acidification, sea level rise, loss of calcifying species and biodiversity ( ''high confidence'' ). Ocean acidification challenges these ecosystems and further limits their habitat suitability ( ''medium confidence'' ) by inhibiting recovery through reduced calcification and enhanced bioerosion. The decline of kelp forests is projected to continue in temperate regions due to warming, particularly under the projected intensification of marine heatwaves, with high risk of local extinctions under RCP8.5 ( ''medium confidence'' ). {5.3, 5.3.5, 5.3.6, 5.3.7, 6.4.2, Figure SPM.3}

'''B.6.2''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] Seagrass meadows and saltmarshes and associated carbon stores are at moderate risk at 1.5°C global warming and increase with further warming ( ''medium confidence).'' Globally, 20–90% of current coastal wetlands are projected to be lost by 2100, depending on projected sea level rise, regional differences and wetland types, especially where vertical growth is already constrained by reduced sediment supply and landward migration is constrained by steep topography or human modification of shorelines ( ''high confidence'' ). {4.3.3, 5.3.2, Figure SPM.3, SPM A6.1}

'''B.6.3''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] Ocean warming, sea level rise and tidal changes are projected to expand salinization and hypoxia in estuaries ( ''high confidence'' ) with high risks for some biota leading to migration, reduced survival, and local extinction under high emission scenarios ( ''medium confidence'' ). These impacts are projected to be more pronounced in more vulnerable eutrophic and shallow estuaries with low tidal range in temperate and high latitude regions ( ''medium confidence'' ). {5.2.2, 5.3.1, Figure SPM.3}

'''B.6.4''' [[File:c2dab058529f43e723961cf4dccd97c2 SPM-Icon-ooxx.png]] Almost all warm-water coral reefs are projected to suffer significant losses of area and local extinctions, even if global warming is limited to 1.5°C ( ''high confidence'' ). The species composition and diversity of remaining reef communities is projected to differ from present-day reefs ( ''very high confidence'' ). {5.3.4, 5.4.1, Figure SPM.3}

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