Editing IPCC:AR6/WGII/Cross-Chapter-Paper-3 (section)

===== Where are we now: Observed impacts and adaptation responses =====

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'''Deserts and semiarid areas have already been affected by climate change, with some areas experiencing increases in aridity. Mixed trends of decreases and increases in vegetation productivity have been observed, depending on the time period, geographic region, detection methods used and vegetation type under consideration (''' '''''high confidence''''' [[#footnote-001|1]] '''). These changes have had varying and location-specific impacts on biodiversity, and have altered ecosystem carbon balance, water availability and the provision of ecosystem services (''' '''''high confidence''''' '''). There is no evidence, however, of a global trend in dryland expansion based on analyses of vegetation patterns, precipitation and soil moisture, with overall, more greening than drying in drylands since the 1980s (''' '''''medium confidence''''' ''').''' Deserts and semiarid areas host unique biodiversity, rich cultural heritage and provide globally valuable ecosystem services. They are also highly vulnerable to climate change. The vitality of natural ecosystems in arid and semiarid regions greatly depends on water availability, as they are highly sensitive to changes in precipitation and potential evapotranspiration, as well as to land management practices. Multiple lines of evidence from 1920–2015 indicate that surface warming of 1.2 ° C–1.3 ° C over global drylands ( [[IPCC:Wg2:Chapter:Chapter-1#1.1.1|Section 1.1.1]] ) exceeded the 0.8 ° C–1.0 ° C warming over humid lands. From 1982 to 2015, unsustainable land use and climate change combined caused desertification of 6% of the global dryland area, while 41% showed significant increases in vegetation productivity (greening) and 53% of the area had no notable change, although greening rates are slowing or declining in some locations. Greening may cause biodiversity loss and ecosystem service degradation in relation to livelihood systems. Observed trends in deserts and semiarid areas have led to varying impacts on flora, fauna, soil, nutrient cycling, the carbon cycle and water resources. Ecological changes in dryland ecosystems detected and attributed primarily to climate change include tree mortality and losses of mesic tree species at specific sites in the African Sahel, particularly during the droughts of the 1970s and 1980s, and in North Africa from 1970 to 2007; and losses of bird species in the Mojave Desert of North America from 1908 to 2016. In contrast, growth in herbaceous vegetation production has increased in some drylands since the 1980s. Widespread woody encroachment has occurred in many shrublands and savannas in Africa, Australia, North America and South America, due to a combination of land use change, changes in rainfall, fire suppression and CO 2 fertilization which, together with unsustainable management, alters biodiversity and reduces ecosystem services, such as water availability and grazing potential {3.2.1, 3.2.2} .

'''The impacts of climate change have affected the ecosystem services that humans can harness from drylands, with largely negative implications for livelihoods, human health and well-being, particularly in deserts and semiarid areas with lower adaptive capacities (''' '''''high confidence''''' ''')''' . Ecosystem degradation ( [[IPCC:Wg2:Chapter:Chapter-16#16.5.2.3|Section 16.5.2.3.2]] ) and desertification threaten the abilities of both natural and human systems to adapt to climate change ( ''high confidence'' ). Changes in desert and semiarid ecosystem services most acutely affect people who are directly dependent on natural resources for their livelihoods and survival. These groups also often have lower capacities to adapt, particularly given structural limitations of some drylands where healthcare, sanitation, infrastructure and efficient markets are lacking, reinforcing existing inequalities ( ''high confidence'' ). In rural drylands in tropical and Mediterranean areas, human populations are steadily expanding with mixed implications for ecosystem services under climate change, while rapid urbanisation in new and existing dryland megacities puts additional pressure on water ecosystem services ( ''high confidence'' ). Impacts resulting from consumption of dryland ecosystem services elsewhere, alongside other teleconnections associated with health, trade, conflict and migration, mean that dryland adaptive capacities have far reaching implications for other locations, while other locations affect dryland adaptation options. {3.1.1, 3.2.1, 3.2.2, 3.4} ''.''

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