Editing IPCC:AR6/SRCCL/Chapter-7 (section)

== 7.3 Consequences of climate – land change for human well-being and sustainable development ==

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To further explore what is at stake for human systems, this section assesses literature about potential consequences of climate and land change for human well-being and ecosystems upon which humans depend. Risks described in Section 7.2 have significant social, spiritual, and economic ramifications for societies across the world and this section explores potential implications of the risks outlined above to food security, livelihood systems, migration, ecosystems, species, infectious disease, and communities and infrastructure. Because food and livelihood systems are deeply tied to one another, combinations of climate and land change could pose higher present risks to humans and ecosystems than examination of individual elements alone might suggest.

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=== 7.3.1 What is at stake for food security? ===

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This section examines risks to food security when access to food is jeopardised by yield shortfall and instability related to climate stressors. Past assessments of climate change impacts have sometimes assumed that, when grain and food yields in one area of the world are lower than expected, world trade can redistribute food adequately to ensure food security. There is ''medium confidence'' that severe and spatially extensive climatic stressors pose high risk to stability of and access to food for large numbers of people across the world.

The 2007–2008, and 2010–2011 droughts in several regions of the world resulted in crop yield decline that in turn led some governments to protect their domestic grain supplies rather than engaging in free trade to offset food shortfalls in other areas of the world. These responses cascaded and strongly affected regional and global food prices. Simultaneous crop yield impacts combined with trade impacts have proven to play a larger and more pervasive role in global food crises than previously thought (Sternberg 2012 <sup>[[#fn:r1620|1620]]</sup> , 2017 <sup>[[#fn:r1621|1621]]</sup> ; Bellemare 2015 <sup>[[#fn:r212|212]]</sup> ; Chatzopoulos et al. 2019 <sup>[[#fn:r213|213]]</sup> ). There is ''high confidence'' that regional climate extremes already have significant negative domestic and international economic impacts (Chatzopoulos et al. 2019 <sup>[[#fn:r214|214]]</sup> ).

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=== 7.3.2 Risks to where and how people live: Livelihood systems and migration ===

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There is ''high confidence'' that climate and land change interact with social, economic, political, and demographic factors that affect how well and where people live (Sudmeier-Rieux et al. 2017 <sup>[[#fn:r215|215]]</sup> ; Government Office for Science 2011 <sup>[[#fn:r216|216]]</sup> ; Laczko and Piguet 2014 <sup>[[#fn:r217|217]]</sup> ; Bohra-Mishra and Massey 2011 <sup>[[#fn:r218|218]]</sup> ; Raleigh et al. 2015 <sup>[[#fn:r219|219]]</sup> ; Warner and Afifi 2011 <sup>[[#fn:r220|220]]</sup> ; Hugo 2011 <sup>[[#fn:r221|221]]</sup> ; Warner et al. 2012 <sup>[[#fn:r222|222]]</sup> ). There is high evidence and ''high agreement'' that people move to manage risks and seek opportunities for their safety and livelihoods, recognising that people respond to climatic change and land-related factors in tandem with other variables (Hendrix and Salehyan 2012 <sup>[[#fn:r223|223]]</sup> ; Lashley and Warner 2015 <sup>[[#fn:r224|224]]</sup> ; van der Geest and Warner 2014 <sup>[[#fn:r225|225]]</sup> ; Roudier et al. 2014 <sup>[[#fn:r226|226]]</sup> ; Warner and Afifi 2014 <sup>[[#fn:r227|227]]</sup> ; McLeman 2013 <sup>[[#fn:r228|228]]</sup> ; Kaenzig and Piguet 2014 <sup>[[#fn:r229|229]]</sup> ; Internal Displacement Monitoring Centre 2017 <sup>[[#fn:r230|230]]</sup> ; Warner 2018 <sup>[[#fn:r231|231]]</sup> ; Cohen and Bradley 2010 <sup>[[#fn:r232|232]]</sup> ; Thomas and Benjamin 2017 <sup>[[#fn:r233|233]]</sup> ). People move towards areas offering safety and livelihoods such as in rapidly growing settlements in coastal zones (Black et al. 2013 <sup>[[#fn:r234|234]]</sup> ; Challinor et al. 2017 <sup>[[#fn:r235|235]]</sup> ; Adger et al. 2013 <sup>[[#fn:r236|236]]</sup> ); burgeoning urban areas also face changing exposure to combinations of storm surges and sea level rise, coastal erosion and soil and water salinisation, and land subsidence (Geisler and Currens 2017 <sup>[[#fn:r237|237]]</sup> ; Maldonado et al. 2014 <sup>[[#fn:r238|238]]</sup> ; Bronen and Chapin 2013 <sup>[[#fn:r239|239]]</sup> ).

There is ''medium confidence'' that livelihood-related migration can accelerate in the short-to-medium term when weather-dependent livelihood systems deteriorate in relation to changes in precipitation, changes in ecosystems, and land degradation and desertification (Abid et al. 2016 <sup>[[#fn:r240|240]]</sup> ; Scheffran et al. 2012 <sup>[[#fn:r241|241]]</sup> ; Fussell et al. 2014 <sup>[[#fn:r242|242]]</sup> ; Bettini and Gioli 2016 <sup>[[#fn:r243|243]]</sup> ; Reyer et al. 2017 <sup>[[#fn:r244|244]]</sup> ; Warner and Afifi 2014 <sup>[[#fn:r245|245]]</sup> ; Handmer et al. 2012 <sup>[[#fn:r246|246]]</sup> ; Nawrotzki and Bakhtsiyarava 2017 <sup>[[#fn:r247|247]]</sup> ; Nawrotzki et al. 2016 <sup>[[#fn:r248|248]]</sup> ; Steffen et al. 2015 <sup>[[#fn:r249|249]]</sup> ; Black et al. 2013 <sup>[[#fn:r250|250]]</sup> ). Slow onset climate impacts and risks can exacerbate or otherwise interact with social conflict corresponding with movement at larger scales (see Section 7.2.3.2). Long-term deterioration in habitability of regions could trigger spatial population shifts (Denton et al. 2014 <sup>[[#fn:r251|251]]</sup> ).

There is medium evidence and ''medium agreement'' that climatic stressors can worsen the complex negative impacts of strife and conflict (Schleussner et al. 2016 <sup>[[#fn:r252|252]]</sup> ; Barnett and Palutikof 2014 <sup>[[#fn:r254|254]]</sup> ; Scheffran et al. 2012 <sup>[[#fn:r255|255]]</sup> ). Climate change and human mobility could be a factor that heightens tensions over scarce strategic resources, a further destabilising influence in fragile states experiencing socio-economic and political unrest (Carleton and Hsiang 2016a <sup>[[#fn:r256|256]]</sup> ). Conflict and changes in weather patterns can worsen conditions for people working in rainfed agriculture or subsistence farming, interrupting production systems, degrading land and vegetation further (Papaioannou 2016 <sup>[[#fn:r257|257]]</sup> ; Adano and Daudi 2012 <sup>[[#fn:r258|258]]</sup> ). In recent decades, droughts and other climatic stressors have compounded livelihood pressures in areas already torn by strife (Tessler et al. 2015 <sup>[[#fn:r259|259]]</sup> ; Raleigh et al. 2015 <sup>[[#fn:r260|260]]</sup> ), such as in the Horn of Africa. Seizing of agricultural land by competing factions, preventing food distribution in times of shortage have, in this region and others, contributed to a triad of food insecurity, humanitarian need, and large movements of people (Theisen et al. 2011 <sup>[[#fn:r261|261]]</sup> ; Mohmmed et al. 2018 <sup>[[#fn:r262|262]]</sup> ; Ayeb-Karlsson et al. 2016 <sup>[[#fn:r263|263]]</sup> ; von Uexkull et al. 2016 <sup>[[#fn:r264|264]]</sup> ; Gleick 2014 <sup>[[#fn:r265|265]]</sup> ; Maystadt and Ecker 2014 <sup>[[#fn:r266|266]]</sup> ). People fleeing complex situations may return if peaceful conditions can be established. Climate change and development responses induced by climate change in countries and regions are likely to exacerbate tensions over water and land, and its impact on agriculture, fisheries, livestock and drinking water downstream. Shared pastoral landscapes used by disadvantaged or otherwise vulnerable communities are particularly impacted on by conflicts that are likely to become more severe under future climate change (Salehyan and Hendrix 2014 <sup>[[#fn:r267|267]]</sup> ; Hendrix and Salehyan 2012 <sup>[[#fn:r268|268]]</sup> ). Extreme events could considerably enhance these risks, in particular long-term drying trends (Kelley et al. 2015 <sup>[[#fn:r269|269]]</sup> ; Cutter et al. 2012a <sup>[[#fn:r270|270]]</sup> ). There is medium evidence and ''medium agreement'' that governance is key in magnifying or moderating climate change impact and conflict (Bonatti et al. 2016 <sup>[[#fn:r271|271]]</sup> ).

There is low evidence and ''medium agreement'' that longer-term deterioration in the habitability of regions could trigger spatial population shifts (Seto 2011 <sup>[[#fn:r272|272]]</sup> ). Heat waves, rising sea levels that salinise and inundate coastal and low-lying aquifers and soils, desertification, loss of geologic sources of water such as glaciers and freshwater aquifers could affect many regions of the world and put life-sustaining ecosystems under pressure to support human populations (Flahaux and De Haas 2016 <sup>[[#fn:r273|273]]</sup> ; Chambwera et al. 2015 <sup>[[#fn:r274|274]]</sup> ; Tierney et al. 2015 <sup>[[#fn:r275|275]]</sup> ; Lilleør and Van den Broeck 2011 <sup>[[#fn:r276|276]]</sup> ).

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=== 7.3.3 Risks to humans from disrupted ecosystems and species ===

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'''Risks of loss of biodiversity and ecosystem services (ES)'''

Climate change poses significant threat to species survival, and to maintaining biodiversity and ES. Climate change reduces the functionality, stability, and adaptability of ecosystems (Pecl et al. 2017 <sup>[[#fn:r277|277]]</sup> ). For example, drought affects cropland and forest productivity and reduces associated harvests (provisioning services). In additional, extreme changes in precipitation may reduce the capacity of forests to provide stability for groundwater (regulation and maintenance services). Prolonged periods of high temperature may cause widespread death of trees in tropical mountains, boreal and tundra forests, impacting on diverse ES, including aesthetic and cultural services (Verbyla 2011 <sup>[[#fn:r278|278]]</sup> ; Chapin et al. 2010 <sup>[[#fn:r279|279]]</sup> ; Krishnaswamy et al. 2014 <sup>[[#fn:r280|280]]</sup> ). According to the Millennium Ecosystem Assessment (2005) <sup>[[#fn:r281|281]]</sup> , climate change is likely to become one of the most significant drivers of biodiversity loss by the end of the century.

There is ''high confidence'' that climate change already poses a moderate risk to biodiversity, and is projected to become a progressively widespread and high risk in the coming decades; loss of Arctic sea ice threatens biodiversity across an entire biome and beyond; the related pressure of ocean acidification, resulting from higher concentrations of carbon dioxide in the atmosphere, is also already being observed (UNEP 2009 <sup>[[#fn:r282|282]]</sup> ). There is ample evidence that climate change and land change negatively affects biodiversity across wide spatial scales. Although there is relatively ''limited evidence'' of current extinctions caused by climate change, studies suggest that climate change could surpass habitat destruction as the greatest global threat to biodiversity over the next several decades (Pereira et al. 2010 <sup>[[#fn:r283|283]]</sup> ). However, the multiplicity of approaches and the resulting variability in projections make it difficult to get a clear picture of the future of biodiversity under different scenarios of global climatic change (Pereira et al. 2010 <sup>[[#fn:r284|284]]</sup> ). Biodiversity is also severely impacted on by climate change induced land degradation and ecosystem transformation (Pecl et al. 2017 <sup>[[#fn:r285|285]]</sup> ). This may affect humans directly and indirectly through cascading impacts on ecosystem function and services (Millennium Assessment 2005 <sup>[[#fn:r286|286]]</sup> ). Climate change related human migration is likely to impact on biodiversity as people move into and contribute to land stress in biodiversity hotspots now and in the future; and as humans concurrently move into areas where biodiversity is also migrating to adapt to climate change (Oglethorpe et al. 2007 <sup>[[#fn:r287|287]]</sup> ).

'''Climate and land change increases risk to respiratory and infectious disease'''

In addition to risks related to nutrition articulated in Figure 7.1, human health can be affected by climate change through extreme heat and cold, changes in infectious diseases, extreme events, and land cover and land use (Hasegawa et al. 2016 <sup>[[#fn:r288|288]]</sup> ; Ryan et al. 2015 <sup>[[#fn:r289|289]]</sup> ; Terrazas et al. 2015 <sup>[[#fn:r290|290]]</sup> ; Kweka et al. 2016 <sup>[[#fn:r291|291]]</sup> ; Yamana et al. 2016 <sup>[[#fn:r292|292]]</sup> ). Evidence indicates that action to prevent the health impacts of climate change could provide substantial economic benefits (Martinez et al. 2015 <sup>[[#fn:r293|293]]</sup> ; Watts et al. 2015 <sup>[[#fn:r294|294]]</sup> ).

Climate change exacerbates air pollution with increasing UV and ozone concentration. It has negative impacts on human health and increases the mortality rate, especially in urban region (Silva et al. 2016 <sup>[[#fn:r1622|1622]]</sup> , 2013 <sup>[[#fn:r295|295]]</sup> ; Lelieveld et al. 2013 <sup>[[#fn:r296|296]]</sup> ; Whitmee et al. 2015 <sup>[[#fn:r297|297]]</sup> ; Anenberg et al. 2010 <sup>[[#fn:r298|298]]</sup> ). In the Amazon, research shows that deforestation (both net loss and fragmentation) increases malaria, where vectors are expected to increase their home range (Alimi et al. 2015 <sup>[[#fn:r299|299]]</sup> ; Ren et al. 2016 <sup>[[#fn:r300|300]]</sup> ), confounded with multiple factors, such as social-economic conditions and immunity (Tucker Lima et al. 2017 <sup>[[#fn:r301|301]]</sup> ; Barros and Honório 2015 <sup>[[#fn:r302|302]]</sup> ). Deforestation has been shown to enhance the survival and development of major malaria vectors (Wang et al. 2016 <sup>[[#fn:r303|303]]</sup> ). The World Health Organization estimates 60,091 additional deaths for climate change induced malaria for the year 2030 and 32,695 for 2050 (World Health Organization 2014 <sup>[[#fn:r304|304]]</sup> ).

Human encroachment on animal habitat, in combination with the bushmeat trade in Central African countries, has contributed to the increased incidence of zoonotic (i.e., animal-derived) diseases in human populations, including the Ebola virus epidemic (Alexander et al. 2015a <sup>[[#fn:r305|305]]</sup> ; Nkengasong and Onyebujoh 2018 <sup>[[#fn:r306|306]]</sup> ). The composition and density of zoonotic reservoir populations, such as rodents, is also influenced by land use and climate change ( ''high confidence'' ) (Young et al. 2017a <sup>[[#fn:r307|307]]</sup> ). The bushmeat trade in many regions of central and west African forests (particularly in relation to chimpanzee and gorilla populations) elevates the risk of Ebola by increasing human–animal contact (Harrod 2015 <sup>[[#fn:r308|308]]</sup> ).

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=== 7.3.4 Risks to communities and infrastructure ===

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There is ''high confidence'' that policies and institutions which accentuate vicious cycles of poverty and ill-health, land degradation and GHG emissions undermine stability and are barriers to achieving climate-resilient sustainable development. There is ''high confidence'' that change in climate and land pose high periodic and sustained risk to the very young, those living in poverty, and ageing populations. Older people are particularly exposed, due to more restricted access to resources, changes in physiology, and the decreased mobility resulting from age, which may limit adaptive capacity of individuals and populations as a whole (Filiberto et al. 2010 <sup>[[#fn:r309|309]]</sup> ).

Combinations of food insecurity, livelihood loss related to degrading soils and ecosystem change, or other factors that diminish the habitability of where people live, disrupt social fabric and are currently detected in most regions of the world (Carleton and Hsiang 2016b <sup>[[#fn:r310|310]]</sup> ) There is ''high confidence'' that coastal flooding and degradation already poses widespread and rising future risk to infrastructure value and stranded infrastructure, as well as livelihoods made possible by urban infrastructure (Radhakrishnan et al. 2017 <sup>[[#fn:r311|311]]</sup> ; Pathirana et al. 2018 <sup>[[#fn:r312|312]]</sup> ; Pathirana et al. 2018 <sup>[[#fn:r313|313]]</sup> ; Radhakrishnan et al. 2018 <sup>[[#fn:r314|314]]</sup> ; EEA 2016 <sup>[[#fn:r315|315]]</sup> ; Pelling and Wisner 2012 <sup>[[#fn:r316|316]]</sup> ; Oke et al. 2017 <sup>[[#fn:r317|317]]</sup> ; Parnell and Walawege 2011 <sup>[[#fn:r318|318]]</sup> ; Uzun and Cete 2004 <sup>[[#fn:r319|319]]</sup> ; Melvin et al. 2017 <sup>[[#fn:r320|320]]</sup> ).

There is ''high evidence'' and ''high agreement'' that climate and land change pose a high risk to communities. Interdependent infrastructure systems, including electric power and transportation, are highly vulnerable and interdependent (Below et al. 2012 <sup>[[#fn:r321|321]]</sup> ; Adger et al. 2013 <sup>[[#fn:r322|322]]</sup> ; Pathirana et al. 2018 <sup>[[#fn:r323|323]]</sup> ; Conway and Schipper 2011 <sup>[[#fn:r324|324]]</sup> ; Caney 2014 <sup>[[#fn:r325|325]]</sup> ; Chung Tiam Fook 2017 <sup>[[#fn:r326|326]]</sup> ). These systems are exposed to disruption from severe climate events such as weather-related power interruptions lasting for hours to days (Panteli and Mancarella 2015 <sup>[[#fn:r327|327]]</sup> ). Increased magnitude and frequency of high winds, ice storms, hurricanes and heat waves have caused widespread damage to power infrastructure and also severe outages, affecting significant numbers of customers in urban and rural areas (Abi-Samra and Malcolm 2011 <sup>[[#fn:r328|328]]</sup> ).

Increasing populations, enhanced per capita water use, climate change, and allocations for water conservation are potential threats to adequate water availability. As climate change produces variations in rainfall, these challenges will intensify, evidenced by severe water shortages in recent years in Cape Town, Los Angeles, and Rio de Janeiro, among other places (Watts et al. 2018 <sup>[[#fn:r329|329]]</sup> ; Majumder 2015 <sup>[[#fn:r330|330]]</sup> ; Ashoori et al. 2015 <sup>[[#fn:r331|331]]</sup> ; Mini et al. 2015 <sup>[[#fn:r332|332]]</sup> ; Otto et al. 2015 <sup>[[#fn:r333|333]]</sup> ; Ranatunga et al. 2014 <sup>[[#fn:r334|334]]</sup> ; Ray and Shaw 2016 <sup>[[#fn:r335|335]]</sup> ; Gopakumar 2014 <sup>[[#fn:r336|336]]</sup> ) (Cross-Chapter Box 5 in Chapter 3).

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