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

=== 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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