Editing IPCC:AR6/WGII/Chapter-9 (section)

=== 9.6.2 Projected Risks of Climate Change for African Biodiversity and Ecosystem Services ===

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==== 9.6.2.1 Projected Biome Distribution ====

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The geography of African biomes is projected to shift due to changes in atmospheric CO 2 concentrations and aridity (Figure 9.18). Grassland expansion into the desert, woody expansion into grasslands and forest expansion into savannas are projected for areas of reduced aridity, caused by reduced moisture stress from CO 2 fertilisation under medium (RCP4.5) and high (SRES A2) emissions scenarios ( [[#Heubes--2011|Heubes et al., 2011]] ; [[#Moncrieff--2016|Moncrieff et al., 2016]] ). This greening trend may slow or reverse with continued temperature increase and/or in areas of increased aridity ( [[#Berdugo--2020|Berdugo et al., 2020]] ). The net impact of these effects on vegetation is highly uncertain ( [[#Trugman--2018|Trugman et al., 2018]] ; [[#Cook--2020a|Cook et al., 2020a]] ; [[#Martens--2021|Martens et al., 2021]] ). The maintenance or re-establishment of natural fire and large mammal herbivory processes can mitigate projected CO 2 and climate-driven changes ( [[#Scheiter--2016|Scheiter and Savadogo, 2016]] ; [[#Stevens--2016|Stevens et al., 2016]] ). Expansion of croplands and pastures will reduce ecosystem carbon storage in Africa, potentially reversing climate- and CO 2 -driven greening in savannas ( [[#Aleman--2018|Aleman et al., 2018]] ; [[#Quesada--2018|Quesada et al., 2018]] ).

Vegetation growth simulated by dynamic vegetation models is often highly sensitive to CO 2 fertilisation. These models project the African tropical forest carbon sink to be stable or strengthened under scenarios of future climate change ( [[#Huntingford--2013|Huntingford et al., 2013]] ; [[#Martens--2021|Martens et al., 2021]] ). In contrast, statistical modelling suggests it has begun to decline and will weaken further, decreasing from current estimates of 0.66 tonnes of carbon removed from the atmosphere per hectare per year to 0.55 tonnes of carbon ( [[#Hubau--2020|Hubau et al., 2020]] ). Increasing rainfall seasonality and aridity over central Africa ( [[#Haensler--2013|Haensler et al., 2013]] ) threatens the massive carbon store in the Congo Basin’s Cuvette Centrale peatlands, estimated at 30.6 billion tonnes ( [[#Dargie--2019|Dargie et al., 2019]] ).

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==== 9.6.2.2 Terrestrial Biodiversity ====

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Local extinction is when a species is extirpated from a local site. The magnitude and extent of local extinctions predicted across Africa increase substantially under all future GWLs ( ''high confidence'' ) (Table 9.5; Figure 9.19). Above 2°C, the risk of sudden disruption or loss of local biodiversity increases and becomes more widespread, especially in central, west and east Africa ( [[#Trisos--2020|Trisos et al., 2020]] ).

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[[File:d2c9e11f54cfd15d667d0193002e6a07 IPCC_AR6_WGII_Figure_9_019.png]]

'''Figure 9.19 |''' '''The loss of African biodiversity under future climate change is projected to be widespread and increasing substantially with every 0.5° above the current (2001–2020) level of global warming (''' high confidence ''').'''

'''(a)''' Projected biodiversity loss, quantified as percentage change in species abundance, range size or area of suitable habitat increases with increasing global warming levels (relative to 1850–1900). Above 1.5°C global warming, half of all assessed species are projected to lose &gt;30% of their population, range size or area of suitable habitat, with losses increasing to &gt;40% for &gt;2°C. The 2001–2020 level of global warming is around 1°C higher than 1850–1900 ( [[#IPCC--2021|IPCC, 2021]] ). Boxplots show the median (horizontal line), 50% quantiles (box), and points are studies of individual species or of multiple species (symbol size indicates the number of species in a study).

'''(b–c)''' The mean projected local extinction of vertebrates, plants and insects within 100 km grid cells increases in severity and extent under increased global warming (relative to 1850–1900). Local extinction &gt;10% is widespread by 1.5°C. Pixel colour shows the projected percentage of species undergoing local extinction and the agreement between multiple biodiversity models.

'''(d–e)''' The mean projected increase in species of freshwater fish vulnerable to local extinction within 10 km grid cells for future global warming. Around a third of fish species are projected to be vulnerable to extinction by 2°C global warming. Pixel colour shows the projected percentage of species vulnerable to extinction and agreement between multiple vulnerability models. In (a), data were obtained from 22 peer-reviewed papers published since 2012 investigating the impacts of projected climate change on African biodiversity. When a paper provided impact projections for several time periods, climate change scenarios or for more than one species, each impact was recorded as an individual biodiversity impact projection, resulting in a database of 1165 biodiversity impact projections. Data were initially collected by [[#Manes--2021|Manes et al. (2021)]] as part of a larger literature review for [https://www.ipcc.ch/chapter/cross-chapter-paper-1 Cross-Chapter Paper 1] on Biodiversity Hotspots and then expanded to include areas outside of African priority conservation areas (see Table SM 9.4). The literature review was limited to peer-reviewed publications that reported quantifiable risks to biodiversity, eliminating non-empirical studies. In (b–c), projections are based on intersecting current and future modelled species distributions at ~10 km spatial resolution from two recent global assessments of climate change impacts on terrestrial vertebrates ( [[#Newbold--2018|Newbold, 2018]] ; [[#Warren--2018|Warren et al., 2018]] ). In (d-e) projections are based on intersecting future species vulnerabilities from two recent assessments of climate change vulnerability of freshwater fish species ( [[#Nyboer--2019|Nyboer et al., 2019]] ; [[#Barbarossa--2021|Barbarossa et al., 2021]] ).

Global extinction is when a species is extirpated from all areas. At 2°C global warming, 11.6% of African species (mean 11.6%, 95% CI 6.8–18.2%) assessed are at risk of global extinction, placing Africa second only to South America in the magnitude of projected biodiversity losses ( [[#Urban--2015|Urban, 2015]] ). At &gt;2°C, 20% of north African mammals may lose all suitable climates ( [[#Soultan--2019|Soultan et al., 2019]] ), and over half of the dwarf succulents in South African Karoo may lose &gt;90% of their suitable habitat ( [[#Young--2016|Young et al., 2016]] ). Among the thousands of species at risk, many are species of ecological, cultural and economic importance such as African wild dogs ( [[#Woodroffe--2017|Woodroffe et al., 2017]] ) and Arabica coffee ( [[#Moat--2019|Moat et al., 2019]] ).

With increasing warming, there is a lower likelihood species can migrate rapidly enough to track shifting climates, increasing global extinction risk and biodiversity loss across more of Africa ( ''high confidence'' ). Immigration of species from elsewhere may partly compensate for local extinctions and lead to local biodiversity gains in some regions ( [[#Newbold--2018|Newbold, 2018]] ; [[#Warren--2018|Warren et al., 2018]] ). However, more regions face net losses than net gains. At 1.5°C global warming, &gt;46% of localities face net declines in vertebrate species richness of &gt;10%, with net increases projected for less than 15% of localities ( [[#Barbet-Massin--2015|Barbet-Massin and Jetz, 2015]] ; [[#Newbold--2018|Newbold, 2018]] ). At &gt;2°C, 9% of species face complete range loss by 2100, regardless of their dispersal ability ( [[#Urban--2015|Urban, 2015]] ). With &gt;4°C global warming, a net loss of &gt;10% of vertebrate species richness is projected across 85% of Africa ( [[#Barbet-Massin--2015|Barbet-Massin and Jetz, 2015]] ; [[#Mokhatla--2015|Mokhatla et al., 2015]] ; [[#Newbold--2018|Newbold, 2018]] ; [[#Warren--2018|Warren et al., 2018]] ). Mountain top endemics and species in north and southern Africa are at risk due to disappearing cold climates ( [[#Milne--2015|Milne et al., 2015]] ; [[#Garcia--2016|Garcia et al., 2016]] ; [[#Bentley--2018|Bentley et al., 2018]] ; [[#Soultan--2019|Soultan et al., 2019]] ). For hot regions such as the Sahara, Congo Basin and Kalahari, no warmer-adapted species are available elsewhere to compensate for local extinctions, so the resilience of local biodiversity will depend entirely on the persistence of species ( [[#Burrows--2014|Burrows et al., 2014]] ; [[#Garcia--2014|Garcia et al., 2014]] ). The capacity for species to avoid extinction through behavioural thermoregulation, plasticity or evolution is uncertain but will become increasingly ''unlikely'' under higher warming scenarios ( [[#Conradie--2019|Conradie et al., 2019]] ).

'''Table 9.5 |''' Risk of local extinction increases across Africa with increasing global warming.

{| class="wikitable"
|-
! '''Global warming level (relative to 1850–1900)'''

! '''Taxa'''

! '''Percentage of species at a site at risk of local extinction'''

! '''Extent across Africa (percentage of the land area of Africa)'''

! '''Areas at risk'''

! '''References'''

|-
| 1.5°C

| Plants, insects, vertebrates

| &gt;10%

| &gt;90%

| Widespread. Hot and/or arid regions especially at risk, including Sahara, Sahel and Kalahari

| Figure 9.29b; [[#Newbold--2018|Newbold (2018)]] ; [[#Warren--2018|Warren et al. (2018)]]

|-
| &gt;2°C

| Plants, insects, vertebrates

| &gt;50%

| 18%

| Widespread

| [[#Newbold--2018|Newbold (2018)]] ; [[#Warren--2018|Warren et al. (2018)]]

|-
| &gt;4°C

| Plants, insects, vertebrates

| &gt;50%

| 45–73%

| Widespread. Higher uncertainty for central African tropical forests due to lower agreement between biodiversity models

| Fig. 9.29c; [[#Newbold--2018|Newbold (2018)]] ; [[#Warren--2018|Warren et al. (2018)]]

|}

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==== 9.6.2.3 Marine Ecosystems ====

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African coastal and marine ecosystems are highly vulnerable to climate change ( ''high confidence'' ). At 1.5°C of global warming, mangroves will be exposed to sedimentation and sea level rise, while seagrass ecosystems will be most affected by heat extremes ( ''high confidence'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ) and turbidity ( [[#Wong--2014|Wong et al., 2014]] ). These risks will be amplified at 2°C and 3°C ( ''virtually certain'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). Over 90% of east African coral reefs are projected to be destroyed by bleaching at 2°C of global warming ( ''very high confidence'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). At around 2.5°C global warming, an important reef-building coral ( ''Diploastrea heliopora'' ) in the central Red Sea is projected to stop growing altogether ( [[#Cantin--2010|Cantin et al., 2010]] ). By 2.5°C, suitable habitat of &gt;50% of species are projected to decline for coastal lobster in east and north Africa, with large declines for the commercially important lobster species ''Jasus lalandii'' in southern Africa ( [[#Boavida-Portugal--2018|Boavida-Portugal et al., 2018]] ). More generally, tropical regions, especially exclusive economic zones in west Africa, are projected to lose large numbers of marine species and may experience sudden declines with extratropical regions having potential net increases as species track shifting temperatures poleward (García Molinos et al., 2016; [[#Trisos--2020|Trisos et al., 2020]] ).

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==== 9.6.2.4 Freshwater Ecosystems ====

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Above 2°C global warming, the proportion of freshwater fish species vulnerable to climate change increases substantially ( ''high confidence'' ) (Figure 9.19). At 2°C, 36.4% of fish species are projected to be vulnerable to local or global extinction by 2100, increasing to 56.4% under 4°C warming (average of values from ( [[#Nyboer--2019|Nyboer et al., 2019]] ; [[#Barbarossa--2021|Barbarossa et al., 2021]] ) (Figure 9.19). Global warming reduces available habitat for freshwater species due to reduced precipitation and increased drought leading to increasing water temperatures above optimal physiological limits in floodplains, estuaries, wetlands, ephemeral pools, rivers and lakes ( [[#Dalu--2017|Dalu et al., 2017]] ; [[#Kalacska--2017|Kalacska et al., 2017]] ; [[#Nyboer--2018|Nyboer and Chapman, 2018]] ). Along the Zambezi River, projected flow reductions could cause a 22% reduction in annual spawning habitat and depletion of food resources for fry and juvenile fish that could impede fish migration and reduce stocks ( [[#Kangalawe--2017|Kangalawe, 2017]] ; [[#Martínez-Capel--2017|Martínez-Capel et al., 2017]] ; [[#Tamatamah--2020|Tamatamah and Mwedzi, 2020]] ). More aquatic species will have the capacity to cope with 2°C compared to 4°C global warming, with more negative effects on physiological performance at 4°C ( [[#Dallas--2016|Dallas, 2016]] ; [[#Pinceel--2016|Pinceel et al., 2016]] ; [[#Zougmoré--2016|Zougmoré et al., 2016]] ; [[#Nyboer--2017|Nyboer and Chapman, 2017]] ; [[#Ross-Gillespie--2018|Ross-Gillespie et al., 2018]] ). Endemic, specialised fish species will have a lower capacity to adjust to elevated water temperatures compared to hardier generalist fishes ( [[#McDonnell--2015|McDonnell and Chapman, 2015]] ; [[#Nyboer--2017|Nyboer and Chapman, 2017]] ; [[#Lapointe--2018|Lapointe et al., 2018]] ; [[#Reizenberg--2019|Reizenberg et al., 2019]] ). More work is needed to understand the risk for invertebrates ( [[#Dallas--2014|Dallas and Rivers-Moore, 2014]] ; [[#Cohen--2016|Cohen et al., 2016]] ), and to understand the potential effects of reduced mixing of water and other climate risks on freshwater biodiversity.

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==== 9.6.2.5 Climate Change and Ecosystem Services ====

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Direct human dependence on provisioning ecosystem services in Africa is high ( [[#Egoh--2012|Egoh et al., 2012]] ; [[#IPBES--2018|IPBES, 2018]] ). For example, natural forests provided 21% of rural household income across 11 African countries ( [[#Angelsen--2014|Angelsen et al., 2014]] ) and wild-harvested foods (including fisheries) provide important nutrition to millions of Africans, including through important micronutrients and increased dietary diversity (Sections 9.8.2.3; 9.8.5; [[#Powell--2013|Powell et al., 2013]] ; [[#Baudron--2019a|Baudron et al., 2019a]] ).

Climate change has affected ecosystem services in Africa by reducing fish stocks, crop and livestock productivity, and water provisioning due to heat and drought (see Sections 9.8.2.1; 9.8.2.2; 9.8.2.4; 9.8.5.1). Woody encroachment is decreasing cattle production and water supply ( [[#Smit--2015|Smit and Prins, 2015]] ; [[#Stafford--2017|Stafford et al., 2017]] ), but can also provide forage for goat production, as well as resins, fuelwood and charcoal ( [[#Reed--2015|Reed et al., 2015]] ; [[#Stafford--2017|Stafford et al., 2017]] ; [[#Charis--2019|Charis et al., 2019]] ). Local communities perceive climate change to have decreased crop and livestock productivity, reduced wild food availability and reduced forest resources across Africa (see Sections 9.8.2.1; 9.8.2.2; 9.8.2.4; 9.8.2.3; [[#Onyekuru--2014|Onyekuru and Marchant, 2014]] ).

With global warming &gt;3°C, and with high population growth and agricultural expansion (SSP3, 2081–2100), 1.2 billion Africans are projected to be negatively affected by pollution of drinking water from reduced water quality regulation by ecosystems and 27 million people affected by reduced coastal protection by ecosystems ( [[#Chaplin-Kramer--2019|Chaplin-Kramer et al., 2019]] ). The number of people affected reduces to 0.4 billion and 22 million, respectively, under a sustainable development scenario with global warming below 2°C (SSP1, 2081–2100). The African tropical forest carbon sink has been more resilient than Amazonia to recent warming but may already have peaked, and this service is predicted to decline with further warming, reducing 14% by the 2030s ( [[#Hubau--2020|Hubau et al., 2020]] ; [[#Sullivan--2020|Sullivan et al., 2020]] ). This declining carbon storage may be offset by CO 2 fertilization ( ''low confidence'' ) ( [[#Martens--2021|Martens et al., 2021]] ). Climate change is projected to shift the geographic distribution of important human and livestock disease vectors (see Sections 9.8.2.4; 9.10.2). Changes in rainfall seasonality compounded with land privatisation and population growth may adversely impact nomadic and semi-nomadic pastoralists who follow shifting patterns of greening vegetation ( [[#Van%20Der%20Ree--2015|Van Der Ree et al., 2015]] ).

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==== 9.6.2.6 Invasive Species ====

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Invasive species threaten African ecosystems and livelihoods ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). For instance, economic impacts were estimated at USD 1 billion per year for smallholder maize farmers in east Africa ( [[#Pratt--2017|Pratt et al., 2017]] ). Climate change is projected to change patterns of invasive species spread ( ''high confidence'' ). The area of suitable climate for ''Lantana camara'' is projected to contract ( [[#Taylor--2012|Taylor et al., 2012]] ) and to expand for ''Prosopis juliflora'' ( [[#Sintayehu--2020|Sintayehu et al., 2020]] ). Bioclimatic suitability for fall armyworm, a major threat to maize, is projected to decrease in central Africa but expand in southern and west Africa ( [[#Zacarias--2020|Zacarias, 2020]] ), and to expand for coffee berry borer ( ''Hypothenemus hampei'' ) in Uganda and around Mount Kenya ( [[#Jaramillo--2011|Jaramillo et al., 2011]] ). Climate suitability for tephritid fruit flies is projected to decrease in central Africa ( [[#Hill--2016|Hill et al., 2016]] ). Increased water temperature is projected to favour invasive over local freshwater fish populations and shift the range of invasive aquatic plants in South Africa ( [[#Hoveka--2016|Hoveka et al., 2016]] ; [[#Shelton--2018|Shelton et al., 2018]] ). Alterations to lake and river connectivity are predicted to modify invasion pathways in Lake Tanganyika and water hyacinth coverage may increase with warmer waters in Lake Victoria ( [[#Masters--2010|Masters and Norgrove, 2010]] ; [[#Plisnier--2018|Plisnier et al., 2018]] ).

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