Editing IPCC:AR6/SRCCL/Chapter-6 (section)

==== 6.3.2.1 Integrated response options based on land management ====

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In this section, the impacts on climate change adaptation of integrated response options based on land management are assessed.

Integrated response options based on land management in agriculture

Increasing food productivity by practices such as sustainable intensification improves farm incomes and allows households to build assets for use in times of stress, thereby improving resilience (Campbell et al. 2014 <sup>[[#fn:r362|362]]</sup> ). By reducing pressure on land and increasing food production, increased food productivity could be beneficial for adaptation (Campbell et al. 2014) (Chapter 2 and Section 6.3). Pretty et al. (2018) report that 163 million farms occupying 4.53 Mkm2 have passed a redesign threshold for application of sustainable intensification, suggesting the minimum number of people benefitting from increased productivity and adaptation benefits under sustainable intensification is &gt;163 million, with the total likely to be far higher (Table 6.21).

Improved cropland management is a key climate adaptation option, potentially affecting more than 25 million people, including a wide range of technological decisions by farmers. Actions towards adaptation fall into two broad overlapping areas: (i) accelerated adaptation to progressive climate change over decadal time scales, for example integrated packages of technology, agronomy and policy options for farmers and food systems, including changing planting dates and zones, tillage systems, crop types and varieties, and (ii) better management of agricultural risks associated with increasing climate variability and extreme events, for example, improved climate information services and safety nets (Vermeulen et al. 2012b <sup>[[#fn:r364|364]]</sup> ; Challinor et al. 2014 <sup>[[#fn:r365|365]]</sup> ; Lipper et al. 2014 <sup>[[#fn:r366|366]]</sup> ; Lobell 2014 <sup>[[#fn:r367|367]]</sup> ). In the same way, improved livestock management is another technological adaptation option potentially benefitting between 1 million and 25 million people. Crop and animal diversification are considered the most promising adaptation measures (Porter et al. 2014 <sup>[[#fn:r368|368]]</sup> ; Rojas-Downing et al. 2017 <sup>[[#fn:r369|369]]</sup> ). In grasslands and rangelands, regulation of stocking rates, grazing field dimensions, establishment of exclosures and locations of drinking fountains and feeders are strategic decisions by farmers to improve grazing management (Taboada et al. 2011 <sup>[[#fn:r370|370]]</sup> ; Mekuria and Aynekulu 2013 <sup>[[#fn:r371|371]]</sup> ; Porter et al. 2014 <sup>[[#fn:r372|372]]</sup> ).

Around 30% of the world’s rural population use trees across 46% of all agricultural landscapes (Lasco et al. 2014 <sup>[[#fn:r373|373]]</sup> ), meaning that up to 2.3 billion people benefit from agroforestry globally (Table 6.21).

Agricultural diversification is key to achieving climatic resilience (Campbell et al. 2014 <sup>[[#fn:r374|374]]</sup> ; Cohn et al. 2017 <sup>[[#fn:r375|375]]</sup> ). Crop diversification is one important adaptation option to progressive climate change (Vermeulen et al. 2012a <sup>[[#fn:r376|376]]</sup> ) and it can improve resilience by engendering a greater ability to suppress pest outbreaks and dampen pathogen transmission, as well as by buffering crop production from the effects of greater climate variability and extreme events (Lin 2011 <sup>[[#fn:r377|377]]</sup> ).

Reduced conversion of grassland to cropland may lead to adaptation benefits by stabilising soils in the face of extreme climatic events (Lal 2001 <sup>[[#fn:r378|378]]</sup> ), thereby increasing resilience, but since it would likely have a negative impact on food production/security (since croplands produce more food per unit area than grasslands), the wider adaptation impacts would likely be negative. However, there is no literature quantifying the global impact of avoidance of conversion of grassland to cropland on adaptation.

Integrated water management provides large co-benefits for adaptation (Dillon and Arshad 2016 <sup>[[#fn:r379|379]]</sup> ) by improving the resilience of food crop production systems to future climate change (Porter et al. 2014 <sup>[[#fn:r380|380]]</sup> ) (Chapter 2 and Table 6.7). Improving irrigation systems and integrated water resource management, such as enhancing urban and rural water supplies and reducing water evaporation losses (Dillon and Arshad 2016 <sup>[[#fn:r381|381]]</sup> ), are significant options for enhancing climate adaptation. Many technical innovations (e.g., precision water management) can lead to beneficial adaptation outcomes by increasing water availability and the reliability of agricultural production, using different techniques of water harvesting, storage, and its judicious utilisation through farm ponds, dams and community tanks in rainfed agriculture areas. Integrated water management response options that use freshwater would be expected to have few adverse side effects in regions where water is plentiful, but large adverse side effects in regions where water is scarce (Grey and Sadoff 2007 <sup>[[#fn:r382|382]]</sup> ; Liu et al. 2017 <sup>[[#fn:r383|383]]</sup> ; Scott et al. 2011 <sup>[[#fn:r384|384]]</sup> ).

Table 6.21 summarises the potentials for adaptation for agricultural response options, with confidence estimates based on the thresholds outlined in Table 6.53 in Section 6.3.6, and indicative (not exhaustive) references upon which the evidence in based.

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''Integrated response options based on land management in forestry''

Forest management positively impacts on adaptation through limiting the negative effects associated with pollution (of air and fresh water), infections and other diseases, exposure to extreme weather events and natural disasters, and poverty (e.g., Smith et al. 2014). There is high agreement on the fact that reduced deforestation and forest degradation positively impact on adaptation and resilience of coupled human-natural systems. Based on the number of people affected by natural disasters (CRED 2015 <sup>[[#fn:r385|385]]</sup> ), the number of people depending to varying degrees on forests for their livelihoods (World Bank et al. 2009 <sup>[[#fn:r386|386]]</sup> ) and the current deforestation rate (Keenan et al. 2015 <sup>[[#fn:r387|387]]</sup> ), the estimated global potential effect for adaptation is largely positive for forest management, and moderately positive for reduced deforestation when cumulated until the end of the century (Table6.22).The uncertainty of these global estimates is high, for example, the impact of reduced deforestation may be higher when the large biophysical impacts on the water cycle (and thus drought) from deforestation (e.g., Alkama and Cescatti 2016 <sup>[[#fn:r388|388]]</sup> ) are taken into account (Chapter 2).

More robust qualitative, and some quantitative, estimates are available at local and regional level. According to Karjalainen et al. (2009) <sup>[[#fn:r389|389]]</sup> , reducing deforestation and habitat alteration contributes to limiting infectious diseases such as malaria in Africa, Asia and Latin America, thus lowering the expenses associated with healthcare treatments. Bhattacharjee and Behera (2017) <sup>[[#fn:r390|390]]</sup> found that human lives lost due to floods increase with reducing forest cover and increasing deforestation rates in India. In addition, maintaining forest cover in urban contexts reduces air pollution and therefore avoids mortality of about one person per year per city in US, and up to 7.6 people per year in New York City (Nowak et al. 2014 <sup>[[#fn:r391|391]]</sup> ). There is also evidence that reducing deforestation and forest degradation in mangrove plantations potentially improves soil stabilisation, and attenuates the impact of tropical cyclones and typhoons along the coastal areas in South and Southeast Asia (Chow 2018 <sup>[[#fn:r392|392]]</sup> ). At local scale, co-benefits between REDD+ and adaptation of local communities can potentially be substantial (Long 2013 <sup>[[#fn:r393|393]]</sup> ; Morita and Matsumoto 2018 <sup>[[#fn:r394|394]]</sup> ), even if often difficult to quantify, and not explicitly acknowledged (McElwee et al. 2017b <sup>[[#fn:r395|395]]</sup> ).

Forest restoration may facilitate the adaptation and resilience of forests to climate change by enhancing connectivity between forest areas and conserving biodiversity hotspots (Locatelli et al. 2011 <sup>[[#fn:r396|396]]</sup> , 2015b; Ellison et al. 2017 <sup>[[#fn:r397|397]]</sup> ; Dooley and Kartha 2018 <sup>[[#fn:r398|398]]</sup> ). Furthermore, forest restoration may improve ecosystem functionality and services, provide microclimatic regulation for people and crops, wood and fodder as safety nets, soil erosion protection and soil fertility enhancement for agricultural resilience, coastal area protection, water and flood regulation (Locatelli et al. 2015b <sup>[[#fn:r399|399]]</sup> ).

Afforestation and reforestation are important climate change adaptation response options (Reyer et al. 2009 <sup>[[#fn:r400|400]]</sup> ; Ellison et al. 2017 <sup>[[#fn:r401|401]]</sup> ; Locatelli et al. 2015b <sup>[[#fn:r402|402]]</sup> ), and can potentially help a large proportion of the global population to adapt to climate change and to associated natural disasters (Table 6.22). For example, trees generally mitigate summer mean warming and temperature extremes (Findell et al. 2017 <sup>[[#fn:r403|403]]</sup> ; Sonntag et al. 2016 <sup>[[#fn:r404|404]]</sup> ).

Table 6.22 summarises the potentials for adaptation for forest response options, with confidence estimates based on the thresholds outlined in Table 6.53 in Section 6.3.6, and indicative (not exhaustive) references upon which the evidence in based.

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''Integrated response options based on land management of soils''

Soil organic carbon increase is promoted as an action for climate change adaptation. Since increasing soil organic matter content is a measure to address land degradation (see Section 6.2.1), and restoring degraded land helps to improve resilience to climate change, soil carbon increase is an important option for climate change adaptation. With around 120,000 km2 lost to degradation every year, and over 3.2 billion people negatively impacted by land degradation globally (IPBES 2018 <sup>[[#fn:r1257|1257]]</sup> ), practices designed to increase soil organic carbon have a large potential to address adaptation challenges (Table 6.23).

Since soil erosion control prevents land degradation and desertification, it improves the resilience of agriculture to climate change and increases food production (Lal 1998 <sup>[[#fn:r406|406]]</sup> ; IPBES 2018 <sup>[[#fn:r407|407]]</sup> ), though the global number of people benefitting from improved resilience to climate change has not been reported in the literature. Using figures from (FAO and ITPS 2015), IPBES (2018) <sup>[[#fn:r407|407]]</sup> estimates that land losses due to erosion are equivalent to 1.5 Mkm2 of land used for crop production to 2050, or 45,000 km2 yr–1 (Foley et al. 2011). Control of soil erosion (water and wind) could benefit 11 Mkm2 of degraded land (Lal 2014 <sup>[[#fn:r408|408]]</sup> ), and improve the resilience of at least some of the 3.2 billion people affected by land degradation (IPBES 2018 <sup>[[#fn:r409|409]]</sup> ), suggesting positive impacts on adaptation. Management of erosion is an important climate change adaptation measure, since it reduces the vulnerability of soils to loss under climate extremes, thereby increasing resilience to climate change (Garbrecht et al. 2015 <sup>[[#fn:r410|410]]</sup> ).

Prevention and/or reversion of topsoil salinisation may require a combined management of groundwater, irrigation techniques, drainage, mulching and vegetation, with all of these considered relevant for adaptation (Qadir et al. 2013 <sup>[[#fn:r411|411]]</sup> ; UNCTAD 2011 <sup>[[#fn:r412|412]]</sup> ; Dagar et al. 2016 <sup>[[#fn:r413|413]]</sup> ). Taking into account the widespread diffusion of salinity problems, many people can benefit from its implementation by farmers. The relation between compaction prevention and/or reversion and climate adaption is less evident, and can be related to better hydrological soil functioning (Chamen et al. 2015 <sup>[[#fn:r414|414]]</sup> ; Epron et al. 2016 <sup>[[#fn:r415|415]]</sup> ; Tullberg et al. 2018 <sup>[[#fn:r416|416]]</sup> ).

Biochar has the potential to benefit climate adaptation by improving the resilience of food crop production systems to future climate change by increasing yield in some regions and improving water holding capacity (Woolf et al. 2010 <sup>[[#fn:r417|417]]</sup> ; Sohi 2012 <sup>[[#fn:r418|418]]</sup> ) (Chapter 2 and Section 6.4). By increasing yield by 25% in the tropics (Jeffery et al. 2017 <sup>[[#fn:r419|419]]</sup> ), this could increase food production for 3.2 billion people affected by land degradation (IPBES 2018 <sup>[[#fn:r420|420]]</sup> ), thereby potentially improving their resilience to climate change shocks (Table 6.23). A requirement for large areas of land to provide feedstock for biochar could adversely impact on adaptation, though this has not been quantified globally.

Table 6.23 summarises the potentials for adaptation for soil-based response options, with confidence estimates based on the thresholds outlined in Table 6.53 in Section 6.3.6, and indicative (not exhaustive) references upon which the evidence in based.

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''Integrated response options based on land management across all/other ecosystems''

For fire management, Doerr et al. (2016) showed that the number of people killed by wildfire was 1940, and the total number of people affected was 5.8 million from 1984 to 2013, globally. Johnston et al. (2012) <sup>[[#fn:r421|421]]</sup> showed that the average mortality attributable to landscape fire smoke exposure was 339,000 deaths annually. The regions most affected were sub-Saharan Africa (157,000) and Southeast Asia (110,000). Estimated annual mortality during La Niña was 262,000, compared with around 100,000 excess deaths across Indonesia, Malaysia and Singapore (Table 6.24).

Management of landslides and natural hazards are usually listed among planned adaptation options in mountainous and sloped hilly areas, where uncontrolled runoff and avalanches may cause climatic disasters, affecting millions of people from both urban and rural areas. Landslide control requires increasing plant cover and engineering practices (see Table 6.8).

For management of pollution, including acidification, Anenberg et al. (2012) estimated that, for particulate matter (PM2.5) and ozone, respectively, fully implementing reduction measures could reduce global population-weighted average surface concentrations by 23–34% and 7–17% and avoid 0.6–4.4 and 0.04–0.52 million annual premature deaths globally in 2030. UNEP and WMO (2011) <sup>[[#fn:r422|422]]</sup> considered emission control measures to reduce ozone and black carbon (BC) and estimated that 2.4 million annual premature deaths (with a range of 0.7 million to 4.6 million) from outdoor air pollution could be avoided. West et al. (2013) <sup>[[#fn:r423|423]]</sup> estimated global 6 GHG mitigation brings co-benefits for air quality and would avoid 0.5 ± 0.2, 1.3 ± 0.5, and 2.2 ± 0.8 million premature deaths in 2030, 2050, and 2100, respectively.

There are no global data on the impacts of management of invasive species/encroachment on adaptation.

Coastal wetlands provide a natural defence against coastal flooding and storm surges by dissipating wave energy, reducing erosion, and by helping to stabilise shore sediments, so restoration may provide significant benefits for adaptation. The Ramsar Convention on Wetlands covers 1.5 Mkm2 across 1674 sites (Keddy et al. 2009 <sup>[[#fn:r424|424]]</sup> ). Coastal floods currently affect 93–310 million people (in 2010) globally, and this could rise to 600 million people in 2100 with sea level rise, unless adaptation measures are taken (Hinkel et al. 2014 <sup>[[#fn:r425|425]]</sup> ). The proportion of the flood-prone population that could avoid these impacts through restoration of coastal wetlands has not been quantified, but this sets an upper limit.

Avoided peat impacts and peatland restoration can help to regulate water flow and prevent downstream flooding (Munang et al. 2014 <sup>[[#fn:r426|426]]</sup> ), but the global potential (in terms of number of people who could avoid flooding through peatland restoration) has not been quantified.

There are no global estimates about the potential of biodiversity conservation to improve the adaptation and resilience of local communities to climate change, in terms of reducing the number of people affected by natural disasters. Nevertheless, it is widely recognised that biodiversity, ecosystem health and resilience improves the adaptation potential (Jones et al. 2012 <sup>[[#fn:r427|427]]</sup> ). For example, tree species mixture improves the resistance of stands to natural disturbances, such as drought, fires, and windstorms (Jactel et al. 2017 <sup>[[#fn:r428|428]]</sup> ), as well as stability against landslides (Kobayashi and Mori 2017 <sup>[[#fn:r429|429]]</sup> ). Moreover, protected areas play a key role for improving adaptation (Watson et al. 2014 <sup>[[#fn:r430|430]]</sup> ; Lopoukhine et al. 2012 <sup>[[#fn:r431|431]]</sup> ), through reducing water flow, stabilising rock movements, creating physical barriers to coastal erosion, improving resistance to fires, and buffering storm damages (Dudley et al. 2010 <sup>[[#fn:r432|432]]</sup> ). Of the largest urban areas worldwide, 33 out of 105 rely on protected areas for some, or all, of their drinking water (Secretariat of the Convention on Biological Diversity 2008 <sup>[[#fn:r433|433]]</sup> ), indicating that many millions are likely to benefit from conservation practices.

Table 6.24 summarises the potentials for adaptation for soil-based response options, with confidence estimates based on the thresholds outlined in Table 6.53 in Section 6.3.6, and indicative (not exhaustive) references upon which the evidence in based.

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''Integrated response options based on land management specifically for CDR''

Enhanced weathering of minerals has been proposed as a mechanism for improving soil health and food security (Beerling et al. 2018 <sup>[[#fn:r434|434]]</sup> ), but there is no literature estimating the global adaptation benefits.

Large-scale bioenergy and BECCS can require substantial amounts of cropland (Popp et al. 2017 <sup>[[#fn:r435|435]]</sup> ; Calvin et al. 2014 <sup>[[#fn:r436|436]]</sup> ; Smith et al. 2016a <sup>[[#fn:r437|437]]</sup> ), forestland (Baker et al. 2019 <sup>[[#fn:r438|438]]</sup> ; Favero and Mendelsohn 2017 <sup>[[#fn:r439|439]]</sup> ), and water (Chaturvedi et al. 2013 <sup>[[#fn:r440|440]]</sup> ; Hejazi et al. 2015 <sup>[[#fn:r441|441]]</sup> ; Popp et al. 2011a <sup>[[#fn:r442|442]]</sup> ; Smith et al. 2016a <sup>[[#fn:r443|443]]</sup> ; Fuss et al. 2018 <sup>[[#fn:r444|444]]</sup> ); suggesting that bioenergy and BECCS could have adverse side effects for adaptation. In some contexts – for example, low inputs of fossil fuels and chemicals, limited irrigation, heat/drought tolerant species, and using marginal land – bioenergy can have co-benefits for adaptation (Dasgupta et al. 2014 <sup>[[#fn:r445|445]]</sup> ; Noble et al. 2014 <sup>[[#fn:r446|446]]</sup> ). However, no studies were found that quantify the magnitude of the effect.

Table 6.25 summarises the impacts on adaptation of land management response options specifically for CDR, with confidence estimates based on the thresholds outlined in Table 6.53 in Section 6.3.6, and indicative (not exhaustive) references upon which the evidence in based.

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