Editing IPCC:AR6/WGII/Chapter-2 (section)

=== 2.6.8 Feasibility of Adaptation Options ===

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The [[#IPCC--2018a|IPCC (2018a)]] defined feasibility as ‘the degree to which climate goals and response options are considered possible and/or desirable’ ( [[#IPCC--2018b|IPCC, 2018b]] ) and set out an approach to assessing the feasibility of pathways to limit the global temperature rise to 1.5°C. [[#Singh--2020|Singh et al. (2020)]] developed this approach for adaptation, recognising six different dimensions of feasibility: economic, technological, institutional, socio-cultural, environmental/ecological and geophysical (Table 2.9). Feasibility is considered more fully in other chapters of this report, including Cross-Chapter Box FEASIB in Chapter 18. Adaptation for biodiversity conservation and EbA encompasses a large range of approaches and techniques (Sections 2.6.2, 2.6.3) and will vary in different contexts globally, as illustrated by the range of case studies ( [[#2.6.5|Section 2.6.5]] ). It is important to take into account specific regional and local circumstances as well as the type of adaptation action envisaged before making a feasibility assessment. It is also important to note that what is a feasible adaptation response at one point in time may change with the level of warming experienced—some techniques will be become less effective at higher levels of warming. With global temperature rises of &lt;2°C, in many cases, it will be realistic to build resilience and maintain species and ecosystems ''in situ'' , but, at higher levels of warming, this will become increasingly difficult; managing inevitable change, including the consequences of loss and damage, will be important ( [[#Prober--2019|Prober et al., 2019]] ). Similarly, to be effective at higher levels of warming may require the adaptation of the EbA approaches themselves ( [[#Calliari--2019|Calliari et al., 2019]] ; [[#Martín--2021|Martín et al., 2021]] ; [[#Ossola--2021|Ossola and Lin, 2021]] ). We have therefore not attempted a global-scale assessment of the feasibility of adaptation options, but rather present some key cross-cutting considerations in assessing feasibility for adaptation of and through ecosystems.

Many of the necessary techniques for climate change adaptation for biodiversity and EbA have been demonstrated and shown to provide a wide range of additional benefits. This does, however, depend on deploying the right techniques in the right place (Box 2.2) as well as engaging local communities (see [[#2.6.6|Section 2.6.6]] ). There is also a challenge where there is high demand for land for other purposes, especially for agriculture and urban development. Table 2.8 summarises the main feasibility considerations, drawing on previous sections. An assessment of constraints on EbA by Nalau et al. (2018) addressed similar issues.

'''Table 2.8 |''' Considerations in assessing the feasibility of ecosystem restoration for climate change adaptation, according to [[#Singh--2020|Singh et al. (2020)]]

{| class="wikitable"
|-
! '''Feasibility''' '''characteristics'''

! '''Feasibility indicators'''

! '''Factors relevant to ecosystem restoration'''

|-
| rowspan="4"| ''Economic''

| Micro-economic viability

| rowspan="4"| Costs are highly variable, depending on techniques and whether land purchase is required. Costs will depend on local rates for labour and materials.

Economic benefits to local communities where employment is created and where loss from extreme events are avoided ( [[#2.6.4|Section 2.6.4]] ; [[#De%20Groot--2013|De Groot et al., 2013]] ).

|-
| Macro-economic viability

|-
| Socioeconomic vulnerability reduction potential

|-
| Employment and productivity enhancement potential

|-
| rowspan="2"| ''Technological''

| Technical resource availability

| rowspan="2"| Techniques are available for restoration of most ecosystems (Sections 2.6.2; 2.6.3), although this can be very difficult to achieve in some circumstances and take a long time, e.g., the restoration of peat swamp forests ( [[#2.6.5.10|Section 2.6.5.10]] ).

Successful implementation may also require skills which are in short supply and training may be required.

|-
| Risks mitigation potential (stranded assets, unforeseen impacts)

|-
| rowspan="4"| ''Institutional''

| Political acceptability

| rowspan="4"| This will vary according to local factors. It should, however, be noted that EbA and adaptation for conservation have been implemented in a wide range of different countries (see the case studies in [[#2.6.5|Section 2.6.5]] ). In many cases, the EbA can meet multiple policy objectives but falls between different decision-makers’ responsibilities.

|-
| Legal, regulatory feasibility

|-
| Institutional capacity and administrative feasibility

|-
| Transparency and accountability potential

|-
| rowspan="5"| ''Socio-cultural''

| Social co-benefits (health, education)

| rowspan="5"| Multiple benefits to local communities are possible, but full engagement and/or leadership of the affected members of these communities has been shown to be critical. IKLK can provide important insights ( [[#2.6.6|Section 2.6.6]] ).

|-
| Socio-cultural acceptability

|-
| Social and regional inclusiveness

|-
| Benefits for gender equity

|-
| Inter-generational equity

|-
| rowspan="2"| ''Environmental/ecological''

| Ecological capacity

| rowspan="2"| It is important to assess the benefits for ecosystems in relation to other potential options. In particular, for some EbA approaches, it may be possible to achieve a range of different outcomes for biodiversity.

|-
| Adaptive capacity/potential

|-
| rowspan="3"| ''Geophysical''

| Physical feasibility

| rowspan="3"| Appropriate measures need to be designed to take account of local geophysical conditions, e.g., catchment characteristics, which define where some habitats can occur. This is also critical for ensuring the effectiveness of EbA in reducing natural hazards.

|-
| LUC enhancement potential

|-
| Hazard risk reduction potential

|}

A key element of economic feasibility is the cost of adaptation options. Costs of adaptation vary greatly depending on the actions taken, the location, the methods used, the need for ongoing maintenance and whether land purchase is necessary. At its simplest, adaptation may be a matter of taking account of actual or potential climate change impacts in the course of conservation planning and have little or no additional cost. For example, if a species of conservation concern colonises or starts to use a new area as a result of climate change, like migrant waterfowl shifting the locations where they overwinter ( [[#Pavón-Jordán--2020|Pavón-Jordán et al., 2020]] ), protection or habitat management may be redirected there. At the other extreme, large-scale restoration can incur significant costs, for example, between 1993 and 2015, the EU-LIFE nature programme invested 167.6 million Euro in 80 projects, which aim to restore over 913 km 2 of peatland habitats in Western European countries ( [[#Andersen--2017|Andersen et al., 2017]] ). This is equivalent to &lt;2% of the remaining peatland area, much of which has been affected to at least some extent by human pressures, and restoring the total affected area will cost considerably more.

[[#De%20Groot--2013|De Groot et al. (2013)]] analysed 94 restoration projects globally and found costs varied by several orders of magnitude, but in terrestrial and freshwater ecosystems mostly in the range of USD 100–10,000 per hectare. They did, however, estimate that the majority of these projects provided net benefits and should be considered as high-yield investments. Some methods can be much cheaper than others, even in the same type of ecosystems in the same country; the estimated cost of restoring forest cover in Brazil varied between a mean of USD 49 using natural regeneration compared to a mean of USD 2041 per hectare using planting ( [[#Brancalion--2019|Brancalion et al., 2019]] ). When assessing costs, it is also important to take into account the benefits delivered by different options, both in economic terms and regarding other wider benefits.

The ‘technological’ dimension of feasibility in the context of ecosystems can be regarded as the range of techniques available and the capacity to implement them. As described in Sections 2.6.2 and 2.6.3 above, a wide range of techniques have been developed and are starting to be implemented. There is good evidence to support adaptation for biodiversity and EbA in general terms and, in many cases, adaptation draws on techniques for habitat creation and restoration which have been developed to meet other objectives. However, feasibility needs to be assessed alongside the likely effectiveness: a feasible but ineffective scheme is of no value and the evaluation of success for specific interventions remains poorly developed ( [[#Morecroft--2019|Morecroft et al., 2019]] ). It is therefore often important to proceed with the use of pilot studies, good monitoring and the evaluation of outcomes to build confidence before greater deployment of approaches. A linked technical area is the availability of specialist skills and knowledge to implement adaptation; this can vary considerably according to the type of adaptation measure.

Institutional dimensions are dealt with more fully in other chapters, but in the specific context of the natural environment it is notable that EbA is relevant to a wide range of organisations and policy objectives, in addition to environmental departments, NGOs and agencies which traditionally deliver conservation. Upscaling implementation is likely to be dependent on this wider range of interests. There can, however, be problems, in that appropriate geographies for decision-making about ecosystems (e.g., a catchment) may not directly map onto governance arrangements.

Socio-cultural factors are important for adaptation of the natural environment. Reviewing the constraints of EbA, Nalau et al. (2018) found that risk perceptions and cultural preferences for particular types of management approaches were frequently identified in studies.

In the IPCC feasibility assessment framework, one integral dimension is ‘environmental/ecological’. In this respect, adaptation by and for ecosystems should perform well, and this may be a reason to prefer EbA to other approaches when there is an alternative. It should, however, be noted that sometimes apparently environmentally positive approaches such as forest creation can be done in ways which are damaging ( [[#2.6.7|Section 2.6.7]] and Box 2.2) and the impacts need to be critically assessed for local circumstances.

Geophysical dimensions are important for ecosystems as they have typically shaped which ecosystems can occur where, and feasibility will depend on implementing adaptation options in places where they are appropriate. Palaeo-ecological studies can help inform potential options ( [[#Wingard--2017|Wingard et al., 2017]] )

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'''Box 2.2 | Risks of Maladaptive Mitigation'''
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To hold global temperature rise to well below 2°C and pursue efforts to limit it to 1.5°C as required by the Paris Agreement requires major changes in land use and management. There are many opportunities for NbS, which can provide climate change mitigation and adaptation in ways that protect and restore biodiversity and provide a wide range of benefits to people (Cross-Chapter Box NATURAL in this chapter). There are also new technologies and approaches to develop the bioeconomy in ways which will provide many benefits (Cross-Working Group Box BIOECONOMY in Chapter 5). Nevertheless, renewable energy is a large and essential element of climate change mitigation and there are adverse impacts on biodiversity associated with some types of renewable energy, including wind and solar technologies ( [[#Rehbein--2020|Rehbein et al., 2020]] ). However, one of the most serious conflicts emerging is that between land-based approaches to mitigation and the protection of biodiversity, particularly as a result of afforestation strategies and potentially large areas devoted to bioenergy, including bioenergy with carbon capture and storage (BECCS). It is important to recognise the impacts of climate change mitigation at the same time as assessing the direct impacts of climate change, and ensure that adaptation and mitigation are joined up.

BECCS is an integral part of all widely accepted pathways to keeping global temperature rise to 1.5°C ( [[#IPCC--2018b|IPCC, 2018b]] ). This requires large areas of land, which can be in conflict with the need to produce food and protect biodiversity ( [[#Smith--2018|Smith et al., 2018]] ). One study examined the combined impacts of climate change and LULCC for bioenergy, and found that severe impacts on species were likely if bioenergy was a major component of strategies for climate change mitigation ( [[#Hof--2018|Hof et al., 2018]] ). A study on the potential impacts of bioenergy production and climate change on European birds found that one scenario for land conversion for bioenergy to meet a 2°C target would have less impact on species range loss than a global temperature increase of 4°C, but noted that if bioenergy were the only mitigation option it would 'very likely result in the negative effects of bioenergy outweighing the positive effects' ( [[#Meller--2015|Meller et al., 2015]] ). To avoid the worst impacts of BECCS, it will need to be carefully targeted according to context and local conditions, and other mitigation strategies prioritised so that its use can be minimised ( [[#IPCC--2019a|IPCC, 2019a]] ; [[#Ohashi--2019|Ohashi et al., 2019]] ).

Reforestation of previously forested areas can bring multiple benefits, but planting trees in places where they do not naturally grow can have serious environmental impacts, including potentially exacerbating the effects of climate change. Savannas are amongst the ecosystems at risk from afforestation programmes. Savannas are grass-dominated, high-diversity ecosystems with endemic species adapted to high-light environments, herbivory and fire ( [[#Staver--2011|Staver et al., 2011]] ; [[#Murphy--2016|Murphy et al., 2016]] ). Interactions between climate change, elevated CO 2 and the disruption of natural disturbance regimes have led to the widespread encroachment of woody plants ( [[#Stevens--2016|Stevens et al., 2016]] ), causing a fundamental shift in ecosystem structure and function with loss of grass and reduced fire frequency ( [[#Archibald--2009|Archibald et al., 2009]] ) and stream flow ( [[#Honda--2016|Honda and Durigan, 2016]] ) (Sections 2.4.3.5, 2.5.2.5, Box 2.1, 2.5.4, TAble 2.5, Figure 2.11). Afforestation exacerbates this degradation ( [[#Bremer--2010|Bremer and Farley, 2010]] ; [[#Veldman--2015|Veldman et al., 2015]] ; [[#Abreu--2017|Abreu et al., 2017]] ). Global-scale analyses aimed at identifying degraded forest areas suitable for reforestation ( [[#Veldman--2019|Veldman et al., 2019]] ) cannot reliably separate naturally grassy ecosystems with sparse tree cover from degraded forests, so local information is essential to ensure tree planting is targeted where it can benefit most and avoid harm. Figure Box 2.2.1 indicates where these issues are most likely to arise.

[[File:aacd2bdfbf1968820cea7b7d587c76f6 IPCC_AR6_WGII_Figure_2_Box_2_2_1.png]]

'''Figure Box 2.2.1 |''' '''Regions where savannas are at potential risk from afforestation.''' Based on ( [[#Veldman--2015|Veldman et al., 2015]] )

A similar issue can occur in naturally treeless peatlands which can be afforested if they are drained, but this leads to the loss of distinctive peatland species and communities as well as high GHG emissions ( [[#Wilson--2014|Wilson et al., 2014]] ). The mitigation benefits of growing timber are reduced or become negative in these conditions due to the CO 2 emissions from the oxidation of the drained peat—they can become a net carbon source rather than a carbon sink ( [[#Simola--2012|Simola et al., 2012]] ; [[#Crump--2017|Crump, 2017]] ; [[#Goldstein--2020|Goldstein et al., 2020]] ) ''.'' (Sections 2.4.3.8, 2.5.2.8)

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