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

=== 2.6.2 Adaptation for Biodiversity Conservation ===

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A variety of approaches have been identified as potential adaptation measures which people can take to reduce the risks of climate change to biodiversity. ( [[#Heller--2009|Heller and Zavaleta, 2009]] ), quoted in AR5, identified 113 categories of recommendation for adaptation from a survey of 112 papers and reports. Since then, the literature has expanded with thousands of relevant publications. Whilst there is increasing interest in adaptation for biodiversity conservation and a wide range of plans and strategies, there is less evidence of these plans being implemented. Since AR5, a number of studies, predominantly from Europe and North America, have investigated the extent to which adaptation has been integrated into conservation planning and is being implemented on a local and regional scale ( [[#Macgregor--2014|Macgregor and van Dijk, 2014]] ; [[#Delach--2019|Delach et al., 2019]] ; [[#Prober--2019|Prober et al., 2019]] ; [[#Clifford--2020|Clifford et al., 2020]] ; [[#Barr--2021|Barr et al., 2021]] ; [[#Duffield--2021|Duffield et al., 2021]] ). A common pattern in these studies is that vulnerability has been assessed and potential adaptation actions identified, but implementation has been limited beyond actions to improve ecological conditions which may increase resilience on a local scale.

To date, most scientific literature on adaptation to reduce the risks to biodiversity from climate change has been based on ecological theory rather than on observations or practical experience. A recent review ( [[#Prober--2019|Prober et al., 2019]] ) concluded that out of 473 papers on adaptation, only 16% presented new empirical evidence and very few assessed the effectiveness of actual adaptation actions. It is also the case that relatively little research is focused on local-scale management interventions rather than on larger-scale strategies ( [[#Ledee--2021|Ledee et al., 2021]] ), although there are some exceptions ( [[#Duffield--2021|Duffield et al., 2021]] ).

Although direct assessments of the effectiveness of adaptation actions are rare, since AR5, there have been an increasing number of empirical analyses of how different land use and management can influence the vulnerability of species and habitats. As climate change often interacts with other factors including ecosystem degradation and fragmentation ( [[#Oliver--2015a|Oliver et al., 2015a]] ), actions to address these other interacting factors is expected to build resilience to climate change. Table 2.6 summarises evidence that supports the main categories of proposed adaptation measures. We have taken an inclusive approach and included studies that address extreme weather events such as droughts, which may be exacerbated by climate change, as well as long-term changes in climate variables. We have not distinguished between studies in which climate change adaptation was an explicit focus and those in which lessons for adaptation can be learnt, that is, when studies were conducted for other reasons but inform the assessment of the impacts of actions identified as potential adaptation measures.

'''Table 2.6 |''' Evidence to support proposed climate change adaptation measures for biodiversity. The evidence highlights that adaptation for biodiversity conservation is a broad concept, encompassing a wide range of actions. It includes targeted interventions to change the microclimate for particular species (e.g., by creating shade) to changing national conservation objectives to take account of changing distributions of species and communities. It includes targeted actions addressing both climate change and the protection and restoration of ecosystems, with multiple additional benefits including reduced vulnerability to climate change. Most of the studies are not direct tests of the impacts of adaptation actions which, as noted above, is an important gap in the evidence. There is also a major limitation in that reported studies are predominantly from Europe, North America and Australasia, with little research in other regions.

{| class="wikitable"
|-
! '''Proposed adaptation measures for biodiversity'''

! '''Uncertainty Assessment'''

! '''Comment'''

! '''Selected references'''

|-
| ''Protect large areas of natural and semi-natural habitat''

| ''robust evidence,''

''high agreement''

| There is considerable evidence that: intact systems provide better quality and quantity of ecosystem services; larger intact areas provide better ecosystem services; the risk of species’ extinctions from disturbances including climate change, is reduced by having large, connected populations; more biodiverse systems provide higher levels of ecosystem services and are more resilient to climate change than degraded systems that have lost species

| ( [[#Pimm--2018|Pimm et al., 2018]] ; [[#Dinerstein--2019|Dinerstein et al., 2019]] ; [[#Woodley--2019|Woodley et al., 2019]] ; [[#Brooks--2020|Brooks et al., 2020]] ; [[#Hannah--2020|Hannah et al., 2020]] ; [[#Luther--2020|Luther et al., 2020]] ; [[#Zhao--2020|Zhao et al., 2020]] ; [[#Sala--2021|Sala et al., 2021]] );

|-
| ''Increase connectivity in terrestrial habitats: corridors, stepping stones''

| ''medium evidence,''

''medium agreement''

| There is good evidence that some species move more quickly in more connected landscapes. However, not all species do and some of those that benefit are invasive/pest/disease species; to date, empirical evidence showing that connectivity has reduced climate change impacts on species is limited.

| ( [[#Keeley--2018|Keeley et al., 2018]] ; [[#Stralberg--2019|Stralberg et al., 2019]] ; [[#von%20Holle--2020|von Holle et al., 2020]] )

|-
| ''Increase connectivity in river networks''

| ''limited evidence,''

''high agreement''

| Connectivity is needed to maintain the movement of species and populations, but river reaches and catchments lack integrated protection

| ( [[#Hermoso--2016|Hermoso et al., 2016]] ; [[#Thieme--2016|Thieme et al., 2016]] ; [[#Abell--2017|Abell et al., 2017]] ; [[#Brooks--2018|Brooks et al., 2018]] )

|-
| ''Increase habitat patch size and expand protected areas''

| ''limited evidence,''

''high agreement''

| Generally increases resilience because of functioning natural processes, large species populations and refugial areas

| ( [[#Eigenbrod--2015|Eigenbrod et al., 2015]] ; [[#Oliver--2015a|Oliver et al., 2015a]] )

|-
| ''Increase replication and representation of protected areas''

| ''limited evidence,''

''high agreement''

| Various benefits inferred, including a wider range of climatic and other conditions and less risk of extreme events affecting many rather than few areas. More sites available for colonisation by range-expanding species and better conditions to maintain species ''in situ'' under range contraction.

| ( [[#Mawdsley--2009|Mawdsley et al., 2009]] ; [[#Thomas--2012|Thomas et al., 2012]] ; [[#Virkkala--2014|Virkkala et al., 2014]] ; [[#Gillingham--2015|Gillingham et al., 2015]] ; [[#Pavón-Jordán--2020|Pavón-Jordán et al., 2020]] )

|-
| ''Protect microclimatic refugia''

| ''medium evidence,''

''high agreement''

| Locally cool areas can be identified and there is evidence that species can survive better in such areas

| ( [[#Haslem--2015|Haslem et al., 2015]] ; [[#Suggitt--2015|Suggitt et al., 2015]] ; [[#Isaak--2016|Isaak et al., 2016]] ; [[#Morelli--2016|Morelli et al., 2016]] ; [[#Merriam--2017|Merriam et al., 2017]] ; [[#Bramer--2018|Bramer et al., 2018]] ; [[#Suggitt--2018|Suggitt et al., 2018]] ; [[#Massimino--2020|Massimino et al., 2020]] )

|-
| ''Creating shade to lower temperatures for vulnerable species''

| ''limited evidence,''

''high agreement''

| Creating shade (e.g., of watercourses) has been used as an adaptation strategy, but improvements in species survival under warming conditions have yet to be demonstrated

| ( [[#Broadmeadow--2011|Broadmeadow et al., 2011]] ; [[#Lagarde--2012|Lagarde et al., 2012]] ; [[#Patino-Martinez--2012|Patino-Martinez et al., 2012]] ; [[#Thomas--2016|Thomas et al., 2016]] )

|-
| ''Restoring hydrological processes of wetlands, rivers and catchments, including by raising water tables and restoring original channels of watercourses''

| ''medium evidence,''

''high agreement''

| Wetland restoration is well established as a conservation measure in some countries. It can reduce vulnerability to drought with climate change, but evidence to demonstrate effectiveness as an adaptation measure is limited and requires the long-term monitoring of a range of sites. There is little restoration of degraded tropical peatlands to date

| ( [[#Carroll--2011|Carroll et al., 2011]] ; [[#Hossack--2013|Hossack et al., 2013]] ; [[#Dokulil--2016|Dokulil, 2016]] ; [[#Timpane-Padgham--2017|Timpane-Padgham et al., 2017]] ; [[#Moomaw--2018|Moomaw et al., 2018]] )

|-
| ''Restoration of natural vegetation dynamics''

| ''medium evidence,''

''medium agreement''

| Includes reintroduction of native herbivores and reversing woody encroachment of savannas. Benefits for biodiversity are well established in a wide range of different regions

| ( [[#Coffman--2014|Coffman et al., 2014]] ; [[#Valkó--2014|Valkó et al., 2014]] ; [[#Batáry--2015|Batáry et al., 2015]] ; [[#Smit--2016|Smit et al., 2016]] ; [[#Stevens--2016|Stevens et al., 2016]] ; [[#Hempson--2017|Hempson et al., 2017]] ; [[#Bakker--2018|Bakker and Svenning, 2018]] ; [[#Cromsigt--2018|Cromsigt et al., 2018]] ; [[#Fulbright--2018|Fulbright et al., 2018]] ; [[#Olofsson--2018|Olofsson and Post, 2018]] )

|-
| ''Reduce non-climatic stressors to increase resilience of ecosystems''

| ''limited evidence,''

''medium agreement''

| As a general principle, climate change is recognised as a ‘threat multiplier’ but specific details are often unclear

| ( [[#Oliver--2017|Oliver et al., 2017]] ; [[#Pearce-Higgins--2019|Pearce-Higgins et al., 2019]] )

|-
| ''Assisted translocation and migration of species''

| ''limited evidence,''

''medium agreement''

| Assisted translocation has been commonly suggested as an adaptation measure, but there have been very few examples of this being trialled. Translocations have been carried out for other reasons and lessons for climate change adaptation have been inferred.

| ( [[#Willis--2009|Willis et al., 2009]] ; [[#Brooker--2018|Brooker et al., 2018]] ; [[#Skikne--2020|Skikne et al., 2020]] )

|-
| ''Intensive management for specific species''

| ''medium evidence,''

''medium agreement''

| A variety of approaches including manipulating microclimate and competition between species to improve chances of survival under climate change

| ( [[#Angerbjörn--2013|Angerbjörn et al., 2013]] ; [[#Greenwood--2016|Greenwood et al., 2016]] ; [[#Pearce-Higgins--2019|Pearce-Higgins et al., 2019]] )

|-
| ''Ex situ conservation (seedbanks/genetic stores, etc.)''

| Not possible to assess at present

| Seed banks have been established but their long-term effectiveness can only be evaluated at a later point

| ( [[#Christmas--2016|Christmas et al., 2016]] )

|-
| ''Adjusting conservation strategies and site objectives to reflect changing species’ distributions and habitat characteristics''

| ''robust evidence,''

''high Agreement''

| Conservation management will need to take account of changes that cannot be prevented (e.g., the distribution of species and composition of communities) to protect and manage biodiversity as effectively as possible in a changing climate

| ( [[#Stein--2013|Stein et al., 2013]] ; [[#Rannow--2014|Rannow et al., 2014]] ; [[#Oliver--2016|Oliver et al., 2016]] ; [[#Stralberg--2019|Stralberg et al., 2019]] ; [[#Duffield--2021|Duffield et al., 2021]] )

|-
| ''Softening the matrix of unsuitable habitats between patches to increase permeability for the movement of species in response to climate change''

| ''limited evidence''

| There is potential for agri-environment schemes to do this in hostile farmed landscapes

| ( [[#Donald--2006|Donald and Evans, 2006]] ; [[#Stouffer--2011|Stouffer et al., 2011]] )

|}

Many climate adaptation actions for biodiversity operate on the landscape scale ( [[#von%20Holle--2020|von Holle et al., 2020]] ). The total area of habitat, how fragmented it is, the size of habitat patches and the connectivity between them are inter-linked properties on this scale. A growing number of studies have investigated how these properties affect species ability to persist ''in situ'' and colonise new areas. Overall, larger areas of semi-natural habitat are associated with increased resilience to ongoing climate change and extreme events as well as the capacity to colonise new areas ( [[#Haslem--2015|Haslem et al., 2015]] ; [[#Oliver--2017|Oliver et al., 2017]] ; [[#Papanikolaou--2017|Papanikolaou et al., 2017]] ). Larger habitat patches can support larger populations of a given species, which are more likely to maintain themselves and recover from periods of adverse conditions. Inhabiting a large patch size has been found to increase the resilience of some populations of species to extreme events such as droughts ( [[#Oliver--2015b|Oliver et al., 2015b]] ). They are also more likely to provide a range of different resources and microclimate conditions, which may increase the chances of the persistence of species under climate change. A larger area of habitat may also enable greater connectivity between patches and increase the chances of species colonising new areas as they track climate change ( [[#Oliver--2015b|Oliver et al., 2015b]] ).

Protecting and restoring natural processes is a general principle for maintaining and building resilience to climate change for biodiversity ( [[#Timpane-Padgham--2017|Timpane-Padgham et al., 2017]] ). One element of this is ensuring naturally functioning hydrology for wetlands and river systems (Table 2.6), which is particularly important in a context of changing rainfall patterns and increased evapotranspiration. An important development in approaches to conservation over recent decades has been the concept of re-wilding ( [[#Schulte%20To%20Bühne--2021|Schulte To Bühne et al., 2021]] ); this encompasses a number of elements of restoring natural processes, including the reintroduction of top predators, larger conservation areas, and less prescriptive outcomes than many previous conservation measures. There are elements of re-wilding which may well contribute to building resilience to climate change, but it will be increasingly important to factor climate change adaptation into the planning of re-wilding schemes ( [[#Carroll--2021|Carroll and Noss, 2021]] ).

The most consistently cited climate change adaptation measure for species is increasing connectivity to facilitate the colonisation of new areas. This reflects the fact that many species’ habitats are highly fragmented in areas with more intensive land management, which prevents them naturally changing their range to track changing climatic conditions. Advances and innovations in modelling techniques can support decision-making about connectivity ( [[#Littlefield--2019|Littlefield et al., 2019]] ). There is evidence from empirical and modelling studies that species can disperse more effectively in better-connected areas in terrestrial habitats ( [[#Keeley--2018|Keeley et al., 2018]] ). The issues are different in more natural landscapes—species may still be threatened in intrinsically isolated habitats, such as mountain tops, but connectivity cannot be created here in the same way. Evidence suggests that increased connectivity will only benefit a subset of species, probably those which are intermediate-habitat specialists that are able to disperse ( [[#Pearce-Higgins--2014|Pearce-Higgins and Green, 2014]] ). Generalists do not require corridors or stepping stones, while many corridors or stepping stones will not be of sufficient quality to be used by most habitat specialists. There should also be a caveat to the general principle that increasing connectivity is a benefit for climate change adaptation. It can increase the spread of invasive, pest and disease-causing species into newly suitable regions. In some places, isolated refugia may better allow vulnerable species and biological communities to survive.

There are many different approaches to increasing connectivity, ranging from increasing the overall area of suitable habitat to ‘corridors’ and ‘stepping stones’, with different strategies likely to be more effective for different species and circumstances ( [[#Keeley--2018|Keeley et al., 2018]] ). Connectivity can also be important in increasing the resilience of populations to extreme climatic events ( [[#Newson--2014|Newson et al., 2014]] ; [[#Oliver--2015b|Oliver et al., 2015b]] ). Within freshwater environments, the connectivity of watercourses is essential. Fluvial corridors are necessary to ensure the survival of migrating fish populations, even without climate change; with climate change, connectivity becomes crucial for relatively cold-adapted organisms to migrate upstream to colder areas. Connectivity is also important for the larvae of benthic invertebrates to be able to drift downstream and hence to disperse ( [[#Brooks--2018|Brooks et al., 2018]] ); for adult benthic invertebrates, riparian and terrestrial habitat features can potentially affect dispersal. Connectivity within river and wetland systems for some species can also mediated by more mobile animal species such as fish and birds ( [[#Martín-Vélez--2020|Martín-Vélez et al., 2020]] ). Which factors are the most important in either promoting their colonisation of new sites or persisting ''in situ'' will differ between species and locations. Some general principles have been recognised and can guide conservation policy and practice ( [[#Natural%20England%20and%20RSPB--2020|Natural England and RSPB, 2020]] ; [[#Stralberg--2020|Stralberg et al., 2020]] ), but this will often require additional investigation and planning based on an individual understanding of the niches of specific species.

Managed translocation, that is, moving species from areas where the climate is becoming unsuitable to places where their persistence under climate change is more likely , has been discussed as an adaptation option for many years. So far, there have been very few examples of this and it is likely to be a last resort in most cases, as it usually requires a large investment of resources, outcomes are uncertain and there may be adverse impacts on the receiving sites. Nevertheless, there are cases where it may be a be a viable option ( [[#Stralberg--2019|Stralberg et al., 2019]] ). This is discussed in more detail as a case study in [[#2.6.5.1|Section 2.6.5.1]] .

The evidence that species can persist in microclimatic refugia where suitable conditions for them are maintained locally (e.g., because of variations in topography) has increased in recent years. This has opened up the potential to include refugia in conservation plans and strategies to facilitate the local survival of species ( [[#Jones--2016|Jones et al., 2016]] ; [[#Morelli--2016|Morelli et al., 2016]] ; [[#Morelli--2020|Morelli et al., 2020]] ), for example, targeting management actions ( [[#Sweet--2019|Sweet et al., 2019]] ) aimed at supporting populations of species. This is likely to become an important aspect of climate change adaptation for biodiversity conservation in future. It is also possible to manipulate microclimate, for example, by creating shelters for birds’ nests; see Case Study in 2.6.5.5 of African penguins; ( [[#Patino-Martinez--2012|Patino-Martinez et al., 2012]] ). One specific approach of this sort is the planting or retention of trees and wooded corridors to shade watercourses ( [[#Thomas--2016|Thomas et al., 2016]] ). Riparian shading can also possibly help to reduce phytoplankton and benthic diatom growth in smaller streams and rivers ( [[#Halliday--2016|Halliday et al., 2016]] ).

Refugia often refer to locally cool places in a landscape, such as shaded slopes or high elevations, but they can also include places where the supply of water may continue during dry periods ( [[#Morelli--2016|Morelli et al., 2016]] ). Monitoring can reveal which streams, wetlands, springs and other aquatic resources retain suitable discharges, water quality, wetland area and ecological integrity, especially during dry years ( [[#Cartwright--2020|Cartwright et al., 2020]] ). Measures to conserve drought refugia may include protecting springs and other groundwater-fed systems from groundwater extraction, contamination, salinisation, surface-water diversion, channelisation of streams, trampling by livestock, recreation activities and invasive species and the effects of disturbances in the surrounding landscape ( [[#Cartwright--2020|Cartwright et al., 2020]] ; [[#Krawchuk--2020|Krawchuk et al., 2020]] ). Restoration of degraded aquatic ecosystems can include removing flow-diversion infrastructure, excluding livestock, reducing other human impacts, geomorphic restructuring, removing invasive species and planting native riparian vegetation.

In fire-prone areas, fire suppression and management are a key element of protecting refugia ( [[#2.6.5.8|Section 2.6.5.8]] below). In ecosystems in which a natural fire regime has been suppressed, restoration practices such as prescribed fires, thinning trees and allowing some wildfire where it benefits the ecosystem can be introduced to reduce increasing risks from severe wildfires ( [[#Meigs--2020|Meigs et al., 2020]] ).

Protected areas—areas of land set aside for species and habitat protection with legal protection from development or exploitation—have been a cornerstone of nature conservation for many years. Their effectiveness under a changing climate has been the subject of debate and investigation. There is now a large body of evidence demonstrating that colonisations by range-shifting species are more likely to occur at protected sites than at non-protected sites for a wide range of taxa (e.g., [[#Thomas--2012|Thomas et al., 2012]] ; [[#Gillingham--2015|Gillingham et al., 2015]] ) including across continents ( [[#Pavón-Jordán--2020|Pavón-Jordán et al., 2020]] ). This is probably because, by protecting large areas of natural and semi-natural habitats, they provide suitable places for colonising species ( [[#Hiley--2013|Hiley et al., 2013]] ) which may not be available in the surrounding landscape. Although the evidence for protected areas being associated with reduced extinctions is weaker, the finding by Gillingham et al. ( [[#Gillingham--2015|Gillingham et al., 2015]] ) that protected sites were associated with reduced extinction rates at low latitudes and elevations is strongly suggestive that they can help species’ persistence in the face of climate change.

It is intrinsically difficult to assess the effectiveness of climate change adaptation measures, the benefit of which will be realised in the years and decades ahead ( [[#Morecroft--2019|Morecroft et al., 2019]] ). Nevertheless, taking into account the wide range of evidence reported above, including the theory, modelling and observations of the impacts of climate change in contrasting circumstances, it is possible to make an overarching assessment that appropriate adaptation measures can reduce the vulnerability of many aspects of biodiversity to climate change ( ''robust evidence'' , ''high agreement'' ). It is also clear, however, that to be most effective and avoid unintended consequences, measures need to be carefully implemented by taking into account specific local circumstances ''(robust evidence, high agreement)'' and include the management of inevitable changes ( ''robust evidence, high agreement'' ). It is also clear that while there are now many plans and strategies for adapting biodiversity conservation to climate change, many have yet to be implemented fully ( ''medium evidence, high agreement'' ).

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