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Rossetto, M. Conserving Refugia. Encyclopedia. Available online: https://encyclopedia.pub/entry/8584 (accessed on 28 March 2024).
Rossetto M. Conserving Refugia. Encyclopedia. Available at: https://encyclopedia.pub/entry/8584. Accessed March 28, 2024.
Rossetto, Maurizio. "Conserving Refugia" Encyclopedia, https://encyclopedia.pub/entry/8584 (accessed March 28, 2024).
Rossetto, M. (2021, April 12). Conserving Refugia. In Encyclopedia. https://encyclopedia.pub/entry/8584
Rossetto, Maurizio. "Conserving Refugia." Encyclopedia. Web. 12 April, 2021.
Conserving Refugia
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Refugia play an important role in contributing to the conservation of species and communities by buffering environmental conditions over time. 

biodiversity conservation landscape management

1. Introduction: Refugia as Conservation Priorities

Protected areas provide in situ persistence and survival opportunities in extreme conditions and in times of change [1][2]. Refugia, by definition, play an important and ongoing role in contributing to the survival and conservation of species and communities by buffering environmental conditions through time [3] and across scales, ranging from microrefugia [4] to continental biodiversity hotspots [5]. Here, we focus on the functional aspects of areas protected from, or buffered against, regular disturbance and change, while contributing to the natural dynamics of the regional community assembly processes as well as biodiversity conservation targets and outcomes [3][6][7].

Globally, large intact natural landscapes are declining, and areas of significant diversity and evolutionary value that include refugia are increasingly threatened by extreme events [8]. Subsequently, the establishment of effective biodiversity protection mechanisms is essential to secure long-term conservation outcomes [9]. For refugia to be incorporated as part of global biodiversity protection strategies, it is critical to understand the evolutionary history and ecological processes that they protect and the type, likelihood, and nature of threats to their dynamic stability. To support conservation management, we need to identify what is being protected by refugia, and to characterize them across temporal and spatial scales.

The scale of the Australian fires of 2019–2020 provide an example of the growing challenges associated with protecting and conserving refugia in the face of extreme events, and how appropriate responses can be hampered by a lack of understanding of the role of refugia and why they are important [10]. Our objective here is to provide a set of definitions for refugia that incorporate ecological and evolutionary dynamics into a management decision framework placed within ever-changing temporal and landscape-level scenarios. Previous frameworks for identifying refugia have advocated for the inclusion of functional traits and the phylogenetic structure of community assemblages (e.g., [11]).

2. Management-Oriented Definitions of Refugia

From an evolutionary perspective, large-scale spatial patterns of biodiversity depend on three variables: diversification (origination) rates, extinction rates, and changes in geographic distributions [12]. From an ecological perspective, the traits that shape persistence, dispersal, abundance, competition, and regeneration influence differently each species’ survival and community assembly role in relation to environmental gradients [13]. In order to better represent varying temporal scales and landscape settings, we characterize refugia into three types: persistent, future and temporary (Table 1). While we acknowledge the inevitable chance of overlaps in location (both spatially and temporally), we suggest that framing refugia within the proposed context of dynamic stability is critical to the improvement of conservation management in continuously changing circumstances [3] and in relation to increasing anthropogenic impacts [14].

Table 1. Summarized definitions of the three types of refugia described, i.e., why they are important, how to identify them, and what the relevant key management strategies are. The identification and core criteria provide the basis for the development of management strategies and conservation policy settings.

The criteria used to first identify refugia and then characterize the key (core) values of such areas are listed in Table 1. The identification criteria and core values provide the basis for the development of both management strategies and important conservation policy settings.

2.1. Persistent Refugia

Persistent refugia can be defined as geographical locations of continuous occupation that represent the maximum range contraction of a species or a vegetation community due to habitat filtering [15][16]. At longer biogeographic timescales, persistent refugia can also be established through habitat tracking across vast geographic distances [17], suggesting that they not only retain a diversity of taxa and lineages but they also protect and promote biotic interactions and adaptations to stable environments representative of ancient epochs [18][19][20]. Persistent refugia offer continuity (persistence) in specific environmental conditions on evolutionary time scales [21], and often protect landscape heterogeneity and preserve diverse faunas and floras that can include ancient lineages and threatened species [22]. In turn, the long-term preservation of evolutionary history and evolutionary potential also establishes opportunities for speciation and specialization through lineage expansion onto new areas.

Traditional approaches to identifying persistent refugia are based on current-day species diversity and endemism [23]. In Australian rainforests, macroecological approaches have identified refugia by investigating compositional changes in regional communities [24], while more complex models have explored turnover at compositional, functional and phylogenetic levels [25][26]. The objective of preserving evolutionary heritage in persistent refugia is a global challenge that has inspired comparable approaches across diverse habitats [18][20][27][28][29].

When available, paleo-ecological and fossil evidence can identify and contrast temporal changes of diversity with community persistence at various scales [17][22][30][31][32]. Such evidence, when combined with landscape genetic and phylogeographic studies from one or more species, can recognize signatures of contraction into, and expansion from refugial areas [15][33][34]. Environmental niche models (ENMs) can then be used to investigate how the distribution of suitable habitat for target species changes through time [35], and in combination with phylogeographic datasets provide validated insights on the geographic location of persistent refugia [36][37][38].

Environmentally stable areas are likely to preserve high lineage diversity and phylogenetic endemism [26]. However, this may not necessarily result in high levels of speciation into the future, as persistence and speciation represent very different aspects of the evolutionary process [39]. In persistent refugia, the protection of lineage diversity and abundance is an evolutionary outcome often reflecting trait conservatism, whereas high levels of speciation suggest adaptation and/or re-expansion into new or previously vacant habitats [40]. Consequently, persistent refugia are of high biodiversity conservation value and should be protected through legislative action. In order to maintain their key attributes of assembly dynamics within persistent habitats, these refugia need to be safeguarded from disturbances that disrupt their capacity to occur in the multiple stable states that reflect natural, within-community assembly processes [7]. In that case, within-community shifts in species abundances provide a potential measure of the number of ways an ecological community can be rearranged without changing its state including, by definition, the disturbance levels associated with organism senescence, natural regeneration, and community-level competition [6].

2.2. Future Refugia

Future refugia may be defined as areas that are predicted to be buffered from anthropogenic climate change and other impacts, thus allowing for environmental and habitat stability and species persistence over time [3]. This definition differs from previous ones that refer more specifically to areas providing spatial and temporal protection from human activities and that will remain suitable for specific taxa in the long-term [14]. The future refugia category revolves around the concept of identifying ‘future proofed’ vegetation and targeting areas that comprise assemblages of species suited to future climate projections (naturally congregated in situ or established via assisted migration). Protecting future refugia includes managing reserves that are likely to be less impacted by ongoing disturbance and, when the relevant knowledge is available, developing strategies targeting adaptive potential. At the narrowest scale of the concept, planning can be focused on predictive modelling targeting the protection of one or more threatened species [41].

Climate models can distinguish areas less susceptible to future environmental change, or areas that in the predicted future will become suitable for specific vegetation types or selected species [42]. ENM-based approaches incorporating future climate uncertainty across large numbers of species, can also identify areas of high environmental stability inferred from contemporary species distributions fitting the definition of future refugia [43]. For species with little protected habitat within those future-proofed areas, active transplant of putatively adapted genomes might be considered as an option to increase overall viability of local populations [44]. Securing future refugia also involves aligning with land-use planning projections and buffering selected areas from disturbance by protecting and restoring surrounding vegetation [45].

Overall, managing future refugia requires an improved understanding of the adaptive capacity of species obtained through the integration of environmental, physiological, ecological and genetic information [46]. The inclusion of the dynamics of community assembly processes and the potential for multiple stable states [7] in the context of probabilistic rather than deterministic recovery trajectories [6] present some interesting challenges and opportunities for interpretation and experimentation. The challenges inherent in identifying and providing clear definitions for future refugia emerge from the uncertainties in current models for ongoing climatic changes. Identification of future refugia is dependent on the accuracy of predictions around such changes [43].

2.3. Temporary Refugia

The temporary refugia category represents current habitat refuges that have not been impacted by recent extreme disturbance events surrounding them (e.g., fire, clearing, grazing, logging, cyclones). Temporary refugia can operate over both shorter and longer time scales and have a critical role in facilitating and favoring localized recovery of surrounding affected areas post disturbance [47]. Temporary refugia might also occur within protected areas at localized scales, and at larger scales in specific landscape contexts (Table 1).

Unlike persistent refugia, the location of temporary refugia can either shift in relation to stochastic extreme events, or be related to specific conditions and therefore be more predictable. A useful example is fire refugia represented by mostly unburned landscape elements within a larger fire-affected landscape matrix [48]. Such unburned areas can support postfire ecosystem functions and biodiversity, as well as provide resilience to further disturbances [49]. They can be small patches spared by fire via localized stochastic events within a continuously burned landscape, or specific areas consistently protected from fire by their location, aspect, structure, and constituent species [50]. Scale, in time and space, can also vary. Within longer-term and spatially broader contexts, temporary refugia can include ‘wilderness areas’, important areas that have been shown to endure with much reduced species losses and localized extinctions than ‘non-wilderness’ or managed landscapes [51].

In the current era of increasingly extreme ecosystem disruptions and breakdown, a final and desperate version of temporary refugia includes ex situ refuges such as germplasm collections. These are likely to be less cost effective and more relevant at the species level (with often a focus for threatened or economically important taxa) than at a whole-community level [52].

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