The challenge of novel abiotic conditions for species undergoing climate-induced range shifts

Coincident with recent global warming, species have shifted their geographic distributions to cooler environments, generally by moving along thermal axes to higher latitudes, higher elevations or deeper waters. While these shifts allow organisms to track their thermal niche, these three thermal axes also covary with non-climatic abiotic factors that could pose challenges to range-shifting plants and animals. Such novel abiotic conditions also present an unappreciated pitfall for researchers – from both empirical and predictive viewpoints – who study the redistribution of species under global climate change. Climate, particularly temperature, is often assumed to be the primary abiotic factor in limiting species distributions, and decades of thermal biology research have made the correlative and mechanistic understanding of temperature the most accessible and commonly used response to any abiotic factor. Receiving far less attention, however, is that global gradients in oxygen, light, pressure, pH and water availability also covary with latitude, elevation, and/or ocean depth, and species show strong physiological and behavioral adaptations to these abiotic variables within their historic ranges. Here, we discuss how non-climatic abiotic factors may disrupt climate-driven range shifts, as well as the variety of adaptations species use to overcome abiotic conditions, emphasizing which taxa may be most limited in this capacity. We highlight the need for scientists to extend their research to incorporate non-climatic, abiotic factors to create a more ecologically relevant understanding of how plants and animals interact with the environment, particularly in the face of global climate change. We demonstrate how additional abiotic gradients can be integrated into global climate change biology to better inform expectations and provide recommendations for addressing the challenge of predicting future species distributions in novel environments.     

Protected areas not likely to serve as steppingstones for species undergoing climate-induced range shifts

Species across the planet are shifting their ranges to track suitable climate conditions in response to climate change. Given that protected areas have higher quality habitat and often harbor higher levels of biodiversity compared to unprotected lands, it is often assumed that protected areas can serve as steppingstones for species undergoing climate-induced range shifts. However, there are several factors that may impede successful range shifts among protected areas, including the distance that must be traveled, unfavorable human land uses and climate conditions along potential movement routes, and lack of analogous climates. Through a species-agnostic lens, we evaluate these factors across the global terrestrial protected area network as measures of climate connectivity, which is defined as the ability of a landscape to facilitate or impede climate-induced movement. We found that over half of protected land area and two-thirds of the number of protected units across the globe are at risk of climate connectivity failure, casting doubt on whether many species can successfully undergo climate-induced range shifts among protected areas. Consequently, protected areas are unlikely to serve as steppingstones for a large number of species under a warming climate. As species disappear from protected areas without commensurate immigration of species suited to the emerging climate (due to climate connectivity failure), many protected areas may be left with a depauperate suite of species under climate change. Our findings are highly relevant given recent pledges to conserve 30% of the planet by 2030 (30 × 30), underscore the need for innovative land management strategies that allow for species range shifts, and suggest that assisted colonization may be necessary to promote species that are adapted to the emerging climate.     

Predicting range shifts of Davidia involucrata Ball. under future climate change

Understanding and predicting how species will respond to climate change is crucial for biodiversity conservation. Here, we assessed future climate change impacts on the distribution of a rare and endangered plant species, Davidia involucrate in China, using the most recent global circulation models developed in the sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC6). We assessed the potential range shifts in this species by using an ensemble of species distribution models (SDMs). The ensemble SDMs exhibited high predictive ability and suggested that the temperature annual range, annual mean temperature, and precipitation of the driest month are the most influential predictors in shaping distribution patterns of this species. The projections of the ensemble SDMs also suggested that D. involucrate is very vulnerable to future climate change, with at least one‐third of its suitable range expected to be lost in all future climate change scenarios and will shift to the northward of high‐latitude regions. Similarly, at least one‐fifth of the overlap area of the current nature reserve networks and projected suitable habitat is also expected to be lost. These findings suggest that it is of great importance to ensure that adaptive conservation management strategies are in place to mitigate the impacts of climate change on D. involucrate.     

Projecting marine species range shifts from only temperature can mask climate vulnerability

Climate change is causing range shifts in many marine species, with implications for biodiversity and fisheries. Previous research has mainly focused on how species' ranges will respond to changing ocean temperatures, without accounting for other environmental covariates that could affect future distribution patterns. Here, we integrate habitat suitability modeling approaches, a high‐resolution global climate model projection, and detailed fishery‐independent and ‐dependent faunal datasets from one of the most extensively monitored marine ecosystems—the U.S. Northeast Shelf. We project the responses of 125 species in this region to climate‐driven changes in multiple oceanographic factors (e.g., ocean temperature, salinity, sea surface height) and seabed characteristics (i.e., rugosity and depth). Comparing model outputs based on ocean temperature and seabed characteristics to those that also incorporated salinity and sea surface height (proxies for primary productivity and ocean circulation features), we explored how an emphasis on ocean temperature in projecting species' range shifts can impact assessments of species' climate vulnerability. We found that multifactor habitat suitability models performed better in explaining and predicting species historical distribution patterns than temperature‐based models. We also found that multifactor models provided more concerning assessments of species' future distribution patterns than temperature‐based models, projecting that species' ranges will largely shift northward and become more contracted and fragmented over time. Our results suggest that using ocean temperature as a primary determinant of range shifts can significantly alter projections, masking species' climate vulnerability, and potentially forestalling proactive management.     

Predicting impacts of climate-induced range expansion: an experimental framework and a test involving key grazers on temperate rocky shores

Climate change has strong potential to modify the structure and functioning of ecosystems, but experimental field studies into its effects are rare. On rocky shores, grazing limpets strongly affect ecosystem structure and their distribution in NW Europe is changing in response to climate change. Three limpet species co-occur in SW Britain ( Patella vulgata, Patella ulyssiponensis and Patella depressa ) on open rock and in pools. Shores in Ireland are similar, but currently lack P. depressa . It is anticipated that P. depressa will expand its range into Ireland as the climate warms, but we currently lack an empirical basis to predict the consequences of this change. Recent studies show that increasing abundance of P. depressa on British shores has been accompanied by a decline of P. vulgata suggesting interspecific competition. In this study, a new experimental framework was used to examine the potential for P. depressa to affect P. vulgata on Irish shores. P. vulgata was experimentally transplanted into enclosures on open rock and in pools in both Ireland and Britain. In pools, treatments also included transplanted P. ulyssiponensis to mimic natural assemblages. Growth and mortality of P. vulgata were measured over 6 months with no differences between Ireland and Britain. In Britain, P. vulgata caged in pools with transplanted P. depressa and P. ulyssiponensis showed reduced growth, compared with when caged in pools with P. ulyssiponensis alone. There was no effect of P. depressa on the growth rate of P. vulgata on open rock. Results indicate that if the range of P. depressa extends into Ireland, it would reduce the growth of P. vulgata where it co-occurs with P. ulyssiponensis in pools. The framework used here provides a field-based approach that could be used to examine the impacts of climate-induced range expansions on the structure and functioning of other ecosystems.     

Consequences of warming up a hotspot: species range shifts within a centre of bee diversity

Aim Bees are the most important pollinators of flowering plants and essential ecological keystone species contributing to the integrity of most terrestrial ecosystems. Here, we examine the potential impact of climate change on bees’ geographic range in a global biodiversity hotspot. Location South Africa with a focus on the Cape Floristic Region (CFR) diversity hotspot. Methods  Geographic ranges of 12 South African bee species representing dominant distribution types were studied, and the climate change impacts upon bees were examined with A2 and B2 climate scenarios of HadCM3 model, using MaxEnt for species distribution modelling. Results The predicted levels of climate change‐induced impacts on species ranges varied from little shifts and range expansion of 5–50% for two species to substantial range contractions between 32% and 99% in another six species. Four species show considerable range shifts. Bees of the winter rainfall area in the west of South Africa generally have smaller range sizes than in the summer rainfall area and generally show eastward range contractions toward the dry interior. Bee species prevalent in summer rainfall regions show a tendency for a south‐easterly shift in geographic range. Main conclusions The bee fauna of the CFR is identified as the most vulnerable to climate change due to the high level of endemism, the small range sizes and the island‐like isolation of the Mediterranean‐type climate region at the SW tip of Africa. For monitoring climate change impact on bees, we suggest to establish observatories in the coastal plains of the west coast that are predicted to be worst affected and areas where persistence of populations is most likely. Likely impacts of climate change on life history traits of bees (phenology, sociality, bee‐host plant synchronization) are discussed but require further investigation.     

Predicting small‐mammal responses to climatic warming: autecology,geographic range,and the Holocene fossil record

Forecasting how species will respond to climatic change requires knowledge of past community dynamics. Here we use time‐series data from the small‐mammal fossil records of two caves in the Great Basin of the American West to evaluate how contrasting and variable local paleoclimates have shaped small‐mammal abundance dynamics over the last ～7500 years of climatic change. We then predict how species and communities will respond to future scenarios of increased warming and aridity coupled with continued spread of an invasive annual grass (Bromus tectorum). We find that most community‐level responses to climatic change occur in the mammalian abundance structure at both sites; the dominance of the community by individuals from species with a southern geographic affinity increases with climatic warming. This suggests that responses occurred in situ rather than by the immigration of new taxa over this time interval. Despite predictability at the community‐scale, species‐level relationships between abundance and climate are variable and are not necessarily explained by a species' geographic affinity. Species present at both sites, however, exhibit remarkably similar responses to climate at each site, indicating that species autecology (specifically dietary functional group) is important in determining response to climatic warming. Regression‐tree analyses show remarkable concordance between the two cave faunas and highlight the importance of a granivorous dietary strategy in this desert ecosystem. Under projections of increased temperature and decreased precipitation over the next 50 years, our results indicate that granivores should thrive as communities become more dominated by individuals with a southern geographic affinity. Granivores, however, are negatively impacted by the invasion of cheatgrass. The last century of anthropogenic impacts has thus placed granivores at a greater risk of extinction than predicted under climate‐only scenarios.     

Temperature‐related geographical shifts among passerines: contrasting processes along poleward and equatorward range margins

Climate change is causing widespread geographical range shifts, which likely reflects different processes at leading and trailing range margins. Progressive warming is thought to relax thermal barriers at poleward range margins, enabling colonization of novel areas, but imposes increasingly unsuitable thermal conditions at equatorward margins, leading to range losses from those areas. Few tests of this process during recent climate change have been possible, but understanding determinants of species’ range limits will improve predictions of their geographical responses to climate change and variation in extinction risk. Here, we examine the relationship between poleward and equatorward range margin dynamics with respect to temperature‐related geographical limits observed for 34 breeding passerine species in North America between 1984–1988 and 2002–2006. We find that species’ equatorward range margins were closer to their upper realized thermal niche limits and proximity to those limits predicts equatorward population extinction risk through time. Conversely, the difference between breeding bird species’ poleward range margin temperatures and the coolest temperatures they tolerate elsewhere in their ranges was substantial and remained consistent through time: range expansion at species’ poleward range margins is unlikely to directly reflect lowered thermal barriers to colonization. The process of range expansion may reflect more complex factors operating across broader areas of species’ ranges. The latitudinal extent of breeding bird ranges is decreasing through time. Disparate responses observed at poleward versus equatorward margins arise due to differences in range margin placement within the realized thermal niche and suggest that climate‐induced geographical shift at equatorward range limits more strongly reflect abiotic conditions than at their poleward range limits. This further suggests that observed geographic responses to date may fail to demonstrate the true cost of climate change on the poleward portion of species’ distributions. Poleward range margins for North American breeding passerines are not presently in equilibrium with realized thermal limits.     

Species traits and climate velocity explain geographic range shifts in an ocean‐warming hotspot

Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean‐warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small‐ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances.     

Illuminating geographical patterns in species' range shifts

Species' range shifts in response to ongoing climate change have been widely documented, but although complex spatial patterns in species' responses are expected to be common, comprehensive comparisons of species' ranges over time have undergone little investigation. Here, we outline a modeling framework based on historical and current species distribution records for disentangling different drivers (i.e. climatic vs. nonclimatic) and assessing distinct facets (i.e. colonization, extirpation, persistence, and lags) of species' range shifts. We used extensive monitoring data for stream fish assemblages throughout France to assess range shifts for 32 fish species between an initial period (1980–1992) and a contemporary one (2003–2009). Our results provide strong evidence that the responses of individual species varied considerably and exhibited complex mosaics of spatial rearrangements. By dissociating range shifts in climatically suitable and unsuitable habitats, we demonstrated that patterns in climate‐driven colonization and extirpation were less marked than those attributed to nonclimatic drivers, although this situation could rapidly shift in the near future. We also found evidence that range shifts could be related to some species' traits and that the traits involved varied depending on the facet of range shift considered. The persistence of populations in climatically unsuitable areas was greater for short‐lived species, whereas the extent of the lag behind climate change was greater for long‐lived, restricted‐range, and low‐elevation species. We further demonstrated that nonclimatic extirpations were primarily related to the size of the species' range, whereas climate‐driven extirpations were better explained by thermal tolerance. Thus, the proposed framework demonstrated its potential for markedly improving our understanding of the key processes involved in range shifting and also offers a template for informing management decisions. Conservation strategies would greatly benefit from identifying both the geographical patterns and the species' traits associated with complex modifications of species' distributions in response to global changes.     

Migration rate limitations on climate change-induced range shifts in Cape Proteaceae

Modelling of climate change-induced species range shifts has generally addressed migration limitations inadequately, often assuming 'null' migration or instantaneous 'full' migration extremes. We describe methods for incorporating simple migration rate assumptions into multispecies modelling, using the Proteaceae of the Cape Floristic Region. Even with optimistic migration assumptions, range loss projections more closely approximate null migration than full migration assumptions. Full migration results were positively skewed by few species with large range increases, an overestimate eliminated by dispersal-limited migration rate assumptions. Wind- and ant/rodent-dispersed species responded differently to climate change. Initially larger ranges of wind-dispersed species were more strongly reduced by climate change, despite far greater assumed dispersal distances — we suggest that these well-dispersed species populate more marginal areas of potential range, causing lower resilience to climatic changes at range margins. Overall, range loss rate slowed with advancing climate change, possibly because species ranges contracted into core areas most resilient to climate change. Thus, a consideration of simple dynamics of range change (rather than single step, present–future comparisons of range) provide new insights relevant for conservation strategies, in particular, and for guiding monitoring efforts to detect and gauge the impacts of climate change on natural populations.     

Evolutionary consequences of climate‐induced range shifts in insects

Range shifts can rapidly create new areas of geographic overlap between formerly allopatric taxa and evidence is accumulating that this can affect species persistence. We review the emerging literature on the short‐ and long‐term consequences of these geographic range shifts. Specifically, we focus on the evolutionary consequences of novel species interactions in newly created sympatric areas by describing the potential (i) short‐term processes acting on reproductive barriers between species and (ii) long‐term consequences of range shifts on the stability of hybrid zones, introgression and ultimately speciation and extinction rates. Subsequently, we (iii) review the empirical literature on insects to evaluate which processes have been studied, and (iv) outline some areas that deserve increased attention in the future, namely the genomics of hybridisation and introgression, our ability to forecast range shifts and the impending threat from insect vectors and pests on biodiversity, human health and crop production. Our review shows that species interactions in de novo sympatric areas can be manifold, sometimes increasing and sometimes decreasing species diversity. A key issue that emerges is that climate‐induced hybridisations in insects are much more widespread than anticipated and that rising temperatures and increased anthropogenic disturbances are accelerating the process of species mixing. The existing evidence only shows the tip of the iceberg and we are likely to see many more cases of species mixing following range shifts in the near future.     

Fitness declines towards range limits and local adaptation to climate affect dispersal evolution during climate‐induced range shifts

Dispersal ability will largely determine whether species track their climatic niches during climate change, a process especially important for populations at contracting (low‐latitude/low‐elevation) range limits that otherwise risk extinction. We investigate whether dispersal evolution at contracting range limits is facilitated by two processes that potentially enable edge populations to experience and adjust to the effects of climate deterioration before they cause extinction: (i) climate‐induced fitness declines towards range limits and (ii) local adaptation to a shifting climate gradient. We simulate a species distributed continuously along a temperature gradient using a spatially explicit, individual‐based model. We compare range‐wide dispersal evolution during climate stability vs. directional climate change, with uniform fitness vs. fitness that declines towards range limits (RLs), and for a single climate genotype vs. multiple genotypes locally adapted to temperature. During climate stability, dispersal decreased towards RLs when fitness was uniform, but increased when fitness declined towards RLs, due to highly dispersive genotypes maintaining sink populations at RLs, increased kin selection in smaller populations, and an emergent fitness asymmetry that favoured dispersal in low‐quality habitat. However, this initial dispersal advantage at low‐fitness RLs did not facilitate climate tracking, as it was outweighed by an increased probability of extinction. Locally adapted genotypes benefited from staying close to their climate optima; this selected against dispersal under stable climates but for increased dispersal throughout shifting ranges, compared to cases without local adaptation. Dispersal increased at expanding RLs in most scenarios, but only increased at the range centre and contracting RLs given local adaptation to climate.     

Likelihood of changes in forest species suitability,distribution, and diversity under future climate: The case of Southern Europe

Forest conservation strategies and plans can be unsuccessful if the new habitat conditions determined by climate change are not considered. Our work aims at investigating the likelihood of future suitability, distribution and diversity for some common European forest species under the projected changes in climate, focusing on Southern Europe. We combine an Ensemble Platform for Species Distribution Models (SDMs) to five Global Circulation Models (GCMs) driven by two Representative Concentration Pathways (RCPs), to produce maps of future climate‐driven habitat suitability for ten categories of forest species and two time horizons. For each forest category and time horizon, ten maps of future distribution (5 GCMs by 2 RCPs) are thus combined in a single suitability map supplied with information about the “likelihood” adopting the IPCC terminology based on consensus among projections. Then, the statistical significance of spatially aggregated changes in forest composition at local and regional level is analyzed. Finally, we discuss the importance, among SDMs, that environmental predictors seem to have in influencing forest distribution. Future impacts of climate change appear to be diversified across forest categories. A strong change in forest regional distribution and local diversity is projected to take place, as some forest categories will find more suitable conditions in previously unsuitable locations, while for other categories the same new conditions will become less suited. A decrease in species diversity is projected in most of the area, with Alpine region showing the potentiality to become a refuge for species migration.     

Escaping the heat: range shifts of reef coral taxa in coastal Western Australia

One of the most critical challenges facing ecologists today is to understand the changing geographic distribution of species in response to current and predicted global warming. Coastal Western Australia is a natural laboratory in which to assess the effect of climate change on reef coral communities over a temporal scale unavailable to studies conducted solely on modern communities. Reef corals composing Late Pleistocene reef assemblages exposed at five distinct localities along the west Australian coast were censused and the results compared with coral occurrence data published for the modern reefs offshore of each locality. The resulting comparative data set comprises modern and Late Pleistocene reef coral communities occurring over approximately 12° of latitude. For the modern reefs this gradient includes the zone of overlap between the Dampierian and Flindersian Provinces. Modern reef coral communities show a pronounced gradient in coral composition over the latitudinal range encompassed by the study, while the gradient in community composition is not as strong for Pleistocene communities. Tropical‐adapted taxa contracted their ranges north since Late Pleistocene time, emplacing two biogeographic provinces in a region in which a single province had existed previously. Beta diversity values for adjacent communities also reflect this change. Modern reefs show a distinct peak in beta diversity in the middle of the region; the peak is not matched by Pleistocene reefs. Beta diversity is correlated with distance only for comparisons between modern reefs in the north and the fossil assemblages, further supporting change in distribution of the biogeographic provinces in the study area. Coral taxa present in modern communities clearly expanded and contracted their geographic ranges in response to climate change. Those taxa that distinguish Pleistocene from modern reefs are predicted to migrate south in response to future climate change, and potentially persist in ‘temperature refugia’ as tropical reef communities farther north decline.     

Ecological correlates of range shifts of Late Pleistocene mammals

Understanding and predicting how species' distributions will shift as climate changes are central questions in ecology today. The late Quaternary of North America represents a natural experiment in which we can evaluate how species responded during the expansion and contraction of the glaciers. Here, we ask whether species' range shifts differ because of taxonomic affinity, life-history traits, body size or topographic heterogeneity and whether the species survived the megafaunal extinction. There was no difference in range shifts between victims and survivors of the megafaunal extinction. In general, the change in the size of a species' range is not well correlated with any of the ecological or life-history traits evaluated. However, there are significant relationships between some variables and the movements of the centroids of ranges. Differences in the distances shifted exist among orders, although this is probably a result of body size differences as larger bodied species show larger shifts. Although there are a few exceptions, the distance that species shifted their range was weakly correlated with life-history traits. Finally, species in more topographically heterogeneous areas show smaller shifts than species in less-diverse areas. Overall, these results indicate that when trying to predict species range shifts in the future, body size, lifespan and the topographic relief of the landscape should be taken into account.