Human-induced climate change is increasingly recognized as a fundamental driver of biological processes and patterns. Historic climate change is known to have caused shifts in the geographic ranges of many taxa and future climate change is expected to result in even greater redistributions of species. As a result, predicting the impact of climate change on future patterns of biodiversity will greatly aid conservation planning. Using the North American Breeding Bird Survey and Audubon Christmas Bird Count, two of the most comprehensive continental datasets of vertebrates in the world, and correlative distribution modeling, we assessed geographic range shifts for 588 North American bird species during both the breeding and non-breeding seasons under a range of future emission scenarios (SRES A2, A1B, B2) through the end of the century. Here we show that 314 species (53%) are projected to lose more than half of their current geographic range across three scenarios of climate change through the end of the century. For 126 species, loss occurs without concomitant range expansion; whereas for 188 species, loss is coupled with potential to colonize new replacement range. We found no strong associations between projected climate sensitivities and existing conservation prioritizations. Moreover, species responses were not clearly associated with habitat affinities, migration strategies, or climate change scenarios. Our results demonstrate the need to include climate sensitivity into current conservation planning and to develop adaptive management strategies that accommodate shrinking and shifting geographic ranges. The persistence of many North American birds will depend on their ability to colonize climatically suitable areas outside of current ranges and management actions that target climate adaptation.

Aim: To inform conservation planning in the face of climate change, our objectives were to map spatial patterns of tree and songbird macrorefugia; to identify climatic limiting factors by region and taxonomic group; and to quantify multi-scale topographic components of end-of-century biotic refugia.Location: United States and Canada outside the far north.Time period: End of the 21st century.Major taxa studied: Trees and songbirds.Methods: We used species distribution models for 324 trees and 268 songbirds to develop a macrorefugia index using species-specific climate velocity. Maps of multispecies refugia potential were developed for each taxonomic/functional group and quantile regression was used to identify climatic limiting factors and relationships with multi-scale topographic variables.Results: End-of-century macrorefugia for both trees and songbirds were concentrated in western mountains and, to a lesser extent, in north-eastern coastal regions. For the highest-value refugia, precipitation was generally most limiting in the north, and warm temperatures and moisture availability were limiting in the south. Tree refugia were more limited by precipitation and moisture, while songbird refugia were more limited by temperature. Upper-percentile refugia, but not median values, were well explained by topographic conditions. Songbird refugia were strongly associated with elevation, while coastal proximity and landform composition (particularly headwaters) were important for both groups. There was a general lack of concordance between patterns of current species richness and future climate refugia.Main conclusions: Macrorefugia patterns are partly explained by steep elevational or latitudinal temperature gradients and/or moderate climates, such as coastal regions. However, climatic limiting factors for these refugia suggest contrasts in the ecological processes governing warm-end range limits for different taxa in different regions. Our framework can be applied to other regions, taxa, and time periods to generate and explain biologically meaningful indices of macrorefugia for conservation planning. K E Y W O R D S biotic refugia, climate change, climate velocity, conservation planning, environmental limiting factors, macrorefugia, passerines, quantile regression, woody plants 690 |

Efficient conservation planning requires knowledge about conservation targets, threats to those targets, costs of conservation and the marginal return to additional conservation efforts. Systematic conservation planning typically only takes a small piece of this complex puzzle into account. Here, we use a return-on-investment (ROI) approach to prioritise lands for conservation at the county level in the conterminous USA. Our approach accounts for species richness, county area, the proportion of species' ranges already protected, the threat of land conversion and land costs. Areas selected by a complementarity-based greedy heuristic using our full ROI approach provided greater averted species losses per dollar spent compared with areas selected by heuristics accounting for richness alone or richness and cost, and avoided acquiring lands not threatened with conversion. In contrast to traditional prioritisation approaches, our results highlight conservation bargains, opportunities to avert the threat of development and places where conservation efforts are currently lacking.

In an emerging climate crisis, effective conservation requires both adaptation and mitigation to improve the resilience of species. The currently pledged emissions reductions outlined in the Paris Agreement framework would still lead to a +3.2°C increase in global mean temperature by the end of this century. In this context, we assess the vulnerability of 604 North American bird species and identify the species and locations most at risk under climate change. We do this based on species distribution models for both the breeding and nonbreeding seasons, projected under two global warming scenarios (an optimistic mitigation scenario 1.5°C and an unmitigated 3.0°C scenario). We evaluate vulnerability under each season and scenario by assessing sensitivity and adaptive capacity based on modeled range loss and range gain, respectively, and based on species specific dispersal abilities. Our study, the first of its magnitude, finds that over two‐thirds of North American birds are moderately or highly vulnerable to climate change under a 3.0°C scenario. Of these climate‐vulnerable species, 76% would have reduced vulnerability and 38% of those would be considered nonvulnerable if warming were stabilized at 1.5°C. Thus, the current pledge in greenhouse gas reductions set by the Paris Agreement is inadequate to reduce vulnerability to North American birds. Additionally, if climate change proceeds on its current trajectory, arctic birds, waterbirds, and boreal and western forest birds will be highly vulnerable to climate change, groups that are currently not considered of high conservation concern. There is an urgent need for both (a) policies to mitigate emissions and (b) prioritization to identify where to focus adaptation actions to protect birds in a changing climate.

Increasing concerns exist about possible decreased wintering duck abundance and hunting opportunities in the southern regions of the Atlantic and Mississippi flyways of North America. Researchers suggest these decreased abundances of ducks may be related to winter warming and related climatic phenomena. Accordingly, we tested predictions that duck abundance was increasing more at northern than southern latitudes, and that trends were related to average winter temperatures (Dec-Jan). We tested predictions using National Audubon Society Christmas Bird Count (CBC) data collected during December 1969 through January 2019 from 31 states in the United States and 6 Canadian provinces that comprise the Atlantic and Mississippi flyways for 16 species of dabbling and diving ducks (Anatinae). We found support for the prediction that CBC trends in duck abundance vary with latitude, and mean winter temperature explained nearly half the variation in CBC trends for 12 of 16 species. For some species, trends were negative in warmer regions and positive in colder regions. For others, trends were stable or slightly positive in warmer regions but more positive in colder regions. These results provide empirical evidence supporting climate-influenced winter range changes by important game duck species and suggest challenges and opportunities for waterfowl population, habitat, and hunting management in North America and the northern hemisphere.

Biodiversity is being lost at an alarming rate across the globe, with extinction rates up to a hundred times greater than historical norms. Climate change will only exacerbate this crisis. The rapid pace of projected climate change is set to push birds to seek new locations, drastically reshuffling the avian communities of North America. In an emerging climate crisis, effective conservation requires both adaptation and mitigation to improve the resilience of species. However, the pledged reductions in greenhouse gas emissions outlined in the Paris Agreement framework would still lead to a 3.2°C or greater increase in global mean temperature by the end of this century. In this study, we use big data analytics to develop species distribution models and assess the vulnerability of 604 North American birds to multiple climate change scenarios. We assess how climate change mitigation can affect the number of species vulnerable to climate change, as well as the species and locations at risk if emissions continue unchecked. Our results indicate that over two-thirds of North American birds are moderately or highly vulnerable to climate change under a 3.0°C global warming scenario. Of these climate-vulnerable species, 76% would have reduced vulnerability and 38% of those would be considered non-vulnerable if warming were stabilized at 1.5°C. Thus, the current pledge in greenhouse gas reductions set by the Paris Agreement is inadequate to reduce vulnerability to birds. Additionally, if climate change proceeds on its current trajectory, arctic birds, waterbirds and boreal and western forest birds will be highly vulnerable to climate change; groups that are currently not considered of high conservation concern. Thus, there is an urgent need for both aggressive policies to mitigate emissions and focused conservation adaptation actions to protect birds and the places they need in a changing climate.

Contemporary climate change is causing large shifts in biotic distributions 1 , which has the potential to bring previously isolated, closely related species into contact 2 . This has led to concern that hybridization and competition could threaten species persistence 3 . Here, we use bioclimatic models to show that future range overlap by the end of the century is predicted for only 6.4% of isolated, congeneric species pairs of New World birds, mammals and amphibians. Projected rates of climate-induced overlap are higher for birds (11.6%) than for mammals (4.4%) or amphibians (3.6%). As many species will have di culty tracking shifting climates 4 , actual rates of future overlap are likely to be far lower, suggesting that hybridization and competition impacts may be relatively modest.Widespread changes in species distributions due to climate change are documented for diverse taxa and are expected to become more pronounced over the coming century as rates of warming increase 1 . One expected outcome of climate change-induced range shifts is the establishment of geographic range overlap among previously isolated taxa, leading to novel species interactions and assemblages 5,6 . The potential for climate change to result in new interactions among closely related species has given rise to conservation concern, as these may have negative consequences for species persistence. Climate-induced range contact between ecologically similar species may introduce high levels of interspecific competition to populations already stressed by changing climatic conditions 7,8 . In addition, recently diverged species with incomplete reproductive barriers may hybridize, reducing population fitness through genetic admixture or leading to species extinctions through asymmetric hybridization 9,10 . Although few studies have empirically documented climate-induced contact among closely related species 2 , many have expressed concern that it could lead to a significant loss of biodiversity 3,11 .Despite potential for negative impacts, no attempt has yet been made to estimate future rates of climate-induced geographic overlap among previously isolated, closely related species. We used bioclimatic models to predict potential end-of-century (2071-2100) areas of climatic suitability for 9,577 congeneric species pairs, including New World birds (n = 3,858), mammals (n = 1,661) and amphibians (n = 4,058). From this data set, we calculated the number of nonoverlapping (that is, allopatric), congeneric species pairs with ranges projected to come into contact (that is, sympatry) in the coming century. We accounted for variability among estimates by including in our results only species pairs projected to come into contact under a majority (>5) of 10 general circulation models (GCMs).We found that 6.4% of 4,796 allopatric species pairs are projected to come into geographic contact by the end of the century (Fig. 1). Rates of future contact for species pairs were significantly greater for birds than mammals or amphibians (generalized linear mixed mode...

Grassland birds have suffered dramatic population declines and are under threat of further grassland conversion. Simultaneously, grassland regions are projected to have high rates of future climate change. We assessed the vulnerability of grassland birds in North America under scenarios of global climate change reflecting the objectives of the Paris Agreement. The assessment incorporated model‐based projections of range losses and gains as well as trait‐based information on adaptive capacity. Nearly half (42%) of grassland birds were highly vulnerable during the breeding season under a 3.0°C increase in global mean temperature scenario representing current commitments under the Paris Accord. This proportion declined to 13% with a 2.0°C increase and to 8% with a 1.5°C increase over preindustrial global mean temperature. Regardless of scenario, more than 70% of grassland birds had some vulnerability to climate change. Policy actions beyond the present‐day national commitments under the Paris Accord are needed to reduce vulnerability of grassland birds in a changing climate.