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Abstract Aim Rarity and geographic aspects of species distributions mediate their vulnerability to global change. We explore the relationships between species rarity and geography and their exposure to climate and land use change in a biodiversity hotspot. Location California, USA. Taxa One hundred and six terrestrial plants. Methods We estimated four rarity traits: range size, niche breadth, number of habitat patches, and patch isolation; and three geographic traits: mean elevation, topographic heterogeneity, and distance to coast. We used species distribution models to measure species exposure—predicted change in continuous habitat suitability within currently occupied habitat—under climate and land use change scenarios. Using regression models, decision‐tree models and variance partitioning, we assessed the relationships between species rarity, geography, and exposure to climate and land use change. Results Rarity, geography and greenhouse gas emissions scenario explained >35% of variance in climate change exposure and >61% for land use change exposure. While rarity traits (range size and number of habitat patches) were most important for explaining species exposure to climate change, geographic traits (elevation and topographic heterogeneity) were more strongly associated with species' exposure to land use change. Main conclusions Species with restricted range sizes and low topographic heterogeneity across their distributions were predicted to be the most exposed to climate change, while species at low elevations were the most exposed to habitat loss via land use change. However, even some broadly distributed species were projected to lose >70% of their currently suitable habitat due to climate and land use change if they are in geographically vulnerable areas, emphasizing the need to consider both species rarity traits and geography in vulnerability assessments. 

Many plant species are likely to face population decline or even extinction in the coming century, especially those with a limited distribution and inadequate dispersal relative to the projected rates of climate change. The obligate seeding California endemic, Ceanothus perplexans is especially at risk, and depending on how climate change interacts with altered fire regimes in Southern California, certain populations are likely to be more at risk than others. To identify which areas within the species’ range might need conservation intervention, we modeled population dynamics of C. perplexans under various climate and fire regime change scenarios, focusing on spatially explicit patterns in fire frequency. We used a species distribution model to predict the initial range and potential future habitat, while adapting a density-dependent, stage-structured population model to simulate population dynamics. As a fire-adapted obligate seeder, simulated fire events caused C. perplexans seeds to germinate, but also killed all adults in the population. Our simulations showed that the total population would likely decline under any combination of climate change and fire scenario, with the species faring best at an intermediate fire return interval of around 30–50 years. Nevertheless, while the total population declines least with a 30–50 year fire return interval, the effect of individual subpopulations varies depending on spatially explicit patterns in fire simulations. Though climate change is a greater threat to most subpopulations, increased fire frequencies particularly threatened populations in the northwest of the species’ range closest to human development. Subpopulations in the mountainous southern end of the range are likely to face the sharpest declines regardless of fire. Through a combination of species distribution modeling, fire modeling, and spatially explicit demographic simulations, we can better prepare for targeted conservation management of vulnerable species affected by global change. 

Species distribution modelling (SDM), also called environmental or ecological niche modelling, has developed over the last 30 years as a widely used tool used in core areas of biogeography including historical biogeography, studies of diversity patterns, studies of species ranges, ecoregional classification, conservation assessment and projecting future global change impacts. In the 50th anniversary year ofJournal of Biogeography, I reflect on developments in species distribution modelling, illustrate how embedded the methodology has become in all areas of biogeography and speculate on future directions in the field. Challenges to species distribution modelling raised in this journal in 2006 have been addressed to a significant degree. Those challenges are clarification of the niche concept; improved sample design for species occurrence data; model parameterization; predictor selection; assessing model performance and transferability; and integrating correlative and process models of species distributions. SDM is used, often in conjunction with other evidence, to understand past species range dynamics, identify patterns and drivers of biological diversity, identify drivers of species range limits, define and delineate ecoregions, estimate the distributions of biodiversity elements in relation to protected status and to prioritize conservation action, and to forecast species range shifts in response to climate change and other global change scenarios. Areas of progress in SDM that may become more widely accessible and useful tools in biogeography include genetically informed models and community distribution models.

 

To examine the climatic and biogeographic drivers of plant trait variation across Caribbean tropical dry forests, a system characterised by high rates of plant endemism despite low moisture availability, high rainfall variability and persistent exposure to hurricanes.

Caribbean tropical dry forests.

Woody plants.

We used a database of 572 woody vegetation plots spanning across the Caribbean, including Florida. We then extracted seed mass, specific leaf area and wood density from global trait databases. We supplemented additional trait data from herbaria collections and calculated phylogenetic imputation of traits. Furthermore, we calculated presence–absence community means and functional diversity and correlated these metrics with bioclimatic variables in addition to island and dry forest area using generalised additive models.

Despite occurring in climatically distinct regions, Caribbean tropical dry forests are functionally similar, and the trait space of many dry forests are nested within the functional space of others. In line with island biogeographic theory, island area, dry forest area and island isolation were correlated with functional diversity. Although temperature and precipitation were important determinants of trait variation and functional diversity, environmental variables differently impacted trait variation and the variance explained was generally low.

The high functional overlap among Caribbean dry forests is remarkable given the broad climatic gradient across these islands. High functional overlap suggests that environmental and biogeographic filters constrain plant form and function in these intrinsically fascinating systems. The trait space of these insular dry forest systems points to dispersal‐limitation, in addition to high temperature and water limitations, and favouring persistence strategies to withstand high frequency hurricane disturbance.

 

As the effects of anthropogenic climate change become more severe, several approaches for deliberate climate intervention to reduce or stabilize Earth’s surface temperature have been proposed. Solar radiation modification (SRM) is one potential approach to partially counteract anthropogenic warming by reflecting a small proportion of the incoming solar radiation to increase Earth’s albedo. While climate science research has focused on the predicted climate effects of SRM, almost no studies have investigated the impacts that SRM would have on ecological systems. The impacts and risks posed by SRM would vary by implementation scenario, anthropogenic climate effects, geographic region, and by ecosystem, community, population, and organism. Complex interactions among Earth’s climate system and living systems would further affect SRM impacts and risks. We focus here on stratospheric aerosol intervention (SAI), a well-studied and relatively feasible SRM scheme that is likely to have a large impact on Earth’s surface temperature. We outline current gaps in knowledge about both helpful and harmful predicted effects of SAI on ecological systems. Desired ecological outcomes might also inform development of future SAI implementation scenarios. In addition to filling these knowledge gaps, increased collaboration between ecologists and climate scientists would identify a common set of SAI research goals and improve the communication about potential SAI impacts and risks with the public. Without this collaboration, forecasts of SAI impacts will overlook potential effects on biodiversity and ecosystem services for humanity. 

The impacts of urbanization on bird biodiversity depend on human–environment interactions that drive land management. Although a commonly studied group, less attention has been given to public perceptions of birds close to home, which can capture people's direct, everyday experiences with urban biodiversity. Here, we used ecological and social survey data collected in the metropolitan region of Phoenix, Arizona, USA, to determine how species traits are related to people's perceptions of local bird communities. We used a trait‐based approach to classify birds by attributes that may influence human–bird interactions, including color, size, foraging strata, diet, song, and cultural niche space based on popularity and geographic specificity. Our classification scheme using hierarchical clustering identified four trait categories, labeled as Metropolitan (gray, loud, seedeaters foraging low to ground), Familiar (yellow/brown generalist species commonly present in suburban areas), Distinctive (species with distinguishing appearance and song), and Hummingbird (hummingbird species, small and colorful). Strongly held beliefs about positive or negative traits were also more consistent than ambivalent ones. The belief that birds were colorful and unique to the regional desert environment was particularly important in fortifying perceptions. People largely perceived hummingbird species and birds with distinctive traits positively. Similarly, urban‐dwelling birds from the metropolitan trait group were related to negative perceptions, probably due to human–wildlife conflict. Differences arose across sociodemographics (including income, age, education, and Hispanic/Latinx identity), but explained a relatively low amount of variation in perceptions compared with the bird traits present in the neighborhood. Our results highlight how distinctive aesthetics, especially color and song, as well as traits related to foraging and diet drive perceptions. Increasing people's direct experiences with iconic species tied to the region and species with distinguishing attributes has the potential to improve public perceptions and strengthen support for broader conservation initiatives in and beyond urban ecosystems.