Explore the vast range of titles available.

Aim Statistical species distribution models (SDMs) are the most common tool to predict the impact of climate change on biodiversity. They can be tuned to fit relationships at various levels of complexity (defined here as parameterization complexity, number of predictors, and multicollinearity) that may co‐determine whether projections to novel climatic conditions are useful or misleading. Here, we assessed how model complexity affects the performance of model extrapolations and influences projections of species ranges under future climate change. Location Europe. Taxon 34 European tree species. Methods We sampled three replicates of predictor sets for all combinations of 10 levels (n = 3–12) of environmental variables (climate, terrain, soil) and 10 levels of multicollinearity. We used these sets for each species to fit four SDM algorithms at three levels of parameterization complexity. The >100,000 resulting SDM fits were then evaluated under environmental block cross‐validation and projected to environmental conditions for 2061–2080 considering four climate models and two emission scenarios. Finally, we investigated the relationships of model design with model performance and projected distributional changes. Results Model complexity affected both model performance and projections of species distributional change. Fits of intermediate parameterization complexity performed best, and more complex parameterizations were associated with higher projected loss of current ranges. Model performance peaked at 10–11 variables but increasing number of variables had no consistent effect on distributional change projections. Multicollinearity had a low impact on model performance but distinctly increased projected loss of current ranges. Main conclusions SDM‐based climate change impact assessments should be based on ensembles of projections, varying SDM algorithms as well as parameterization complexity, besides emission scenarios and climate models. The number of predictor variables should be kept reasonably small and the classical threshold of maximum absolute Pearson correlation of 0.7 restricts collinearity‐driven effects in projections of species ranges.

Altitudinal gradients provide a useful space‐for‐time substitution to examine the capacity for plant competition and facilitation to mediate responses to climate change. Decomposing net interactions into their facilitative and competitive components, and quantifying the performance of plants with and without neighbours along altitudinal gradients, may prove particularly informative in understanding the mechanisms behind plant responses to environmental change. To decouple the inherent responses of species to climate from the responses of plant–plant interactions to climate, we conducted a meta‐analysis. Using data from 16 alpine experiments, we tested if changes in net interactions along altitudinal gradients were due to a change in the performance of target species without neighbours (i.e. environmental severity effects only) or with neighbours (neighbour trait mediated effects). There was a global shift from competition to facilitation with increasing altitude driven by both environmental severity and neighbour trait effects. However, this global pattern was strongly influenced by the high number of studies in mesic climates and driven by competition at low altitude in temperate climates (neighbour trait effect), and facilitation at high altitude in arctic and temperate climates (environmental severity effect). In Mediterranean systems, there was no significant effect of competition, and facilitation increased with decreasing altitude. Changes in facilitation with altitude could not unambiguously be attributed to either neighbour trait effects or environmental severity effects, probably because of the opposing stress gradients of cold and aridity in dry environments. Partitioning net interactions along altitudinal gradients led to the prediction that climate change should decrease the importance of facilitation in mesic alpine communities, which might in turn exacerbate the negative effects of climate change in these regions. In xeric climates, the importance of facilitation by drought‐tolerant species should increase at low altitudes which should mitigate the negative effect of climate change. However, the importance of facilitation by cold‐tolerant species at high altitudes may decrease and exacerbate the effects of climate change.

Aim Anthropogenic environmental modifications such as climate or land‐use change are causing species to move on their own beyond their native ranges. As this phenomenon will increase in the near future, it is crucial to determine whether range‐expanding species, or neonatives, are more or less likely than native and alien species to impact their recipient ecosystems. Here, we compared impact magnitudes of bark beetle species from their native, neonative and alien ranges, simultaneously. Location Global. Methods We formulated four general scenarios about the magnitude of environmental impacts in different ranges (native, neonative and alien) based on hypotheses commonly used in invasion biology. We tested these scenarios globally on Dendroctonus bark beetles, asking whether they have the most harmful impacts in their native, neonative or alien ranges. Impacts reported in the literature were assessed with the IUCN Environmental Impact Classification for Alien Taxa (EICAT). Results We found that bark beetles cause the most harmful impacts in their native ranges, followed by the neonative ranges, while impacts in their alien ranges are the lowest. This indicates that the more dissimilar the environment is from that in the native range, the lower the probability of high‐impact magnitudes. Our results align with several non‐exclusive hypotheses, e.g. pre‐adaptation and habitat filtering, while they do not support others, e.g. enemy release or Darwin’s naturalization. The results are also in contrast with previous studies on vertebrates and plants, which found no or mixed differences in impact magnitudes with biogeographic origin. Main conclusions Our analysis suggests that bark beetles, like other species that are keystone and abundant in their native ranges, have generally lower impacts when introduced to novel environments due to biotic resistance or lack of pre‐adaptation. Research and management implications regarding the impacts of neonative and alien populations are also discussed.

World governments have committed to increase the global protected areas coverage by 2020, but the effectiveness of this commitment for protecting biodiversity depends on where new protected areas are located. Threshold‐ and complementarity‐based approaches have been independently used to identify important sites for biodiversity. We brought together these approaches by performing a complementarity‐based analysis of irreplaceability in important bird and biodiversity areas (IBAs), which are sites identified using a threshold‐based approach. We determined whether irreplaceability values are higher inside than outside IBAs and whether any observed difference depends on known characteristics of the IBAs. We focused on 3 regions with comprehensive IBA inventories and bird distribution atlases: Australia, southern Africa, and Europe. Irreplaceability values were significantly higher inside than outside IBAs, although differences were much smaller in Europe than elsewhere. Higher irreplaceability values in IBAs were associated with the presence and number of restricted‐range species; number of criteria under which the site was identified; and mean geographic range size of the species for which the site was identified (trigger species). In addition, IBAs were characterized by higher irreplaceability values when using proportional species representation targets, rather than fixed targets. There were broadly comparable results when measuring irreplaceability for trigger species and when considering all bird species, which indicates a good surrogacy effect of the former. Recently, the International Union for Conservation of Nature has convened a consultation to consolidate global standards for the identification of key biodiversity areas (KBAs), building from existing approaches such as IBAs. Our results informed this consultation, and in particular a proposed irreplaceability criterion that will allow the new KBA standard to draw on the strengths of both threshold‐ and complementarity‐based approaches.

Climate change is happening due to natural factors and human activities. It expressively alters biodiversity, agricultural production, and food security. Mainly, narrowly adapted and endemic species are under extinction. Accordingly, concerns over species extinction are warranted as it provides food for all life forms and primary health care for more than 60–80% of humans globally. Nevertheless, the impact of climate change on biodiversity and food security has been recognized, little is explored compared to the magnitude of the problem globally. Therefore, the objectives of this review are to identify, appraise, and synthesize the link between climate change, biodiversity, and food security. Data, climatic models, emission, migration, and extinction scenarios, and outputs from previous publications were used. Due to climate change, distributions of species have shifted to higher elevations at a median rate of 11.0 m and 16.9 km per decade to higher latitudes. Accordingly, extinction rates of 1103 species under migration scenarios, provide 21–23% with unlimited migration and 38–52% with no migration. When an environmental variation occurs on a timescale shorter than the life of the plant any response could be in terms of a plastic phenotype. However, phenotypic plasticity could buffer species against the long-term effects of climate change. Furthermore, climate change affects food security particularly in communities and locations that depend on rain-fed agriculture. Crops and plants have thresholds beyond which growth and yield are compromised. Accordingly, agricultural yields in Africa alone could be decline by more than 30% in 2050. Therefore, solving food shortages through bringing extra land into agriculture and exploiting new fish stocks is a costly solution, when protecting biodiversity is given priority. Therefore, mitigating food waste, compensating food-insecure people conserving biodiversity, effective use of genetic resources, and traditional ecological knowledge could decrease further biodiversity loss, and meet food security under climate change scenarios. However, achieving food security under such scenario requires strong policies, releasing high-yielding stress resistant varieties, developing climate resilient irrigation structures, and agriculture. Therefore, degraded land restoration, land use changes, use of bio-energy, sustainable forest management, and community based biodiversity conservation are recommended to mitigate climate change impacts.

In the Anthropocene, the ranges of introduced species are expanding, while extinction‐prone species are contracting. Introductions and extinctions are caused by how species respond to human impacts, but it is unknown why the ranges of some species expand and some contract. Here, we test whether this opposite response of human impact is due to introduced and extinction‐prone species falling at opposite ends of geographic, evolutionary, or ecological trait continua. We constructed a database of native range maps, traits, phylogenetic relationships, and the introduction and extinction‐prone status of squamate reptiles with ranges native to the Western Hemisphere. Across > 3000 snake and lizard species (88% of known native squamates), 142 had been introduced elsewhere and 483 were extinction‐prone (i.e. vulnerable, endangered, critically endangered, extinct in the wild, extinct). To explain variation in status, we first tested if the same human‐impacted regions in the Americas contained the native ranges of species of either status. Second, we tested for phylogenetic signal in species status. Finally, we tested the explanatory power of multiple trait continua. The native ranges of introduced and extinction‐prone reptiles were clustered in island regions with high human impact versus mainland regions with lower human impact. Phylogenetic signal was weak for status, but introduced and extinction‐prone species were clustered in different clades. All geographic and ecological traits that explained each status supported the opposite ends hypothesis. Introduced species had larger, edgier ranges, while extinction‐prone species had smaller, simpler ranges. Introduced species were mostly herbivorous/omnivorous, while extinction‐prone species were mostly carnivorous. Introduced species produced larger clutches, while extinction‐prone species had smaller body sizes. In the Anthropocene, the native ranges of introduced and extinction‐prone species are in the same human‐impacted regions where trait continua, having opposite effects, determine whether species ranges expand or contract in the continuing face of global change.

Aim: The importance of anthropogenic activities in reshaping biodiversity is increasing fast. Interactive effects of climate change, biological invasions and species replacement are poorly understood, particularly at large scales and in megadiverse biomes. We aimed to assess the effects of climate change as a driver of spatio-temporal biodiversity patterns and homogenization of woody plants at multiple scales, in a hyperdiverse species assemblage. Location: The Atlantic Forest, Brazil. Time period: Present, future projections. Major taxa studied: Woody plants. Methods: We used ecological niche modeling to estimate geographic distributions of 2,255 plant species under present and future climates. Range-diversity plots based on species presence-absence matrices and null models were used to explore changes in alpha and beta diversity, range size and covariance in species composition across ecoregions, climatic scenarios and within protected areas. We also partitioned dissimilarity into turnover and nestedness components and explored expansions and retractions of species' ranges to infer invasive potential and implications for conservation in the future. Results: Despite a general increase in local richness, beta diversity decreased with time. Similarity among sites was accentuated in severe climate change scenarios enhancing biotic homogenization at large scales. Changes were not constant or homogeneous across ecoregions and at smaller scales, but a consistent pattern was the reduction of beta diversity accompanied by increments in the mean range size of widespread species. Likewise, subsets of assemblages within protected areas presented higher similarity, increased mean range size and invariability of richness through time, indicating potential compositional turnover promoted by the expansion of widespread species. Main conclusions: Expansion of current generalist and disturbance-tolerant species rather than extinction or retraction of local endemics may lead to woody plant homogenization in the tropics. The woody plant assemblage in the Atlantic Forest is prone to a structural reorganization due to climate change, threatening conservation of biodiversity and potentially leading to severe large-scale biotic homogenization in the near future.

Understanding coexistence in high biodiversity ecosystems requires knowledge of how rare and common species share the multidimensional environmental space. Climatic and edaphic conditions can provide a plethora of habitats, supporting different compositional and structural communities where species can adapt and differentiate. We used a large data set consisting of 580 tropical tree species sampled in 163 25 × 25 m quadrats along an altitudinal gradient covering an area of 160 km² of tropical rain forest in Jianfengling reserve (Hainan Island, China). For each plot, the data include tree species and abundance, altitude and six soil properties from which a two dimensional environmental space was constructed. With this extensive data set, we tested the hypothesis that different combination of environmental factors can generate multiple hotspots on three axes of diversity: species richness, Shannon‐equivalent species richness and habitat preference, a measure of evenness in the distribution of individuals across an environmental gradient. We found that humid and cool areas with more nitrogen availability were occupied by richer and more diverse communities of wide range species. Rare (in terms of number of individuals) and range‐restricted species instead, tended to prefer minor habitats, generally warmer with high potassium, calcium, magnesium and, in particular, phosphorous. As a result, wide and range‐restricted species were segregated across the environmental space. Synthesis. Our findings indicate rare species tend to occur more frequently where common species are less abundant. A clear pattern of species richness and diversity was driven by a combination of several environmental factors (soil properties and climate). The complexity of the environment not only explains the different species distribution along each habitat, but also determines the relative abundance of each species in the entire community. Although some habitats have low species richness and diversity, they are highly preferred by rare species; therefore, biodiversity conservation efforts should consider protecting these fragile ecosystems.

ContextThere have been many studies using species distribution models (SDMs) to predict shifts in species distributions due to environmental changes, but few consider effects of data quantity, data quality, or species response shape. Modeling studies using field-sampled data may be impaired to an unknown degree by lack of knowledge on species’ true relationships with environmental changes.ObjectivesUsing simulations with known relationships we assess model predictions, and investigate which models are more sensitive to sample size, detection limit, or species response shape issues when different SDMs are used for predicting species distribution shifts under environmental changes.MethodsWe simulated 16 species response relationships to ecological gradients differing in response shape (skewness and kurtosis) using a generalized β-function. Populations were randomly sampled at different sample sizes and detection limits. Linear discriminant analysis (LDA), multiple logistic regression (MLR), generalized additive models (GAM), boosted regression trees (BRT), random forests (RF), artificial neural networks (ANN), and maximum entropy models (MaxEnt) were developed on sampled datasets and compared for predicting species occurrence. We used these SDMs to predict distribution patterns for virtual species with different response shapes across a real landscape of varying heterogeneity in environmental conditions, and compared them with the probability of occurrence generated by the β-function.ResultsGAM and BRT were sensitive to both sample size and detection limit changes; RF was more affected by detection limit; ANN and MaxEnt were more affected by sample size; LDA and MLR were sensitive to species response shape changes.ConclusionsOverall, if little is known about species response to environmental changes, ANN is recommended especially for large sample size. If a focal species is likely to occur only in a narrow range of environmental conditions, GAM and BRT are preferred for large good-quality datasets, and GAM tends to perform slightly better under varied data conditions; RF is recommended for limited amounts of good-quality data. If a focal species is likely to be present in a wide range of environmental conditions, MaxEnt is preferred but caution should be taken for small sample size. If the goal is to identify potential distributions of invasive or endangered species but data quantity and quality are very limited, LDA and MLR are recommended as they generally provide reasonable model sensitivity.

Introduced mammals can cause extinction of native species due to replacement competition, disease, predation or hybridization. We studied the colonization of Piedmont (NW-Italy) by American grey squirrel ( Sciurus carolinensis ) and its effect on the native red squirrel ( Sciurus vulgaris ). Presence/absence data (2 × 2 km 2 ), of both species were (re)constructed using questionnaires, literature, existing databases, unpublished information, and direct monitoring with hair-tubes. In 1970 red squirrels were still widespread and greys were restricted to forests near the introduction site. By 1990, grey squirrels had increased their range to 220 km 2 , which coincided with the disappearance of native squirrels from 33 squares inside this range. The invasive species continued its spread occupying an area of 2,016 km 2 in 2010; within this area red squirrels went extinct in 88 squares. Overall, from 1970 to 2010 red squirrel went extinct in 62 % of 2 × 2 km 2 (ca. 1,689 km 2 ), and were replaced by grey squirrels. The spread of the alien species was slow in the first 20 years, but doubled in the successive two decades. Nevertheless spread was slower than in Ireland and England. Grey squirrel adapt to climate and habitats in both North and South Europe, causing extinction of the native red squirrel. A EU LIFE co-funded project with the aim to control the grey squirrel in North Italy and recent trade-restrictions and trade-ban are a first step in reducing the risk of grey squirrels invading other countries, but their effectiveness will have to be evaluated.