Contrasting response of native and alien plant species richness to environmental energy and human impact along alpine elevation gradients

Aim We tested whether the species–energy and species–human relationships vary between native and both naturalized and casual alien species richness when other environmental variables had been taken into account. Location Trento Province, a region (c. 6200 km²) on the southern border of the European Alps (Italy), subdivided into 156 contiguous (c. 37.5 km²) cells and ranging in elevation from 66 to 3769 m. Methods Data were separated into three subsets, representing richness of natives, naturalized aliens and casual aliens and separately related to temperature, human population and various environmental correlates of plant species diversity. We applied ordinary least squares and simultaneous autoregressive regressions to identify potential contrasting responses of the three plant status subsets and hierarchical partitioning to evaluate the relative importance of the predictor variables. Results Variation in alien plant species richness along the region was almost entirely explained by temperature and human population density. The relationships were positive but strongly curvilinear. Native species richness was less strongly related to either factor but was positively related to the presence of calcareous bedrock. Native species richness had a decelerating positive relationship with temperature (R²= 55%), whereas naturalized and casual aliens had a positive accelerating relationship explaining 86% and 62% of the variation in richness, respectively. Native species richness had a positive decelerating relationship with population density (R²= 42%), whilst both alien subsets had a positive accelerating relationship. Main conclusions Alien species richness was higher in areas with the most rich and diverse assemblages of native species. Areas at high altitudes are not especially prone to alien invasion due to energy constraints, low propagule pressure and disturbance, even considering a potential increased in temperature. Thus, if we consider future environmental change, we should expect a stronger response of aliens than natives in the currently warm, urbanized, low‐altitude areas than in cold, high‐altitude areas where human population density is low.     

Non‐native fishes and climate change: predicting species responses to warming temperatures in a temperate region

1. Temperate regions with fish communities dominated by cold‐water species (physiological optima <20 °C) are vulnerable to the effects of warming temperatures caused by climate change, including displacement by non‐native cool‐water (physiological optima 20–28 °C) and warm‐water fishes (physiological optima >28 °C) that are able to establish and invade as the thermal constraints on the expression of their life history traits diminish. 2. England and Wales is a temperate region into which at least 38 freshwater fishes have been introduced, although 14 of these are no longer present. Of the remaining 24 species, some have persisted but failed to establish, some have established populations without becoming invasive and some have become invasive. The aim of the study was to predict the responses of these 24 non‐native fishes to the warming temperatures of England and Wales predicted under climate change in 2050. 3. The predictive use of climate‐matching models and an air and water temperature regression model suggested that there are six non‐native fishes currently persistent but not established in England and Wales whose establishment and subsequent invasion would benefit substantially from the predicted warming temperatures. These included the common carp Cyprinus carpio and European catfish Silurus glanis, fishes that also exert a relatively high propagule pressure through stocking to support angling and whose spatial distribution is currently increasing significantly, including in open systems. 4. The potential ecological impacts of the combined effects of warming temperatures, current spatial distribution and propagule pressure on the establishment and invasion of C. carpio and S. glanis were assessed. The ecological consequences of C. carpio invasion were assessed as potentially severe in England and Wales, with impacts likely to relate to habitat destruction, macrophyte loss and increased water turbidity. However, evidence of ecological impacts of S. glanis elsewhere in their introduced range was less clear and so their potential impacts in England and Wales remain uncertain.     

Alien and native plants show contrasting responses to climate and land use in Europe

Aim We tested whether the distribution and cover of alien plant species in Europe was related to human disturbance and microclimate. Location Surveys were conducted at 13 sites across Europe, each containing a pair of landscapes with different land‐use intensities. Methods Sampling locations were chosen based on land use and microclimate at two scales: land use was characterized at the patch and landscape scale; climate was expressed as regional and local temperature. The slope of each sample location was derived from a digital elevation model. Cover of plant species was measured using point counts and analysed using mixed effect models. Species were classified as native, archaeophytes and neophytes (pre‐ versus post‐ad 1500 immigrants). Due to the zero inflation observed in the alien groups, their cover was analysed conditional on their presence. Results Anthropogenic disturbance was a significant explanatory variable, increasing the presence and cover of alien species and decreasing the cover of native species. Alien presence was increased in sites under agricultural management, while their cover responded to land use at both local and landscape scales (and to their interaction), such that only natural habitats in semi‐natural landscapes had low alien cover. Microclimate was important for neophytes, with presence concentrated around mesic conditions. Slope was relevant for archaeophytes and native species, suppressing the former group and promoting the latter one. Main conclusions We found that, at the European scale, the distribution of alien plants is related to anthropogenic disturbance more than to microclimatic differences. The presence of neophytes, however, was influenced by climate at local and regional scales, with the highest incidence under mesic conditions. The different patterns observed for the presence and cover of alien species suggest different mechanisms acting during their establishment and spread. They also suggest that to counteract the expansion of alien species natural habitats may need to be maintained at landscape scales.     

Phenology in a warming world: differences between native and non‐native plant species

Phenology is a harbinger of climate change, with many species advancing flowering in response to rising temperatures. However, there is tremendous variation among species in phenological response to warming, and any phenological differences between native and non‐native species may influence invasion outcomes under global warming. We simulated global warming in the field and found that non‐native species flowered earlier and were more phenologically plastic to temperature than natives, which did not accelerate flowering in response to warming. Non‐native species' flowering also became more synchronous with other community members under warming. Earlier flowering was associated with greater geographic spread of non‐native species, implicating phenology as a potential trait associated with the successful establishment of non‐native species across large geographic regions. Such phenological differences in both timing and plasticity between native and non‐natives are hypothesised to promote invasion success and population persistence, potentially benefiting non‐native over native species under climate change.     

Forest bees are replaced in agricultural and urban landscapes by native species with different phenologies and life‐history traits

Anthropogenic landscapes are associated with biodiversity loss and large shifts in species composition and traits. These changes predict the identities of winners and losers of future global change, and also reveal which environmental variables drive a taxon's response to land use change. We explored how the biodiversity of native bee species changes across forested, agricultural, and urban landscapes. We collected bee community data from 36 sites across a 75,000 km² region, and analyzed bee abundance, species richness, composition, and life‐history traits. Season‐long bee abundance and richness were not detectably different between natural and anthropogenic landscapes, but community phenologies differed strongly, with an early spring peak followed by decline in forests, and a more extended summer season in agricultural and urban habitats. Bee community composition differed significantly between all three land use types, as did phylogenetic composition. Anthropogenic land use had negative effects on the persistence of several life‐history strategies, including early spring flight season and brood parasitism, which may indicate adaptation to conditions in forest habitat. Overall, anthropogenic communities are not diminished subsets of contemporary natural communities. Rather, forest species do not persist in anthropogenic habitats, but are replaced by different native species and phylogenetic lineages preadapted to open habitats. Characterizing compositional and functional differences is crucial for understanding land use as a global change driver across large regional scales.     

Environmental gradients shift the direction of the relationship between native and alien plant species richness

Aim

To assess how environmental, biotic and anthropogenic factors shape native–alien plant species richness relationships across a heterogeneous landscape.

Location

Banks Peninsula, New Zealand.

Methods

We integrated a comprehensive floristic survey of over 1200 systematically located 6 × 6 m plots, with corresponding climate, environmental and anthropogenic data. General linear models examined variation in native and alien plant species richness across the entire landscape, between native‐ and alien‐dominated plots, and within separate elevational bands.

Results

Across all plots, there was a significant negative correlation between native and alien species richness, but this relationship differed within subsets of the data: the correlation was positive in alien‐dominated plots but negative in native‐dominated plots. Within separate elevational bands, native and alien species richness were positively correlated at lower elevations, but negatively correlated at higher elevations. Alien species richness tended to be high across the elevation gradient but peaked in warmer, mid‐ to low‐elevation sites, while native species richness increased linearly with elevation. The negative relationship between native and alien species richness in native‐dominated communities reflected a land‐use gradient with low native and high alien richness in more heavily modified native‐dominated vegetation. In contrast, native and alien richness were positively correlated in very heavily modified alien‐dominated plots, most likely due to covariation along a gradient of management intensity.

Main conclusions

Both positive and negative native–alien richness relationships can occur across the same landscape, depending on the plant community and the underlying human and environmental gradients examined. Human habitat modification, which is often confounded with environmental variation, can result in high alien and low native species richness in areas still dominated by native species. In the most heavily human modified areas, dominated by alien species, both native and alien species may be responding to similar underlying gradients.

     

Susceptibility of European freshwater fish to climate change: Species profiling based on life‐history and environmental characteristics

Climate change is expected to strongly affect freshwater fish communities. Combined with other anthropogenic drivers, the impacts may alter species spatio‐temporal distributions and contribute to population declines and local extinctions. To provide timely management and conservation of fishes, it is relevant to identify species that will be most impacted by climate change and those that will be resilient. Species traits are considered a promising source of information on characteristics that influence resilience to various environmental conditions and impacts. To this end, we collated life‐history traits and climatic niches of 443 European freshwater fish species and compared those identified as susceptible to climate change to those that are considered to be resilient. Significant differences were observed between the two groups in their distribution, life history, and climatic niche, with climate‐change‐susceptible species being distributed within the Mediterranean region, and being characterized by greater threat levels, lesser commercial relevance, lower vulnerability to fishing, smaller body and range size, and warmer thermal envelopes. Based on our results, we establish a list of species of highest priority for further research and monitoring regarding climate‐change susceptibility within Europe. The presented approach represents a promising tool to efficiently assess large groups of species regarding their susceptibility to climate change and other threats, and to identify research and management priorities.     

An empirical test of the relative and combined effects of land‐cover and climate change on local colonization and extinction

Land‐cover and climate change are two main drivers of changes in species ranges. Yet, the majority of studies investigating the impacts of global change on biodiversity focus on one global change driver and usually use simulations to project biodiversity responses to future conditions. We conduct an empirical test of the relative and combined effects of land‐cover and climate change on species occurrence changes. Specifically, we examine whether observed local colonization and extinctions of North American birds between 1981–1985 and 2001–2005 are correlated with land‐cover and climate change and whether bird life history and ecological traits explain interspecific variation in observed occurrence changes. We fit logistic regression models to test the impact of physical land‐cover change, changes in net primary productivity, winter precipitation, mean summer temperature, and mean winter temperature on the probability of Ontario breeding bird local colonization and extinction. Models with climate change, land‐cover change, and the combination of these two drivers were the top ranked models of local colonization for 30%, 27%, and 29% of species, respectively. Conversely, models with climate change, land‐cover change, and the combination of these two drivers were the top ranked models of local extinction for 61%, 7%, and 9% of species, respectively. The quantitative impacts of land‐cover and climate change variables also vary among bird species. We then fit linear regression models to test whether the variation in regional colonization and extinction rate could be explained by mean body mass, migratory strategy, and habitat preference of birds. Overall, species traits were weakly correlated with heterogeneity in species occurrence changes. We provide empirical evidence showing that land‐cover change, climate change, and the combination of multiple global change drivers can differentially explain observed species local colonization and extinction.     

Amazon's vulnerability to climate change heightened by deforestation and man‐made dispersal barriers

Species migrations in response to climate change have already been observed in many taxonomic groups worldwide. However, it remains uncertain if species will be able to keep pace with future climate change. Keeping pace will be especially challenging for tropical lowland rainforests due to their high velocities of climate change combined with high rates of deforestation, which may eliminate potential climate analogs and/or increase the effective distances between analogs by blocking species movements. Here, we calculate the distances between current and future climate analogs under various climate change and deforestation scenarios. Under even the most sanguine of climate change models (IPSL_CM4, A1b emissions scenario), we find that the median distance between areas in the Amazon rainforest and their closest future (2050) climate analog as predicted based on just temperature changes alone is nearly 300 km. If we include precipitation, the median distance increases by over 50% to >475 km. Since deforestation is generally concentrated in the hottest and driest portions of the Amazon, we predict that the habitat loss will have little direct impact on distances between climate analogs. If, however, deforested areas also act as a barrier to species movements, nearly 30% or 55% of the Amazon will effectively have no climate analogs anywhere in tropical South America under projections of reduced or Business‐As‐Usual deforestation, respectively. These ‘disappearing climates’ will be concentrated primarily in the southeastern Amazon. Consequently, we predict that several Amazonian ecoregions will have no areas with future climate analogs, greatly increasing the vulnerability of any populations or species specialized on these conditions. These results highlight the importance of including multiple climatic factors and human land‐use in predicting the effects of climate change, as well as the daunting challenges that Amazonian diversity faces in the near future.     

A socio‐ecological model for predicting impacts of land‐use and climate change on regional plant diversity in the Austrian Alps

Climate and land‐use change jointly affect the future of biodiversity. Yet, biodiversity scenarios have so far concentrated on climatic effects because forecasts of land use are rarely available at appropriate spatial and thematic scales. Agent‐based models (ABMs) represent a potentially powerful but little explored tool for establishing thematically and spatially fine‐grained land‐use scenarios. Here, we use an ABM parameterized for 1,329 agents, mostly farmers, in a Central European model region, and simulate the changes to land‐use patterns resulting from their response to three scenarios of changing socio‐economic conditions and three scenarios of climate change until the mid of the century. Subsequently, we use species distribution models to, first, analyse relationships between the realized niches of 832 plant species and climatic gradients or land‐use types, respectively, and, second, to project consequent changes in potential regional ranges of these species as triggered by changes in both the altered land‐use patterns and the changing climate. We find that both drivers determine the realized niches of the studied plants, with land use having a stronger effect than any single climatic variable in the model. Nevertheless, the plants' future distributions appear much more responsive to climate than to land‐use changes because alternative future socio‐economic backgrounds have only modest impact on land‐use decisions in the model region. However, relative effects of climate and land‐use changes on biodiversity may differ drastically in other regions, especially where landscapes are still dominated by natural or semi‐natural habitat. We conclude that agent‐based modelling of land use is able to provide scenarios at scales relevant to individual species distribution and suggest that coupling ABMs with models of species' range change should be intensified to provide more realistic biodiversity forecasts.     

Upslope Range Shifts of Andean Dung Beetles in Response to Deforestation: Compounding and Confounding Effects of Microclimatic Change

Warmer, and sometimes drier, conditions associated with global climate change are driving many species to shift poleward and/or upslope. I hypothesized that microclimatic changes related to deforestation cause similar shifts for forest species persisting within degraded landscapes. This appears to be the first study to examine this novel hypothesis. I examined elevational distributions of dung beetle communities along parallel intact and disturbed elevational gradients from 290 to 3450 m asl in the Andes of southeastern Peru. Deforested sites were consistently warmer and drier than forested sites. To maintain the same ambient temperature as in forest, species in a deforested landscape would need to shift on average 489±59 m upslope. Dung beetle species showed a mean upslope range shift of 132±64 m (maximum=743 m) in the deforested landscape. Eight species occurred farther upslope in the degraded landscape, while none shifted downslope. In addition to upper range limit expansions, six species shifting upslope also showed range contractions or population declines at their lower range boundary. High elevation and disturbance‐tolerant species did not show range shifts. These findings suggest that land‐use change may both confound and compound the influence of global climate change on biodiversity. Synergies between habitat degradation and climate change could more than double previous range shift projections for this century, leading to unexpectedly rapid changes in biodiversity, especially for sensitive organisms such as tropical insects. On the other hand, range shifts caused by habitat degradation may be mistakenly attributed to global climate change. Abstract in Spanish is available in the online version of this article.     

Human land use is comparable to climate as a driver of global plant occurrence and abundance across life forms

Aim

Historically, climate has been a dominant driver of global vegetation patterns. Recently, ecological understanding has been updated to acknowledge the influence of human land use (the dominant driver of biodiversity change) in shaping global vegetation patterns. We test whether Raunkiær's life form, a plant classification system designed to reflect climatic drivers, affects how plants respond to both land use and climate.

Location

Forty-one countries across six continents.

Time period

1990 to 2013.

Major taxa studied

Terrestrial plants.

Methods

Combining data from the biodiversity and land use database PREDICTS, and plant trait databases TRY and BIEN, we use generalized linear mixed models with weighted effects coding to test whether Raunkiær's life form affects plant response to land use and climate in over 4800 species at over 300 sites globally.

Results

We provide evidence that human land use is comparable to climate in influencing life form occurrence and that land use produces divergent outcomes across life forms.

Main conclusions

Combined with climatic suitability, land use acts as a filter contracting the realized niche of trees and expanding the realized niche of disturbance-tolerant species. Our results highlight the fundamental role of human activity in shaping species' distribution.     

Crop‐based biofuels and associated environmental concerns

Current Life Cycle Analysis (LCA) models indicate that crop‐based biofuels generate greenhouse gas savings, compared with fossil fuels. We argue that they do so only because they ignore the emissions of CO₂ from vehicles burning the biofuels without determining if the biomass is “additional,” and because they underestimate the ultimate emissions of N₂O from nitrogen fertiliser use. Taking proper account of these factors would result in very different findings. It would be far better to derive biofuels from biomass, from waste feedstocks or high‐yielding bioenergy crops with low nitrogen demand, grown on currently unproductive land.     

Relative importance of long‐term changes in climate and land‐use on the phenology and abundance of legume crop specialist and generalist aphids

Abstract Insect populations are prone to respond to global changes through shifts in phenology, distribution and abundance. However, global changes cover several factors such as climate and land-use, the relative importance of these being largely unknown. Here, we aim at disentangling the effects of climate, land-use, and geographical drivers on aphid abundance and phenology in France, at a regional scale and over the last 40 years. We used aerial data obtained from suction traps between 1978 and 2015 on five aphid species varying in their degree of specialization to legumes, along with climate, legume crop area and geographical data. Effects of environmental and geographical variables on aphid annual abundance and spring migration dates were analyzed using generalized linear mixed models. We found that within the last four decades, aphids have advanced their spring migration by a month, mostly due to the increase in temperature early in the year, and their abundance decreased by half on average, presumably in response to a combination of factors. The influence of legume crop area decreased with the degree of specialization of the aphid species to such crops. The effect of geographical variation was high even when controlling for environmental variables, suggesting that many other spatially structured processes act on aphid population characteristics. Multifactorial analyses helped to partition the effects of different global change drivers. Climate and land-use changes have strong effects on aphid populations, with important implications for future agriculture. Additionally, trait-based response variation could have major consequences at the community scale.     

Projecting impacts of global climate and land‐use scenarios on plant biodiversity using compositional‐turnover modelling

Nations have committed to ambitious conservation targets in response to accelerating rates of global biodiversity loss. Anticipating future impacts is essential to inform policy decisions for achieving these targets, but predictions need to be of sufficiently high spatial resolution to forecast the local effects of global change. As part of the intercomparison of biodiversity and ecosystem services models of the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services, we present a fine‐resolution assessment of trends in the persistence of global plant biodiversity. We coupled generalized dissimilarity models, fitted to >52 million records of >254 thousand plant species, with the species–area relationship, to estimate the effect of land‐use and climate change on global biodiversity persistence. We estimated that the number of plant species committed to extinction over the long term has increased by 60% globally between 1900 and 2015 (from ~10,000 to ~16,000). This number is projected to decrease slightly by 2050 under the most optimistic scenario of land‐use change and to substantially increase (to ~18,000) under the most pessimistic scenario. This means that, in the absence of climate change, scenarios of sustainable socio‐economic development can potentially bring extinction risk back to pre‐2000 levels. Alarmingly, under all scenarios, the additional impact from climate change might largely surpass that of land‐use change. In this case, the estimated number of species committed to extinction increases by 3.7–4.5 times compared to land‐use‐only projections. African regions (especially central and southern) are expected to suffer some of the highest impacts into the future, while biodiversity decline in Southeast Asia (which has previously been among the highest globally) is projected to slow down. Our results suggest that environmentally sustainable land‐use planning alone might not be sufficient to prevent potentially dramatic biodiversity loss, unless a stabilization of climate to pre‐industrial times is observed.