How do various maize crop models vary in their responses to climate change factors?

Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO₂], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly ?0.5 Mg ha^?1 per °C. Doubling [CO₂] from 360 to 720 μmol mol^?1 increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO₂] among models. Model responses to temperature and [CO₂] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.     

From plains to inselbergs: species in special habitats as indicators for climate change?

Aim This study proposes a process to select plant species that would provide suitable candidates for monitoring climate change impacts in areas where complete biological inventories are lacking. Location Inselberg floras of nine inselberg landscapes (i.e. isolated mountains) in the arid Desert and Nama Karoo biome in Namibia were analysed to develop a selection process. Methods Data from detailed field surveys were summarized to determine species only occurring on inselberg habitats (i.e. inselberg specialists). Detrended correspondence analysis and a step‐by‐step selection process based on species distribution patterns were used to determine species occurring on inselbergs beyond their zonal distribution ranges. Results The systematic selection process initially identified 88 plant species. Based on field observations and published sources eliminating species (1) with a wide distribution elsewhere, (2) distribution influenced by local effects and (3) for which their status of knowledge of distribution was clearly inadequate, this list was further reduced to 25 species. This included southern species occurring on inselbergs likely beyond their zonal distribution, such as Adenolobus garipensis, Aloe dichotoma and Euphorbia gummifera, as well as savanna and escarpment species at their western zonal distribution edge (e.g. Cordia sinensis, Commiphora glaucescens and Moringa ovalifolia). Main conclusions The step‐by‐step selection process proposed in this study to assist with the selection of indicators for climate change provides an objective tool in areas where biodiversity coverage is not adequate and little is known about physiology, growth and reproductive patterns of individual species. As such it introduces a method for preliminary screening of species, but will require further input based on field observations and expert knowledge.     

Phenological asynchrony between herbivorous insects and their hosts: signal of climate change or pre-existing adaptive strategy?

Climate change alters phenological relations between interacting species. We might expect the historical baseline, or starting-point, for such effects to be precise synchrony between the season at which a consumer most requires food and the time when its resources are most available. We synthesize evidence that synchrony was not the historical condition in two insect–plant interactions involving Edith''s checkerspot butterfly (Euphydryas editha), the winter moth (Operophtera brumata) and their host plants. Initial observations of phenological mismatch in both systems were made prior to the onset of anthropogenically driven climate change. Neither species can detect the phenology of its host plants with precision. In both species, evolution of life history has involved compromise between maximizing fecundity and minimizing mortality, with the outcome being superficially maladaptive strategies in which many, or even most, individuals die of starvation through poor synchrony with their host plants. Where phenological asynchrony or mismatch with resources forms the starting point for effects of anthropogenic global warming, consumers are particularly vulnerable to impacts that exacerbate the mismatch. This vulnerability likely contributed to extinction of a well-studied metapopulation of Edith''s checkerspot, and to the skewed geographical pattern of population extinctions underlying a northward and upward range shift in this species.     

Nonlinear flowering responses to climate: are species approaching their limits of phenological change?

Many alpine and subalpine plant species exhibit phenological advancements in association with earlier snowmelt. While the phenology of some plant species does not advance beyond a threshold snowmelt date, the prevalence of such threshold phenological responses within plant communities is largely unknown. We therefore examined the shape of flowering phenology responses (linear versus nonlinear) to climate using two long-term datasets from plant communities in snow-dominated environments: Gothic, CO, USA (1974–2011) and Zackenberg, Greenland (1996–2011). For a total of 64 species, we determined whether a linear or nonlinear regression model best explained interannual variation in flowering phenology in response to increasing temperatures and advancing snowmelt dates. The most common nonlinear trend was for species to flower earlier as snowmelt advanced, with either no change or a slower rate of change when snowmelt was early (average 20% of cases). By contrast, some species advanced their flowering at a faster rate over the warmest temperatures relative to cooler temperatures (average 5% of cases). Thus, some species seem to be approaching their limits of phenological change in response to snowmelt but not temperature. Such phenological thresholds could either be a result of minimum springtime photoperiod cues for flowering or a slower rate of adaptive change in flowering time relative to changing climatic conditions.     

Biodiversity monitoring: some proposals to adequately study species’ responses to climate change

Climate change affects all levels of biology and is a major threat for biodiversity. Hence, it is fundamental to run biodiversity monitoring programs to understand the effects of climate change on the biota and to be able to adjust management and conservation accordingly. So far, however, very few existing monitoring programs allow for the detection of climate change effects, as shown by a survey undertaken by the European project EuMon. Despite this shortcoming, several methods exist which allow to make inferences from existing data by integrating data across different monitoring programs: correlative analyses, meta-analyses and models. In addition, experiments are thought to be useful tools to understand the effects of climate change on plants and animals. Here, we evaluate the utility of these four main approaches. All these methods allow to evaluate long term effects of climate change and make predictions of species’ future development, but they are arguable. We list and compare their benefits and inconveniences, which can lead to uncertainties in the extrapolation of species responses to global climate change. Individual characteristics and population parameters have to be more frequently monitored. The potential evolution of a species should be also modelled, to extrapolate results across spatial and temporal scales as well as to analyse the combined effects of different climatic and biotic factors, including intra but also interspecific relationships. We conclude that a combination of methodologies would be the most promising tool for the assessment of biological responses to climate change, and we provide some thoughts about how to do so. Particularly, we encourage long-term studies along natural gradients (altitudinal or latitudinal) on the same species/habitats to be able to extrapolate to large geographic scales, and to have more complete data sets, necessary to understand the mechanisms of responses. Such data may provide a more accurate base for simulations across spatial and temporal scales, especially if they are publicly available in a common database. These recommendations could allow the adaptation of species management and the development of conservation tools to climate change which threatens species.     

Is there evidence for a shift in fish growth and recruitment success linked to climate change?

This study investigated whether a putative shift in climate regime in the North Atlantic in the 1990s coincided with changes in the growth and recruitment of roach Rutilus rutilus in the north-east of England. The relationships between R. rutilus growth and recruitment and the environment were significantly different before and after the putative shift in climate regime. Water temperature, river discharge, growth, recruitment success and the Gulf Stream Index co-varied until the late 1990s, indicating a gradual progression between periods of warm-and-dry and cold-and-wet summers. Since the late 1990s, there has been an increased prevalence of warm-and-wet summers, and recruitment success has oscillated between extremes on an almost annual basis. The north wall (northern boundary) of the Gulf Stream has been undergoing a displacement south since the late 1990s, and the speed and amplitude of the change appears to support the hypothesis that there was a regime shift in the climate of the North Atlantic Ocean. It is possible that a continued displacement south of the north wall of the Gulf Stream will lead to further increases in river discharge, reductions in water temperature and reduced fish growth and recruitment success in the long term.     

Will variation among genetic individuals influence species responses to global climate change?

Increased anthropogenic CO₂ emissions in the last two centuries have lead to rising sea surface temperature and falling ocean pH, and it is predicted that current global trends will worsen over the next few decades. There is limited understanding of how genetic variation among individuals will influence the responses of populations and species to these changes. A microcosm system was set up to study the effects of predicted temperature and CO₂ levels on the bryozoan Celleporella hyalina. In this marine species, colonies grow by the addition of male, female and feeding modular individuals (zooids) and can be physically subdivided to produce a clone of genetically identical colonies. We studied colony growth rate (the addition of zooids), reproductive investment (the ratio of sexual to feeding zooids) and sex ratio (male to female zooids) in four genetically distinct clonal lines. There was a significant effect of clone on growth rate, reproductive investment and sex ratio, with clones showing contrasting responses to the various temperature and pH combinations. Overall, decreasing pH and increasing temperature caused reduction of growth, and eventual cessation of growth was often observed at the highest temperature, especially during the latter half of the 15‐day trials. Reproductive investment increased with increasing temperature and decreasing pH, varying more widely with temperature at the lowest pH. The increased production of males, a general stress response of the bryozoan, was seen upon exposure to reduced pH, but was not expressed at the highest temperature tested, presumably due to the frequent cessation of growth. Further to the significant effect of pH on the measured whole‐colony parameters, observation by scanning electron microscopy revealed surface pitting of the calcified exoskeleton in colonies that were exposed to increased acidity. Studying ecologically relevant processes of growth and reproduction, we demonstrate the existence of relevant levels of variation among genetic individuals which may enable future adaptation via non‐mutational natural selection to falling pH and rising temperature.     

Maternal modulation of natal dispersal in a passerine bird: an adaptive strategy to cope with parasitism?

The decision of how far to disperse from the natal territory has profound and long-lasting consequences for young animals, yet the optimal dispersal behavior often depends on environmental factors that are difficult or impossible to assess by inexperienced juveniles. Natural selection thus favors mechanisms that allow the adaptive and flexible adjustment of the offspring's dispersal behavior by their parents via either paternal or maternal effects. Here we show that different dispersal strategies maximize the reproductive success of young great tits (Parus major) originating from a parasite-infested or a parasite-free nest and demonstrate that differential transfer of maternal yolk androgens in response to parasitism can result in a modification of the offspring's dispersal behavior that appears adaptive. It demonstrates that prenatal maternal effects are an important yet so far neglected determinant of natal dispersal and highlights the potential importance of maternal effects in mediating coevolutionary processes in host-parasite systems.     

Linking variability in climate to wetland habitat suitability: is it possible to forecast regional responses from simple climate measures?

Wetlands Ecology and Management - Temporary wetlands have value to both ecological and social systems. Interactions between local climate and the surrounding landscape result in patterns of...     

A trait‐based approach for predicting species responses to environmental change from sparse data: how well might terrestrial mammals track climate change?

Estimating population spread rates across multiple species is vital for projecting biodiversity responses to climate change. A major challenge is to parameterise spread models for many species. We introduce an approach that addresses this challenge, coupling a trait‐based analysis with spatial population modelling to project spread rates for 15 000 virtual mammals with life histories that reflect those seen in the real world. Covariances among life‐history traits are estimated from an extensive terrestrial mammal data set using Bayesian inference. We elucidate the relative roles of different life‐history traits in driving modelled spread rates, demonstrating that any one alone will be a poor predictor. We also estimate that around 30% of mammal species have potential spread rates slower than the global mean velocity of climate change. This novel trait‐space‐demographic modelling approach has broad applicability for tackling many key ecological questions for which we have the models but are hindered by data availability.     

Atypical responses to morphine in mice: a possible relationship to anorexia nervosa?

According to our previously proposed auto-addiction hypothesis of chronic anorexia nervosa, patients become addicted to an initial period of dieting through endogenous opioid mediated mechanisms. Morphine causes hyperactivity and anorexia in the mouse, symptoms of anorexia nervosa but responses opposite to those of most species including rats and normal human subjects. This suggests that the atypical opioid systems in the mouse may resemble those of the chronic anorexia nervosa patient in contrast to those of most species including the normal human. Characterization of this atypical opioid system may be useful in understanding the pathophysiology of anorexia nervosa.     

Plant community responses to 5 years of simulated climate change in meadow and heath ecosystems at a subarctic-alpine site

Climate change was simulated by increasing temperature and nutrient availability in an alpine landscape. We conducted a field experiment of BACI-design (before/after control/impact) running for five seasons in two alpine communities (heath and meadow) with the factors temperature (increase of ca. 1.5–3.0°C) and nutrients (5 g N, 5 g P per m²) in a fully factorial design in northern Swedish Lapland. The response variables were abundances of plant species and functional types. Plant community responses to the experimental perturbations were investigated, and the responses of plant functional types were examined in comparison to responses at the species level. Nutrient addition, exclusively and in combination with enhanced temperature increase, exerted the most pronounced responses at the species-specific and community levels. The main responses to nutrient addition were increases in graminoids and forbs, whereas deciduous shrubs, evergreen shrubs, bryophytes, and lichens decreased. The two plant communities of heath or meadow showed different vegetation responses to the environmental treatments despite the fact that both communities were located on the same subarctic-alpine site. Furthermore, we showed that the abundance of forbs increased in response to the combined treatment of temperature and nutrient addition in the meadow plant community. Within a single-plant functional type, most species responded similarly to the enhanced treatments although there were exceptions, particularly in the moss and lichen functional types. Plant community structure showed BACI responses in that vegetation dominance relationships in the existing plant functional types changed to varying degrees in all plots, including control plots. Betula nana and lichens increased in the temperature-increased enhancements and in control plots in the heath plant community during the treatment period. The increases in control plots were probably a response to the observed warming during the treatment period in the region. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Accounting for soil organic carbon role in land use contribution to climate change in agricultural LCA: which methods? Which impacts?

The International Journal of Life Cycle Assessment - Soil organic carbon (SOC) plays a key role in soil functioning and in greenhouse gas exchange with the atmosphere. Land use and land use changes...     

A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change?

A cline in the frequency of melanic morphs of the two-spot ladybird, Adalia bipunctata, was first surveyed in 1980 along a transect extending inland from the coast in the Netherlands. At that time, the frequency of melanics increased over some 40 km from 10% near the coast to nearly 60% inland. Additional surveys made in 1991 and 1995 demonstrated some progressive change in cline shape. New samples from 1998 and 2004 confirm these dynamics, and show that over a period of about 50 generations for the beetle, the cline had decayed rapidly to yield rather uniform frequencies of melanic morphs at around 20% along the whole transect by 2004. Climate data and evidence for thermal melanism in this species support our contention that these dynamics reflect a dramatic example of a rapid genetic response within populations to climate change and local selection.     

Can we predict ectotherm responses to climate change using thermal performance curves and body temperatures?

Thermal performance curves (TPCs), which quantify how an ectotherm's body temperature (T_b) affects its performance or fitness, are often used in an attempt to predict organismal responses to climate change. Here, we examine the key – but often biologically unreasonable – assumptions underlying this approach; for example, that physiology and thermal regimes are invariant over ontogeny, space and time, and also that TPCs are independent of previously experienced T_b. We show how a critical consideration of these assumptions can lead to biologically useful hypotheses and experimental designs. For example, rather than assuming that TPCs are fixed during ontogeny, one can measure TPCs for each major life stage and incorporate these into stage‐specific ecological models to reveal the life stage most likely to be vulnerable to climate change. Our overall goal is to explicitly examine the assumptions underlying the integration of TPCs with T_b, to develop a framework within which empiricists can place their work within these limitations, and to facilitate the application of thermal physiology to understanding the biological implications of climate change.     

Altitudinal patterns of tick and host abundance: a potential role for climate change in regulating tick-borne diseases?

The impact of climate change on vector-borne infectious diseases is currently controversial. In Europe the primary arthropod vectors of zoonotic diseases are ticks, which transmit Borrelia burgdorferi sensu lato (the agent of Lyme disease), tick-borne encephalitis virus and louping ill virus between humans, livestock and wildlife. Ixodes ricinus ticks and reported tick-borne disease cases are currently increasing in the UK. Theories for this include climate change and increasing host abundance. This study aimed to test how I. ricinus tick abundance might be influenced by climate change in Scotland by using altitudinal gradients as a proxy, while also taking into account the effects of hosts, vegetation and weather effects. It was predicted that tick abundance would be higher at lower altitudes (i.e. warmer climates) and increase with host abundance. Surveys were conducted on nine hills in Scotland, all of open moorland habitat. Tick abundance was positively associated with deer abundance, but even after taking this into account, there was a strong negative association of ticks with altitude. This was probably a real climate effect, with temperature (and humidity, i.e. saturation deficit) most likely playing an important role. It could be inferred that ticks may become more abundant at higher altitudes in response to climate warming. This has potential implications for pathogen prevalence such as louping ill virus if tick numbers increase at elevations where competent transmission hosts (red grouse Lagopus lagopus scoticus and mountain hares Lepus timidus) occur in higher numbers.     

Bird community responses to habitat fragmentation: how consistent are they across landscapes?

Aim The woodland ecosystems of south‐eastern Australia have been extensively disturbed by agriculture and urbanization. Herein, the occurrence of birds in woodland remnants in three distinct landscapes was analysed to examine the effects of different types of landscape matrices on species richness vs. area and species richness vs. isolation relationships and individual species responses to woodland fragmentation. Location The study system comprised three distinct woodland landscapes of the northern Australian Capital Territory and bordering areas of New South Wales. These landscapes (termed agricultural, peri‐urban and urban) are located within 50 km of each other, have remnant fragments of similar age, size, isolation, woodland cover, elevation and climates. The major distinguishing feature of the three landscapes was the properties of the habitats surrounding the numerous woodland remnants. Methods Bird surveys, using an area‐search methodology, were conducted in 1999 and 2000 in 127 remnants in the three landscapes to determine bird species presence/absence. Each remnant was characterized by measures of remnant area, isolation and habitat complexity. To characterize differences between each landscape, we conducted an analysis of the amount of tree cover and human disturbance in each landscape using SPOT imagery and aerial photographs. Linear regressions of woodland‐dependent species richness vs. remnant area and remnant isolation for the three different landscapes were calculated to see if there were any apparent differences. Binomial logistic regressions were used to determine the relationships between the occurrence of each species and the size and isolation of woodland habitat, in each landscape. Results All the landscapes displayed a significant (P < 0.01) species vs. area relationship, but the slope of the urban relationship was significantly greater than those of the other landscapes. In contrast, only the agricultural landscape displayed a significant (P < 0.01) species richness vs. isolation relationship. When individual species were investigated, we found species that were: (1) apparently insensitive to reduction in remnant area and increase in isolation across all landscapes, (2) absent in small remnants in all landscapes, (3) absent in small remnants in all landscapes and also absent in isolated remnants in the agricultural landscape, (4) absent in isolated remnants in the agricultural landscape, and (5) absent in small remnants in the urban landscape. Threshold values (50% probability of occurrence) for area and isolation for individual species were highly variable across the three landscapes. Main conclusions These results indicate that woodland bird communities have a varying response to habitat fragmentation in different landscapes. Whilst we cannot be sure how representative our chosen landscapes are of other similarly composed landscapes, these results suggest that the type of landscape matrix may have a considerable influence on how bird species are affected by woodland fragmentation in the region. For instance, the properties of a matrix may influence both the resources available in the landscape as a whole for different bird species, and the connectivity (dispersal of birds), between woodland remnants. We encourage further research that examines these hypotheses and argue that the management of the matrix should be included in conservation strategies for fragmented landscapes.     

Responses of benthic–pelagic coupling to climate change in a temperate estuary

This article reports the first demonstration of the impact of climate change on benthic–pelagic coupling and the biogeochemical cycles of a coastal marine system. Over the last 30 years Narragansett Bay, a 328-km² temperate estuary on the east coast of the United States, has undergone a variety of ecological changes. Building on a robust data set that spans three decades, we present a link between warming (+1.7°C in annual mean water temperature) in the bay and a marked decrease in sediment oxygen consumption, in the fluxes of ammonium and phosphate from sediments to the overlying water, and in sediment denitrification. We attribute this reduction in biogeochemical exchange to a dramatic drop in the standing crop of water-column chlorophyll as the system has shifted from one characterized by a dominant winter–spring bloom to one supported by more ephemeral and less intense summer–autumn blooms. The recent climate-induced oligotrophication of the bay will be further exacerbated by forthcoming nitrogen reductions due to tertiary sewage treatment. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark