Potential effects of future climate change on global reptile distributions and diversity

Aim

Until recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale.

Location

Global, excluding Antarctica.

Time period

1995, 2050 and 2080.

Major taxa studied

Reptiles.

Methods

We modelled the distribution of 6296 reptile species and assessed potential global and realm-specific changes in species richness, the change in global species richness across climate space, and species-specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range-restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non-modelled species.

Results

Reptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non-modelled species were significantly stronger affected by projected climatic changes than modelled species.

Main conclusions

With ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re-assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change.     

Potential effects of climate change on plant species in the Faroe Islands

Aim To identify the effect of climate change on selected plant species representative of the main vegetation types in the Faroe Islands. Due to a possible weakening of the North Atlantic Current, it is difficult to predict whether the climate in the Faroe Islands will be warmer or colder as a result of global warming. Therefore, two scenarios are proposed. The first scenario assumes an increase in summer and winter temperature of 2 °C, and the second a decrease in summer and winter temperature of 2 °C. Location Temperate, low alpine and alpine areas in the northern and central part of the Faroe Islands. Methods The responses of 12 different plant species in the Faroe Islands were tested against measured soil temperature, expressed as T_min, T_max, snow cover and growing degree days (GDD), using generalised linear modelling (GLM). Results The tolerance to changes in winter soil temperature (0.3–0.8 °C) was found to be lower than the tolerance to changing summer soil temperature (0.7–1.0 °C), and in both cases lower than the predicted climate changes. Conclusions The species most affected by a warming scenario are those that are found with a limited distribution restricted to the uppermost parts of the mountains, especially Salix herbacea, Racomitrium fasciculare, and Bistorta vivipara. For other species, the effect will mainly be a general upward migration. The most vulnerable species are those with a low tolerance, especially Calluna vulgaris, and also Empetrum nigrum, and Nardus stricta. If the climate in the Faroe Islands should become colder, the most vulnerable species are those at low altitudes. A significantly lower temperature would be expected to produce a serious reduction in the extent of Vaccinium myrtillus and Galium saxatilis. Species like Empetrum nigrum, Nardus stricta, and Calluna vulgaris may also be vulnerable. In any case, these species can be expected to migrate downwards.     

Radiocarbon bomb spike reveals biological effects of Antarctic climate change

The Antarctic has experienced major changes in temperature, wind speed and stratospheric ozone levels during the last 50 years. However, until recently continental Antarctica appeared to be little impacted by climate warming, thus biological changes were predicted to be relatively slow. Detecting the biological effects of Antarctic climate change has been hindered by the paucity of long‐term data sets, particularly for organisms that have been exposed to these changes throughout their lives. We show that radiocarbon signals are preserved along shoots of the dominant Antarctic moss flora and use these to determine accurate growth rates over a period of several decades, allowing us to explore the influence of environmental variables on growth and providing a dramatic demonstration of the effects of climate change. We have generated detailed 50‐year growth records for Ceratodon purpureus and three other Antarctic moss species using the 1960s radiocarbon bomb spike. Our growth rate and stable carbon isotope (δ¹³C) data show that C. purpureus’ growth rates are correlated with key climatic variables, and furthermore that the observed effects of climate variation on growth are mediated through changes in water availability. Our results indicate the timing and balance between warming, high‐wind speeds and elevated UV fluxes may determine the fate of these mosses and the associated communities that form oases of Antarctic biodiversity.     

Upper temperature limits for trout in New Zealand and climate change

The significance of temperature in determining the northernmost limit of trout in New Zealand is discussed, and the river temperature records available suggest that high winter temperatures, rather than high summer temperatures are involved. The predicted climate changes consequent on increased concentrations of atmospheric gases, are used to predict changes in trout distribution. A 1.5 °C increase is likely to result in a contraction of the distribution of brown trout in northern areas, but the effects elsewhere on brown trout would be limited. A 3 °C increase is likely to eliminate both species from borthern latitudes, while heat stress could alter distributions of both species throughout the country. The possibilities of genetic responses to the changes are discussed.     

Making weed biological control predictable,safer and more effective: perspectives from New Zealand

A persistent problem in weed biocontrol is how to reliably predict whether a plant that supports development in laboratory host-specificity testing will be utilized in field conditions, and this is undoubtedly preventing releases of safe and effective agents. Moreover, the potential for unanticipated undesirable indirect effects of weed biocontrol on ecological networks has raised concerns by policy-makers and the general public. The key to minimizing risks of non-target impacts is prioritizing candidate agents that are both host-specific and effective, such that the number of agents required to bring the weed under control is minimized. As a consequence both the weed and its biocontrol agents become minor components of the local biota. Here we review recent attempts in New Zealand to improve the predictive ability of host-range testing, to avoid potentially safe and effective agents being rejected. Research in New Zealand aimed at predicting whether an agent is likely to experience enemy-release (i.e. reduced parasitism and predation) could assist agent prioritization, potentially making biocontrol both environmentally safer and more effective.     

Environmental safety of biological control: Policy and practice in New Zealand

Introduction of biological control agents into New Zealand is regulated under the Hazardous Substances and New Organisms Act 1996 (HSNO). The legislation is strongly focused on the health and safety of people and the environment. HSNO is implemented by the Environmental Risk Management Authority, a quasi-judicial body of 6–8 people appointed by the Minister for the Environment. The process by which biological control applications are received and processed is described. Two case studies of weed biological control agents which have been through the HSNO process, and the scientific issues that arose in considering the environmental safety of these agents are discussed. The case studies presented are the applications to release the gall fly Procecidochares alani (Diptera: Tephritidae) to control mist flower Ageratina riparia, and three biological control agents, Macrolabis pilosellae (Diptera: Cecidomyiidae), Cheilosia urbana, and Cheilosia psilophthalma (Diptera: Syrphidae) for biological control of hawkweeds (Hieracium spp.). Both applications were approved for agent release into the environment.     

Impact of winter climate change on nitrogen biogeochemistry in forest ecosystems: A synthesis from Japanese case studies

Nitrogen (N) is a critical ecological and environmental indicator under changing environments. The impact of winter climate change on N biogeochemical processes in forest ecosystems has gained increasing recognition. Decreasing snowfall has caused a decrease in the heat insulation properties of the snowpack, resulting in an increase in the frequency and magnitude of freezing and thawing cycles in surface soil, where biological processes are most active. Here I synthesize recent research findings from integrated field observations and experiments conducted in northern Japan and compare these results with previous research outcomes from other regions to identify current research gaps and develop the next research agenda to further advance our understanding of this complex problem. Japanese case studies indicated that net ammonium production (ammonification) was mostly dominant in terms of available soil N fertility in cold environments and was sensitive to the increase in soil freezing and thawing cycles because of the decreased snowpack. On the other hands, nitrate dynamics were more stable or conservative than those of ammonium. The soil characteristics (i.e., N pool and microbial activities) were significant explanatory factors of the responses of soil N dynamics and N leakage among different soils to increased freezing–thawing cycles at watershed and national scale. This synthesis indicates that winter climate change had significant impacts on soil N biogeochemistry (such as soil N pool size and microbial N transformation) during the winter and snowmelt season and also during the following growing season. Several research gaps and possible research topics (path dependency and soil microbial community composition) are also presented by synthesizing the current research findings. Further field experiments and observations quantifying the pools and fluxes of inorganic N with modeling analysis under freeze–thaw environments would contribute to increase the understandings of N transformation processes under winter climate change.     

Review article: Race/ethnic studies: The New Zealand case

Terrence Loomis, PACIFIC MIGRANT LABOUR, CLASS AND RACISM IN NEW ZEALAND, Aldershot: Avebury, 1990, xx + 235 pp., £29.50

Richard Mulgan, MAORI, PAKEHA AND DEMOCRACY, Auckland: Oxford University Press, 1989, viii + 159 pp., £12.95

David Pearson, A DREAM DEFERRED: THE ORIGINS OF ETHNIC CONFLICT IN NEW ZEALAND, Wellington: Allen & Unwin, 1990, ix + 301 pp., NZ $29.95

Paul Spoonley, RACISM AND ETHNICITY, Auckland: Oxford University Press, 1988, xiv + 138 pp., NZ $16.95.     

Water temperature and upstream migration of glass eels in New Zealand: implications of climate change

Glass eels migrating upstream in a New Zealand river showed a clear preference for water temperatures between 12 and 20°C, with an optimum of 16.5°C. Water temperatures <12°C and >22°C almost completely inhibited migration, which implies that warmer temperatures associated with global climate change might have a detrimental impact on glass eel recruitment in their current ranges. We established this by trapping glass eels of shortfin, Anguilla australis, and longfin, A. dieffenbachii, eels nightly from September to November. Eels caught in 2001 (50,287) outnumbered those caught in 2002 (19,954); shortfin glass eels dominated catches in both years, comprising 91–93% of the catch. Longfins were larger than shortfins, and size and pigmentation in both species increased as the seasons progressed. Temperatures within the migratory season in 2001 showed ∼14-day intervals between maxima that appeared to be associated with the new and full moons.     

Integrated models of livestock systems for climate change studies. 1. Grazing systems

The potential impact of climate change by the year 2050 on British grazing livestock systems is assessed through the use of simulation models of farming systems. The submodels, consisting of grass production, livestock feeding, livestock thermal balance, the thermal balance of naturally ventilated buildings and a stochastic weather generator, are described. These are integrated to form system models for sheep, beef calves and dairy cows. They are applied to scenarios representing eastern (dry) lowlands, western (wet) lowlands and uplands. The results show that such systems should be able to adapt to the expected climatic changes. There is likely to be a small increase in grass production, possibly allowing an increase in total productivity in some cases.     

Integrated models of livestock systems for climate change studies. 2. Intensive systems

The potential impact of climate change by the year 2050 on intensive livestock systems in Britain is assessed through the use of simulation models of farming systems. The submodels comprise livestock feeding, livestock thermal balance and the thermal balance of controlled environment buildings and a stochastic weather generator. These are integrated to form system models for growing pigs and broiler chickens. They are applied to scenarios typical of SE England, which is the warmest region of the country and represents the worst case. For both species the frequency of severe heat stress is substantially increased, with a consequent risk of mortality. To offset this, it would be necessary to reduce stocking densities considerably, or to invest in improved ventilation or cooling equipment. Other effects on production are likely to be small.     

Potential soil carbon sequestration in a semiarid Mediterranean agroecosystem under climate change: Quantifying management and climate effects

Repeated defoliation and flooding trigger opposite plant morphologies, prostrated and erect ones, respectively; while both induce the consumption of carbohydrate reserves to sustain plant recovery. This study is aimed at evaluating the effects of the combination of defoliation frequency and flooding on plant regrowth and levels of crown reserves of Lotus tenuis Waldst. & Kit., a forage legume of increasing importance in grazing areas prone to soil flooding. Adult plants of L. tenuis were subjected to 40 days of flooding at a water depth of 4 cm in combination with increasing defoliation frequencies by clipping shoot mass above water level. The following plant responses were assessed: tissue porosity, plant height, biomass of the different organs, and utilization of water-soluble carbohydrates (WSCs) and starch in the crown. Flooding consistently increased plant height independently of the defoliation frequency. This response was associated with a preferential location of shoot biomass above water level and a reduction in root biomass accumulation. As a result, a second defoliation in the middle of the flooding period was more intense among plants that are taller due to flooding. These plants lost ca. 90% of their leaf biomass vs. ca. 50% among non-flooded plants. The continuous de-submergence shoot response of frequently defoliated plants was attained in accordance to a decrease of their crown reserves. Consequently, these plants registered only 27.8% of WSCs and 9.1% of starch concentrations with respect to controls. Under such stressful conditions, plants showed a marked reduction in their regrowth as evidenced by the lowest biomass in all plant compartments: shoot, crowns and roots. Increasing defoliation frequency negatively affects the tolerance of the forage legume L. tenuis to flooding stress. Our results reveal a trade-off between the common increase in plant height to emerge from water and the amount of shoot removed to tolerate defoliation. When both factors are combined and defoliation persists, plant regrowth would be constrained by the reduction of crown reserves.     

Conceptualising the interactive effects of climate change and biological invasions on subarctic freshwater fish

Climate change and species invasions represent key threats to global biodiversity. Subarctic freshwaters are sentinels for understanding both stressors because the effects of climate change are disproportionately strong at high latitudes and invasion of temperate species is prevalent. Here, we summarize the environmental effects of climate change and illustrate the ecological responses of freshwater fishes to these effects, spanning individual, population, community and ecosystem levels. Climate change is modifying hydrological cycles across atmospheric, terrestrial and aquatic components of subarctic ecosystems, causing increases in ambient water temperature and nutrient availability. These changes affect the individual behavior, habitat use, growth and metabolism, alter population spawning and recruitment dynamics, leading to changes in species abundance and distribution, modify food web structure, trophic interactions and energy flow within communities and change the sources, quantity and quality of energy and nutrients in ecosystems. Increases in temperature and its variability in aquatic environments underpin many ecological responses; however, altered hydrological regimes, increasing nutrient inputs and shortened ice cover are also important drivers of climate change effects and likely contribute to context‐dependent responses. Species invasions are a complex aspect of the ecology of climate change because the phenomena of invasion are both an effect and a driver of the ecological consequences of climate change. Using subarctic freshwaters as an example, we illustrate how climate change can alter three distinct aspects of species invasions: (1) the vulnerability of ecosystems to be invaded, (2) the potential for species to spread and invade new habitats, and (3) the subsequent ecological effects of invaders. We identify three fundamental knowledge gaps focused on the need to determine (1) how environmental and landscape characteristics influence the ecological impact of climate change, (2) the separate and combined effects of climate and non‐native invading species and (3) the underlying ecological processes or mechanisms responsible for changes in patterns of biodiversity.     

Potential impacts of global climate change on freshwater fisheries

Despite uncertainty in all levels of analysis, recent and long-term changes in our climate point to the distinct possibility that greenhouse gas emissions have altered mean annual temperatures, precipitation and weather patterns. Modeling efforts that use doubled atmospheric CO₂ scenarios predict a 1–7°C mean global temperature increase, regional changes in precipitation patterns and storm tracks, and the possibility of “surprises” or sudden irreversible regime shifts. The general effects of climate change on freshwater systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants. In lotic systems, altered hydrologic regimes and increased groundwater temperatures could affect the quality of fish habitat. In lentic systems, eutrophication may be exacerbated or offset, and stratification will likely become more pronounced and stronger. This could alter food webs and change habitat availability and quality. Fish physiology is inextricably linked to temperature, and fish have evolved to cope with specific hydrologic regimes and habitat niches. Therefore, their physiology and life histories will be affected by alterations induced by climate change. Fish communities may change as range shifts will likely occur on a species level, not a community level; this will add novel biotic pressures to aquatic communities. Genetic change is also possible and is the only biological option for fish that are unable to migrate or acclimate. Endemic species, species in fragmented habitats, or those in east–west oriented systems will be less able to follow changing thermal isolines over time. Artisanal, commercial, and recreational fisheries worldwide depend upon freshwater fishes. Impacted fisheries may make it difficult for developing countries to meet their food demand, and developed countries may experience economic losses. As it strengthens over time, global climate change will become a more powerful stressor for fish living in natural or artificial systems. Furthermore, human response to climate change (e.g., increased water diversion) will exacerbate its already-detrimental effects. Model predictions indicate that global climate change will continue even if greenhouse gas emissions decrease or cease. Therefore, proactive management strategies such as removing other stressors from natural systems will be necessary to sustain our freshwater fisheries.     

Disentangling climate change from air pollution effects on epiphytic bryophytes

At the interface between atmosphere and vegetation, epiphytic floras have been largely used as indicators of air quality. The recovery of epiphytes from high levels of SO₂ pollution has resulted in major range changes, whose interpretation has, however, been challenged by concomitant variation in other pollutants as well as climate change. Here, we combine historical and contemporary information on epiphytic bryophyte species distributions, climatic conditions, and pollution loads since the 1980s in southern Belgium to disentangle the relative impact of climate change and air pollution on temporal shifts in species composition. The relationship between the temporal variation of species composition, climatic conditions, SO₂, NO₂, O₃, and fine particle concentrations, was analyzed by variation partitioning. The temporal shift in species composition was such, that it was, on average, more than twice larger than the change in species composition observed today among communities scattered across the study area. The main driver, contributing to 38% of this temporal shift in species composition, was the variation of air quality. Climate change alone did not contribute to the substantial compositional shifts in epiphytic bryophyte communities in the course of the last 40 years. As a consequence of the substantial drop of N and S loads over the last decades, present-day variations of epiphytic floras were, however, better explained by the spatial variation of climatic conditions than by extant pollution loads. The lack of any signature of recolonization delays of formerly polluted areas in the composition of modern floras suggests that epiphytic bryophytes efficiently disperse at the landscape scale. We suggest that a monitoring of epiphyte communities at 10-year intervals would be desirable to assess the impact of raising pollution sources, and especially pesticides, whose impact on bryophytes remains poorly documented.     

Potential effects of climate change on the distribution of Scarabaeidae dung beetles in Western Europe

Dung beetles are indispensable in pasturelands, especially when poor efficiency of earthworms and irregular rainfall (e.g. under a Mediterranean climate) limit pad decomposition. Although observed and projected species range shifts and extinctions due to climate change have been documented for plants and animals, little effort has focused on the response of keystone species such as the scarab beetles of dung beetle decomposers. Our study aims to forecast the distribution of 37 common Scarabaeidae dung beetle species in France, Portugal and Spain (i.e. more than half of the western European Scarabaeidae fauna) in relation to two climate change scenarios (A2 and B1) for the period leading to 2080. On average, 21 % of the species should change in each 50-km UTM grid cell. The highest faunistic turnover rate and a significant increase in species richness are expected in the north of the study area while a marked impoverishment is expected in the south, with little difference between scenarios. The potential enrichment of northern regions depends on the achievement of the northward shift of thermophilous species, and climate change is generally likely to reduce the current distribution of the majority of species. Under these conditions, the distribution of resource—i.e. the extent and distribution of pastures—will be a key factor limiting species’ responses to climate change. The dramatic abandonment of extensive grazing across many low mountains of southern Europe may thus represent a serious threat to dung beetle distribution changes.