Developing biodiverse plantings suitable for changing climatic conditions 1: Underpinning scientific methods

Summary Governments across Australia have long been investing in revegetation in an effort to restore biodiversity and, more recently, mitigate climate change. However, no readily available methods have been described to assist project leaders identify species and provenance material likely to be sustainable under the changing climatic conditions of coming decades. Focussing particularly on trees, as trees are important for biosequestration as well as for providing habitat for other native species, Paper 1 of this two part series briefly reviews species distribution models and growth simulation models that could provide the scientific underpinning to improve and refine selection processes. While these previous scientific studies provide useful insights into how trees may respond to climate change, it is concluded that a readily accessible and easy‐to‐use approach is required to consider the potential adaptability of the many trees, shrubs and ground cover species that may be needed for biodiverse plantings. In Part 2 of this paper, the Atlas of Living Australia is used to provide preliminary information to assist species selection by assessing the climatic range of individual species based on their current distributions and, where available, cultivated locations. While using the Atlas can assist current selections, ways are outlined in Part 2 in which more reliable selections for changing climatic conditions could be made, building on the methods described here.     

Leaf trait associations with environmental variation in the wide‐ranging shrub Dodonaea viscosa subsp. angustissima (Sapindaceae)

Intra‐species variation in specific leaf area (SLA) and leaf area (LA) provides mechanistic insight into the persistence and function of plants, including their likely success under climate change and their suitability for revegetation. We measured SLA and LA in 101 Australian populations of the perennial shrub Dodonaea viscosa (L.) Jacq. subsp. angustissima (narrow‐leaf hop‐bush) (Sapindaceae). Populations were located across about a 1000 km north–south gradient, with climate grading from arid desert to mesic Mediterranean. We also measured leaves from 11 populations across an elevational gradient (300–800 m asl), where aridity and temperature decrease with elevation. We used regression and principal component analyses to relate leaf traits to the abiotic environment. SLA displayed clinal variation, increasing from north to south and correlated with latitude and the first principal component of joint environmental variables. Both SLA and LA correlated positively with most climatic and edaphic variables. Across latitude, LA showed more variability than SLA. Changes in leaf density and thickness may have caused the relative stability of SLA. Only LA decreased with elevation. The absence of a SLA response to elevation could be a consequence of abiotic conditions that favour low SLA at both ends of the elevational gradient. We demonstrated that the widely distributed narrow‐leaf hop‐bush shows considerable variability in LA and SLA, which allows it to persist in a broad environmental envelope. As this shrub is widely used for revegetation in Australia, South America and the Asia‐Pacific region, our results are consistent with the notion that seed used to revegetate mesic environments could be sourced from more arid areas to increase seed suitability to future climate change.     

Soil moisture's underestimated role in climate change impact modelling in low‐energy systems

Shifts in precipitation regimes are an inherent component of climate change, but in low‐energy systems are often assumed to be less important than changes in temperature. Because soil moisture is the hydrological variable most proximally linked to plant performance during the growing season in arctic‐alpine habitats, it may offer the most useful perspective on the influence of changes in precipitation on vegetation. Here we quantify the influence of soil moisture for multiple vegetation properties at fine spatial scales, to determine the potential importance of soil moisture under changing climatic conditions. A fine‐scale data set, comprising vascular species cover and field‐quantified ecologically relevant environmental parameters, was analysed to determine the influence of soil moisture relative to other key abiotic predictors. Soil moisture was strongly related to community composition, species richness and the occurrence patterns of individual species, having a similar or greater influence than soil temperature, pH and solar radiation. Soil moisture varied considerably over short distances, and this fine‐scale heterogeneity may contribute to offsetting the ecological impacts of changes in precipitation for species not limited to extreme soil moisture conditions. In conclusion, soil moisture is a key driver of vegetation properties, both at the species and community level, even in this low‐energy system. Soil moisture conditions represent an important mechanism through which changing climatic conditions impact vegetation, and advancing our predictive capability will therefore require a better understanding of how soil moisture mediates the effects of climate change on biota.     

A comprehensive landscape genomics approach for seed sourcing strategies in landscapes under varying degrees of habitat disturbance

As most ecosystems around the world are threatened by anthropogenic degradation and climate change, there is an increasing urgency to implement restoration strategies aiming at ensuring ecosystem self‐sustainability and resilience. An initial step towards that goal relies on selecting the most suitable seed sources for a successful revegetation, which can be extremely challenging in highly degraded landscapes. The most common seed sourcing strategy is to select local seeds because it is assumed that plants experience strong adaptations to their natal sites. An alternative strategy is the selection of climate‐adapted genotypes to future conditions. While considering future climatic projections is important to account for spatial shifts in climate to inform assisted gene flow and translocations, to restore highly degraded landscapes we need a comprehensive approach that first accounts for species adaptations to current at‐site environmental conditions. In this issue of Molecular Ecology Resources, Carvalho et al. present a novel landscape genomics framework to identify the most appropriate seed sourcing strategy for moderately and highly degraded sites by integrating genotype, phenotype and environmental data in a spatially explicit context for two native plant species with potential to help restore iron‐rich Amazonian savannas. This framework is amenable to be applicable and adapted to a broad range of restoration initiatives, as the dichotomy between focusing on the current or future climatic conditions should depend on the goals and environmental circumstances of each restoration site.     

Co‐occurrence patterns of trees along macro‐climatic gradients and their potential influence on the present and future distribution of Fagus sylvatica L.

Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences.     

Should I plant or should I sow? Restoration outcomes compared across seven riparian revegetation projects

To revegetate native plant communities, it is often cheaper to direct seed than to plant nursery‐grown stock. However, the outcomes of direct seeding can be quite variable, and it is unclear whether direct seeding or planting is more likely to facilitate the restoration of diverse plant communities. To address this question, we compared the outcomes of each method across several recent riparian revegetation projects where both direct seeding and tube‐stock planting were used. We surveyed riparian revegetation projects at seven sites within the greater Melbourne area that had been revegetated between 1 and 4 years previously. Sites were all on land previously used for agriculture or degraded public land and ranged in environmental and climatic conditions. Woody plant density, establishment of target species, species richness, species diversity (evenness) and plant heights were assessed. Direct seeding tended to result in higher plant densities and similar species richness, but lower rates of species establishment and diversity compared with planting. A median of 67% of target species established via direct seeding compared with 100% for planting, with direct seeded areas often dominated by one or two species. In general, overall revegetation outcomes were often driven by climatic and site factors, rather than revegetation method. We suggest that to achieve good restoration outcomes from revegetation in riparian areas, a bet‐hedging or combined approach using both sowing and planting may be the best strategy.     

Can postmining revegetation create habitat for a threatened mammal?

Most revegetation conducted for biodiversity conservation aims to mimic reference ecosystems present predisturbance. However, revegetation can overshoot or undershoot targets, particularly in the early stages of a recovery process, resulting in conditions different from the reference model. Revegetation that has, as yet, failed to fully meet revegetation targets may, nonetheless, provide habitat for threatened species not present in reference ecosystems. To investigate this possibility, we surveyed Quokka (Setonix brachyurus), a threatened macropod, in a mining landscape in south‐western Australia. We established four sites in each of riparian forest, which is the preferred habitat of quokkas but is not mined, mid‐slope forest, which is the premining reference ecosystem but is not suitable habitat for quokkas, and revegetated forest on mine pits 16–21 years postmining. We recorded quokkas in all riparian forest sites and two revegetated forest sites but not in any mid‐slope forest sites. Occupied revegetated sites had greater cover between 0 and 2 m and were spatially closer to riparian forest than unoccupied revegetated sites, suggesting predation pressure was likely influencing which mine pits were occupied. Our study demonstrated postmining revegetation can provide new habitat for a threatened species and suggested that revegetating a small proportion of sites to provide new habitat for threatened species could be considered as a management option in some scenarios. This could improve landscape connectivity and increase both the area of available habitat and between‐site heterogeneity, which could all potentially increase the ability of revegetation to conserve biodiversity.     

How Far Could the Alien Boatman Trichocorixa verticalis verticalis Spread? Worldwide Estimation of Its Current and Future Potential Distribution

Invasions of alien species are considered among the least reversible human impacts, with diversified effects on aquatic ecosystems. Since prevention is the most cost-effective way to avoid biodiversity loss and ecosystem problems, one challenge in ecological research is to understand the limits of the fundamental niche of the species in order to estimate how far invasive species could spread. Trichocorixa verticalis verticalis (Tvv) is a corixid (Hemiptera) originally distributed in North America, but cited as an alien species in three continents. Its impact on native communities is under study, but it is already the dominant species in several saline wetlands and represents a rare example of an aquatic alien insect. This study aims: i) to estimate areas with suitable environmental conditions for Tvv at a global scale, thus identifying potential new zones of invasion; and ii) to test possible changes in this global potential distribution under a climate change scenario. Potential distributions were estimated by applying a multidimensional envelope procedure based on both climatic data, obtained from observed occurrences, and thermal physiological data. Our results suggest Tvv may expand well beyond its current range and find inhabitable conditions in temperate areas along a wide range of latitudes, with an emphasis on coastal areas of Europe, Northern Africa, Argentina, Uruguay, Australia, New Zealand, Myanmar, India, the western boundary between USA and Canada, and areas of the Arabian Peninsula. When considering a future climatic scenario, the suitability area of Tvv showed only limited changes compared with the current potential distribution. These results allow detection of potential contact zones among currently colonized areas and potential areas of invasion. We also identified zones with a high level of suitability that overlap with areas recognized as global hotspots of biodiversity. Finally, we present hypotheses about possible means of spread, focusing on different geographical scales.     

An approach to consider behavioral plasticity as a source of uncertainty when forecasting species' response to climate change

The rapid ecological shifts that are occurring due to climate change present major challenges for managers and policymakers and, therefore, are one of the main concerns for environmental modelers and evolutionary biologists. Species distribution models (SDM) are appropriate tools for assessing the relationship between species distribution and environmental conditions, so being customarily used to forecast the biogeographical response of species to climate change. A serious limitation of species distribution models when forecasting the effects of climate change is that they normally assume that species behavior and climatic tolerances will remain constant through time. In this study, we propose a new methodology, based on fuzzy logic, useful for incorporating the potential capacity of species to adapt to new conditions into species distribution models. Our results demonstrate that it is possible to include different behavioral responses of species when predicting the effects of climate change on species distribution. Favorability models offered in this study show two extremes: one considering that the species will not modify its present behavior, and another assuming that the species will take full advantage of the possibilities offered by an increase in environmental favorability. This methodology may mean a more realistic approach to the assessment of the consequences of global change on species' distribution and conservation. Overlooking the potential of species' phenotypical plasticity may under‐ or overestimate the predicted response of species to changes in environmental drivers and its effects on species distribution. Using this approach, we could reinforce the science behind conservation planning in the current situation of rapid climate change.     

Germination behaviour of annual plants under changing climatic conditions: separating local and regional environmental effects

The role of local adaptation and factors other than climate in determining extinction probabilities of species under climate change has not been yet explicitly studied. Here we performed a field experiment with annual plants growing along a steep climatic gradient in Israel to isolate climatic effects for local trait expression. The focus trait was seed dormancy, for which many theoretical predictions exist regarding climate-driven optimal germination behaviour. We evaluated how germination is consistent with theory, indicating local adaptation to current and changing climatic conditions, and how it varies among species and between natural and standardised soil conditions. We reciprocally sowed seeds from three or four origins for each of three annual species, Biscutella didyma, Bromus fasciculatus and Hymenocarpos circinnatus, in their home and neighbouring sowing locations along an aridity gradient. Our predictions were: lower germination fraction for seeds from more arid origins, and higher germination at wetter sowing locations for all seed origins. By sowing seeds in both local and standard soil, we separated climatic effects from local conditions. At the arid sowing location, two species supported the prediction of low germination of drier seed origins, but differences between seed origins at the other sites were not substantial. There were no clear rainfall effects on germination. Germination fractions were consistently lower on local soil than on standard soil, indicating the important role of soil type and neighbour conditions for trait expression. Local environmental conditions may override effects of climate and so should be carefully addressed in future studies testing for the potential of species to adapt or plastically respond to climate change.     

Plant community responses to Scotland's changing environment

Summary

The ecological dangers of global climatic change are frequently discussed in relation to their threat to biodiversity. Oceanic Scotland, however, differs in many respects from else- where, both in the nature of the current climatic change and the biodiversity of the flora on which it reacts. Scottish habitats, such as those in the more peripheral regions, are rarely rich in species and biodiversity may not be a relevant concept for assessing the impact of environmental change. In species-poor habitats ecosystem health may be a more useful measure of potential survival capacity than species wealth. Examination of the homeo-static properties of plant communities, and their ability to withstand environmental change, could provide a more practical method of predicting which sections of the Scottish flora are at risk from climatic change as well as indicating possible remedial action. Case histories from coastal, wetland, forest and mountain sites are discussed in terms of their present ecological robustness and future potential for surviving expected changes in the Scottish environment.     

Identifying particular areas for potential seed collections for restoration plantings under climate change

A method to assist identifying potential sites for seed collections for restoration plantings is demonstrated using the Atlas of Living Australia (ALA) and an example site near Albury (New South Wales). The mean annual temperature (MAT) and mean annual precipitation (MAP) of the example site are determined using the ALA. Data on likely changes in MAT and MAP are accessed from the ‘Climate Change in Australia’ website. The ALA's ‘define environmental envelope’ function is then used to identify areas currently experiencing conditions similar to the future climatic conditions projected for the site. Species distribution data in the ALA indicate locations where suitable provenances of the chosen species are likely to be present. In the case of trees, satellite images in the ALA can indicate whether isolated trees or extensive stands, that may be genetically diverse, exist at locations of interest. Shrublands, grasslands or wetlands may also be identified from the satellite images. The Monitoring, Evaluation, Reporting and Improvement Tool (MERIT) within the ALA can be used to identify existing trials that may already be using suitable provenances for the restoration site. Some considerations for provenance selection under climate change are outlined, as well as the advantages and limitations of using the ALA for this purpose.     

Using restoration as an experimental framework to test provenancing strategies and climate adaptability

Restoring degraded Australian landscapes through revegetation is a key concern of land holders, NGOs and government agencies. With the advent of climate change, it is increasingly important that revegetation activities take into consideration the species and provenance of plant materials to ensure that environmental plantings will be resilient to future climate conditions. A major strength of the past 30 years restoration programmes is the development of a distributed network of educated and experienced practitioners. We have recently invited stakeholders from among this network to participate in a process to cost‐effectively build Environmental Research Infrastructure – a nationally distributed network of restoration plantings that explore a broad range of research activities including a better understanding of the adaptive responses of different species and provenances. This would also facilitate long‐term monitoring of change and adaptation across Australia, providing a wealth of information to inform future conservation and restoration programmes.     

Habitat assessment of Marco Polo sheep (Ovis ammon polii) in Eastern Tajikistan: Modeling the effects of climate change

Identifying the factors predicting the high‐elevation suitable habitats of Central Asian argali wild sheep and how these suitable habitats are affected by the changing climate regimes could help address conservation and management efforts and identify future critical habitat for the species in eastern Tajikistan. This study used environmental niche models (ENMs) to map and compare potential present and future distributions of suitable environmental conditions for Marco Polo argali. Argali occurrence points were collected during field surveys conducted from 2009 to 2016. Our models showed that terrain ruggedness and annual mean temperature had strong correlations on argali distribution. We then used two greenhouse gas concentration trajectories (RCP 4.5 and RCP 8.5) for two future time periods (2050 and 2070) to model the impacts of climate change on Marco Polo argali habitat. Results indicated a decline of suitable habitat with majority of losses observed at lower elevations (3,300–4,300 m). Models that considered all variables (climatic and nonclimatic) predicted losses of present suitable areas of 60.6% (6,928 km²) and 63.2% (7,219 km²) by 2050 and 2070, respectively. Results also showed averaged habitat gains of 46.2% (6,106 km²) at much higher elevations (4,500–6,900 m) and that elevational shifts of habitat use could occur in the future. Our results could provide information for conservation planning for this near threatened species in the region.     

A climate change context for the decline of a foundation tree species in south-western Australia: insights from phylogeography and species distribution modelling

Background and Aims A worldwide increase in tree decline and mortality has been linked to climate change and, where these represent foundation species, this can have important implications for ecosystem functions. This study tests a combined approach of phylogeographic analysis and species distribution modelling to provide a climate change context for an observed decline in crown health and an increase in mortality in Eucalyptus wandoo, an endemic tree of south-western Australia.Methods Phylogeographic analyses were undertaken using restriction fragment length polymorphism analysis of chloroplast DNA in 26 populations across the species distribution. Parsimony analysis of haplotype relationships was conducted, a haplotype network was prepared, and haplotype and nucleotide diversity were calculated. Species distribution modelling was undertaken using Maxent models based on extant species occurrences and projected to climate models of the last glacial maximum (LGM).Key Results A structured pattern of diversity was identified, with the presence of two groups that followed a climatic gradient from mesic to semi-arid regions. Most populations were represented by a single haplotype, but many haplotypes were shared among populations, with some having widespread distributions. A putative refugial area with high haplotype diversity was identified at the centre of the species distribution. Species distribution modelling showed high climatic suitability at the LGM and high climatic stability in the central region where higher genetic diversity was found, and low suitability elsewhere, consistent with a pattern of range contraction.Conclusions Combination of phylogeography and paleo-distribution modelling can provide an evolutionary context for climate-driven tree decline, as both can be used to cross-validate evidence for refugia and contraction under harsh climatic conditions. This approach identified a central refugial area in the test species E. wandoo, with more recent expansion into peripheral areas from where it had contracted at the LGM. This signature of contraction from lower rainfall areas is consistent with current observations of decline on the semi-arid margin of the range, and indicates low capacity to tolerate forecast climatic change. Identification of a paleo-historical context for current tree decline enables conservation interventions to focus on maintaining genetic diversity, which provides the evolutionary potential for adaptation to climate change.     

Increases in the evolutionary potential of upper thermal limits under warmer temperatures in two rainforest Drosophila species

Tropical and subtropical species represent the majority of biodiversity. These species are predicted to lack the capacity to evolve higher thermal limits in response to selection imposed by climatic change. However, these assessments have relied on indirect estimates of adaptive capacity, using conditions that do not reflect environmental changes projected under climate change. Using a paternal half‐sib full‐sib breeding design, we estimated the additive genetic variance and narrow‐sense heritability for adult upper thermal limits in two rainforest‐restricted species of Drosophila reared under two thermal regimes, reflecting increases in seasonal temperature projected for the Wet Tropics of Australia and under standard laboratory conditions (constant 25°C). Estimates of additive genetic variation and narrow‐sense heritability for adult heat tolerance were significantly different from zero in both species under projected summer, but not winter or constant, thermal regimes. In contrast, significant broad‐sense genetic variation was apparent in all thermal regimes for egg‐to‐adult viability. Environment‐dependent changes in the expression of genetic variation for adult upper thermal limits suggest that predicting adaptive responses to climate change will be difficult. Estimating adaptive capacity under conditions that do not reflect future environmental conditions may provide limited insight into evolutionary responses to climate change.     

Using species distribution models to assess the long-term impacts of changing oceanographic conditions on abalone density in south east Australia

Warming from climate change and resulting increases in energy stored in the oceans is causing changes in the hydrodynamics and biogeochemistry of marine systems, exacerbating current challenges facing marine fisheries. Although studies have evaluated effects of rising temperatures on marine species, few have looked at these impacts along with other environmental drivers over long time periods. In this study, we associate long-term density of blacklip abalone to changing oceanographic conditions in a climate change ‘hot-spot’ off southeast Australia. We downscaled and hind-casted existing hydrodynamic models to provide information on waves and currents over 25 yr and used this information to run biophysical connectivity models. We combined the connectivity models with 21 yr of data on abalone density, temperature, seafloor habitat, and the effects of a disease outbreak in an machine learning modeling approach to develop a spatio-temporal model of abalone density. We found that the combination of temperature, connectivity, current speed, wave orbital velocity, fishery catch, depth, reef structure and a disease outbreak explain 70% of variation in abalone density and allowed us to create 30 m resolution predictive grids with 75% accuracy. An emerging hotspot analysis run on the individual predictive grids from each year detected a predominance of low-density grids across the region, with 49.5% of cells classified as cold spots, 14.3% as hotspots and 36.2% with no significant patterns observed. This type of spatio-temporal analysis provides important insights into how changing environmental conditions are impacting density in an important fishery species, allowing for better adaptive management in the face of future climate change.     

Modelling species distributions without using species distributions: the cane toad in Australia under current and future climates

Accurate predictions of the potential distribution of range-shifting species are required for effective management of invasive species, and for assessments of the impact of climate change on native species. Range-shifting species pose a challenge for traditional correlative approaches to range prediction, often requiring the extrapolation of complex statistical associations into novel environmental space. Here we take an alternative approach that does not use species occurrence data, but instead captures the fundamental niche of a species by mechanistically linking key organismal traits with spatial data using biophysical models. We demonstrate this approach with a major invasive species, the cane toad Bufo marinus in Australia, assessing the direct climatic constraints on its ability to move, survive, and reproduce. We show that the current range can be explained by thermal constraints on the locomotor potential of the adult stage together with limitations on the availability of water for the larval stage. Our analysis provides a framework for biologically grounded predictions of the potential for cane toads to expand their range under current and future climate scenarios. More generally, by quantifying spatial variation in physiological constraints on an organism, trait-based approaches can be used to investigate the range-limits of any species. Assessments of spatial variation in the physiological constraints on an organism may also provide a mechanistic basis for forecasting the rate of range expansion and for understanding a species' potential to evolve at range-edges. Mechanistic approaches thus have broad application to process-based ecological and evolutionary models of range-shift.     

Forest Pattern, Fire, and Climatic Change in the Sierra Nevada

In the Sierra Nevada, distributions of forest tree species are largely controlled by the soil-moisture balance. Changes in temperature or precipitation as a result of increased greenhouse gas concentrations could lead to changes in species distributions. In addition, climatic change could increase the frequency and severity of wildfires. We used a forest gap model developed for Sierra Nevada forests to investigate the potential sensitivity of these forests to climatic change, including a changing fire regime. Fuel moisture influences the fire regime and couples fire to climate. Fires are also affected by fuel loads, which accumulate according to forest structure and composition. These model features were used to investigate the complex interactions between climate, fire, and forest dynamics. Eight hypothetical climate-change scenarios were simulated, including two general circulation model (GCM) predictions of a 2 × CO₂ world. The response of forest structure,species composition, and the fire regime to these changes in the climate were examined at four sites across an elevation gradient. Impacts on woody biomass and species composition as a result of climatic change were site specific and depended on the environmental constraints of a site and the environmental tolerances of the tree species simulated. Climatic change altered the fire regime both directly and indirectly. Fire frequency responded directly to climate's influence on fuel moisture, whereas fire extent was affected by changes that occurred in either woody biomass or species composition. The influence of species composition on fuel-bed bulk density was particularly important. Future fires in the Sierra Nevada could be both more frequent and of greater spatial extent if GCM predictions prove true. Received 5 May 1998; accepted 4 November 1998.