Shifts In Suitable Habitat Research Articles

Distribution models for Panicum virgatum (Poaceae) reveal an expanded range in present and future climate regimes in the northeastern United States.

Expanded area cultivated with the bioenergy crop Panicum virgatum (switchgrass) could alter the genetics of native populations through gene flow, so understanding current and future species distribution is a first step toward estimating ecological impacts. We surveyed switchgrass distribution in the northeastern United States and generated statistical models to address hypotheses about current distribution relative to historical records and responses to climate change. Surveys were conducted on 1600 km of road verges along environmental gradients. Switchgrass abundance became the training data for two multivariate generalized linear models that generated maps representing the probability of switchgrass in road verges. Models were evaluated and the superior model was used with variables from three climate change scenarios for 2050 and 2099. Switchgrass populations were found in 41% of roadside plots and up to 188 km from the coast. The environmental variables temperature, urban areas, and sandy soils were positively correlated with switchgrass presence, while elevation, soil pH, and distance to the coast were negatively correlated. The model without spatial autocorrelation performed better. Models and maps incorporating climate change predictions showed a sharp northward shift in suitable habitat. Switchgrass populations in the northeastern United States occur on inland road verges, supporting the idea that species distribution has expanded relative to historical descriptions of a restricted coastal habitat. The optimal model showed that mean temperature, elevation, and urban development were important in switchgrass distribution today, and climate change will increase suitable habitat for future bioenergy production and wild populations.

Idiosyncratic responses of grizzly bear habitat to climate change based on projected food resource changes.

Climate change vulnerability assessments for species of conservation concern often use species distribution and ecological niche modeling to project changes in habitat. One of many assumptions of these approaches is that food web dependencies are consistent in time and environmental space. Species at higher trophic levels that rely on the availability of species at lower trophic levels as food may be sensitive to extinction cascades initiated by changes in the habitat of key food resources. Here we assess climate change vulnerability for Ursus arctos (grizzly bears) in the southern Canadian Rocky Mountains using projected changes to 17 of the most commonly consumed plant food items. We used presence-absence information from 7088 field plots to estimate ecological niches and to project changes in future distributions of each species. Model projections indicated idiosyncratic responses among food items. Many food items persisted or even increased, although several species were found to be vulnerable based on declines or geographic shifts in suitable habitat. These included Hedysarum alpinum (alpine sweet vetch), a critical spring and autumn root-digging resource when little else is available. Potential habitat loss was also identified for three fruiting species of lower importance to bears: Empetrum nigrum (crowberry), Vaccinium scoparium (grouseberry), and Fragaria virginiana (strawberry). A general trend towards uphill migration of bear foods may result in higher vulnerability to bear populations at low elevations, which are also those that are most likely to have human-bear conflict problems. Regardless, a wide diet breadth of grizzly bears, as well as wide environmental niches of most food items, make climate change a much lower threat to grizzly bears than other bear species such as polar bears and panda bears. We cannot exclude, however, future alterations in human behavior and land use resulting from climate change that may reduce survival rates.

Loss of frugivore seed dispersal services under climate change.

The capacity of species to track shifting climates into the future will strongly influence outcomes for biodiversity under a rapidly changing climate. However, we know remarkably little about the dispersal abilities of most species and how these may be influenced by climate change. Here we show that climate change is projected to substantially reduce the seed dispersal services provided by frugivorous vertebrates in rainforests across the Australian Wet Tropics. Our model projections show reductions in both median and long-distance seed dispersal, which may markedly reduce the capacity of many rainforest plant species to track shifts in suitable habitat under climate change. However, our analyses suggest that active management to maintain the abundances of a small set of important frugivores under climate change could markedly reduce the projected loss of seed dispersal services and facilitate shifting distributions of rainforest plant species.

Climate change impacts on freshwater fish, coral reefs, and related ecosystem services in the United States

We analyzed the potential physical and economic impacts of climate change on freshwater fisheries and coral reefs in the United States, examining a reference case and two policy scenarios that limit global greenhouse gas (GHG) emissions. We modeled shifts in suitable habitat for three freshwater fish guilds and changes in coral reef cover for three regions. We estimated resulting economic impacts from projected changes in recreational fishing and changes in recreational use of coral reefs. In general, coldwater fisheries are projected to be replaced by less desirable fisheries over the 21st century, but these impacts are reduced under the GHG mitigation scenarios. Similarly, coral cover is projected to decline over the 21st century primarily due to multiple bleaching events, but the GHG mitigation scenarios delay these declines in Hawaii (but not in South Florida or Puerto Rico). Using a benefit-transfer approach, we estimated that global policies limiting GHG emissions would provide economic benefits in the range of $10–28 billion over the 21st century through maintaining higher values for recreational services for all freshwater fisheries and coral reefs, compared to the reference scenario. These economic values are a subset of the total economic and societal benefits associated with avoiding projected future declines in freshwater fisheries and coral reef cover due to unmitigated climate change.

Continental-Scale Assessment of Risk to the Australian Odonata from Climate Change

Climate change is expected to have substantial impacts on the composition of freshwater communities, and many species are threatened by the loss of climatically suitable habitat. In this study we identify Australian Odonata (dragonflies and damselflies) vulnerable to the effects of climate change on the basis of exposure, sensitivity and pressure to disperse in the future. We used an ensemble of species distribution models to predict the distribution of 270 (85%) species of Australian Odonata, continent-wide at the subcatchment scale, and for both current and future climates using two emissions scenarios each for 2055 and 2085. Exposure was scored according to the departure of temperature, precipitation and hydrology from current conditions. Sensitivity accounted for change in the area and suitability of projected climatic habitat, and pressure to disperse combined measurements of average habitat shifts and the loss experienced with lower dispersal rates. Streams and rivers important to future conservation efforts were identified based on the sensitivity-weighted sum of habitat suitability for the most vulnerable species. The overall extent of suitable habitat declined for 56–69% of the species modelled by 2085 depending on emissions scenario. The proportion of species at risk across all components (exposure, sensitivity, pressure to disperse) varied between 7 and 17% from 2055 to 2085 and a further 3–17% of species were also projected to be at high risk due to declines that did not require range shifts. If dispersal to Tasmania was limited, many south-eastern species are at significantly increased risk. Conservation efforts will need to focus on creating and preserving freshwater refugia as part of a broader conservation strategy that improves connectivity and promotes adaptive range shifts. The significant predicted shifts in suitable habitat could potentially exceed the dispersal capacity of Odonata and highlights the challenge faced by other freshwater species.

Spatial and temporal shifts in suitable habitat of juvenile southern flounder (Paralichthys lethostigma)

Factors influencing suitable habitats of juvenile southern flounder (Paralichthys lethostigma) within the Galveston Bay Complex (GBC), Texas, were assessed using generalized additive models (GAM). Fishery independent data collected with bag seines throughout the GBC from 1999 to 2009 were used to predict the probability of southern flounder occurrence. Binomial GAMs were used to assess presence/absence of southern flounder and models included temporal variables, benthic variables such as distance to habitats generated within a geographic information system, and physicochemical conditions of the water column. Separate models were generated for newly settled southern flounder, young-of-the-year (YOY) southern flounder observed in the summer, and YOY southern flounder observed in fall based on size and collection month. Factors affecting southern flounder occurrence changed seasonally, as did the corresponding shifts in the spatial distribution of suitable habitat. Temporal effects (year and month) were retained in all models. Physicochemical conditions (temperature, turbidity, and measures of environmental variability), and the presence of seagrass beds were influential for newly settled southern flounder. Distance to marine and/or freshwater sources were found to be important for YOY southern flounder in the summer and fall seasons. The abundance of brown shrimp was found to only influence the distribution of YOY southern flounder in the fall, when intermediate abundances of the potential prey item increased the occurrence of southern flounder. After model completion, the availability and spatial distribution of suitable habitat within the GBC was predicted using available environmental and spatial data for 2005. Spatial distributions of predicted suitable habitat stress the relative importance of West Bay during the newly settled stage and in the fall season, and Upper Bay during the summer and fall of the first year of life. These models demonstrate the potential dynamics of suitable habitats for juvenile southern flounder and provide insight into ontogenetic shifts in habitat preference during the first year of life.

Potential redistribution of tree species habitat under five climate change scenarios in the eastern US

Global climate change could have profound effects on the Earth’s biota, including large redistributions of tree species and forest types. We used DISTRIB, a deterministic regression tree analysis model, to examine environmental drivers related to current forest-species distributions and then model potential suitable habitat under five climate change scenarios associated with a doubling of atmospheric CO 2. Potential shifts in suitable habitat for 76 common tree species in the eastern US were evaluated based on more than 100,000 plots and 33 environmental variables related to climate, soils, land use, and elevation. Regression tree analysis was used to devise prediction rules from current species–environment relationships. These rules were used to replicate the current distribution and predict the potential suitable habitat for more than 2100 counties east of the 100th meridian. The calculation of an importance value-weighted area score, averaged across the five climate scenarios, allowed comparison among species for their overall potential to be affected by climate change. When this score was averaged across all five climate scenarios, 34 tree species were projected to expand by at least 10%, while 31 species could decrease by at least 10%. Several species ( Populus tremuloides, P. grandidentata, Acer saccharum, Betula papyrifera, Thuja occidentalis) could have their suitable habitat extirpated from US. Depending on the scenario, the optimum latitude of suitable habitat moved north more than 20 km for 38–47 species, including 8–27 species more than 200 km or into Canada. Although the five scenarios were in general agreement with respect to the overall tendencies in potential future suitable habitat, significant variations occurred in the amount of potential movement in many of the species. The five scenarios were ranked for their severity on potential tree habitat changes. Actual species redistributions, within the suitable habitat modeled here, will be controlled by migration rates through fragmented landscapes, as well as human manipulations.