Colonization Potential of Oaks under Climate Change

by Elizabeth Medford

While the impact of climate change on a variety of animal populations and their ranges has been studies extensively in the past, the study of the impact of warming on tree species also provides useful information for policymaking. A variety of different modeling systems apply different variables and make predictions about tree species distribution in the future as temperatures rise. In this study however, Prasad et al. (2013) combine two different commonly used technologies to overcome the constraint of computation time and allow assessment of colonization potential for oak species. Four oak species were chosen to focus on because they are strongly climate-driven species: black oak, post oak, chestnut oak, and white oak. Using the DISTRIB and SHIFT models together the authors were able to determine the future dominant forest types in the northeastern United States. This study determined that even under optimistic conditions ignoring some influential factors, only a small fraction of suitable oak habitat is likely to be occupied by oaks within 100 years. The authors urge that the information garnered in this study be used to inform assisted migration practices for vulnerable tree species. They additionally call for further studies focusing on how each individual species will adapt to increases in temperature. Continue reading

Diversity Loss Increases Vulnerability to Ecosystem Collapse

by Elizabeth Medford

The value of biodiversity for the resilience of ecological systems has become common knowledge in ecology spheres. Moreover, the affects of humans on the diversity of many ecosystems around the world have been proven previously. This study connects these two pieces of knowledge in stating that the combination of diversity loss caused by human activities and environmental change increase the risk for sudden ecosystem collapse. MacDougall et al. (2013) demonstrated this connection in a degraded but species-rich grassland that was subject to fire suppression techniques as well as invasion by non-native species. The authors conclude that human disturbance created a negative relationship between diversity and function but that the elimination of the buffering effects of high species diversity has led to a vulnerability to sudden environmental change. The findings of this study can be applied more generally to many different ecosystems because of the prevalent combination of long-term land management and species loss. This study relates to climate change because as global temperatures cause fires to increase in occurrence and severity, trophic collapse because of human-caused diversity loss may also increase. Continue reading

Temperature Drives the Continental-Scale Distribution of Key Microbes in Topsoil Communities

by Elizabeth Medford

While it has become fairly well known that global warming will cause plant and animal species to migrate toward cooler areas or cause range loses, until now it has been unclear whether this will also be true for microorganisms. Microorganisms play a key role in soil fertility and erodibility making this study relevant both for future agricultural endeavors as well as future efforts relating to ecological protection. Garcia-Pitchel et al. (2013) conducted continental-scale compositional surveys of soil crust microbial communities in the arid regions of North America. The results from these surveys imply that temperature caused latitudinal replacement between two key topsoil cyanobacteria. The cyanobacteria Microcoleus vaginatus behaved more psychrotolerant and less thermotolerant while M. steenstrupii behaved more thermotolerant. These results imply that the later may replace the former as temperature increases globally. Further studies are required to fully understand the impact of this microbial replacement. Continue reading

Species Most Vulnerable to Climate Change

by Elizabeth Medford

While it has been recognized in the past that climate change will have impacts on biodiversity, many approaches ignore the differences between species that will increase or reduce their vulnerability. Foden et al. (2013) chose to address three different aspects of climate change vulnerability to account for species’ biological traits: sensitivity, exposure, and adaptive capacity. In combining these traits with the modeled exposure to projected climate change, the authors assessed the species with the greatest relative vulnerability to climate change. These methods were applied to each of the world’s birds, amphibians, and corals. The authors also identified the geographic areas in which the most vulnerable species are concentrated. These included the Amazon basin for amphibians and birds, and the Indo-west Pacific for corals. The aim of Foden et al. is that Continue reading

The shaping of genetic variation in the edge-of-range populations under past and future climate change

As the climate continues to warm because of human influences on the chemical composition of the atmosphere, organisms will need to adapt to new conditions or move to new habitats. While many species have proven able to adjust their ranges when faced with changes in temperature or food availability, the consequences of range-shift have not been widely studied. Razgour et al. studied a species of bat (Plecotus austriacus) in the hopes of better understanding the decreases in genetic diversity that can occur after range shifting caused by climate change. The authors extracted genomic DNA from 259 individuals and conducted various genetic analysis tests on the DNA including PCR. Additional data included genetic diversity information from models of past climate-related range shifts in Europe. The data were combined to predict future declines in genetic diversity for P. austriacus populations in Europe. The study provides evidence that geographical barriers shape genetic variation and that in the future, genetic diversity in P. austriacuswill be reduced by more than half, as it will for many other temperate European species. –Lizzie Medford

Razgour, O., Juste, J., Ibanez, C., Kiefer, A., 2013. The shaping of genetic variation in edge-of- range populations
under past and future climate change. Ecology Letters doi 10.111/ele. 12158

Future changes in temperature and precipitation will not only affect the population sizes of species but may also affect the genetic diversity of different communities by killing off all but a select few individuals in a particular habitat. Studying the genetic diversity of current bat populations can provide insight into how past climate events have shaped genetic diversity. Razgour et al. constructed phylogenetic trees and utilized numerous genetic analysis programs to determine Iberia as the location of the most diverse populations of bats with the greatest number of unique haplotypes and private alleles. This is likely the origin of the species after the Last Glacial Maximum (LGM), which cause range shifts and reduced genetic diversity in the species.
Evidence of past destruction of genetic diversity can be found in fossil records from the past climate changes in Europe following the LGM and receding of the glaciers. Ecological niche modeling and ABC inference of demographic history models were both used to construct a hypothetical range for the bats in the past and future. These studies predicted that most of the current habitat range for the bats would no longer be suitable habitats by 2080. This range restriction will cause more than half of the species’ genetic diversity to be located in unsuitable locations, which will result in vast diversity losses. Additionally, limited contemporary gene flow across the Pyrenees Mountains suggests that geographic barriers like mountains will further restrict the range of P. austriacus.

Razgour et al. studied P. austriacus for the species’ diversity, wide distribution, keystone ecological roles, and sensitivity to changes in temperature. Besides these attributes, bats also have a longevity and reproductive rate that suggest that they may not be able to evolve quickly enough for future changes in temperature and precipitation. The study concludes that the future for these bats will include northern range expansion and southern range contraction by the end of the century. These range shifts will likely cause the most extensive loss of genetic diversity in the most diverse populations. Moreover, this loss of genetic diversity may make the bats more vulnerable to threats like disease and challenges relating to more severe changes climate. Therefore, the authors of this study urge further research into the effects of climate change on leading-edge populations, as they will play a significant role in range shifts and spreading genetic diversity.

How Does Climate Change Cause Extinction?

One concern related to the consequences of anthropogenic climate change is the extinction of vulnerable species. While climate change has been predicted to affect the populations of these species, few studies have concretely identified the precise mechanisms through which populations will be affected. Using population studies and the empirical support for climate related extinctions, Cahill et al. (2013) reviewed the many different avenues through which extinction may occur as a result of climate change. By examining both the direct and proximate factors causing extinction, this review outlines each possible cause and presents any known empirical support for each cause. Cahill et al. additionally provides instruction on mechanisms for finding proximate causes for extinction. The reviewed data highlight that changes in species interactions are the important proximate cause of extinction relating to global climate change and that further studies will be crucial for developing effective conservation strategies. –Lizzie Medford

Cahill, A., Aiello-Lammens, M., Fisher-Reid, M., 2013. How does climate change cause extinction? Proceedings of 
The Royal Society Proc R Soc B 280: 20121890

                  Many different causes for extinction relating to changes in the earth’s climate have been proposed, however few have ample empirical evidence due to the complex nature of population dynamics and species interactions. In the past, these proximate causes have included negative impact of heat-avoidance behavior, loss of host and pollinator species, increased pathogen and competitor populations, among others. In their review, Cahill et al.grouped proximate causes into different categories helping to evaluate the validity of each. Categories included, temperature, precipitation, temporal mismatch between species, negative impacts on beneficial species, and positive impacts on harmful species. Once the causes were clearly stated and organized, they could be properly evaluated on scientific validity as causes. The clearest change in species behavior resulting from climate change is a pattern of range shifts documented in hundreds of species. The patterns of warm-edge contraction specifically provide evidence that local extinctions have already occurred as a result of climate change. The online supplementary material for this review includes an extensive list of studies on extinctions occurring in the recent past. Of these 864 global species extinctions, only 20 are considered by the International Union for Conservation of Nature (IUCN) to have resulted from climate change and all thoroughly related to climate. Specifically, Cahill et al. referenced coral bleaching and chytrid fungus in amphibians as two examples of climate related extinctions. Of these 20 extinctions, seven were amphibian species, four were snails, two fish species, six bird species, and one rodent. Interestingly, none of these twenty became extinct as a result of limited tolerances to high temperatures.

The authors found that climate change will cause extinctions mostly by changing the way species interact with each other, which will affect food availability and breeding patterns. Surprisingly, species’ ability to adjust to higher body temperatures has not been the prominent proximal cause of global extinction. This review urges for further studies on the effects of climate change on species interaction and extinctions in general. Biophysical modeling and population range surveys are the two methods suggested by Cahill et al. for increasing the amount of data on populations that may be affected by the negative results of climate change. These additional studies would to help improve the effectiveness of conservation strategies, which will undoubtedly become more critical as climate change progresses and the number of related extinctions continues to rise.