Partial Protection in Mexican MPA Only Marginally Effective in Restoring Reef Ecosystem

by Katie Huang

Loreto Bay National Park (LBNP) is a marine protected area (MPA) in the Gulf of California, Mexico, which bans fishing in some areas and allows limited amounts in others. However, since only a small region of the MPA is completely protected, it is possible that the benefits of a no-take area do not offset the effects of the permitted fishing. From 1998 to 2010, Rife et al. (2013) surveyed the biomasses of fish in sites within the LBNP and in open control areas and compared the data from before and after the MPA was established. They found that the biomasses of protected and open area fish were not significantly different. Although the biomasses of herbivorous and zooplanktivorous fish increased significantly within the MPA’s restricted area, the authors did not observe changes in apex predator and carnivore biomasses which suggests that the reef ecosystem is still unhealthy even after 13 years of protection. Possible explanations include poor enforcement of regulations as well as the small size of the restricted area, and management solutions should address these issues to make the LBNP more effective. Continue reading

Hawaiian Marine Protected Areas Produce Spillover

by Katie Huang

Marine protected areas (MPAs) can be beneficial to fisheries through spillover effects, which occur when protected fish stocks recover and migrate into open areas. As a result, fishers tend to react by increasing fishing pressure near MPA boundaries to capitalize on these biomass gradients. To supplement previous research on spillover, Stamoulis and Friedlander (2013) studied a Hawaiian MPA with a new seascape approach that incorporated habitat variables, multiple scales of study, and information on fishing pressure. They took visual surveys of fish populations both targeted and not targeted for conservation along random transects and determined their biomass, species abundance, and density in protected and open areas. The authors found that all fish wellbeing measures were observed to be significantly higher inside the reserve. Also, as distance increased from the MPA boundaries, biomass decreased for resource fish but remained constant for non-resource fish, indicating the existence of a spillover gradient. Although fishing was more concentrated near MPA borders, current harvest rates are sustainable for the time being. The authors suggest that similar comprehensive studies be made throughout Hawaii but that further research should also include analysis on larval and egg export, a second benefit to fisheries besides spillover. Continue reading

Protecting Deepwater Fish Populations in Hawaii

by Katie Huang

Starting in 1998, specific types of marine protected areas (MPAs) called bottomfish restricted fishing areas (BRFAs) were implemented throughout Hawaii to address conservation concerns over deep-sea species. Although much research has been conducted on how MPAs benefit shallow reef fish populations, less is known about how protection affects deepwater ecosystems. Sackett et al. (2014) studied four BRFAs of differing ages to determine whether relative abundance, mean length, and species richness of seven commonly exploited species varied when compared to unprotected regions. The authors took video surveys along the deep sea floor in both types of areas and counted the number and type of fish in each. They found that mean fish length Continue reading

Sea Cucumbers Going Down in the Seychelles: Will MPAs Help?

Over the last century, increasing demand for marine invertebrates has led to overexploitation by fisheries. As a result, conservation of sea cucumbers, which play critical ecological roles as nutrient recyclers and filter feeders, is becoming increasingly important. Although there are few marine protected areas (MPAs) explicitly designed to protect sea cucumbers, protective regions already established for other species can still help populations recover. To determine the effects of protection on sea cucumber populations, Cariglia et al. (2013) examined a network of long-established MPAs in the Seychelles islands. They conducted scuba studies to count and identify various species in sites both inside and outside the MPAs and grouped them by economic worth. After performing statistical analyses, they found that 76% of all observed individuals were found within the MPAs and that within protected areas, there were both higher species abundance and a greater probability of encountering economically valuable species. The authors also analyzed habitat types and found that species preferred different types depending on whether they were in fished or unfished areas. Although the Seychelles MPAs were not specifically designed to protect sea cucumbers, they were nevertheless effective in facilitating recovery. —Posted by Katie Huang

Cariglia N., Wilson S.K., Graham N.A.J., Fisher R., Robinson J., Aumeeruddy R., Quatre R., Polunin N.V.C., 2013. Sea cucumbers in the Seychelles: effects of marine protected areas on high-value species. Aquatic Conservation: Marine and Freshwater Ecosystems 23, 418–428.

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Precipitation and Flooding Decrease Salamander Metamorphosis Survival and Adult Abundance

Although several worldwide amphibian declines have been attributed to climate change, a lack of long-term data has limited studies of non pond-breeding species. In this study, Lowe (2012) analyzed the effects of climate change on Gyrinophilus porphyriticus, a stream salamander, in New Hampshire’s Merrill Brook from 1999–2010. Using capture-mark-capture surveys, Lowe compared observed salamander abundances to the results of annual abundance surveys in order to determine long-term trends for adults and larvae. He found that while larval abundances remained constant, the proportion of adults declined significantly. Their abundance was negatively related to annual precipitation, as increasing rainfall caused more flooding events. The trends observed can possibly be explained by the mortality of metamorphosing individuals increasing during spring and fall floods, leading overall to declines in adult salamander recruitment. If precipitation increases as predicted, the results of this study suggest that populations of stream salamanders may decline as a result of climate change.—Katie Huang
Lowe, W.H., 2012. Climate change is linked to long-term decline in a stream salamander. Biological Conservation 145, 48–53.
Lowe conducted his study by gathering samples along a 1-km long section of Merrill Brook, a stream in northern New Hampshire. Throughout 3-day periods in mid-June, mid-July, and mid-August of 1999–2004, he took capture-mark-capture surveys of G. porphyriticus by overturning 1200 rocks within the channel and capturing both larvae and adult salamanders with a dip-net. Individuals were marked by subcutaneous injection of fluorescent elastomer and data for length and life history stage were recorded. From 2005–2010, Lowe took annual abundance surveys by using the nearly the same methods as the capture-mark-recapture surveys except he ignored existing marks and did not make new ones. He then used count data from surveys in the Julys of 1999–2010 to test for trends in abundance as well as in the mean size of larvae and adults. He also tested if abundances were related to mean annual air temperature and cumulative annual precipitation using linear regression analyses. Finally, he modeled larval, adult, and metamorphosis survival probabilities to help explain long-term trends.
The results of the study found that adult abundance declined significantly from 1999–2010, although there was no trend in larval abundance. As larvae are likely to partially recruit independently due to the salamander’s long lifespan and multiple reproductive cycles, these results do not appear to be abnormal. However, it is possible that larval abundances may decrease rapidly once the adult population reaches a minimum threshold for larval recruitment. Adult abundances were also found to be negatively related to annual precipitation, which can possibly be explained by a decline in larvae surviving metamorphosis. Although larvae and adults had constant survival probabilities, metamorphosing individuals showed a downward survival trend from 2000–2003. Lowe suggests that since these individuals cannot exploit flood-avoidance strategies used by larvae and adults, flooding events caused by increased precipitation may increase susceptibility to mortality and reduce adult recruitment rates. In particular, this species of salamanders is exposed to prolonged flooding effects due to its extended period of metamorphosis. The author recommends further research between metamorphosis survival ability and declines in adult abundance. He also found that although there was no trend in larval size, the mean size of adults increased significantly. These results are consistent with reduced recruitment of smaller adults via metamorphosis and an aging adult population. If the adult abundance of G. porphyriticus continues to decline, the population may be led to local extinction, and similar results may be observed in other amphibians in other headwater systems in North America.

Sea-level Rise Causes Significant Flooding and Human Relocation into Habitat Areas in Southeast Asia and the Pacific

Sea-level rise (SLR), one of the predicted effects of climate change, is expected to significantly affect coastal biodiversity of islands in Southeast Asia and the Pacific. While its primary effects are flooding and erosion, SLR also has important secondary impacts such as human relocation into wildlife habitats that are often overlooked. To assess the primary effects of SLR, Wetzel et al. (2012) modeled levels of inundation and erosion under scenarios of 1, 3, and 6 meter sea-level rises on 1,287 islands in Australasia, Oceania, and Indo-Malaysia. They also estimated secondary effects by analyzing flooded urban and intensive agricultural areas and assuming that equal proportions of habitat were lost in the hinterland due to human migration. By comparing these areas to 106 mammal distributions, they determined the habitat areas and ranges that could potentially be lost. The authors found that depending on the scenario, islands lost 3–32% of their coastal zones and displaced 8–52 million people, leading to dramatic losses of habitat areas for terrestrial species. However, the relative importance of primary versus secondary effects ultimately differed greatly by region due to variance in influential factors such as island geographies and individual species distributions.—Katie Huang
Wetzel, F.T., Kissling, W.D., Beissmann, H., Penn, D.J., 2012. Future climate change driven sea-level rise: secondary consequences from human displacement for island biodiversity. Global Change Biology 18, 2707–2719.

Wetzel et al. studied 1,287 islands in the biogeographical realms of Australasia, Oceania, and Indo-Malaysia, regions particularly vulnerable to biodiversity loss because of coastal flooding. Although they initially considered 12,983 islands, the authors ultimately excluded those that were likely to become completely submerged as well as those that would not be exposed to secondary effects. To determine the primary effects of SLR, they modeled scenarios of 1, 3, and 6 meter sea-level rises and calculated the area of land affected by flooding and shoreline recession due to erosion. They estimated the secondary effects of SLR by determining the proportion of inundated urban and agricultural areas. Under the assumption that the populations of these areas would relocate to similarly sized regions in the hinterland, they were able to determine how much land would be converted from potential habitat to human populated areas. Wetzel et al. also assessed how primary and secondary SLR effects affected species distributions using data concerning 109 species of mammals. Assigning this data to 106 islands, they analyzed how habitat ranges were affected, making sure to account for individual habitat data for each species by assuming that species ranges were reduced proportionally to the loss of hinterland.
The authors found that primary effects led to large area losses of the coastal zone throughout the entire Southeast Asian and Pacific area, although the magnitude of effect varied greatly by region. Under a 1 m scenario, 3% of total coastal area was flooded, with losses increasing to 13% in a 3 m scenario and 32% in a 6 m scenario across all 1,287 islands. The Oceanic region was most vulnerable to inundation, suffering a 7­–46% area loss, followed by Indo-Malaysia (4–35%) and Australasia (2–25%). The amount of flooded urban and intensive agricultural land, which determined the extent of the secondary effects, tended to vary by region. Islands in Indo-Malaysia and Oceania were more susceptible to urban and intensive agricultural flooding and lost 30% and 20–35% respectively. In contrast, Australasian islands only suffered 12–16% losses, making them less vulnerable to secondary SLR effects. Primary effects were most prominent on Oceanic islands, while secondary effects were more pronounced in Indo-Malaysia. Secondary effects affected only 5% of land on Oceanic islands, while losses were much greater on Australasian (14%) and Indo-Malaysian islands (18%).
Depending on the SLR scenario, islands were projected to lose 11–45% of potential terrestrial wildlife habitat due to primary effects. The loss was increased by secondary impacts, which were more pronounced on islands with high degrees of urban and intensive agricultural area, as these regions were more likely to be affected by human relocation. The authors estimated that approximately 8–52 million people, 4–27% of the population, were expected to migrate, leading to considerable effects on hinterland habitat. Although islands with large human ecological impacts were already projected to lose 13–44% of habitat area, secondary effects increased the estimate by an additional 6–24%. In contrast, islands with low proportions of urban and intensive agricultural areas only suffered minor losses of 0–1% of habitat from secondary effects. The authors suggested that range loss was hurt more by secondary than primary effects for 10–46% of species because most habitat ranges were located in the hinterland where SLR driven human relocation occurs. They also indicated that smaller islands were more greatly affected than larger islands by SLR effects. However, the extent of primary and secondary effects still varied enormously by region, depending on factors such as coastal geomorphology, species distributions, and other climate change effects.
The authors concluded their study by suggesting further research be conducted using other vertebrate classes or taxonomic groups, as vulnerability to SLR may vary. They also emphasized that their results were conservative estimates due to range loss assumptions, the exclusion of non-intensive types of land conversion, and the elimination of small islands from their analysis. They also only accounted for three types of SLR scenarios, excluded human population growth and resource extraction, and did not consider other ecological factors such as potential benefits from sea-level rise. They urged conservation planning to account for both primary and secondary affects of SLR in determining potential management actions.

Microclimate Model of Sea Turtle Sex Ratios Predicts Increase in Female Hatchlings

As egg-laying reptiles, sea turtles depend on the temperature of the soil to determine the sex of their hatchlings. However, with climate change expected to raise temperatures globally, the sex ratios of their offspring are at risk of becoming imbalanced, threatening their populations. To analyze the potential impacts of climate change on sea turtle hatchlings, Fuentes and Porter (2013) used the Niche Mapper™ microclimate model to project soil temperatures at three green turtle nesting sites in the northern Great Barrier Reef under various emissions scenarios. They compared their results to existing correlative models, as well as to observational data of current climate conditions. The authors found that because the microclimate model required more data inputs than the correlative models, it produced more detailed predictions. However, both ultimately reached the same overall prediction that under an extreme emissions scenario, temperature increases are likely to skew sex ratios to favor female hatchlings as early as 2030. By 2070, turtle populations may become exclusively female or at worst, will no longer be able to incubate.—Katie Huang
Fuentes, M.M.P.B., Porter, W.P., 2013. Using a microclimate model to evaluate impacts of climate change on sea turtles. Ecological Modeling 251, 150–157.

Fuentes and Porter used the Niche Mapper™ microclimate model to estimate soil temperatures at Bramble Cay, Raine Island, and Sandbank 7, three green turtle nesting grounds in the northern Great Barrier Reef. Temperatures were projected under current climate conditions as well as under conservative and extreme emissions scenarios of climate change for 2030 and 2070. The two major data inputs required for the model were climate maximum and minimum data and physical properties of the soil. To calculate the climate inputs, the authors took hourly measurements of unshaded nesting grounds from November 2007 to March 2008. Variables such as daily air temperature, relative humidity, and wind speed were obtained from various data sources for the three sites. Soil properties were taken from samples of nesting beach dunes from November 2007. The authors calculated their reflexivity properties and ran a sensitivity analysis in order to determine their potential effect on soil temperature. Other soil properties such as thermal conductivity ranges and specific heat values were taken from other data sources. Fuentes and Porter also compacted the existing model to allow users to input conditions such as variations in soil water level or snow deposition that would affect hatchlings. In order to simulate projected increases in temperature, they increased the minimum and maximum air temperatures in the microclimate submodel by projected seasonal increments. To apply the temperature data to sea turtle hatchling sex ratios, they assumed sand temperatures at 29.3°C produced a 1:1 sex ratio, while temperatures below 27.8°C produced all males and temperatures above 30.8°C produced all females. They then assumed that the proportion of females increased linearly between 27.8 and 30.8°C. In order to analyze the accuracy of the microclimate model, the authors compared their results with those of correlative models comparing air and sea surface temperatures with soil temperature. They then ran the microclimate and correlative models for the current climate scenario and compared those results with observational data.
The temperatures constructed with Niche Mapper™ were not significantly different from observational data. The model was able to explain over 58% of variation in sand temperature at each of the nesting grounds, making it an appropriate model for future climate change scenarios if applied with caution. Based on soil temperature projections at 50 cm, Bramble Cay was the nesting site most susceptible to warming, while Sandbank 7 was the least. Under an extreme emissions scenario, Bramble Cay would produce mainly female hatchlings by 2030, while the other two sites would still produce male and female hatchlings. By 2070, Bramble Cay may reach temperatures near the upper thermal threshold for incubation, while Sandbank 7 would produce mainly female offspring. The 2070 projections for Raine Island differed by model, with the microclimate model predicting only female offspring and the correlative model suggesting that a small proportion of male offspring would still be produced. However, these results do not account for other influential factors such as nesting behavior, embryonic development, and potential capacity to adapt. Since sea turtles lay eggs at various depths and nest at different beach locations, they may learn to adapt to temperature changes in the future. Also, the models only predicted temperatures for one depth, leading to an incomplete prediction of future incubating environments. The authors suggest that temperatures at various depths need to be modeled in order to create more accurate predictions of sea turtle hatchling sex ratios.
Both the microclimate and correlative models were able to explain the variability in sand temperature at the three nesting grounds. However, the microclimate model is more useful in determining the suitability of nesting environments because it creates hourly projections at multiple specified depths. While the correlative model produced strong correlations between the mean monthly observed and modeled temperatures, it did not clearly illustrate the effects of daily fluctuations. The differences can be attributed to the amount of data inputted into each model: the microclimate dataset is more extensive and thus produces more detailed results. Furthermore, the microclimate model is capable of projecting soil temperatures at multiple depths simultaneously, while separate correlative models are needed for each desired depth. With further use, the microclimate model may be refined to help implement more effective short-term management strategies by creating site-specific approaches. However, both models are capable of producing similar range projections, with differences varying from 0.04 to 1.32°C. Despite the variation, the models ultimately reached the same projective implications. 

Climate Change Produces Cascading Consequences for Snow Leopard Populations in the Himalayas

Already endangered due to threats such as poaching and retaliatory killing, the snow leopard is also likely to be adversely affected by climate change. With temperatures and precipitation expected to rise in the Himalaya, the snow leopard’s preferred alpine habitat may be overrun with forests due to shifts in treeline range. To estimate the potential effects of alpine loss, Forrest et al. (2012) mapped current snow leopard habitats and monitored their responses to various climate change scenarios from 2070–2099. Depending on the severity of emissions, 10–30% of snow leopard habitat could be lost, potentially isolating populations of snow leopards in eastern China and northern India. The increase in forested areas may also add further adverse effects by increasing resource competition with the introduction of additional predatory species. Human activity is also likely to displace snow leopard prey, increasing the risk of snow leopards being killed by herders if they are forced to hunt livestock. The authors suggest that potential conservation efforts should account for such influences by human activity and that actions be concentrated in areas resilient to climate change, where populations are likely to remain intact.—Katie Huang
Forrest, J.L., Wikramanayake, E., Shrestha, R., Areendran, G., Gyeltshen, K., Maheshwari, A., Mazumar, S., Naidoo, R., Thapa, G.J., Thapa, K., 2012. Conservation and climate change: assessing the vulnerability of snow leopard habitat to treeline shift in the Himalaya. Biological Conservation 150, 129–135.

Forrest et al. used snow leopard observation data, published literature, and expert opinions to map snow leopard habitats. They defined potential habitats as grassland, shrubland, bare areas, or agricultural mosaic in rugged alpine regions below an elevation of 5500 m. Forest regions and areas with an altitude above 5500 m were not considered to be likely habitats for snow leopards, assumptions they confirmed with observational data. To examine the relationships between different blocks of habitat, the authors determined the dispersal range of snow leopards by modeling their costs of movement. In order to estimate the effects of climate change on the habitat regions, Forrest et al. identified four independent variables that were found to influence the treeline and created a logistic regression model. With its use, they analyzed changes in alpine zones under low, medium-low, and high emissions scenarios, using projected precipitation and temperature values from 2070–2099 that account for a wide range of plausible future climates. However, due to data limitations in regards to factors such as local weather patterns and rate of soil formation, the authors consider their model only to be a potential map under the conditions of adequate prey and limited human impact.
The authors found that their model had a 98% chance of predicting alpine zone accurately. With its use, they estimated a current habitat of 217,000 km2, most of which is in large interconnected habitat blocks. Under a high emissions scenario, about 30% of the current habitat range is threatened. Habitat blocks were found to likely decrease and become smaller on average, potentially isolating parts of the snow leopard population in eastern China and northern India. Most of the loss would occur in the southern area of the snow leopard range and in deep river mountain valleys. Under low emissions scenarios, up to 10% of habitat could still be lost. However, a large population of snow leopards along the southern border of China is likely to remain intact and may accumulate populations pushed northwards from Bhutan, Myanmar, and Nepal. In light of these results, the authors suggest that regions with resilient populations of snow leopards that are less vulnerable to climate change should be the focus of conservation actions.
If snow leopards are unable to adjust physiologically and ecologically to climate change, they may be also be impacted by other effects associated with a shift in treeline. The movement of forests may introduce other predatory species to the area, intensifying competition for limited resources. As a result, snow leopards might be driven upward past a 5500 m altitude, and the resulting decrease in oxygen would likely hurt their ability to hunt and survive. Changes in human behavior may also affect snow leopard habitats. As herders shift their livestock from nomadic to sedentary grazing, alpine grasslands become more quickly depleted. Combined with an increased harvest of native plants for medicinal and aromatic purposes, the loss of snow leopard habitats may be greater than expected. Human interactions can also potentially harm snow leopard prey species as they become displaced by livestock or eliminated as resource competition, forcing snow leopards to feed on livestock and putting them at risk of retaliatory killing by herders. As the effects of climate change include human-influenced dangers as well, Forrest et al. advise that both ecological and anthropogenic effects should be incorporated into any potential conservation actions.
Although their model was designed specifically for snow leopards, the authors suggest that it can also be applied to umbrella species in order to prioritize areas in need of conservation. They further recommend their treeline model as a means of predicting potential shifts in other regions of the world.

Observed Variations in Snake Diet More Likely Due to Local Effects Than Climate Change

By analyzing changes in the diets of opportunistic predator species, it is possible to observe the effects of climate change on prey populations. The asp viper, a small snake found in a variety of habitats in Central and Southern Europe, is prime for analysis due to the prevalence of data on its feeding ecology and the wide range of its inhabitance. In their study, Rugiero et al. (2012) hypothesized that if climate change had significant effects on asp viper diets, they would increase consumption of Mediterranean climate species, decrease consumption of temperate climate species, and decrease in diversity. However, their results found that despite decreased rainfall and increased temperatures as a result of climate change, asp vipers maintained relatively consistent diets. Only two prey species showed consistent trends of change, with the consumption of bank voles increasing and the consumption of shrews decreasing. However, as these are temperate climate species and thus both predicted to decline, these observations are more likely due to a local cessation of logging than climate change.—Katie Huang
Rugiero, L., Milana, G., Capula, M., Amori, G., Luiselli, L., 2012. Long term variations in small mammal composition of a snake diet do not mirror climate change trends. Acta Oecologica 43, 158–164.

                  Rugiero et al. studied field data from 1987–2010 on the diets of the asp viper (V. aspis), a small snake found in Central and Southern Europe. The asp viper is able to survive in a wide variety of habitats, including those with Mediterranean and temperate climates, and its diet consists mainly of rodents and species in the order Soricomorpha. The authors hypothesized that if asp viper diets were affected by global warming, they should increase in Mediterranean climate prey species consumed and decrease in diversity. If they were adversely affected by logging, species sensitive to forest loss would decrease. The authors collected data in the Tolfa Hills of central Italy, a region that was affected by a 13% decrease in rainfall and significant increases in annual mean temperature, likely due to climate change. In the region, they observed 11 prey species of rodents and eight species of soricomorphes, six of which lived in Mediterranean climates and two in temperate climates. To analyze snake diets, they randomly captured free-living individuals, marked and sexed them, and palpated their abdomens until the ingested prey were regurgitated or defecated. In order to determine the abundance of mammals in the field to compare those frequencies with those that occurred in the snake diets, Rugiero et al. conducted trapping sessions using live traps in the spring and autumn of 1992, 1993, 1997, 1999, and 2006.
                  The authors found that fluctuations in the composition of the snake diet reflected changes in the relative abundances of their prey, reinforcing studies showing that the asp viper is an opportunistic feeder. In general, asp vipers preferred rodents to soricomorphes, except for the period from 1987–1989 when the two groups has similar species abundances. There was also a significant decrease of soricomorphes over time. However, asp vipers tended to consume similar proportions of both rodents and soricomorphes despite annual fluctuations in species abundance, suggesting that the asp vipers’ opportunistic behavior creates a compensation effect. Rugiero et al. also found a significantly positive relationship between the abundance of small mammals in the field and the frequency of occurrence in viper diet. However, contrary to their hypotheses, the authors did not find that the composition of snake diets changed significantly over time. Asp vipers consistently preferred the same three types of prey, and only two species of prey showed consistent trends over time. The frequency of bank vole consumed increased significantly and the frequency of shrews consumed declined linearly. For all other species, there were no significant trends. According to the authors’ predictions, the bank vole, which lives in a temperate climate, should have declined in population, but its increase may signify that climate change did not significantly affect asp viper diets. Rugiero et al. instead suggest that the cessation of logging may explain these observations, as it likely affected the separate regions inhabited by the two groups differently. They conclude that changes in the viper diet are more attributed to local disturbances than climate change.

Predicted Upward Shifts in Mountaintop Plant Species Ranges Impact Biodiversity Differently by Zone

With climate change expected to continue to increase temperatures, the distribution of vascular plants on European mountain summits may change significantly according to predicted shifts in species ranges. An upward movement is expected to increase biodiversity at higher altitudes, at the cost of extinctions of plants on elevation gradient margins that cannot move up further. In their study, Pauli et al. compared the species richness of vascular plants on 66 mountain summits to determine how climate change might affect European vascular plant species richness. They found that while species richness tended to increase overall and in boreal and temperate climate zones due to upward species range shifts, biodiversity decreased in Mediterranean regions, possibly due to shortages in water availability. As a high proportion of endemic plants originate in Mediterranean zones, climate change may result in homogenized mountaintop communities due to the extinction of vascular plants.—Katie Huang
Pauli, H., Gottfried, M., Dullinger, S., Abdaladze, O., Akhalkatsi, M., Alonso, J.L.B., Coldea, G., Dick, J., Erschbamer, B., Calzado, R., Ghosn, D., Holten, J.I., Kanka, R., Kazakis, G., Kollár., Larsson, P., Moiseev, P., Molau, U., Mesa, J.M., Nagy, L., Pelino, G., Puşcaş, M., Rossi, G., Stanisci, A., Syverhuset, A.O., Theurillat, J., Tomaselli, M., Unterluggauer, P., Villar, L., Vittoz, P., Grabherr, G., 2012. Recent plant diversity changes on Europes mountain summits. Science 336, 353355.

Pauli et al. compared records from 2001 and 2008 of vascular plant species occurrence on 66 European mountain summits. The areas studied were distributed across 17 study regions, representing all major mountain systems in Europe. The altitudinal ranges of the summits spanned from the treelines to the uppermost peaks on lower mountain ranges or to the transition zone between alpine grassland and sparsely vegetated snowy ground on higher mountain ranges. Summits were also sorted into groups of four in order to compare regional differences in biodiversity. The authors accounted for observation errors by filtering out singular records and potentially misidentified species data. In order to compare the data from 2001 and 2008, Pauli et al. used linear mixed-effect models to compare differences in the number of species observed. The authors also calculated altitudinal indexes for each species in order to determine whether changes in species richness were possibly related to the movement of species ranges.
The authors found that across the 66 summits, the number of vascular plant species increased on average from 34.9 to 37.7, which was a statistically significant gain. However, while a majority of summits in boreal and temperate regions tended to acquire additional species, eight out of 14 summits in Mediterranean regions decreased their species counts. Similar results were observed on the regional level in that species richness only increased in regions in boreal or temperate zones, with species counts decreasing in three out of four Mediterranean regions. Models evaluating whether the changes in species richness were related to movement of species ranges suggest that species shifted their distributions to higher altitudes, likely due to the heightened effects on biodiversity on lower summits. Assuming warm-adapted plants thrive and cold-adapted plants decline in this higher elevation European alpine summit vegetation, the upward shift in species range can explain both increases and decreases in biodiversity counts.
The authors suggest that range expansion in boreal and temperate mountains is likely due to warmer conditions, while range retraction in Mediterranean zones may be due to a combination of rising summer temperatures and decreases in precipitation. As plants respond quickly to changes in water availability, the decrease in species richness in Mediterranean regions may be significant under climate change predictions. If climate change continues to increase temperatures, Mediterranean summits, which contain high proportions of endemic plants, may be threatened with the extinction of its vascular plants. Although endemic species are not inherently threatened, they tend to increase in richness at slower rates than nonendemic species, suggesting that their loss may be more drastic. If the annual rates of species gains remain constant for both endemic and nonendemic plants for the next 25 years, mountaintop communities may become homogenized due to decreases in endemic plant species richness.