It is with great pleasure that we announce the launch of our Biodiversity Conservation Collection. This Collection showcases research on a broad range of conservation science related topics, including anthropogenic impacts on biodiversity, such
It is with great pleasure that we announce the launch of our Biodiversity Conservation Collection. This Collection showcases research on a broad range of conservation science related topics, including anthropogenic impacts on biodiversity, such as habitat degradation, the spread of invasive species and global warming; conservation of key ecosystem services, such as carbon sequestration and pest regulation; and new management strategies to prevent further biodiversity loss.
We are extremely grateful to our team of Guest Editors, Steve Beissinger (University of California, Berkeley), Thomas Couvreur (Pontificia Universidad Catolica del Ecuador), Carlos Duarte (KAUST), Claudia Mettke-Hoffmann (Liverpool John Moores University) and Stuart Pimm (Duke University), for evaluating all submitted research and selecting articles for inclusion in the Collection. We also want to express our thanks to the PLOS ONE Academic Editors involved in the handling of submissions, to the reviewers, and to all the authors who submitted their research to this Call for Papers.
Eight of the studies published in the initial Collection release focus on habitat destruction in a wide range of regions, ecosystems and species. In the North Pacific Ocean, Edwards et al. investigated the ecological consequences of marine deforestation caused by shifting trophic interactions in the Aleutian Archipelago. They show that the rapid decline of sea otter populations, caused by increased predation pressure from killer whales, led to high sea urchin densities causing widespread deforestation of the kelp forests and general loss of biodiversity and ecosystem function. In the mainland USA, Bradshaw et al. evaluated whether wetland management practices for waterfowl were also beneficial to other wetland-dependent species such as bitterns, grebes and crakes. Habitats for marsh bird species have more than halved in the last 50 years due to wetland loss and degradation; their results highlight the importance of maintaining wetland hydrologic and vegetation complexity for the conservation of breeding marsh birds.
In Brazil, three independent studies provide evidence of the impacts of habitat fragmentation in the Amazon rain forest, where biodiversity has rapidly declined in recent decades. Palmeirim et al. quantified the effect of deforestation on small mammals and found that forest dwelling species are being replaced by open-habitat species as the deforestation frontier expands. Teixeira-Santos et al. studied four endangered emblematic large terrestrial mammals and showed that the survival ability was different for each species and that some species can adapt to tolerate anthropogenically altered habitats. Paschoalini et al. studied the effects of habitat fragmentation on the Araguaian river dolphin, whose populations have been dramatically reduced due to dam construction. This research provides potential practical applications to help species management and conservation in the region, as occupation and development of the Amazon is currently being encouraged in Brazil.
When the habitat is fragmented, isolated populations lose genetic diversity, leaving them more vulnerable to changing environmental conditions and with a higher risk of extinction. In the Midwestern USA, Douglas et al. examined the genetic population structure of three upland game birds inhabiting the declining American prairie grasslands, including the endangered Greater Prairie Chicken, and found that their populations are experiencing a genetic bottleneck. They advocate for a multi-species approach as a more effective management strategy for endangered upland game birds and for making more land available to prairie species. In the United Kingdom, Ball et al. conducted a study on the conservation genetic state of adder populations and found that the species’ polyandrous breeding system is, for the moment, protecting it against inbreeding. However, this might become a problem in the future as loss of connectivity prevents movement of individuals between patches of suitable habitat. Dondina et al. studied the suitability of ecological corridors to connect two isolated wolf populations through the degraded lowlands of Northern Italy and showed the importance of keeping natural areas, such as rivers, for maintaining habitat connectivity for the conservation of endangered species in a fragmented landscape.
Three studies among the first batch of articles published in this Collection address the impacts of climate change on biodiversity and potential mitigation strategies. Carbon sequestration has been suggested as a potential approach to mitigating the effects of greenhouse gas emissions responsible for global warming. In Spain, Morant et al. investigated the relationships between wetlands’ ecological characteristics, conservation measures and carbon emissions in the Ebro Delta wetlands. Wetlands are an important ecosystem service acting as natural carbon sinks but are under threat due to habitat destruction.
Large-scale empirical studies of the existing and projected impacts of climate change on wildlife are vital to scientifically-informed conservation management strategies aimed at minimizing and mitigating these impacts. In Southern California, Fogarty et al. used a large bird abundance dataset to investigate whether annual variation in seasonal temperature and precipitation was associated with relative abundances of breeding bird species. They found that species in arid areas may be negatively affected by increased temperature and aridity, but species from cooler areas may respond positively to those fluctuations in climate. Carbon pricing policies can also have unintended consequences for biodiversity through changing land management. Hashida et al. modelled forest habitat changes in response to forest landowner decision-making under multiple carbon pricing scenarios in Western USA. Their results predict a major shift from coniferous forest to hardwoods which could result in a dramatic loss of biodiversity in the region.
Three studies published in the Collection showcase research on species invasions. International trade is a major pathway of introduction of invasive species. Lucardi et al. conducted a comprehensive survey of the plant community at the largest container terminal in the USA . Their research identified the presence of a high number of invasive plant species in the port, providing important evidence that shipping ports are crucial sources of emergent plant invasions but are largely under-researched. Invasive species can have complex ecological impacts on the regions of invasion. Besterman et al. studied the ecological impacts of the establishment of one of the most invasive macroalgae on habitat selection and foraging behaviour of shorebirds in the mid-Atlantic region of the USA and found that generalist species preferred invaded habitats while specialist shorebirds preferred uninvaded mudflats. Invasive species also cause major economic losses in the regions of invasion. One of the most successful methods for sustainable management of invasive species is using their own natural enemies against them. In Morocco, Qessaoui et al. discovered the insecticidal activity of native rhizobacteria present in the soil against an important pest of tomato crops and suggested that using biological control agents would reduce the amount of synthetic chemical pesticides being used to control plant pests.
Finally three papers report methodological advances in conservation of endangered species. Endangered species are usually difficult to study because their population densities are low which hampers conservation efforts. Here, Nagarajan et al. report successful results of a non-invasive method for monitoring a wood-boring beetle species threatened by habitat loss in California. Current monitoring efforts require extensive field work looking for this rare species. In this study, the authors collected faecal samples from exit holes on trees and applied genetic barcoding techniques to identify the makers of the holes.
Large terrestrial carnivores are often keystone species in the ecosystems but have historically been persecuted and their populations are in decline globally. In the USA, sport hunting is used as a tool for managing puma populations. Laundré et al. investigated the effectiveness of this strategy for reducing conflict with humans, livestock and game species. Their results indicate that there is little evidence that puma control reduces conflict, and remark the need to reassess traditional predator control practices.
Management of captive populations is crucial for conservation of endangered species whose wild populations are at high risk of extinction. Fazio et al. studied the stress physiology of the fishing cat, a threatened wild cat from Southeast Asia, that is notoriously difficult to breed in captivity. Their study suggests that management actions such as transfers between facilities increases levels of stress while reduced animal-keeper interaction and social housing could lower stress levels and increase breeding success. This study might provide insights to better manage translocations of captive individuals of easily stressed species.
At the time of launch, there are 17 research articles featured in the Collection but more papers will be added as they are published over the coming weeks – so do check back for updates!
About the Guest Editors:
Steve Beissinger is Professor of Ecology & Conservation Biology at the University of California, Berkeley, where he held the A. Starker Leopold Chair in Wildlife Biology (2003-13), is a research associate of the Museum of Vertebrate Zoology, and is the co-Director of the Berkeley Institute for Parks, People and Biodiversity. Professor Beissinger’s current research centers on wildlife responses to global change and species’ extinctions – with recent fieldwork carried out in protected areas and working landscapes in California and Latin America. He directs the Grinnell Resurvey Project – a 15 year effort to revisit locations throughout California first surveyed by Joseph Grinnell in the early 1900’s in order to quantify the impacts of a century of climate and land-use change on the birds and mammals of California. Steve’s studies of parrotlets in Venezuela extend more than 30 years. Integrative studies of secretive, threatened rails in California provide a model for understanding coupled natural and human systems. He has authored over 200 scientific publications and is senior editor of three books. He served on the editorial boards of Ecology Letters, Ecology, Conservation Biology, Studies in Avian Biology, and Climate Change Responses. Steve is a Fellow of the American Association for the Advancement of Science, the Ecological Society of America (ESA), the Wissenschaftskolleg zu Berlin, and the American Ornithological Society, which awarded him the William Brewster Memorial Award in 2010 for his research on Western Hemisphere birds.
Thomas L.P. Couvreur is a senior researcher at the French National Institute for Sustainable Development, and is currently based at the “Pontificia Universidad Catolica del Ecuador”, in Quito Ecuador. He received his PhD in tropical biodiversity from the Wageningen University in the Netherlands, and worked as post doc at the Osnabruck University in Germany and The New York Botanical Garden in the USA. His main interest lies in understanding the evolution, resilience and diversity of tropical biodiversity, and rain forests in particular, one of the most complex and diverse ecosystems on the planet. He undertakes research in taxonomy, conservation, molecular phylogenetics and phylogeography of tropical plants. His research mainly focuses on tropical Africa and South America. He is chair of the IUCN Species Survival Commission for palms since 2018.
Professor Carlos M. Duarte (Ph.D. McGill University, 1987) is the Tarek Ahmed Juffali Research Chair in Red Sea Ecology at the King Abdullah University of Science and Technology (KAUST), in Saudi Arabia. Before this he was Research Professor with the Spanish National Research Council (CSIC) and Director of the Oceans Institute at The University of Western Australia.
Duarte’s research focuses on understanding the effects of global change in aquatic ecosystems, both marine and freshwater. He has conducted research across all continents and oceans, spanning most of the marine ecosystem types, from inland to near-shore and the deep sea and from microbes to whales. Professor Duarte led the Malaspina 2010 Expedition that sailed the world’s oceans to examine the impacts of global change on ocean ecosystems and explore their biodiversity. Professor Duarte served as President of the American Society of Limnology and Oceanography between 2007 and 2010. In 2009, was appointed member of the Scientific Council of the European Research Council (ERC), the highest-level scientific committee at the European Level, where he served until 2013. He has published more than 700 scientific papers and has been ranked within the top 1% Highly-Cited Scientist by Thompson Reuters in all three assessments of this rank, including the 2018 assessment released by Clarivate Analytics.
Dr Claudia Mettke-Hofmann is Reader in Animal Behaviour at Liverpool John Moores University, UK, and Subject Leader of the Animal Behaviour team. She received her externally conducted PhD from Free University of Berlin, Germany, and subsequently worked as a postdoc at the Max-Planck Institute for Ornithology in Radolfzell and Andechs, Germany, in collaboration with the Konrad Lorenz Institute for Comparative Behaviour, Vienna, Austria, before moving to the Smithsonian Migratory Bird Center, Washington DC, USA. She is now based at Liverpool John Moores University. Her research area is cognitive ecology, mainly in birds, with strong links to conservation aspects and animal welfare. She investigates how animals collect and store environmental information in relation to their ecology on the species level but also on the individual level (personality). A focus is how animals respond to environmental change, particularly in species that differ in their movement patterns such as being resident, migratory or nomadic. Differences in cognitive abilities in these groups help explain and predict population developments in our rapidly changing environments. More recently, her research has focussed on individual differences in cognition in colour-polymorphic species highlighting exciting differences in responses to environmental change between colour morphs. Claudia has been a PLOS ONE Section Editor since 2014.
Stuart Pimm is the Doris Duke Chair of Conservation Ecology at the Nicholas School of the Environment at Duke University. He is a world leader in the study of present day extinctions and what we can do to prevent them. Pimm received his BSc degree from Oxford University in 1971 and his Ph.D from New Mexico State University in 1974. Pimm is the author of over 300 scientific papers and four books. Pimm directs SavingSpecies, a 501c3 non-profit that uses funds for carbon emissions offsets to fund local conservation groups to restore degraded lands in areas of exceptional tropical biodiversity. His international honours include the Tyler Prize for Environmental Achievement (2010), the Dr. A.H. Heineken Prize for Environmental Sciences from the Royal Netherlands Academy of Arts and Sciences (2006).
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Rock lizards, pigment producing fungus, eagle rays, ant garden parasites, and Antarctic sea anemones: new species are discovered all the time and there are likely still millions that we simply haven’t yet discovered or assessed. Species are identified by researchers using a range of criteria including DNA, appearance, and habitat. PLOS ONE typically publishes several new species articles every month, and below we are pleased to help introduce five that were discovered in 2013.
Thought previously to consist of only three species, this group of lizards are now seven distinct species. They appear very similar to one another, making it difficult to tell which characteristics define different species, and which are just variations present in the same species. They also have a variety of habitats, from trees to rocky outcrops, and the genus is widespread. Iranian, German, and Portuguese scientists used genetic variation and habitat to help describe four new species of Iranian rock lizards, Darevskia caspica, D. Kamii, D. kopetdaghica, and D. schaekeli. These techniques, in addition to analysis of the the lizards’ physical features, as in the photo of the four new species’ heads at the top of this page, helped to identify them definitively.
Found in soil, indoor environments, and fruit, Talaromyces atroroseus produces a red pigment that might be good for manufacturing purposes, especially in food. Some other species of this type of fungus produce red pigments, but they are not always as useful because they can also produce toxins. T. atroroseus produces a stable red pigment with no known toxins, making it safer for human use, according to the Dutch and Danish researchers who identified it.
Fish, like rays and sharks, are at high risk for extinction as a group, but as rare as they are, they can be plentiful enough in some locations to make them undesirable to locals. The discovery of the Naru eagle ray, Aetobatus narutobiei, splits a previously defined species, A. flagellum, that, due to its shellfish-eating habits, is considered a pest and culled in southern Japan. The discovery by Australian and Japanese scientists that this species is actually two species prompted the authors to encourage a reassessment of the conservation status of the rays.
In the Brazilian rainforest of Minas Gerais, leafcutter ants cultivate fungus, their primary source of food, on harvested leaf clippings. But scientists from Brazil, United Kingdom, and The Netherlands have discovered that their food source is threatened by four newly identified mycoparasites, Escovopsis lentecrescens, E. microspora, E. moellieri, and Escovopsioides nivea. The parasites grow like weeds in the ants’ gardens, crowding out more desirable fungus used for food. Unfortunately for the ants, researchers expect there are many similar unidentified species yet to be discovered.
Living on the previously undocumented ecosystem of the underside of the Ross Ice Shelf in Antarctica, American researchers discovered the first species of sea anemone known to live in ice, Edwardsiella andrillae. Fields of anemone were discovered using a scientist-driven remote-controlled submersible. The anemone burrows and lives within the ice and dangles a tentacle into the water beneath, almost as if it is dipping a toe in the water to test the chilly temperature.
Look here to read more about new species.
Ahmadzadeh F, Flecks M, Carretero MA, Mozaffari O, Böhme W, et al. (2013) Cryptic Speciation Patterns in Iranian Rock Lizards Uncovered by Integrative Taxonomy. PLoS ONE 8(12): e80563. doi:10.1371/journal.pone.0080563
Frisvad JC, Yilmaz N, Thrane U, Rasmussen KB, Houbraken J, et al. (2013)Talaromyces atroroseus, a New Species Efficiently Producing Industrially Relevant Red Pigments. PLoS ONE 8(12): e84102. doi:10.1371/journal.pone.0084102
White WT, Furumitsu K, Yamaguchi A (2013) A New Species of Eagle RayAetobatus narutobiei from the Northwest Pacific: An Example of the Critical Role Taxonomy Plays in Fisheries and Ecological Sciences. PLoS ONE 8(12): e83785. doi:10.1371/journal.pone.0083785
Augustin JO, Groenewald JZ, Nascimento RJ, Mizubuti ESG, Barreto RW, et al. (2013) Yet More “Weeds” in the Garden: Fungal Novelties from Nests of Leaf-Cutting Ants. PLoS ONE 8(12): e82265. doi:10.1371/journal.pone.0082265
Daly M, Rack F, Zook R (2013) Edwardsiella andrillae, a New Species of Sea Anemone from Antarctic Ice. PLoS ONE 8(12): e83476. doi:10.1371/journal.pone.0083476
Figures are all from their respective articles.
Borneo: the third largest island in the world, one-third of which is home to 220,000 km2 of diverse and beautiful rainforest. Borneo is divided among three countries—Brunei, Indonesia, and Malaysia—and at approximately 130 million years old, the Borneo rainforests are some of the oldest in the world.
The landscape of Borneo, however, is rapidly changing. Natural forest resources provide significant income for both Malaysia and Indonesia, and oil palm plantations, which require the clearing of natural land cover, produced an annual revenue of US $40 billion for Indonesia and Malaysia in 2012. In contrast, Borneo rainforests present the only opportunity for large-scale conservation in Southeast Asia and are one of the few places still called home by large, endangered animals like orang-utans, elephants, bears and rhinos.
This summer, three different PLOS ONE studies addressed the complex issues surrounding deforestation. Separate groups of researchers mapped forest cover and logging roads, conducted statistical analyses on different uses of land, and investigated how Indonesian and Malaysian villagers of Borneo value and use these forests.
To better understand the troubling state of forests in Malaysian Borneo, researchers in one PLOS ONE study mapped forest coverage and conditions. Tracking the condition of big areas of land is no easy task. To accomplish the feat, scientists imaged forests areas using high-definition satellite imagery, charted logging roads, and did some serious number crunching.
Key to this assessment was the actual condition of the rainforests. Are they intact, or have they been degraded—maybe severely so—by the effects of repeated logging? Critical damage is done to soil, waterways, and forest structure when forests are repeatedly logged without enough time to regenerate properly. To assess the condition of the residual forest, researchers distinguished between different types of coverage—bare, mangrove, plantation, and various levels of degradation, for example—and charted the number of logging roads created between 1990 and 2009. The image below depicts the forest cover and condition of Malaysian Borneo and Brunei in 2009.
If one road was built in an area since 1990, the area was classified as degraded. If more than one road had been built in an area since 1990, that area was classified as severely degraded. Researchers charted enough roads built between 1990 and 2009 to circle Earth nine times if placed end-to-end. The image below depicts the new roads constructed in a forested region known as the ‘Heart of Borneo’ in purple.
Needless to say, a great deal of the forests in Malaysian Borneo was classified as severely degraded. Researchers found that rainforests covered only 22% of land area in Malaysian Borneo in 2009, and of that 22%, only 38% remained intact. What then is the future for these degraded rainforests?
The researchers of a second PLOS ONE study evaluated the role logged forests play in maintaining natural rainforests in Kalimantan, Indonesian Borneo, by conducting statistical analyses on areas designated as protected areas, areas designated for logging, and industrial plantations. Researchers concluded that, when logged responsibly, areas designated for logging, called timber concessions, maintained forest cover just as well as protected areas during 2000-2010. Protecting timber concessions would increase the amount of land dedicated to sustaining larger forest landscapes.
The alternative to returning these logged areas, often considered beyond the point of regeneration, to a state of natural regrowth is reclassification as industrial plantation. Palm oil plantations are economically viable options for Indonesia. However, to make the land viable for industrial planation use, workers must first strip larger trees, burn smaller trees and shrubs, and finally clear the remaining land. These researchers view responsible logging as a compromise in which forests continue to provide economic output to communities, but also are allowed to maintain the veracity of their biodiversity. Rather than being seen as wastelands and turned into industrial plantations, researchers consider timber concessions as valuable areas of tree coverage and biodiversity, which merit classification as IUCN Protected Areas.
However, as researchers from a third PLOS ONE paper state, “Striking a balance between economic development and maintenance of biodiversity is increasingly challenging in the face of climate change, rapid human production growth, and concomitant demand for natural resources.” To address the range of ways the forest is valuable, researchers assessed Indonesian and Malaysian Borneo’s peoples’ perceptions of the values and uses of forests, as well as the factors influencing these perceptions.
Of 1,837 people surveyed from 185 villages in Indonesian and Malaysian Borneo, 67% considered the forest to be important for maintaining their good health. The authors state that the forest was generally perceived as a provider of good health. Moreover, natural forest resources, even in those forests degraded by repeated logging, are important for local people. In their responses, participants frequently mentioned using forests for timber, rattan, fire wood, bushmeat and fish, traditional medicine, and forest gardens. Most people reported using forest resources even in areas severely degraded by logging, or where no canopy cover exists. Researchers therefore concluded that considering these areas “wastelands” or degraded beyond the point of use, with the result that these areas are converted into industrial plantations, is not warranted due to the value placed on resources obtained from forests, regardless of level of degradation.
Researchers also found that many believed small-scale deforestation benefitted welfare. 48% of respondents reported small scale clearing for purposes of farming as positive. Respondents were much less supportive of large-scale deforestation.
Initiatives to strike a balance between economic need and maintenance of these diverse rainforests in Borneo are ongoing. Researchers are divided about the most effective ways to conserve Borneo’s important natural forests; whereas the construction of palm oil plantations in place of forests is unquestionably destructive to conservation efforts, the place of logging in Borneo remains less defined. Conserving biodiversity, responsibly maintaining the economy, and valuing the input of local people must all be taken into account when devising compromises for the difficult issue of deforestation. In the meantime, research in Borneo continues to enable a better understanding of Borneo’s complex balancing act.
Bryan JE, Shearman PL, Asner GP, Knapp DE, Aoro G, et al. (2013) Extreme Differences in Forest Degradation in Borneo: Comparing Practices in Sarawak, Sabah, and Brunei. PLoS ONE 8(7): e69679. doi:10.1371/journal.pone.0069679
Gaveau DLA, Kshatriya M, Sheil D, Sloan S, Molidena E, et al. (2013) Reconciling Forest Conservation and Logging in Indonesian Borneo. PLoS ONE 8(8): e69887. doi:10.1371/journal.pone.0069887
Meijaard E, Abram NK, Wells JA, Pellier A-S, Ancrenaz M, et al. (2013) People’s Perceptions about the Importance of Forests on Borneo. PLoS ONE 8(9): e73008. doi:10.1371/journal.pone.0073008
Image 2: Figure 2 journal.pone.0069679
Image 3: Figure 1 journal.pone.0069679
Image 4: Figure 2 journal.pone.0069887
Post authored by Collection Curator Ben Bond-Lamberty
The ecological impacts of climate change are broad and diverse, and include alterations to species’ range limits, plant phenology and growth, carbon and nutrient cycling, as well as biodiversity and extinction risk. Recent PLOS articles have used a variety of experimental and observational approaches to examine these subjects.
Identifying at-risk regions, taxa, and species is a critical first step in adaptation and conservation efforts. A study by Mouillot et al. suggested that rare species are particularly important in conservation efforts, as rare species in diverse ecosystems are not replaceable by other species that fulfill the same ecological functions. At the same time, both rare and more common species experience the ecological impacts of climate change. Foden et al. combined biology and ecology to assess, on a global scale, the climate change vulnerability of birds, amphibians, and corals based on expert assessment and literature surveys. In a more regionally focused study, Gardali et al. assessed climate-change risk for California’s vulnerable bird species.
Birds were also the focus of two studies documenting how particular species can be ‘winners’ or ‘losers’ in a changing climate. Receding glaciers and thus increased breeding habitat have led to population increases for Adélie penguins in the southern Ross Sea. The outlook was more mixed for Pacific western grebes , which have shifted south, perhaps in response to changes in their forage fish prey. Further down the food chain, Suikkanen et al. used thirty years of marine data to infer that climate change and eutrophication drove a trophic shift in Baltic Sea food webs.
Long-term data were also used to study how flowering dates have changed since the mid-19th century. In a study that received extensive media coverage, Ellwood et al. used flowering records initiated as early as 1852 to show that high spring temperatures in 2010 and 2012 resulted in the earliest flowering in recorded history in the eastern United States. The biological pathways through which temperature affects seasonal timing in endotherms were discussed by Caro et al. Two other widely-covered studies focused on coffee: predicting future trends and identifying priorities, and climate change impacts on this plant and one of its important pests. Both examine adaptation possibilities for managing coffee crops over the coming century.
Adaptation and vulnerability were central themes for Guest et al., who reported that corals under thermal stress showed lower bleaching susceptibility at locations that bleached a decade earlier, implying an adaptive or acclimatization response. The molecular mechanisms behind such thermal tolerance were explored by Bellantuono et al.
Finally, the ecological impacts of climate change affect our health, the urban environment, and the agricultural economy. Airborne pollen counts have been increasing across Europe, and Ziello et al. suggest that rising CO2 levels may be influencing this increase. In another study, Meineke et al. used an elegant combination of observation and manipulative experiments to show that urban warming was a key driver of insect pest outbreaks in the southeastern U.S. Rising temperatures are a significant driver for the expanding range of Asian tiger mosquitoes, known vectors for West Nile and other viral infections. Warming was also found to contribute to the decreasing quality of grassland for grazers such as bison and cattle, although the effects are often exerted via complex interactions with other factors.
The broad range of these papers emphasize not only the multi-faceted impacts of climate change on ecological and human systems, but also the breadth and depth of research on these subject being reported in the PLOS journals. These journals seem a particularly appropriate venue for the ‘citizen science’ and other long-term data used by many of these studies.
Collection Citation: Ecological Impacts of Climate Change Collection (2013) http://www.ploscollections.org/ecoclimatechange
Image Credit: (Clockwise from top) William Warby. Flickr.com. Thomas Vignaud. PLOS Biology. 2011. 9(4). Colombi et al. PLOS ONE. 2013. Soto-Azat et al. PLOS ONE. 2013.
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Scientists interested in helping endangered species like the African elephant and the black rhinoceros would like to know whether these animals compete for resources in the wild, as such food contests could impact the population and health of both species. Unfortunately, our favorite rough-skinned big guys have IUCN statuses of vulnerable and critically endangered, respectively, so competition for food between them may present a bit of an ecological puzzle.
To gain evidence of food competition, researchers from Australia and the Centre for African Conservation Ecology took a close look at elephant and rhino poop (no, seriously) across different seasons to identify the types of plants each herbivore was eating. Poop collecting was performed at times of the year when rhinos and elephants ate in the same region, and then again when only rhinos grazed in the area (in the absence of elephants). Variations in the plant types found in the feces were counted as indicators of dietary differences.
While it’s been shown that the presence of elephants can help some herbivores with habitat and food access, limited studies have been conducted on how the elephants’ foraging behavior may affect that of specifically megaherbivores. The authors state that there is clear evidence that elephants hog and monopolize food, a behavior that they suspected would affect the diets of other large herbivores. Indeed, the results of this study revealed that resource use was clearly separated by season, and rhinos munched on different grasses depending on whether or not the elephants were present. Without elephants around, rhinos ate more diverse plants, like woody shrubs and succulents, but in their presence, rhinos restrained themselves and consumed more grasses. This may not seem like a big deal, but rhinos are known to be strict browsers (read: picky about their food choices), so this dietary difference discovery was surprising to researchers.
The authors go on to suggest that elephants living at high population densities in certain regions may significantly affect the foraging opportunities of other grazers, and these close living quarters may have long-term effects on the overall fitness of the other animals. These behaviors may have particularly important consequences in smaller or fenced-in wildlife parks, where populations tend to grow at the same time that food availability goes down.
Citation: Landman M, Schoeman DS, Kerley GIH (2013) Shift in Black Rhinoceros Diet in the Presence of Elephant: Evidence for Competition? PLoS ONE 8(7): e69771. doi:10.1371/journal.pone.0069771
From rainforests to rocky glaciers, the life of an ecosystem is rooted in the balance of nutrients in its soil. Shifting levels of soil nitrogen (N) and phosphorus (P) define how ecosystems evolve, and understanding the dynamics of these key nutrients can help ecologists identify crucial factors to help mitigate climate change.
A new model to understand N and P dynamics over different time scales was described in the PLOS ONE paper, “Nitrogen and Phosphorus Limitation over Long-term Ecosystem Development in Terrestrial Ecosystems”. Recently awarded the Ecological Society of America’s prize for an outstanding theoretical ecology paper, the study determines whether N or P are more likely to limit the productivity of ecosystems over short, intermediate and long timescales. Author Duncan Menge explains the background and results of their study:
How do N and P levels change with the age of an ecosystem like a rainforest?
A good question. Levels of both N and P are very low in very young ecosystems (which typically have rocky soils; see picture above), higher in intermediate-aged ecosystems (see picture), and often lower in old ecosystems. How N levels change relative to P, though, is a trickier subject. The best-studied sites show relatively low N in younger ecosystems and relatively high N in older ecosystems, but there are some places that show opposing trends.
Prior to your research, how did theoretical models assess the impact of these two nutrients on ecosystem dynamics?
Prior to our work there were a series of conceptual developments, which I will call “the classic model,” but there was no previous mathematical model of N and P dynamics during long-term ecosystem development. The classic model states that ecosystems should progress from N deficiency in younger ecosystems to P deficiency in older ecosystems, as is seen on the best-studied sites. According to the classic model, this happens because of the differences in where N and P come from. P is present in most rocks, whereas N is not, so P inputs are largely controlled by the weathering of rocks. Consequently, very young ecosystems have large P inputs, whereas very old ecosystems have small P inputs. On the other hand, N comes primarily from rain, so N inputs don’t necessarily depend on ecosystem age.
There are a number of missing elements that jumped out as potentially important. First, the input side of the story isn’t as simple as “P comes from rocks, N comes from rain.” P also comes from dust that is blown in from upwind, whereas N can also come from organisms like soybean or alder that “fix” N from the air. Second, N and P losses from ecosystems should be as important as inputs in determining N and P levels, but these weren’t the focus of the classic model. These facts have been known for a long time in the scientific community, but no one had looked at what their implications might be for ecosystem development.
What was your new model and how did it cover these aspects?
Our model is novel for a couple of reasons. First, we considered a broader set of N and P input and loss dynamics than the classic model, which made for a richer set of possible ecosystem trajectories. Second, the type of mathematical analysis we did was unlike anything previous researchers had done in this particular field, and made it possible to pin down the types of conditions that might lead to different soil conditions.
What were some of the key data accounted for in your model that were overlooked in previous analyses?
Aside from the input and loss dynamics mentioned above, one piece of data we keyed in on was that microbes in the soil have an easier time accessing P than N in dead plant material. Again, this “preferential P mineralization” is something that has been known for a long time, but we thought that the effects of this quirk might not be fully appreciated.
What were the main findings of your analyses?
In addition to the classic “N limitation to P limitation” path, our model shows that many other trajectories are feasible. For example, if dust deposition is high and N-fixing organisms are abundant in young ecosystems (as they often are), an ecosystem might start out P limited and end N limited. One of the more surprising findings was that the levels of N and P in soil organic matter (mostly dead plant material) don’t necessarily correspond to N versus P limitation in an intuitive way.
What are some of the practical applications of this model- for example, for developmental activities in rainforests, or human activities planned in other ecosystems?
Whether N or P has a greater effect in an ecosystem has important implications for many environmental issues. The most important application is enhancing our climate models. Excess N can be transformed into a greenhouse gas, whereas P cannot. So, a better understanding of nutrient levels will improve predictions about the extent of climate change.
Citation: Menge DNL, Hedin LO, Pacala SW (2012) Nitrogen and Phosphorus Limitation over Long-Term Ecosystem Development in Terrestrial Ecosystems. PLoS ONE 7(8): e42045. doi:10.1371/journal.pone.0042045
Photos by Duncan Menge:
top: the rocky soil of a very young ecosystem, Franz Josef glacier in New Zealand. The rainforests in the valley formed by the Franz Josef glacier are some of the best studied ecosystem development sites in the world.
below: a rainforest on 500 year old soil near the Franz Josef glacier.