Showing papers in "Frontiers in Ecology and the Environment in 2015"

Interval squeeze: altered fire regimes and demographic responses interact to threaten woody species persistence as climate changes

Abstract: Projected effects of climate change across many ecosystems globally include more frequent disturbance by fire and reduced plant growth due to warmer (and especially drier) conditions. Such changes affect species - particularly fire-intolerant woody plants - by simultaneously reducing recruitment, growth, and survival. Collectively, these mechanisms may narrow the fire interval window compatible with population persistence, driving species to extirpation or extinction. We present a conceptual model of these combined effects, based on synthesis of the known impacts of climate change and altered fire regimes on plant demography, and describe a syndrome we term interval squeeze. This model predicts that interval squeeze will increase woody plant extinction risk and change ecosystem structure, composition, and carbon storage, especially in regions projected to become both warmer and drier. These predicted changes demand new approaches to fire management that will maximize the in situ adaptive capacity of species to respond to climate change and fire regime change.

Toward an old-growth concept for grasslands, savannas, and woodlands

Abstract: We expand the concept of “old growth” to encompass the distinct ecologies and conservation values of the world's ancient grass-dominated biomes. Biologically rich grasslands, savannas, and open-canopy woodlands suffer from an image problem among scientists, policy makers, land managers, and the general public, that fosters alarming rates of ecosystem destruction and degradation. These biomes have for too long been misrepresented as the result of deforestation followed by arrested succession. We now know that grassy biomes originated millions of years ago, long before humans began deforesting. We present a consensus view from diverse geographic regions on the ecological characteristics needed to identify old-growth grasslands and to distinguish them from recently formed anthropogenic vegetation. If widely adopted, the old-growth grassland concept has the potential to improve scientific understanding, conservation policies, and ecosystem management.

The portfolio concept in ecology and evolution

Abstract: Biological systems have similarities to efficient financial portfolios; the emergent properties of aggregate systems are often less volatile than their components. These portfolio effects derive from statistical averaging across the dynamics of system components, which often correlate weakly or negatively with each other through time and space. The “portfolio” concept when applied to ecological research provides important insights into how ecosystems are organized, how species interact, and how evolutionary strategies develop. It also helps identify appropriate scales for developing robust management and conservation schemes, and offers an approach that does not rely on prescriptive predictions about threats in an uncertain future. Rather, it presents a framework for managing risk from inevitable perturbations, many of which we will not be able to understand or anticipate.

Marine urbanization: an ecological framework for designing multifunctional artificial structures

Abstract: Underwater cities have long been the subject of science fiction novels and movies, but the “urban sprawl” of artificial structures being developed in marine environments has widespread ecological consequences. The practice of combining ecological principles with the planning, design, and operation of marine artificial structures is gaining in popularity, and examples of successful engineering applications are accumulating. Here we use case studies to explore marine ecological engineering in practice, and introduce a conceptual framework for designing artificial structures with multiple functions. The rate of marine urbanization will almost certainly escalate as “aquatourism” drives the development of underwater accommodations. We show that current and future marine developments could be designed to reduce negative ecological impacts while promoting ecosystem services.

The biogeography of the Plastisphere: implications for policy

Abstract: Microplastics (particles less than 5 mm) numerically dominate marine debris and occur from coastal waters to mid-ocean gyres, where surface circulation concentrates them. Given the prevalence of plastic marine debris (PMD) and the rise in plastic production, the impacts of plastic on marine ecosystems will likely increase. Microscopic life (the “Plastisphere”) thrives on these tiny floating “islands” of debris and can be transported long distances. Using next-generation DNA sequencing, we characterized bacterial communities from water and plastic samples from the North Pacific and North Atlantic subtropical gyres to determine whether the composition of different Plastisphere communities reflects their biogeographic origins. We found that these communities differed between ocean basins – and to a lesser extent between polymer types – and displayed latitudinal gradients in species richness. Our research reveals some of the impacts of microplastics on marine biodiversity, demonstrates that the effects and fa...

Engineering away our natural defenses: an analysis of shoreline hardening in the US

Abstract: Rapid population growth and coastal development are primary drivers of marine habitat degradation. Although shoreline hardening or armoring (the addition of concrete structures such as seawalls, jetties, and groins), a byproduct of development, can accelerate erosion and loss of beaches and tidal wetlands, it is a common practice globally. Here, we provide the first estimate of shoreline hardening along US Pacific, Atlantic, and Gulf of Mexico coasts and predict where future armoring may result in tidal wetland loss if coastal management practices remain unchanged. Our analysis indicates that 22 842 km of continental US shoreline – approximately 14% of the total US coastline – has been armored. We also consider how socioeconomic and physical factors relate to the pervasiveness of shoreline armoring and show that housing density, gross domestic product, storms, and wave height are positively correlated with hardening. Over 50% of South Atlantic and Gulf of Mexico coasts are fringed with tidal wetlands that...

Desertification, land use, and the transformation of global drylands

Abstract: Desertification is an escalating concern in global drylands, yet assessments to guide management and policy responses are limited by ambiguity concerning the definition of “desertification” and what processes are involved. To improve clarity, we propose that assessments of desertification and land transformation be placed within a state change–land-use change (SC–LUC) framework. This framework considers desertification as state changes occurring within the context of particular land uses (eg rangeland, cropland) that interact with land-use change. State changes that can be readily reversed are distinguished from regime shifts, which are state changes involving persistent alterations to vegetation or soil properties. Pressures driving the transformation of rangelands to other types of land uses may be low, fluctuating, or high, and may influence and be influenced by state change. We discuss how the SC–LUC perspective can guide more effective assessment of desertification and management of drylands.

The capacity of refugia for conservation planning under climate change

Abstract: Refugia – areas that may facilitate the persistence of species during large-scale, long-term climatic change –are increasingly important for conservation planning. There are many methods for identifying refugia, but the ability to quantify their potential for facilitating species persistence (ie their “capacity”) remains elusive. We propose a flexible framework for prioritizing future refugia, based on their capacity. This framework can be applied through various modeling approaches and consists of three steps: (1) definition of scope, scale, and resolution; (2) identification and quantification; and (3) prioritization for conservation. Capacity is quantified by multiple indicators, including environmental stability, microclimatic heterogeneity, size, and accessibility of the refugium. Using an integrated, semi-mechanistic modeling technique, we illustrate how this approach can be implemented to identify refugia for the plant diversity of Tasmania, Australia. The highest-capacity climate-change refugia we...

Recreational demand for clean water: evidence from geotagged photographs by visitors to lakes

Abstract: More than 41 000 water bodies are listed as impaired by the US Environmental Protection Agency under the Clean Water Act. Implementation and enforcement of regulations designed to address these impairments can be costly, raising questions about the value of the public benefits derived from improved surface water quality. Here, we assess the recreational value of changes in water quality using freely available geotagged photographs, taken by members of the public, as a proxy for recreational visits to lakes. We found that improved water clarity is associated with increased numbers of visits to lakes and that lake users were willing to incur greater costs to visit clearer lakes. Lake users were willing to travel 56 minutes farther (equivalent to US$22 in travel costs) for every one-meter increase in water clarity in Minnesota and Iowa lakes, when controlling for other lake attributes. Our approach demonstrates the potential for social-media data to inform social–ecological research, including assessment of the recreational benefits of improvements in water quality.

Why do we map threats? Linking threat mapping with actions to make better conservation decisions

Abstract: Spatial representations of threatening processes – “threat maps” – can identify where biodiversity is at risk, and are often used to identify priority locations for conservation In doing so, decision makers are prone to making errors, either by assuming that the level of threat dictates spatial priorities for action or by relying primarily on the location of mapped threats to choose possible actions We show that threat mapping can be a useful tool when incorporated within a transparent and repeatable structured decision-making (SDM) process SDM ensures transparent and defendable conservation decisions by linking objectives to biodiversity outcomes, and by considering constraints, consequences of actions, and uncertainty If used to make conservation decisions, threat maps are best developed with an understanding of how species respond to actions that mitigate threats This approach will ensure that conservation actions are prioritized where they are most cost-effective or have the greatest impact, rather than where threat levels are highest

Going with the flow or against the grain? The promise of vegetation for protecting beaches, dunes, and barrier islands from erosion

Abstract: Coastlines have traditionally been engineered to maintain structural stability and to protect property from storm-related damage, but their ability to endure will be challenged over the next century. The use of vegetation to reduce erosion on ocean-facing mainland and barrier island shorelines – including the sand dunes and beaches on these islands – could be part of a more flexible strategy. Although there is growing enthusiasm for using vegetation for this purpose, empirical data supporting this approach are lacking. Here, we identify the potential roles of vegetation in coastal protection, including the capture of sediment, ecological succession, and the building of islands, dunes, and beaches; the development of wave-resistant soils by increasing effective grain size and sedimentary cohesion; the ability of aboveground architecture to attenuate waves and impede through-flow; the capability of roots to bind sediments subjected to wave action; and the alteration of coastline resiliency by plant structur...

Connectivity in dryland landscapes: shifting concepts of spatial interactions

Abstract: Dryland ecosystems are often characterized by patchy vegetation and exposed soil. This structure enhances transport of soil resources and seeds through the landscape (primarily by wind and water, but also by animals), thus emphasizing the importance of connectivity – given its relation to the flow of these materials – as a component of dryland ecosystem function. We argue that, as with the fertile-islands conceptual model before it, the concept of connectivity explains many phenomena observed in drylands. Further, it serves as an organizing principle to understand dryland structure and function at scales from individual plants to entire landscapes. The concept of connectivity also helps to organize thinking about interactions among processes occurring at different scales, such as when processes at one scale are overridden by processes at another. In these cases, we suggest that state change occurs when fine-scale processes fail to adjust to new external conditions through resource use or redistribution at the finer scale. The connectivity framework has practical implications for land management, especially with respect to decision making concerning the scale and location of agricultural production or habitat restoration in the world's drylands.

Context‐dependent conservation responses to emerging wildlife diseases

Abstract: Emerging infectious diseases pose an important threat to wildlife. While established protocols exist for combating outbreaks of human and agricultural pathogens, appropriate management actions before, during, and after the invasion of wildlife pathogens have not been developed. We describe stage-specific goals and management actions that minimize disease impacts on wildlife, and the research required to implement them. Before pathogen arrival, reducing the probability of introduction through quarantine and trade restrictions is key because prevention is more cost effective than subsequent responses. On the invasion front, the main goals are limiting pathogen spread and preventing establishment. In locations experiencing an epidemic, management should focus on reducing transmission and disease, and promoting the development of resistance or tolerance. Finally, if pathogen and host populations reach a stable stage, then recovery of host populations in the face of new threats is paramount. Successful management of wildlife disease requires risk-taking, rapid implementation, and an adaptive approach.

Rangeland ecosystem services: Shifting focus from supply to reconciling supply and demand

Abstract: Ecosystem services have been extensively studied in recent decades. Most of the thousands of scholarly papers published on the subject have focused on describing the production, spatial extent, and valuation of such services. Human reliance on ecosystem services is a function of ecosystems' capacity to supply and societal demand for these benefits. However, considerably more attention has been devoted to the supply side than to the demand for them. Sustainable land management depends on reconciling supply of and demand for ecosystem services among different stakeholders. The emphasis is now shifting from the supply of ecosystem services to attaining a balance between supply and demand. Here, we illustrate the demand for rangeland ecosystem services, describe current changes in societal demand, and present a specific provisioning service to exemplify the dynamic nature of reconciling ecosystem-service supply and demand.

Arctic tundra fires: natural variability and responses to climate change

Abstract: Anthropogenic climate change may result in novel disturbances to Arctic tundra ecosystems. Understanding the natural variability of tundra-fire regimes and their linkages to climate is essential in evaluating whether tundra burning has increased in recent years. Historical observations and charcoal records from lake sediments reveal a wide range of fire regimes in Arctic tundra, with fire-return intervals varying from decades to millennia. Analysis of historical data shows strong climate–fire relationships, with threshold effects of summer temperature and precipitation. Projections based on 21st-century climate scenarios suggest that annual area burned will approximately double in Alaskan tundra by the end of the century. Fires can release ancient carbon from tundra ecosystems and catalyze other biogeochemical and biophysical changes, with local to global consequences. Given the increased likelihood of tundra burning in coming decades, land managers and policy makers need to consider the ecological and so...

Creating space for large-scale restoration in tropical agricultural landscapes

Abstract: Poorly planned, large-scale ecological restoration projects may displace agricultural activities and potentially lead to the clearance of native vegetation elsewhere, with associated impacts on biodiversity and ecosystem services. Yet few studies have considered these risks and the ways in which restoration can increase competition for land. Here, we address this issue by examining whether large-scale restoration of the Brazilian Atlantic Forest could displace cattle production, as a result of land shortages. Although the risks of displacement are indeed high when reforestation is planned in areas with high cattle productivity, we discuss how these risks can be minimized through a combination of productivity increases, a regional restoration planning framework, and the prioritization of marginal agricultural land for restoration. We also consider how restoration can, in some circumstances, be made more economically sustainable by incorporating income-generating activities such as exploitation of timber an...

Can polar bears use terrestrial foods to offset lost ice‐based hunting opportunities?

Abstract: Increased land use by polar bears (Ursus maritimus) due to climate-change-induced reduction of their sea-ice habitat illustrates the impact of climate change on species distributions and the difficulty of conserving a large, highly specialized carnivore in the face of this global threat. Some authors have suggested that terrestrial food consumption by polar bears will help them withstand sea-ice loss as they are forced to spend increasing amounts of time on land. Here, we evaluate the nutritional needs of polar bears as well as the physiological and environmental constraints that shape their use of terrestrial ecosystems. Only small numbers of polar bears have been documented consuming terrestrial foods even in modest quantities. Over much of the polar bear's range, limited terrestrial food availability supports only low densities of much smaller, resident brown bears (Ursus arctos), which use low-quality resources more efficiently and may compete with polar bears in these areas. Where consumption of terr...

A world without parasites: exploring the hidden ecology of infection

Abstract: Parasites have historically been considered a scourge, deserving of annihilation. Although parasite eradications rank among humanity's greatest achievements, new research is shedding light on the collateral effects of parasite loss. Here, we explore a "world without parasites": a thought experiment for illuminating the ecological roles that parasites play in ecosystems. While there is robust evidence for the effects of parasites on host individuals (eg affecting host vital rates), this exercise highlights how little we know about the influence of parasites on communities and ecosystems (eg altering energy flow through food webs). We present hypotheses for novel, interesting, and general effects of parasites. These hypotheses are largely untested, and should be considered a springboard for future research. While many uncertainties exist, the available evidence suggests that a world without parasites would be very different from the world we know, with effects extending from host individuals to populations, communities, and even ecosystems.

Mitigation-driven translocations: are we moving wildlife in the right direction?

Abstract: Despite rapid growth in the field of reintroduction biology, results from scientific research are often not applied to translocations initiated when human land-use change conflicts with the continued persistence of a species' population at a particular site. Such mitigation-driven translocations outnumber and receive more funding than science-based conservation translocations, yet the conservation benefit of the former is unclear. Because mitigation releases are economically motivated, outcomes may be less successful than those of releases designed to serve the biological needs of species. Translocation as a regulatory tool may be ill-suited for biologically mitigating environmental damage caused by development. Evidence suggests that many mitigation-driven translocations fail, although the application of scientific principles and best practices would probably improve the success rate. Lack of transparency and failure to document outcomes also hinder efforts to understand the scope of the problem. If miti...

Land sparing is crucial for urban ecosystem services

Abstract: The world's cities must grow to accommodate an increasing urban population, and achieving this with minimal impact on ecosystem structures and functions is a major challenge. At opposite ends of a possible development spectrum are “land sharing” – extensive sprawling urbanization where built land and natural space are interspersed – and “land sparing” – intensive and extremely compact urbanization alongside separate, large, contiguous green space. Using case studies across urbanization gradients, we demonstrate that land sparing is crucial for sustaining a majority of ecosystem services. Conversely, some land sharing may also be necessary to ensure that people benefit from urban green space. Future urban development should carefully consider green space provision, to maximize the services provided by urban ecosystems. This can be achieved by optimizing distributions of development intensity across cities by means of top-down, policy-led approaches.

Using cultural ecosystem services to inform restoration priorities in the Laurentian Great Lakes

Abstract: Ecological restoration programs often attempt to maintain or enhance ecosystem services (ES), but fine-scale maps of multiple ES are rarely available to support prioritization among potential projects. Here we use agency reports, citizen science, and social media as data sources to quantify the spatial distribution of five recreational elements of cultural ES (CES) – sport fishing, recreational boating, birding, beach use, and park visitation – across North America's Laurentian Great Lakes, where current restoration investments exceed US$1.5 billion. These recreational CES are widely yet unevenly distributed, and spatial correlations among all except park visitation indicate that many locations support multiple CES benefits. Collectively, these five service metrics correlate with tourism gross domestic product, indicating that local economies benefit from ecosystem conditions that support CES. However, locations of high recreational CES delivery are often severely affected by environmental stressors, suggesting that either ecosystem condition or human enjoyment of these recreational CES is resilient even to substantial levels of stress. Our analyses show that spatial assessments of recreational CES are an informative complement to ecosystem stress assessments for guiding large-scale restoration efforts.

Legacy effects in linked ecological–soil–geomorphic systems of drylands

Abstract: A legacy effect refers to the impacts that previous conditions have on current processes or properties. Legacies have been recognized by many disciplines, from physiology and ecology to anthropology and geology. Within the context of climatic change, ecological legacies in drylands (eg vegetative patterns) result from feedbacks between biotic, soil, and geomorphic processes that operate at multiple spatial and temporal scales. Legacy effects depend on (1) the magnitude of the original phenomenon, (2) the time since the occurrence of the phenomenon, and (3) the sensitivity of the ecological–soil–geomorphic system to change. Here we present a conceptual framework for legacy effects at short-term (days to months), medium-term (years to decades), and long-term (centuries to millennia) timescales, which reveals the ubiquity of such effects in drylands across research disciplines.

Climate-change adaptation on rangelands: linking regional exposure with diverse adaptive capacity

Abstract: The ecological consequences of climate change are predicted to vary greatly throughout US rangelands. Projections show warming and drying in the southern Great Plains and the Southwest, warmer and drier summers with reduced winter snowpack in the Northwest, and warmer and wetter conditions in the northern Great Plains. Primarily through their combined effects on soil water availability, these climatic changes will modify plant production and community composition, which will, in turn, affect the livelihoods of humans who rely upon livestock grazing. The ability of rangeland managers to assess risk and prepare for climate change varies greatly and reflects their different adaptive capacities. Geographically specific exposure to climate change and a diverse adaptive capacity to counteract these changes will require development of varied adaptation strategies that can accommodate the various needs and abilities of livestock managers.

Experiments to confront the environmental extremes of climate change

Abstract: Extreme climate conditions can dramatically alter ecosystems and are expected to become more common in the future; however, our understanding of species and ecosystem responses to extreme conditions is limited. We must meet this challenge by designing experiments that cover broad ranges of environmental stress, extending to levels well beyond those observed currently. Such experiments are important because they can identify physiological, community, and biogeochemical thresholds, and improve our understanding of mechanistic ecological responses to climate extremes. Although natural environmental gradients can be used to observe a range of ecological responses, manipulation experiments – including those that impose drought and heat gradients – are necessary to induce variation beyond common limits. Importantly, manipulation experiments allow for determination of the cause and effect of species and ecosystem threshold responses. We present a rationale and recommendations for conducting extreme experiments that extend beyond the historical and even the predicted ranges of environmental conditions.

Urban climate and adaptation strategies

Abstract: Extreme heat poses a threat to the livability and sustainability of cities, and disproportionally harms marginalized groups. The frequency of extreme heat events is expected to increase in the future as climate change exacerbates urban heat island (UHI) effects. Common UHI mitigation strategies – such as cool pavements (light-colored surfacing or permeable pavements), cool roofs (often categorized as “white”, “blue”, or “green” roof strategies to differentiate the approaches), and increased planting of vegetation – vary in effectiveness depending on a city's baseline climate, as well as on city size and layout. Microclimate mitigation efforts must move beyond exterior site-level strategies to consider land-use planning at the neighborhood level and the role of passive cooling strategies for buildings. Green infrastructure offers benefits in the form of improved stormwater management, air quality, carbon sequestration, and microclimate regulation. The creation of a new utility – one akin to a public compan...

Wastewater-effluent-dominated streams as ecosystem-management tools in a drier climate

Abstract: Water withdrawals and discharges from municipal wastewater-treatment plants in semiarid regions result in more urban streams becoming dependent on wastewater effluent for base flows. Such wastewater-effluent-dominated streams support perennial-stream ecosystems that would not otherwise exist. At the same time, ecosystems downstream of effluent discharges can improve water quality, support water re-use, create habitat, and provide urban amenities. By identifying measures of success for biota, habitat, hydrology, geomorphology, and water quality, water managers can better design, operate, and monitor effluent-dominated water courses under future climate conditions. This requires the development of clearly defined ecological and social objectives, as well as a better understanding of the consequences of increasing reliance on wastewater effluent to sustain the biota of effluent-dominated streams. Successful quantification of the costs and benefits of these projects is likely to attract the attention of agencies and communities that have the power to turn the environmental perturbations associated with effluent discharges into new forms of environmental enhancement.

Low mislabeling rates indicate marked improvements in European seafood market operations

Abstract: Over the span of a decade, genetic identification methods have progressively exposed the inadequacies of the seafood supply chain, revealing previously unrecognized levels of seafood fraud, raising awareness among the public, and serving as a warning to industry that malpractice will be detected. Here we present the outcome of the latest and largest multi-species, transnational survey of fish labeling accuracy to date, which demonstrates an apparent sudden reduction of seafood mislabeling in Europe. We argue that recent efforts in legislation, governance, and outreach have had a positive impact on industry regulation. Coordinated, technology-based, policy-oriented actions can play a pivotal role in shaping a transparent, sustainable global seafood market and in bolstering healthier oceans.

The ethics of offsetting nature

Abstract: Biodiversity offsetting is transforming conservation practice around the world. Development activities that degrade or destroy biodiversity at one location are now increasingly acceptable because of compensatory environmental gains generated elsewhere. This change represents a major shift in how nature is protected, and yet its philosophical justification has received little attention. We argue that biodiversity offsetting aligns most easily with a utilitarian ethic, where outcomes rather than actions are the focus. However, offsetting schemes often neglect to account for the multiple values that people assign to biodiversity – including unique, place-based values. Furthermore, the implications of defining nature as a tradeable commodity may affect our sense of obligation to protect biodiversity. Ironically, offsetting may exacerbate environmental harm because it erodes ethical barriers based on moral objections to the destruction of biodiversity. By failing to consider the ethical implications of biodive...

Marine seismic surveys and ocean noise: time for coordinated and prudent planning

Abstract: Marine seismic surveys use intense (eg ≥ 230 decibel [dB] root mean square [RMS]) sound impulses to explore the ocean bottom for hydrocarbon deposits, conduct geophysical research, and establish resource claims under the United Nations Convention on the Law of the Sea. The expansion of seismic surveys necessitates greater regional and international dialogue, partnerships, and planning to manage potential environmental risks. Data indicate several reasons for concern about the negative impacts of anthropogenic noise on numerous marine species, including habitat displacement, disruption of biologically important behaviors, masking of communication signals, chronic stress, and potential auditory damage. The sound impulses from seismic surveys – spanning temporal and spatial scales broader than those typically considered in environmental assessments – may have acute, cumulative, and chronic effects on marine organisms. Given the international and transboundary nature of noise from marine seismic surveys, we suggest the creation of an international regulatory instrument, potentially an annex to the existing International Convention on the Prevention of Pollution from Ships, to address the issue.

Coastal infrastructure: a typology for the next century of adaptation to sea-level rise

Abstract: Categorizing the choices in coastal infrastructure that are available to policy makers will allow for comparisons of their potential impacts on ecosystems and of their value in preparation for long-term sea-level rise. Although similar approaches have been described elsewhere in different policy contexts, this article focuses on evaluating physical infrastructure types – including hybrid structures that combine landforms with concrete and steel elements –based on historical differences in engineering practices. Such structures can be optimized for different phases of coastal adaptation and can provide multiple benefits (eg supporting ecosystems as well as minimizing flooding in coastal cities). Key factors in a geomorphological, ecological, and land-use context must be taken into account when selecting various infrastructure strategies, to ensure that they function as intended. The San Francisco Bay region provides an example of how this typology can be applied to help policy makers choose more successful strategies as coastal areas plan for sea-level rise.