Habitat Restoration Strategies Research Articles

An evaluation of tradeoffs in restoring ephemeral vs. perennial habitats to conserve animal populations

IntroductionHabitat loss and degradation pose significant threats to global fish and wildlife populations, prompting substantial investments in habitat creation and restoration efforts. Not all habitats provide equal benefits, leading to challenges in prioritizing restoration actions. For example, juvenile anadromous salmonids require high quality rearing aquatic habitats to achieve the physiological requirements needed to successfully migrate to the ocean. However, there are profound disagreements among anadromous salmon restoration managers whether it is best to focus efforts on restoring in-channel habitats that are available for the entire rearing period or floodplain habitats that, while facilitating greater growth and survival than in-channel habitats, are only available for a few weeks at a time and are typically only activated every two-to-three years.MethodsWe used an existing fall-run Chinook salmon decision-support model to evaluate under what conditions floodplain restoration would provide greater benefits than in-channel habitat restoration. The simulations included a wide range of floodplain inundation frequencies and durations and floodplain benefits in the form of increased survival and growth relative to in-channel habitats.ResultsThe simulations results indicated that in-channel habitat restoration was always the best habitat restoration action when there was no existing in-channel habitat despite simulating a wide range of flood frequency, duration, and growth and survival benefits. Floodplain restoration was generally best when there was sufficient in-channel habitat available to successfully rear most of the juveniles produced by the returning adult salmon.DiscussionWe hypothesize that in-channel and floodplain habitats have different roles in salmon population maintenance with in-channel habitats regulating the overall population size and floodplains acting as recurrent resource pulses. Our study provides a quantitative framework to evaluate the benefit of these two habitat types and provides generalizable rulesets that can be used by managers when implementing habitat restoration strategies for species that inhabit both in-channel and floodplain habitats.

Spatiotemporal analysis of landscape dynamics and their use as input for the design of a habitat suitability index: A case study of Oryctolagus cuniculus in a Mediterranean region

The connectivity of landscapes is increasingly threatened by urban sprawl, which leads to the fragmentation of habitats and thus endangers the species that live there. To address this situation, landscape dynamics in the literature have mostly been analyzed using predefined land cover classes, which were then not used to assess habitat suitability, but instead relied on physical variables. As a bridge between both aspects, this study aimed to model the spatiotemporal patterns of landscape fragmentation by analyzing the landscape metrics associated with four land cover groups classified according to their naturalness. Landscape metrics were then combined with a range of terrain, climate and proximity variables to develop a Habitat Suitability Index (HSI) for terrestrial animal species. The proposed methodology was tested using a case study in the Mediterranean region of the Valencian Community (Spain): landscape dynamics were assessed over the period 1992–2015, while the HSI was tested with the European rabbit (Oryctolagus cuniculus) as the target species. The results obtained in terms of landscape dynamics showed a growing presence of artificial surfaces at the expense of fewer transformed areas, which became progressively fragmented over time. Moreover, the results of the developed HSI were highly concordant with observations of rabbit abundance in the region, based in particular on variables related to the temperature in the area and the patch shape in the preferred habitats of this species. These outputs can be used to support the implementation of habitat restoration strategies aimed at increasing ecological connectivity through measures such as wildlife crossings.

Grass Species Diversity and Conservation in Shivaram Wildlife Sanctuary, Telangana, India

This study delves into the diversity of grass species within the Shivaram Wildlife Sanctuary, located in Telangana State, identifying 51 species belonging to 36 genera and 7 tribes. Among the seven tribes, Andropogoneae dominated with 18 species and 15 genera, followed by Paniceae with 12 species and 9 genera, Cynodonteae with 9 species and 8 genera and Eragrostideae, Aristideae, Paspaleae, and Bambuseae are represented by each single genus and 6, 3, 2, and 1 species respectively. Preserving this diversity is vital for ecosystem resilience amid environmental changes. Conservation efforts are needed to safeguard the sanctuary's grasslands, which are ecologically and culturally significant. Our research informs wildlife management and habitat restoration strategies, emphasizing holistic biodiversity conservation and sustainability approaches.

Cushions serve as conservation refuges for the Himalayan alpine plant diversity: Implications for nature-based environmental management

Globally, rapid climate and land-use changes in alpine environments are posing severe risks to their bountiful biodiversity and ecosystem services. Currently, nature-based solutions are fast-emerging as the preferred approach to address the challenges of environmental sustainability. In alpine environments, cushion plants owing to their unique architecture and adaptability offer a potential nature-based system to plan biodiversity conservation and habitat restoration strategies. Here, we employed an analytical framework to test whether and how the cushion plants facilitate the sustenance of alpine plant diversity in Kashmir Himalaya. We specifically aimed to answer: what are the effects of the cushion plants on the patterns of alpine species richness and phylogenetic diversity, and whether these effects vary across spatial scales (local versus landscape), cushion types, and changing elevation. We randomly selected pairs of cushion and neighbouring non-cushion plots (size 100 m2) across 34 different alpine sites in the study region. Within each plot, we randomly laid three 5 m2 quadrats for vegetation sampling, and sampled a total of 204 quadrats in 68 plots with seven cushion types along elevation ranging from 3100 to 3850 m. Our results revealed positive effects of the cushions by supporting a higher community species richness (SR) and phylogenetic diversity (PD). The effects were consistent both at the local (i.e., quadrat) and landscape (i.e., plot) scales, but varied significantly with the cushion type. Interestingly, SR and PD showed an increasing trend with increase in elevation in cushion communities, thereby supporting stress gradient hypothesis. Along the elevational gradient, the cushion communities showed phylogenetic overdispersion, but clustering by non-cushions. Overall, our study provides empirical evidence to reinforce the role of the cushions as conservation refugia for an imperilled alpine plant diversity in the Himalaya. Looking ahead, we highlight the far-reaching implications of our findings in guiding the nature-based environmental management of alpine ecosystems worldwide.

Creating landscape‐appropriate habitat restoration strategies: success of a novel nesting habitat design for imperiled freshwater turtles

Turtle nesting habitat can be created as a restoration strategy to increase habitat availability or provide suitable habitat away from threats. Traditional nest habitat restoration consists of creating nesting mounds using a mix of sand and gravel. However, nesting mounds do not resemble natural turtle nesting habitat in a rock barren landscape where turtles nest in crevices and cracks in the bedrock. Therefore, our objective was to design and evaluate the success of a landscape‐appropriate design for turtle nesting habitat in a rock barren landscape. To evaluate success of the nest habitat design, we assessed the (1) survival of transplanted moss and lichen cover on created nest sites, (2) ecohydrological and physical conditions at created and natural sites, and (3) turtle egg hatching success at created and natural sites using a split‐clutch experiment. We found no difference in productivity between lichen transplants and natural sites, indicating that intact lichen transplants were successful. Moss transplant success was more variable due to moisture stress because transplants were conducted during dry conditions. In general, created nest habitat tended to have a more stable thermal and moisture regime compared to natural sites. When accounting for maternal effects, the odds of an egg hatching successfully was 6.6 times higher in a created site than a natural site. Overall, the success of our nest habitat design in the first few years suggests that this landscape‐appropriate design will be a useful restoration strategy for increasing turtle nesting habitat in rock barren landscapes.

Using state-and-transition simulation models to scope post-fire success in restoring greater sage-grouse habitat

Wildfires are increasingly modifying wildlife habitat in the western United States and managers need ways to scope the pace and degree to which post-fire restoration actions can re-create habitat in dynamic landscapes. We developed a spatially explicit state-transition simulation model (STSM) to project post-fire revegetation and the potential for sage-grouse habitat restoration in sagebrush ecosystems. The model included annual fires, annual grass invasion, conifer encroachment, and projected annual vegetation growth caused by natural regeneration as well as sagebrush seeding and planting. We cross-referenced resulting vegetation maps with greater sage-grouse (Centrocercus urophasianus) habitat needs and evaluated trajectories of potential habitat at three Priority Areas for Conservation in the Great Basin. We compared outcomes among different types of revegetation actions (natural regeneration, seeding, planting), treatment durations, and treatment area sizes. In all scenarios, sagebrush cover was generally insufficient to meet sage-grouse needs for at least a decade post-fire, and the best habitat classes declined or remained at low proportions of landscapes for >50 years post-fire. Under current fire patterns, the pace of habitat restoration is likely to lag behind losses from wildfires. Our results indicate additional efforts beyond sagebrush revegetation actions (e.g., fire suppression, invasive grass treatment) will likely be necessary to maintain and restore areas to meet sage-grouse habitat needs in burned landscapes. Our results also underscore the need for broad-scale habitat restoration strategies that expand the ability to reestablish sagebrush in large, burned areas, as well as strategies for defining which areas should be prioritized for revegetation within the biome. Our landscape models and resulting vegetation maps can be integrated with other restoration prioritization or wildlife monitoring tools that support land manager decision-making. By gauging potential benefits of restoration decisions, our approach can provide information to aid choices on where to invest time, money, and effort and how best to mitigate losses and plan long-term restoration and recovery for landscapes across the sagebrush biome.

How does habitat restoration influence resilience of salmon populations to climate change?

AbstractA pressing question for managing recovery of depressed or declining species is: Can habitat restoration increase resilience to climate change? We addressed this question for salmon populations with varying life histories, where resilience is defined as maintaining or increasing population size despite climate change effects. Previous studies indicate that several interrelated mechanisms may influence salmon resilience to climate change, including improving either habitat capacity or productivity, and ameliorating climate change effects on flood flow, low flow, or stream temperature. Using the Habitat Assessment and Restoration Planning (HARP) model, we first examined the relative importance of each mechanism for increasing salmon population resilience by comparing projected salmon spawner abundance for seven individual restoration action types under current and projected mid‐ and late‐century climates. We found that restoring habitats with the greatest restoration potential most increased resilience for all species, but the most beneficial restoration actions varied among species. Increasing habitat capacity and productivity both contributed to resilience, and ameliorating climate change effects was important in a few subbasins where the restoration opportunity was widespread. Cool‐water climate refuges contributed to resilience of some subpopulations by reducing late‐century declines in spawner abundance even without restoration. We also modeled more complex habitat restoration strategies comprised of several restoration action types at varying restoration intensities and found that the restoration action types and level of restoration effort needed to increase resilience varied among species. Less vulnerable species such as coho salmon responded well to four restoration actions (floodplain reconnection, wood augmentation, increased shade, and increased beaver ponds) applied at low restoration intensity and over a large area. More vulnerable species such as spring Chinook responded to fewer action types (floodplain reconnection, wood augmentation, and increased shade), but at much higher intensity and over a much smaller area. The analysis also identified important locations for each restoration action type for each species, which helps focus habitat restoration effort on areas that are likely to provide the largest increases in resilience.

Habitat split as a driver of disease in amphibians.

Anthropogenic habitat disturbance is fundamentally altering patterns of disease transmission and immunity across the vertebrate tree of life. Most studies linking anthropogenic habitat change and disease focus on habitat loss and fragmentation, but these processes often lead to a third process that is equally important: habitat split. Defined as spatial separation between the multiple classes of natural habitat that many vertebrate species require to complete their life cycles, habitat split has been linked to population declines in vertebrates, e.g. amphibians breeding in lowland aquatic habitats and overwintering in fragments of upland terrestrial vegetation. Here, we link habitat split to enhanced disease risk in amphibians (i) by reviewing the biotic and abiotic forces shaping elements of immunity and (ii) through a spatially oriented field study focused on tropical frogs. We propose a framework to investigate mechanisms by which habitat split influences disease risk in amphibians, focusing on three broad host factors linked to immunity: (i) composition of symbiotic microbial communities, (ii) immunogenetic variation, and (iii) stress hormone levels. Our review highlights the potential for habitat split to contribute to host-associated microbiome dysbiosis, reductions in immunogenetic repertoire, and chronic stress, that often facilitate pathogenic infections and disease in amphibians and other classes of vertebrates. We highlight that targeted habitat-restoration strategies aiming to connect multiple classes of natural habitats (e.g. terrestrial-freshwater, terrestrial-marine, marine-freshwater) could enhance priming of the vertebrate immune system through repeated low-load exposure to enzootic pathogens and reduced stress-induced immunosuppression.

Floral diversity increases butterfly diversity in a multitrophic metacommunity.

The impact of multitrophic interactions on metacommunity structure, despite extensive theory and modeling/manipulative studies, has remained largely unexplored within naturally occurring metacommunities. We investigated the impacts of mutualistic partners and predators on a butterfly metacommunity, as well as the impacts that local and landscape characteristics have across three trophic levels: flowering plants, butterflies, and butterfly predators. Using data for butterfly diversity/richness, flowering plant diversity/richness, and butterfly predation (on clay butterfly models) across 15 grassland sites, we posed 3 questions. (1) How do mutualist metacommunity structure, predation pressure, and local and regional habitat characteristics affect butterfly metacommunity structure? (2) How do local and regional habitat characteristics affect flowering plant metacommunity structure? (3) How do local and regional habitat characteristics affect predation pressure? Floral diversity and richness had a positive effect on butterfly diversity and richness (Question 1). Site size positively affected floral diversity and richness (Question 2), and through this relationship site size had an indirect positive effect on butterfly diversity and richness (Question 1). In contrast to previous work, no other variables impacted butterfly diversity/richness. This result was particularly surprising for predation pressure: Our results suggest that within our study system, butterfly community diversity and richness are not strongly impacted by predation. Predator attacks occurred more in larger and more isolated sites (Question 3), suggesting that predators respond more strongly to landscape characteristics than abundance or diversity of butterfly prey species. This decoupling of predation pressure and butterfly communities suggests that conserving and restoring healthy predator populations may not negatively impact butterfly communities. If diverse plant communities are maintained, even small and isolated habitat patches can be valuable for butterfly conservation, which may influence reserve design and habitat restoration strategies.

Do metapopulations and management matter for relict headwater bull trout populations in a warming climate?

Mountain headwater streams have emerged as important climate refuges for native cold-water species due to their slow climate velocities and extreme physical conditions that inhibit non-native invasions. Species persisting in refuges often do so as fragmented, relict populations from broader historical distributions that are subject to ongoing habitat reductions and increasing isolation as climate change progresses. Key for conservation planning is determining where remaining populations will persist and how habitat restoration strategies can improve biological resilience to enhance the long-term prospects for species of concern. Studying bull trout, a headwater species in the northwestern USA, we developed habitat occupancy models using a data set of population occurrence in 991 natal habitat patches with a suite of novel geospatial covariates derived from high-resolution hydroclimatic scenarios and other sources representing watershed and instream habitat conditions, patch geometry, disturbance, and biological interactions. The best model correctly predicted bull trout occupancy status in 82.6% of the patches and included effects for: patch size estimated as habitat volume, extent of within-patch reaches <9°C mean August temperature, distance to nearest occupied patch, road density, invasive brook trout prevalence, patch slope, and frequency of high winter flows. The model was used to assess 16 scenarios of bull trout occurrence within the study streams that represented a range of restoration strategies under three climatic conditions (baseline, moderate change, and extreme change). Results suggested that regional improvements in bull trout status were difficult to achieve in realistic restoration strategies due to the pervasive nature of climate change and the limited extent of restoration actions given their high costs. However, occurrence probabilities in a subset of patches were highly responsive to restoration actions, suggesting that targeted investments to improve the resilience of some populations may be contextually beneficial. A possible strategy, therefore, is focusing effort on responsive populations near more robust population strongholds, thereby contributing to local enclaves where dispersal among populations further enhances resilience. Equally important, strongholds constituted a small numerical percentage of patches (5%-21%), yet encompassed the large majority of occupied habitat by volume (72%-89%) and their protection could have significant conservation benefits for bull trout.

Use of affinity analysis to guide habitat restoration and enhancement for the imperiled delta smelt

Habitat restoration efforts in the upper San Francisco Estuary, including the Sacramento-San Joaquin Delta, California, move forward, despite a paucity of information on the environmental requirements of many targeted species. The endemic delta smeltHypomesus transpacificus, protected under the federal Endangered Species Act, is a primary focus of those efforts despite uncertainties regarding many aspects of its relationship with the estuary’s physical and biotic resources. Here we use time-series data from 4 trawl surveys and data on environmental attributes collected from throughout the delta smelt’s distribution to identify ranges of conditions acceptable to delta smelt for each of 5 environmental attributes: water-body type, temperature, turbidity, salinity, and prey availability. Low turbidity and elevated water temperatures render a large portion of the estuary seasonally unsuitable for delta smelt. Within areas in which water quality is suitable, patterns of delta smelt occurrences indicate that habitat is found in subregions where channels of intermediate depth adjoin shallow water. In certain subregions, conditions are inadequate for at least one of the environmental attributes for periods up to several months. We suggest a habitat-restoration strategy that can achieve adequate habitat conditions for delta smelt regardless of through-Delta flow levels, and which can be carried out at a number of locations, but not necessarily the same locations, during each life stage.

Habitat utilisation of Pseudobarbus afer and Sandelia capensis in headwaters of the Swartkops River, Eastern Cape, South Africa

Habitat degradation is one of the greatest threats to endemic freshwater fish in the Cape Fold Ecoregion. One habitat restoration strategy is the replication of critical habitat using artificial materials. In this paper, we evaluate the habitat occupancy of two small, endemic headwater fish of the Cape Fold Ecoregion, namely the Eastern Cape redfin Pseudobarbus afer (Peters, 1864) and the Cape Kurper Sandelia capensis (Cuvier, 1829). Habitat occupancy was observed in five pool microhabitats (inflow, woody debris, deep open, fern-root wads, and outflow) using action cameras. Changes in habitat occupancy were assessed following the introduction of an artificial habitat in the form of PVC pipes. Pseudobarbus afer preferred deeper open habitats, whereas Sandelia capensis preferred more structured woody debris habitat. Habitat occupancies differed significantly across all microhabitats for both species; excluding those between the inflow and outflow, and the open deep and fern-root wads for Sandelia capensis. Pseudobarbus afer and S. capensis occupancies in the natural microhabitats reduced significantly following the introduction of the artificial habitat. For species restricted to degraded habitats that require habitat restoration, the use of artificial habitat may be beneficial in accelerating the recovery of such species.

A “cray‐zy” dam solution for an iconic species

The decline in freshwater crayfishes is occurring on a global scale. A gastronomic delicacy and a Western Australian freshwater icon, Cherax cainii (the smooth marron) is the third largest freshwater crayfish in the world and has been an important food source for the human inhabitants of southwestern Australia for tens of thousands of years. However, the species has disappeared from much of its historical range due to anthropogenic salinization of waterways, which has prompted interest and investigations into restoring the smooth marron's habitat. Severe and ongoing flow declines due to climate change-related drought threaten to further exacerbate past environmental degradation of the region's watersheds. This will make the existing network of artificial reservoirs almost functionally obsolete as primary sources of drinking water but will not lead to the network's total elimination. Currently, the smooth marron thrives in these freshwater reservoirs. Harnessing these impoundments as arks to support the region's highly endemic and imperiled aquatic fauna represents a tangible, albeit controversial, way to maintain aquatic biodiversity in an area largely devoid of dam-impacted migratory species. Habitat restoration strategies, such as providing logs and wood for shelter to protect the smooth marron from predation by birds and alien fishes, will be a crucial part of the solution. Are we willing to similarly prioritize the restoration of anthropogenic aquatic habitats and natural – though severely degraded – systems to conserve such iconic aquatic species? Such decisions regarding the allocation of restoration efforts remain hotly debated.

Estimating the intensity of use by interacting predators and prey using camera traps.

Understanding how organisms distribute themselves in response to interacting species, ecosystems, climate, human development and time is fundamental to ecological study and practice. A measure to quantify the relationship among organisms and their environments is intensity of use: the rate of use of a specific resource in a defined unit of time. Estimating the intensity of use differs from estimating probabilities of occupancy or selection, which can remain constant even when the intensity of use varies. We describe a method to evaluate the intensity of use across conditions that vary in both space and time. We demonstrate its application on a large mammal community where linear developments and human activity are conjectured to influence the interactions between white-tailed deer (Odocoileus virginianus) and wolves (Canis lupus) with possible consequences on threatened woodland caribou (Rangifer tarandus caribou). We collect and quantify intensity of use data for multiple, interacting species with the goal of assessing management efficacy, including a habitat restoration strategy for linear developments. We test whether blocking linear developments by spreading logs across a 200-m interval can be applied as an immediate mitigation to reduce the intensities of use by humans, predator and prey species in a boreal caribou range. We deployed camera traps on linear developments with and without restoration treatments in a landscape exposed to both timber and oil development. We collected a three-year dataset and employed spatial recurrent event models to analyse intensity of use by an interacting human and large mammal community across a range of environmental and climatic conditions. Spatial recurrent event models revealed that intensity of use by humans influenced the intensity of use by all five large mammal species evaluated, and the intensities of use by wolves and deer were inextricably linked in space and time. Conditions that resist travel on linear developments had a strong negative effect on the intensity of human and large mammal use. Mitigation strategies that resist, or redirect, animal travel on linear developments can reduce the effects of resource development on interacting human and predator-prey interactions. Our approach is easily applied to other continuous time point-based survey methodologies and shows that measuring the intensity of use within animal communities can help scientists monitor, mitigate and understand ecological states and processes.

Using Applied Science for Effective Watershed Restoration and Coho Salmon Recovery in Coastal Oregon Streams

Coos Bay, located on the southern Oregon Coast, is the largest estuary between the Columbia River and San Francisco Bay. Palouse and Larson Creeks in the northern section of Coos Bay are the two most productive streams for coho salmon. Such productivity occurs despite the pressure salmon habitats have experienced through a long history of anthropogenic alterations, and continue to face from the region’s robust industrial economy, including recreational and commercial fisheries, agricultural production, and forestry. Restoration efforts since the 1980s have helped mitigate environmental impacts, but the turn of the century brought a new era of coordinated research, monitoring, and restoration. Forming a multi-stakeholder partnership with the goal of restoring salmon runs, the local nonprofitnon-profit Coos Watershed Association and its partners worked together to learn about the strategies that coho use to survive in these altered landscapes and apply research findings to restore habitats. Specifically, they examined the most appropriate habitat restoration strategies for various life histories of coho salmon, while working within social and political constraints. As a result, these efforts over the past 35 years have led to a better understanding of salmon populations in Palouse and Larson Creeks and an effective restoration program that continues till today.

Hydrological and thermal properties of moss and lichen species on rock barrens: Implications for turtle nesting habitat

AbstractIn central Ontario, Canadian Shield rock barrens are a dominant geographic feature supporting at‐risk reptiles near their northern range limit. To better understand the characteristics of the organic soil that make Canadian Shield rock barrens suitable turtle nesting habitat, we measured moisture retention and evaporative potential and calculated the thermal properties of lichen (Cladonia) mats and moss (Sphagnum and Polytrichum) cushions, as well as their underlying mineral–organic soils. The upper soil profile consisted almost entirely of low density (14–49 kg m−3), high porosity (72–98%) organic matter (loss on ignition [LOI] of 84–99%), which transitioned rapidly to comparatively high density (304–815 kg m−3) mineral–organic soil (LOI of 10–85%). In contrast to Sphagnum and Cladonia, under laboratory conditions, Polytrichum was able to maintain an evaporation rate well above the open‐water potential for several days during a drying experiment. Overall, contrasts in composition and water retention between soil layers are likely to dampen diurnal temperature fluctuations. However, differences in potential water loss between species will have a direct impact on soil thermal dynamics, particularly if substantial water loss occurs in the mineral–organic layer. Because soil depth and temperature regulation by moisture content and soil composition are an important component of nesting habitat, this research provides evidence for the need to conserve moss/lichen‐dominated habitats within turtle species' home ranges. Understanding the ecohydrological controls and limits to how these key moss/lichen species develop and influence primary peat formation represents a critical research need for habitat restoration strategies.

Vegetation structure and decreased moth abundance limit the recolonisation of restored habitat by the European Nightjar

Woodland ecosystems of Europe have undergone major transitions in the last centuries. Changes in land use and the loss of natural forest dynamics have often led to structurally poor, uniform and dense stands. Not surprisingly, open forest species relying on a heterogeneous stand structure have suffered dramatic population declines. The European Nightjar Caprimulguseuropaeus, a nocturnal insectivorous bird, has undergone such a decline in its main Swiss stronghold in Valais. Despite the species’ potential to colonize new sites and habitat restoration measures implemented since 2001, recolonisation of restored sites has not taken place, suggesting problems with the current habitat restoration strategy. In order to refine management recommendations, we compared habitat structure and moth abundance, a key Nightjar food source, at sites that are still occupied and at sites that had been abandoned but have recently been restored. Vegetation structure was more heterogeneous and moth abundance greater at occupied than at abandoned sites. More specifically, occupied sites harboured a greater coverage of bare ground, while abandoned sites exhibited a higher amount of regeneration and intermediate shrub layer. The occurrence of natural perches was also higher in occupied sites. Abandoned sites are thus characterised by lower prey abundance and denser vegetation cover, the combination of which is likely to lead to lower prey availability for hunting Nightjars. Restoration action would benefit from maintaining snags and dead branches and by targeting unproductive habitats characterised by mineral soils, thereby slowing down regeneration and shrub regrowth. For future successful management of Nightjar habitats, it seems thereby essential trying to find the balance between actions that allow opening the lower and mid-strata of the forest while sustaining high moth populations.

Global Warming of Salmon and Trout Rivers in the Northwestern U.S.: Road to Ruin or Path Through Purgatory?

AbstractLarge rivers constitute small portions of drainage networks but provide important migratory habitats and fisheries for salmon and trout when and where temperatures are sufficiently cold. Management and conservation of coldwater fishes in the current era of rapid climate change require knowing how riverine thermal environments are evolving and the potential for detrimental biological impacts. Robust estimates of warming rates, however, are lacking due to limited long‐term temperature monitoring, so we compiled the best available multidecadal records and estimated trends at 391 sites in the 56,500‐km river network of the northwestern USA. Warming trends were prevalent during summer and early fall months in recent 20‐ and 40‐year periods (0.18–0.35°C per decade during 1996–2015 and 0.14–0.27°C per decade during 1976–2015), paralleled air temperature trends, and were mediated by discharge trends at regional and local levels. To illustrate the biological consequences of warming later in this century, trend estimates were used to inform selection of river temperature scenarios and assess changes in thermal exposure of adult Sockeye Salmon Oncorhynchus nerka migrating to four population areas as well as thermal habitat shifts for resident Brown Trout Salmo trutta and Rainbow Trout O. mykiss populations throughout the region. Future warming of 1–3°C would increase Sockeye Salmon exposure by 5–16% (3–143 degree‐days) and reduce thermally suitable riverine trout habitats by 8–31% while causing their upstream shift. Effects of those changes on population persistence and fisheries are likely to be context dependent, and strategic habitat restoration or adaptation strategies could ameliorate some biological impairments, but effectiveness will be tempered by the size of rivers, high costs, and pervasiveness of thermal effects. Most salmon and trout rivers will continue to provide suitable habitats for the foreseeable future, but it also appears inevitable that some river reaches will gradually become too warm to provide traditional habitats.

Quantifying the spatial and temporal distribution of tanglehead (Heteropogon contortus) on South Texas rangelands

IntroductionTanglehead is a grass native to southwestern US rangelands; however, its prevalence as a native invasive on South Texas rangelands has increased rapidly during the last decade. Large areas of monotypic stands have emerged in Jim Hogg, Duval, Brooks, and Kleberg counties. The aim of this research is to understand the spatial and temporal dynamics of these invasions as a model for the assessment of native invasive species. Our specific objectives were to (1) evaluate the feasibility of classifying tanglehead using 1-m resolution imagery data, (2) assess the spatial and temporal distribution of tanglehead in relation to soil type and distance from roads, and (3) quantify the temporal and spatial distribution of tanglehead on our study sites. We combined remote sensing approaches with landscape metrics to quantify the spatial and temporal distribution of tanglehead in five locations across our study area. We calculated the normalized difference vegetation index and combined it with the original aerial imagery to conduct an unsupervised classification with the following land cover classes: woody vegetation, tanglehead, non-tanglehead herbaceous, and bare ground. Soil type and the distance from roads were assessed to determine the relationship between these factors and tanglehead spatial distribution.ResultsWe were able to successfully map tanglehead using the 1-m imagery. Our image classification approach resulted in accuracies greater than 85% for all sites. Tanglehead occurred in sandy, loamy sand, and sandy loam soils. Over 70% of tanglehead cover occurred within the first 150 m from the edge of roads. This cover increased from 7.1% (SE = 1.1%) in 2008 to 17.8% (SE = 5.4%) in 2014. Once established, small patches of tanglehead began aggregating or coalescing with existing stands, thereby creating larger patches over larger areas.ConclusionsOur study has shown the value of analyzing spatiotemporal dynamics of tanglehead with remote sensing techniques and landscape metrics to improve our understanding of establishment and dispersal processes of a native invasive. This study provides useful information to improve rangeland management decisions as well as assessing native invasive dynamics with potential applications for assessing its effects on wildlife habitat, livestock operations, and habitat restoration strategies.

Mechanism matters: the cause of fluctuations in boom-bust populations governs optimal habitat restoration strategy.

Many populations exhibit boom-bust dynamics in which abundance fluctuates dramatically over time. Past research has focused on identifying whether the cause of fluctuations is primarily exogenous, e.g., environmental stochasticity coupled with weak density dependence, or endogenous, e.g., over-compensatory density dependence. Far fewer studies have addressed whether the mechanism responsible for boom-bust dynamics matters with respect to at-risk species management. Here, we ask whether the best strategy for restoring habitat across a landscape differs under exogenously vs. endogenously driven boom-bust dynamics. We used spatially explicit individual-based models to assess how butterfly populations governed by the two mechanisms would respond to habitat restoration strategies that varied in the level of resource patchiness, from a single large patch to multiple patches spaced at different distances. Our models showed that the restoration strategy that minimized extinction risk and boom-bust dynamics would be markedly different depending on the governing mechanism. Exogenously governed populations fared best in a single large habitat patch, whereas for endogenously driven populations, boom-bust dynamics were dampened and extinction risk declined when the total restored area was split into multiple patches with low to moderate inter-patch spacing. Adding environmental stochasticity to the endogenous model did not alter this result. Habitat fragmentation lowered extinction risk in the endogenously driven populations by reducing their growth rate, precluding both "boom" phases and, more importantly, "bust" phases. Our findings suggest that (1) successful restoration will depend on understanding the causes of fluctuations in at-risk populations, (2) the level and pattern of spatiotemporal environmental heterogeneity will also affect the ideal management approach, and (3) counterintuitively, for at-risk species with endogenously governed boom-bust dynamics, lowering the intrinsic population growth rate may decrease extinction risk.