Stream Vulnerability to Widespread and Emergent Stressors: A Focus on Unconventional Oil and Gas

Multiple stressors threaten stream physical and biological quality, including elevated nutrients and other contaminants, riparian and in-stream habitat degradation and altered natural flow regime. Unconventional oil and gas (UOG) development is one emerging stressor that spans the U.S. UOG development could alter stream sedimentation, riparian extent and composition, in-stream flow, and water quality. We developed indices to describe the watershed sensitivity and exposure to natural and anthropogenic disturbances and computed a vulnerability index from these two scores across stream catchments in six productive shale plays. We predicted that catchment vulnerability scores would vary across plays due to climatic, geologic and anthropogenic differences. Across-shale averages supported this prediction revealing differences in catchment sensitivity, exposure, and vulnerability scores that resulted from different natural and anthropogenic environmental conditions. For example, semi-arid Western shale play catchments (Mowry, Hilliard, and Bakken) tended to be more sensitive to stressors due to low annual average precipitation and extensive grassland. Catchments in the Barnett and Marcellus-Utica were naturally sensitive from more erosive soils and steeper catchment slopes, but these catchments also experienced areas with greater UOG densities and urbanization. Our analysis suggested Fayetteville and Barnett catchments were vulnerable due to existing anthropogenic exposure. However, all shale plays had catchments that spanned a wide vulnerability gradient. Our results identify vulnerable catchments that can help prioritize stream protection and monitoring efforts. Resource managers can also use these findings to guide local development activities to help reduce possible environmental effects.     

Bringing indices of species vulnerability to climate change into geographic space: an assessment across the Coronado national forest

Indices that rate the vulnerability of species to climate change in a given area are increasingly used to inform conservation and climate change adaptation strategies. These species vulnerability indices (SVI) are not commonly associated with landscape features that may affect local-scale vulnerability. To do so would increase their utility by allowing managers to examine how the distributions of vulnerable species coincide with environmental features such as topography and land use, and to detect landscape-scale patterns of vulnerability across species. In this study we evaluated 15 animal species that had been scored with the USDA-Forest Service Rocky Mountain Research Station’s system for assessing vulnerability of species to climate change. We applied the vulnerability scores to each species’ respective habitat models in order to visualize the spatial patterns of cross-species vulnerability across the biologically diverse Coronado national forest, and to identify the considerations of spatially referencing such indices. Across the study extent, cross-species vulnerability was higher in higher-elevation woodlands and lower in desert scrub. The results of spatially referencing SVI scores may vary according to the species examined, the area of interest, the selection of habitat models, and the method by which cross-species vulnerability indices are created. We show that it is simple and constructive to bring species vulnerability indices into geographic space: landscape-scale patterns of vulnerability can be detected, and relevant ecological and socioeconomic contexts can be taken into account, allowing for more robust conservation and management strategies.     

Adaptation to natural flow regimes

Floods and droughts are important features of most running water ecosystems, but the alteration of natural flow regimes by recent human activities, such as dam building, raises questions related to both evolution and conservation. Among organisms inhabiting running waters, what adaptations exist for surviving floods and droughts? How will the alteration of the frequency, timing and duration of flow extremes affect flood- and drought-adapted organisms? How rapidly can populations evolve in response to altered flow regimes? Here, we identify three modes of adaptation (life history, behavioral and morphological) that plants and animals use to survive floods and/or droughts. The mode of adaptation that an organism has determines its vulnerability to different kinds of flow regime alteration. The rate of evolution in response to flow regime alteration remains an open question. Because humans have now altered the flow regimes of most rivers and many streams, understanding the link between fitness and flow regime is crucial for the effective management and restoration of running water ecosystems.     

Downstream fish assemblage response to river impoundment varies with degree of hydrologic alteration

River impoundments can fundamentally restructure downstream fish assemblages by altering flow regimes. However, the degree of alteration and associated ecological change may depend on pre-existing hydrologic regimes. We used long-term datasets to compare downstream hydrological and fish assemblage responses to impoundment in two catchments classified as having intermittent and perennial-flashy natural hydrologic regimes. We observed significant shifts in fish assemblage structure at both sites after stream impoundment. The historically intermittent stream shifted to a stable perennial flow regime. Changes in fish assemblage structure covaried with changes in five different components of the flow regime; most species that increased in abundance require fluvial habitats and likely benefited from increased flows during historically low flow seasons. Shifts in fish assemblage structure were also observed in the perennial stream, despite minimal flow alteration after impoundment; however, most species shifts were associated with lentic environments, and were more likely related to proximity of reservoirs in the drainage system rather than changes in stream flow. Findings from this study confirm that downstream fish assemblage response to river impoundment can be associated with high levels of hydrologic alteration, but other factors including expansion of lentic species into lotic environments also influence shifts in assemblage structure.     

Use of arthropod rarity for area prioritisation: insights from the Azorean Islands

We investigated the conservation concern of Azorean forest fragments and the entire Terceira Island surface using arthropod species vulnerability as defined by the Kattan index, which is based on species rarity. Species rarity was evaluated according to geographical distribution (endemic vs. non endemic species), habitat specialization (distribution across biotopes) and population size (individuals collected in standardized samples). Geographical rarity was considered at 'global' scale (species endemic to the Azorean islands) and 'regional' scale (single island endemics). Measures of species vulnerability were combined into two indices of conservation concern for each forest fragment: (1) the Biodiversity Conservation Concern index, BCC, which reflects the average rarity score of the species present in a site, and (2) one proposed here and termed Biodiversity Conservation Weight, BCW, which reflects the sum of rarity scores of the same species assemblage. BCW was preferable to prioritise the areas with highest number of vulnerable species, whereas BCC helped the identification of areas with few, but highly threatened species due to a combination of different types of rarity.A novel approach is introduced in which BCC and BCW indices were also adapted to deal with probabilities of occurrence instead of presence/absence data. The new probabilistic indices, termed pBCC and pBCW, were applied to Terceira Island for which we modelled species distributions to reconstruct species occurrence with different degree of probability also in areas from which data were not available. The application of the probabilistic indices revealed that some island sectors occupied by secondary vegetation, and hence not included in the current set of protected areas, may in fact host some rare species. This result suggests that protecting marginal non-natural areas which are however reservoirs of vulnerable species may also be important, especially when areas with well preserved primary habitats are scarce.     

Conforming to the status flow: The influence of altered habitat on fish body-shape characteristics

1. Anthropogenic stream impoundments often result in altered flow regimes and reservoir formations. Functional fish characteristics may change in response to altered flow conditions, and understanding the underlying mechanisms at work (e.g. natural selection and phenotypic plasticity) is of great importance in both evolutionary and conservation contexts. Cyprinella lutrensis is a widely distributed minnow native to stream systems in Missouri, U.S.A. Following impoundment of the Osage River, C. lutrensis currently occurs in the resultant Truman Reservoir and surrounding tributaries. To examine the impacts of this habitat alteration on functional fish characteristics, we hypothesised that C. lutrensis populations in altered systems with no-flow would show an overall less streamlined body shape as compared to those in flowing systems, assuming body streamlining is beneficial for locomotion in flowing environments.
2. We conducted field and laboratory studies to test effects of flow and no-flow on C. lutrensis body shape. Geometric morphometric techniques were used to quantify body shape in field and laboratory individuals, and non-structural lipid extractions were conducted to assess whether fat storage contributes to body shape under flow and no-flow treatments.
3. Morphological comparisons between C. lutrensis from Truman Reservoir and surrounding streams yielded significant differences in body shape, with greater body streamlining in stream populations. A laboratory experiment using artificial stream units revealed similar significant differences in body streamlining between flow and no-flow treatments within a single generation. In addition, individuals under no-flow treatment had significantly higher levels of non-structural lipids compared to flow treatment individuals.
4. Our results indicate that changes in flow regime can alter the evolutionary trajectories (i.e. related to morphology) of fish populations. We suggest that body shape alterations are likely to occur within and across generations in a cumulative manner, therefore, it is plausible that both natural selection and plastic response mechanisms play roles in defining minnow body shape following flow alteration.

     

A climate change vulnerability assessment of California's at-risk birds

Conservationists must develop new strategies and adapt existing tools to address the consequences of anthropogenic climate change. To support statewide climate change adaptation, we developed a framework for assessing climate change vulnerability of California's at-risk birds and integrating it into the existing California Bird Species of Special Concern list. We defined climate vulnerability as the amount of evidence that climate change will negatively impact a population. We quantified climate vulnerability by scoring sensitivity (intrinsic characteristics of an organism that make it vulnerable) and exposure (the magnitude of climate change expected) for each taxon. Using the combined sensitivity and exposure scores as an index, we ranked 358 avian taxa, and classified 128 as vulnerable to climate change. Birds associated with wetlands had the largest representation on the list relative to other habitat groups. Of the 29 state or federally listed taxa, 21 were also classified as climate vulnerable, further raising their conservation concern. Integrating climate vulnerability and California's Bird Species of Special Concern list resulted in the addition of five taxa and an increase in priority rank for ten. Our process illustrates a simple, immediate action that can be taken to inform climate change adaptation strategies for wildlife.     

Mapping tree species vulnerability to multiple threats as a guide to restoration and conservation of tropical dry forests

Understanding the vulnerability of tree species to anthropogenic threats is important for the efficient planning of restoration and conservation efforts. We quantified and compared the effects of future climate change and four current threats (fire, habitat conversion, overgrazing and overexploitation) on the 50 most common tree species of the tropical dry forests of northwestern Peru and southern Ecuador. We used an ensemble modelling approach to predict species distribution ranges, employed freely accessible spatial datasets to map threat exposures, and developed a trait‐based scoring approach to estimate species‐specific sensitivities, using differentiated trait weights in accordance with their expected importance in determining species sensitivities to specific threats. Species‐specific vulnerability maps were constructed from the product of the exposure maps and the sensitivity estimates. We found that all 50 species face considerable threats, with an average of 46% of species’ distribution ranges displaying high or very high vulnerability to at least one of the five threats. Our results suggest that current levels of habitat conversion, overexploitation and overgrazing pose larger threats to most of the studied species than climate change. We present a spatially explicit planning strategy for species‐specific restoration and conservation actions, proposing management interventions to focus on (a) in situ conservation of tree populations and seed collection for tree planting activities in areas with low vulnerability to climate change and current threats; (b) ex situ conservation or translocation of populations in areas with high climate change vulnerability; and (c) active planting or assisted regeneration in areas under high current threat vulnerability but low climate change vulnerability, provided that interventions are in place to lower threat pressure. We provide an online, user‐friendly tool to visualize both the vulnerability maps and the maps indicating priority restoration and conservation actions.     

Morphological divergence and flow‐induced phenotypic plasticity in a native fish from anthropogenically altered stream habitats

Understanding population‐level responses to human‐induced changes to habitats can elucidate the evolutionary consequences of rapid habitat alteration. Reservoirs constructed on streams expose stream fishes to novel selective pressures in these habitats. Assessing the drivers of trait divergence facilitated by these habitats will help identify evolutionary and ecological consequences of reservoir habitats. We tested for morphological divergence in a stream fish that occupies both stream and reservoir habitats. To assess contributions of genetic‐level differences and phenotypic plasticity induced by flow variation, we spawned and reared individuals from both habitats types in flow and no flow conditions. Body shape significantly and consistently diverged in reservoir habitats compared with streams; individuals from reservoirs were shallower bodied with smaller heads compared with individuals from streams. Significant population‐level differences in morphology persisted in offspring but morphological variation compared with field‐collected individuals was limited to the head region. Populations demonstrated dissimilar flow‐induced phenotypic plasticity when reared under flow, but phenotypic plasticity in response to flow variation was an unlikely explanation for observed phenotypic divergence in the field. Our results, together with previous investigations, suggest the environmental conditions currently thought to drive morphological change in reservoirs (i.e., predation and flow regimes) may not be the sole drivers of phenotypic change.     

Convergence of bark investment according to fire and climate structures ecosystem vulnerability to future change

Fire regimes in savannas and forests are changing over much of the world. Anticipating the impact of these changes requires understanding how plants are adapted to fire. In this study, we test whether fire imposes a broad selective force on a key fire‐tolerance trait, bark thickness, across 572 tree species distributed worldwide. We show that investment in thick bark is a pervasive adaptation in frequently burned areas across savannas and forests in both temperate and tropical regions where surface fires occur. Geographic variability in bark thickness is largely explained by annual burned area and precipitation seasonality. Combining environmental and species distribution data allowed us to assess vulnerability to future climate and fire conditions: tropical rainforests are especially vulnerable, whereas seasonal forests and savannas are more robust. The strong link between fire and bark thickness provides an avenue for assessing the vulnerability of tree communities to fire and demands inclusion in global models.     

Assessment of an index of biological integrity (IBI) to quantify the quality of two tributaries of river Chenab,Sialkot, Pakistan

Nullah Aik and Nullah Palkhu, two tributaries of river Chenab, were investigated for the assessment of fish habitat degradation as indicator of stream health. Fish abundance data were collected from 18 sites from September 2004 to April 2006 to develop multimetric indices for fish assemblage integrity and to detect the intensity of habitat degradation. A total of 12 metrics were calculated on the basis of taxonomic richness, habitat preference, trophic guild, stress tolerance and origin of species to develop stepped and continuous index of biological integrity (IBI) criteria. Cluster analysis (CA) classified sites based on species composition into three groups, viz., reference, moderately impaired and impaired groups. Non-metric multidimensional scaling (NMDS) was applied to identify underlying ecological gradient to highlight the habitat degradation. NMDS segregated two sites as less impaired, five sites as moderately impaired and eleven sites as impaired groups. Axes 1 and 2 explained a total variation of 53.3%. First axis explained the level of habitat impairment, whereas axis 2 indicated species richness along longitudinal gradient of streams. Sites located upstream of Nullah Aik showed higher IBI scores which dropped to its lowest in downstream sites near Sialkot city. Lowest values of IBI of sites in close proximity of city indicated the role of anthropogenic activities in catchment areas. The results indicated that variability in water chemistry can be related as a function of stream sites impairments (i.e., unimpaired, moderately impaired, and severely impaired). Water quality parameters showed strong correlation with IBI scores. Significantly negative correlation of IBI scores with COD, TDS, turbidity, Fe, Cr, Zn and positive correlation with DO and pH was found. The results can be used for restoration and future management of small streams passing through urban areas of Pakistan. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. A. Cambray     

Ecological traits and landscape characteristics predicting bird sensitivity to urbanization in city parks

Habitat loss and fragmentation caused by urbanization often have negative impacts on wildlife in cities. There are considerable studies investigating the relationship between species traits and fragmentation vulnerability. However, so far, very few studies have examined the influence of species traits combined with landscape factors on vulnerability to urbanization in urbanized landscapes. In this study, we investigated how species traits and park characteristics influenced bird sensitivity to urbanization in the highly urbanized city of Nanjing, China. We used the line-transect method to survey birds in 37 urban parks. For each bird species, we collected data on nine life-history and ecological traits that are commonly assumed to influence urbanization vulnerability. For each park, we selected six landscape variables that are commonly considered to influence bird response to urbanization. After phylogenetic correction, the nine species traits were used separately and in combination to evaluate their associations with species abundance, an indicator of urbanization vulnerability. We then used the RLQ and fourth-corner analyses to test relationships between species traits and environmental variables. We found that the 75 species analyzed demonstrated considerable variation in vulnerability to urbanization. Using PGLS analyses and model averaging, we found that habitat specificity was the single best ecological predictor of urbanization vulnerability in birds in Nanjing city parks. The RLQ analysis showed that body size and habitat specificity were correlated with distance to city center and connectivity of the parks, reflecting strong effects of trait-mediated environmental filters that selectively benefit species with smaller body mass and lower habitat specificity in urbanized landscape. Therefore, conservation efforts giving priority to species with high habitat specificity and to parks with high connectivity and far away from the city center may prove effective for the preservation of bird diversity in our highly urbanized system. Meanwhile, preventing future habitat loss and destruction in existing city parks may also effectively conserve these vulnerable species.     

Fish community structure in the Missouri and lower Yellowstone rivers in relation to flow characteristics

Human alteration is commonplace among large rivers and often results in changes in the flow regime which can lead to changes in fish community structure. We explored the features of fish community structure, morphological characteristics, functional composition, and life-history attributes in relation to six unique flow regimes in the Missouri and lower Yellowstone rivers where we found significant differences in community composition and abundance. The clearest pattern was the distinction between the channelized portion of the river below the mainstem reservoirs and all other parts of the Missouri and lower Yellowstone rivers due to a marked reduction of species richness above the reservoirs. We also found morphological, functional, and life-history differences among the flow units, with the inter-reservoir communities consisting of slightly more generalist characteristics. Our results suggest some relation between flow and fish community structure, but that human alteration may have the strongest influence in distinguishing community differences in the Missouri and lower Yellowstone rivers.     

Temperature extremes: geographic patterns,recent changes,and implications for organismal vulnerabilities

Extreme temperatures can injure or kill organisms and can drive evolutionary patterns. Many indices of extremes have been proposed, but few attempts have been made to establish geographic patterns of extremes and to evaluate whether they align with geographic patterns in biological vulnerability and diversity. To examine these issues, we adopt the CLIMDEX indices of thermal extremes. We compute scores for each index on a geographic grid during a baseline period (1961–1990) and separately for the recent period (1991–2010). Heat extremes (temperatures above the 90th percentile during the baseline period) have become substantially more common during the recent period, particularly in the tropics. Importantly, the various indices show weak geographic concordance, implying that organisms in different regions will face different forms of thermal stress. The magnitude of recent shifts in indices is largely uncorrelated with baseline scores in those indices, suggesting that organisms are likely to face novel thermal stresses. Organismal tolerances correlate roughly with absolute metrics (mainly for cold), but poorly with metrics defined relative to local conditions. Regions with high extreme scores do not correlate closely with regions with high species diversity, human population density, or agricultural production. Even though frequency and intensity of extreme temperature events have – and are likely to have – major impacts on organisms, the impacts are likely to be geographically and taxonomically idiosyncratic and difficult to predict.     

Applying complementary species vulnerability assessments to improve conservation strategies in the Galapagos Marine Reserve

Marine biodiversity can be protected by identifying vulnerable species and creating marine protected areas (MPAs) to ensure their survival. A wide variety of methods are employed by environmental managers to determine areas of conservation priority, however which methods should be applied is often a subject of debate for practitioners and scientists. We applied two species vulnerability assessments, the International Union for the Conservation of Nature (IUCN) red list of threatened species and FishBase’s intrinsic vulnerability assessment, to fish communities in three coastal habitats (mangrove, rocky and coral) on the island of San Cristobal, Galapagos. When using the IUCN red list of threatened species, rocky reefs hosted the greatest number of vulnerable species, however when applying the FishBase assessment of intrinsic vulnerability mangroves hosted the greatest abundance of ‘very-highly’ vulnerable species and coral ecosystems hosted the greatest abundance of ‘highly’ vulnerable species. The two methods showed little overlap in determining habitat types that host vulnerable species because they rely on different biological and ecological parameters. Since extensive data is required for IUCN red list assessments, we show that the intrinsic vulnerability assessment from FishBase can be used to complement the IUCN red list especially in data-poor areas. Intrinsic vulnerability assessments are based on less data-intensive methods than the IUCN red list, but nonetheless may bridge information gaps that can arise when using the IUCN red list alone. Vulnerability assessments based on intrinsic factors are not widely applied in marine spatial planning, but their inclusion as a tool for forming conservation strategies can be useful in preventing species loss.     

Lessons from Red Data Books: Plant Vulnerability Increases with Floral Complexity

The architectural complexity of flower structures (hereafter referred to as floral complexity) may be linked to pollination by specialized pollinators that can increase the probability of successful seed set. As plant—pollinator systems become fragile, a loss of such specialized pollinators could presumably result in an increased likelihood of pollination failure. This is an issue likely to be particularly evident in plants that are currently rare. Using a novel index describing floral complexity we explored whether this aspect of the structure of flowers could be used to predict vulnerability of plant species to extinction. To do this we defined plant vulnerability using the Red Data Book of Rare and Threatened Plants of Greece, a Mediterranean biodiversity hotspot. We also tested whether other intrinsic (e.g. life form, asexual reproduction) or extrinsic (e.g. habitat, altitude, range-restrictedness) factors could affect plant vulnerability. We found that plants with high floral complexity scores were significantly more likely to be vulnerable to extinction. Among all the floral complexity components only floral symmetry was found to have a significant effect, with radial-flower plants appearing to be less vulnerable. Life form was also a predictor of vulnerability, with woody perennial plants having significantly lower risk of extinction. Among the extrinsic factors, both habitat and maximum range were significantly associated with plant vulnerability (coastal plants and narrow-ranged plants are more likely to face higher risk). Although extrinsic and in particular anthropogenic factors determine plant extinction risk, intrinsic traits can indicate a plant’s proneness to vulnerability. This raises the potential threat of declining global pollinator diversity interacting with floral complexity to increase the vulnerability of individual plant species. There is potential scope for using plant—pollinator specializations to identify plant species particularly at risk and so target conservation efforts towards them.     

Vulnerable taxa of European Plecoptera (Insecta) in the context of climate change

We evaluated 516 species and/or subspecies of European stoneflies for vulnerability to climate change according to autoecological data. The variables considered were stream zonation preference, altitude preference, current preference, temperature range preference, endemism and rare species. Presence in ecoregions was used to analyse the vulnerability of taxa in relation to their distribution. We selected the variables that provided information on vulnerability to change in climate. Thus, we chose strictly crenal taxa, high-altitude taxa, rheobionts, cold stenotherm taxa, micro-endemic taxa and rare taxa. Our analysis showed that at least 324 taxa (62.79%) can be included in one or more categories of vulnerability to climate change. Of these, 43 taxa would be included in three or more vulnerability categories, representing the most threatened taxa. The most threatened species and the main factors affecting their distribution are discussed. Endangered potamal species, with populations that have decreased mainly as a consequence of habitat alteration, also could suffer from the effects of climate change. Thus, the total number of taxa at risk is particularly high. Not only are a great diversity of European stoneflies concentrated in the Alps, Pyrenees and Iberian Peninsula, but so are the most vulnerable taxa. These places are likely to be greatly affected by climate change according to climate models. In general, an impoverishment of European Plecoptera taxa will probably occur as a consequence of climate change, and only taxa with wide tolerance ranges will increase in abundance, resulting in lower overall faunal diversity.     

Predicting which tropical tree species are vulnerable to forest disturbances

Tropical forest management often focuses on a few high‐value timber species because they are thought to be the most vulnerable in logged forests. However, other tree species may be vulnerable to secondary effects of logging, like loss of vertebrate dispersers. We examined vulnerability of tree species to loss of vertebrate dispersers in Mabira, a heavily disturbed tropical rainforest in Uganda. Fruit characteristics and shade tolerance regimes of 269 tree species were compiled. Stem densities of tree species producing fruits of various sizes and having different shade tolerance regimes were computed for Mabira and compared with densities of conspecifics in Budongo, a less disturbed forest with similar floral composition. Seventy per cent of tree species in Mabira are animal‐dispersed, of which 10% are large‐fruited light demanders. These species are the most vulnerable because they rarely recruit beneath adult conspecifics and are exclusively dispersed by large vertebrates, also vulnerable in heavily disturbed forests. Comparison of densities between Mabira and Budongo showed that large‐fruited light demanders had a lower density in Mabira. Other categories of tree species had similar densities in both forests. It is plausible that the low density of large‐fruited light demanders is due to limited recruitment caused by dispersal limitations.     

Comparison of bird community indices for riparian restoration planning and monitoring

The use of a bird community index that characterizes ecosystem integrity is very attractive to conservation planners and habitat managers, particularly in the absence of any single focal species. In riparian areas of the western USA, several attempts at arriving at a community index signifying a functioning riparian bird community have been made previously, mostly resorting to expert opinions or national conservation rankings for species weights. Because extensive local and regional bird monitoring data were available for Nevada, we were able to develop three different indices that were derived empirically, rather than from expert opinion. We formally examined the use of three species weighting schemes in comparison with simple species richness, using different definitions of riparian species assemblage size, for the purpose of predicting community response to changes in vegetation structure from riparian restoration. For the three indices, species were weighted according to the following criteria: (1) the degree of riparian habitat specialization based on regional data, (2) the relative conservation ranking of landbird species, and (3) the degree to which a species is under-represented compared to the regional species pool for riparian areas. To evaluate the usefulness of these indices for habitat restoration planning and monitoring, we modeled them using habitat variables that are expected to respond to riparian restoration efforts, using data from 64 sampling sites in the Walker River Basin in Nevada and California. We found that none of the species-weighting schemes performed any better as an index for evaluating overall habitat condition than using species richness alone as a community index. Based on our findings, the use of a fairly complete list of 30–35 riparian specialists appears to be the best indicator group for predicting the response of bird communities to the restoration of riparian vegetation.