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USGS2020

Energy development and production in the Great Plains: Implications and restoration opportunities

Energy is an integral part of society. The major US energy sources of fossil fuels (coal, oil, natural gas); biofuels (ethanol); and wind are concentrated in grassland ecosystems of the Great Plains. As energy demand continues to increase, mounting pressures will be placed on North American grassland systems. In this review, we present the ecological effects of energy development and production on grassland systems. We then identify opportunities to mitigate these effects during the planning, construction, and production phases by using informed methodology and improved technology. Primary effects during energy development include small- and large-scale soil disturbance and vegetation removal as small patches of grasslands are used to host oil or gas wells, wind turbine pads, associated roadways, and pipelines or through the conversion of large grassland areas to biofuel croplands. Direct habitat loss or habitat fragmentation can affect wildlife directly through increased mortality or indirectly through reduction in habitat quantity and quality. During energy production, air and water quality can be affected through regular emissions or unplanned spills. Energy development can also affect the economy and health of local communities. During planning, energy development and production effects can be reduced by carefully considering effects on grasslands during siting and even by selecting different energy source types. During construction, effects on soil and plant systems can be minimized by eliminating weed populations before disturbance, salvaging and stockpiling topsoil for future revegetation, and harvesting native local seed for postsite restoration. During energy production operations, noise and road traffic reduction plans and atmospheric monitoring will enable more informed mitigation measures. Continued research on energy development effects and mitigation measures is necessary to establish best management practices beneficial to grassland health while providing needed energy for the United States.

Colorado, Illinois, Indiana, Iowa, Kansas, Minneso↗

USGS2019

Forest restoration, wildfire, and habitat selection by female mule deer

Decades of fire suppression, logging, and overgrazing have led to increased densities of small diameter trees which have been associated with decreases in biodiversity, reduced habitat quality for wildlife species, degraded foraging conditions for ungulates, and more frequent and severe wildfires. In response, land managers are implementing forest restoration treatments using prescribed fire and thinning to mitigate the risk of catastrophic wildfires and improve habitat conditions for a variety of wildlife species. We monitored habitat selection by female mule deer ( Odocoileus hemionus ) in relation to forest restoration treatments and wildfires in northern New Mexico in 2015. Our specific objectives were to assess changes in forage abundance and determine habitat selection patterns of mule deer in relation to recent wildfires, forest restoration treatments, including duration of the post-treatment recovery, and other habitat characteristics. Herbaceous forage biomass was greater in wildfire-burned areas than in untreated areas or those treated with prescribed burns or thinning. Oak forage biomass was greater in wildfire-burned areas compared to prescribed burns, forest thinning, and untreated areas. However, thinned areas tended to have higher oak forage biomass than untreated areas. Mule deer selected for areas burned by prescribed fire and generally avoided wildfire-burned and thinned areas <5 years old. Mule deer strongly selected for thinned areas ≥5 years old. At both the landscape and home-range scale, grasslands were avoided during most seasons, pinyon-juniper woodlands were selected in winter, and oak vegetation and mixed-conifer forests were selected during summer. Our data suggests that mule deer may benefit from recent prescribed burns and older forest thinning, but the duration of post-treatment vegetation recovery influences the strength and direction of selection. Knowledge of the short- and long-term effects of restoration treatments will provide managers with the means to make more informed decisions regarding implementation of forest restoration and other vegetation treatments intended to benefit mule deer.

New Mexico↗

USGS2003

Composition, complexity, and tree mortality in riparian forests in the central Western Cascades of Oregon

Riparian forests contribute to the diversity and function of both terrestrial and aquatic ecosystems. To assess some of these contributions, we compared tree composition, stand complexity, and temporal patterns of tree mortality on permanent plots in seven mature and old-growth stands representing upland forests and forests along low- and mid-order streams in the Western Cascade Range of Oregon. We also assessed recruitment of large wood into stream channels due to tree mortality, both by direct measurement and by estimation from tree mortality and location data. Stands differed in composition due to both stream order and successional stage. Stands on mid-order streams had high abundance of hardwood trees and/or Thuja plicata . Stand complexity (variability in tree diameters, tree life-form diversity, and tree species diversity), was high in stands on mid-order streams and in the upland, old-growth stand. Tree mortality was exceptionally high in six of the seven stands in 1996, the year in which the largest flood during the study occurred. However, only in the one stand on an unconstrained reach of a mid-order stream was mortality primarily due to flooding. Estimated recruitment of wood was much higher from the stand on the unconstrained reach than from the other stands on mid-order streams, suggesting that unconstrained reaches may be important for efforts to maintain or restore large wood in streams.

Oregon↗

USGS2024

Projecting the long-term effects of large-scale human influence on the spatial and functional persistence of extant longleaf pine ecosystems in the Florida Flatwoods Pyrome

Decades of human activities and fire suppression have adversely affected longleaf pine ( Pinus palustris ) ecosystems, which are home to high levels of diversity and endemism. These iconic ecosystems also now face challenges from urbanization and climate change, which will alter conservation outcomes over the remainder of the 21st century. To explore how long-term, large-scale human influences could affect the spatial and functional persistence of extant longleaf pine ecosystems in the Florida Flatwoods Pyrome, we extracted a set of 2400 longleaf pine patches ≥40 ha in size from the Florida Longleaf Pine Ecosystem Geodatabase. Projections from the FUTURES urban growth model and the Florida 2070 project indicate that development will lead to losses of existing longleaf pine habitat, reductions in longleaf pine patch size, and patches that are predominantly located in close proximity to developed areas. Finer-scale patterns of longleaf pine loss in three focal landscapes highlighted differences in land protection, ecological setting, and development pressure and the value of using of multiple urbanization iterations. The occurrence of suitable conditions to conduct prescribed fires, a crucial tool for maintaining, improving, and restoring longleaf pine ecosystems, is projected to decrease seasonally throughout the study area. As a result, the functional persistence of ecosystems is at risk due to climate changes that increase barriers to the safe and reliable application of intentional fire. The long-term viability of this critical ecosystem will warrant the evaluation of adaptive strategies that explicitly account for the individual and compounding effects of urban development and changing fire management conditions when considering options for ecosystem protection, management, and restoration.

Florida↗

USGS2022

The past, present, and future of coral reef growth in the Florida Keys

Coral-reef degradation is driving global-scale reductions in reef-building capacity and the ecological, geological, and socioeconomic functions it supports. The persistence of those essential functions will depend on whether coral-reef management is able to rebalance the competing processes of reef accretion and erosion. Here, we reconstructed census-based carbonate budgets of 46 reefs throughout the Florida Keys from 1996 to 2019. We evaluated the environmental and ecological drivers of changing budget states and compared historical trends in reef-accretion potential to millennial-scale baselines of accretion from reef cores and future projections with coral restoration. We found that historically, most reefs had positive carbonate budgets, and many had reef-accretion potential comparable to the ~3 mm year −1 average accretion rate during the peak of regional reef building ~7000 years ago; however, declines in reef-building Acropora palmata and Orbicella spp. corals following a series of thermal stress events and coral disease outbreaks resulted in a shift from positive to negative budgets for most reefs in the region. By 2019, only ~15% of reefs had positive net carbonate production. Most of those reefs were in inshore, Lower Keys patch-reef habitats with low water clarity, supporting the hypothesis that environments with naturally low irradiance may provide a refugia from thermal stress. We caution that our estimated carbonate budgets are likely overly optimistic; comparison of reef-accretion potential to measured accretion from reef cores suggests that, by not accounting for the role of nonbiological physical and chemical erosion, census-based carbonate budgets may underestimate total erosion by ~1 mm year −1 (−1.15 kg CaCO 3 m −2 year −1 ). Although the present state of Florida's reefs is dire, we demonstrate that the restoration of reef-building corals has the potential to help mitigate declines in reef accretion in some locations, which could allow some key ecosystem functions to be maintained until the threat of global climate change is addressed.

Florida↗

USGS2022

Genetic analyses provide new insight on the mating strategies of the American Black Swift (Cypseloides niger)

Avian mating strategies play a vital role in the demographic and genetic dynamics of a species and understanding avian reproductive tactics is important to conservation, population management and restoration. Classifications of avian mating strategies have historically been based on direct physical observations and tend to be rigid population-level generalizations that overlook the variations inherent in most ecological systems. Based on limited empirical field observations, the American Black Swift Cypseloides niger borealis is considered to be a socially monogamous species with pair bonds lasting for many years. To test this hypothesis, we collected genomic DNA samples from banded swifts from six American Black Swift colonies in the western United States from 2004 to 2019 and isolated and developed primers for highly polymorphic microsatellite loci and used them to genotype our samples. Our parentage analysis revealed that sampled females never mated with the same male in subsequent years, suggesting that they are not sexually monogamous with a single partner for many years as previously hypothesized.

Colorado, Idaho, New Mexico↗

USGS2011

A riverscape perspective of Pacific salmonids and aquatic habitats prior to large-scale dam removal in the Elwha River, Washington, USA

Dam removal has been increasingly proposed as a river restoration technique. In 2011, two large hydroelectric dams will be removed from Washington State’s Elwha River. Ten anadromous fish populations are expected to recolonise historical habitats after dam removal. A key to understanding watershed recolonisation is the collection of spatially continuous information on fish and aquatic habitats. A riverscape approach with an emphasis on biological data has rarely been applied in mid-sized, wilderness rivers, particularly in consecutive years prior to dam removal. Concurrent snorkel and habitat surveys were conducted from the headwaters to the mouth (rkm 65–0) of the Elwha River in 2007 and 2008. This riverscape approach characterised the spatial extent, assemblage structure and patterns of relative density of Pacific salmonids. The presence of dams influenced the longitudinal patterns of fish assemblages, and species richness was the highest downstream of the dams, where anadromous salmonids still have access. The percent composition of salmonids was similar in both years for rainbow trout, Oncorhynchus mykiss (Walbaum), coastal cutthroat trout, Oncorhynchus clarkii clarkii (Richardson) (89%; 88%), Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (8%; 9%), and bull trout, Salvelinus confluentus (Suckley) (3% in both years). Spatial patterns of abundance for rainbow and cutthroat trout ( r = 0.76) and bull trout ( r = 0.70) were also consistent between years. Multivariate and univariate methods detected differences in habitat structure along the river profile caused by natural and anthropogenic factors. The riverscape view highlighted species-specific biological hotspots and revealed that 60–69% of federally threatened bull trout occurred near or below the dams. Spatially continuous surveys will be vital in evaluating the effectiveness of upcoming dam removal projects at restoring anadromous salmonids.

Washington↗

USGS2014

Intrinsic variability in shell and soft tissue growth of the freshwater mussel Lampsilis siliquoidea

Freshwater mussels are ecologically and economically important members of many aquatic ecosystems, but are globally among the most imperiled taxa. Propagation techniques for mussels have been developed and used to boost declining and restore extirpated populations. Here we use a cohort of propagated mussels to estimate the intrinsic variability in size and growth rate of Lampsilis siliquoidea (a commonly propagated species). Understanding the magnitude and pattern of variation in data is critical to determining whether effects observed in nature or experimental treatments are likely to be important. The coefficient of variation (CV) of L. siliquoidea soft tissues (6.0%) was less than the CV of linear shell dimensions (25.1-66.9%). Size-weight relationships were best when mussel width (the maximum left-right dimension with both valves appressed) was used as a predictor, but 95% credible intervals on these predictions for soft tissues were ~145 mg wide (about 50% of the mean soft tissue mass). Mussels in this study were treated identically, raised from a single cohort and yet variation in soft tissue mass at a particular size class (as determined by shell dimensions) was still high. High variability in mussel size is often acknowledged, but seldom discussed in the context of mussel conservation. High variability will influence the survival of stocked juvenile cohorts, may affect the ability to experimentally detect sublethal stressors and may lead to incongruities between the effects that mussels have on structure (via hard shells) and biogeochemical cycles (via soft tissue metabolism). Given their imperiled status and longevity, there is often reluctance to destructively sample unionid mussel soft tissues even in metabolic studies (e.g., studies of nutrient cycling). High intrinsic variability suggests that using shell dimensions (particularly shell length) as a response variable in studies of sublethal stressors or metabolic processes will make confident identifications of smaller effect sizes difficult.

PLoS ONE↗

USGS2011

Joint Ecosystem Modeling (JEM) ecological model documentation volume 2: roseate spoonbill ( Platalea ajaja ) landscape habitat suitability index v1.0.0

Ecological conditions in the Greater Everglades have changed due to human activities, including the construction of canals to divert water away from the core of the landscape. Current and planned restoration projects are designed to produce a natural sheetflow of water across the landscape. This restoration of water flow should provide an increase in freshwater needed to restore natural salinities to the fringing estuarine ecosystem. In this report, we describe a Landscape Habitat Suitability Index model designed to evaluate alternative restoration plans for the benefit of a key species, the roseate spoonbill (Platalea ajaja). Model output has shown to be a good indicator of areas capable of supporting spoonbills. Use of this model will allow examination of the potential response of this key species to water management proposed through the Greater Everglades restoration process.

Florida↗

USGS2016

A method for characterizing late-season low-flow regime in the upper Grand Ronde River Basin, Oregon

This report describes a method for estimating ecologically relevant low-flow metrics that quantify late‑season streamflow regime for ungaged sites in the upper Grande Ronde River Basin, Oregon. The analysis presented here focuses on sites sampled by the Columbia River Inter‑Tribal Fish Commission as part of their efforts to monitor habitat restoration to benefit spring Chinook salmon recovery in the basin. Streamflow data were provided by the U.S. Geological Survey and the Oregon Water Resources Department. Specific guidance was provided for selection of streamgages, development of probabilistic frequency distributions for annual 7-day low-flow events, and regionalization of the frequency curves based on multivariate analysis of watershed characteristics. Evaluation of the uncertainty associated with the various components of this protocol indicates that the results are reliable for the intended purpose of hydrologic classification to support ecological analysis of factors contributing to juvenile salmon success. They should not be considered suitable for more standard water-resource evaluations that require greater precision, especially those focused on management and forecasting of extreme low-flow conditions.

Oregon↗

USGS2018

A framework for identifying and characterising coral reef “oases” against a backdrop of degradation

Human activities have led to widespread ecological decline; however, the severity of degradation is spatially heterogeneous due to some locations resisting, escaping, or rebounding from disturbances. We developed a framework for identifying oases within coral reef regions using long‐term monitoring data. We calculated standardised estimates of coral cover ( z ‐scores) to distinguish sites that deviated positively from regional means. We also used the coefficient of variation (CV) of coral cover to quantify how oases varied temporally, and to distinguish among types of oases. We estimated “coral calcification capacity” (CCC), a measure of the coral community's ability to produce calcium carbonate structures and tested for an association between this metric and z ‐scores of coral cover. We illustrated our z ‐score approach within a modelling framework by extracting z ‐scores and CVs from simulated data based on four generalized trajectories of coral cover. We then applied the approach to time‐series data from long‐term reef monitoring programmes in four focal regions in the Pacific (the main Hawaiian Islands and Mo'orea, French Polynesia) and western Atlantic (the Florida Keys and St. John, US Virgin Islands). Among the 123 sites analysed, 38 had positive z ‐scores for median coral cover and were categorised as oases. Synthesis and applications . Our framework provides ecosystem managers with a valuable tool for conservation by identifying “oases” within degraded areas. By evaluating trajectories of change in state (e.g., coral cover) among oases, our approach may help in identifying the mechanisms responsible for spatial variability in ecosystem condition. Increased mechanistic understanding can guide whether management of a particular location should emphasise protection, mitigation or restoration. Analysis of the empirical data suggest that the majority of our coral reef oases originated by either escaping or resisting disturbances, although some sites showed a high capacity for recovery, while others were candidates for restoration. Finally, our measure of reef condition (i.e., median z ‐scores of coral cover) correlated positively with coral calcification capacity suggesting that our approach identified oases that are also exceptional for one critical component of ecological function.

Florida, Hawaii↗

USGS2018

Linking animals aloft with the terrestrial landscape

Despite using the aerosphere for many facets of their life, most flying animals (i.e., birds, bats, some insects) are still bound to terrestrial habitats for resting, feeding, and reproduction. Comprehensive broad-scale observations by weather surveillance radars of animals as they leave terrestrial habitats for migration or feeding flights can be used to map their terrestrial distributions either as point locations (e.g., communal roosts) or as continuous surface layers (e.g., animal densities in habitats across a landscape). We discuss some of the technical challenges to reducing measurement biases related to how radars sample the aerosphere and the flight behavior of animals. We highlight a recently developed methodological approach that precisely and quantitatively links the horizontal spatial structure of birds aloft to their terrestrial distributions and provides novel insights into avian ecology and conservation across broad landscapes. Specifically, we present case studies that (1) elucidate how migrating birds contend with crossing ecological barriers and extreme weather events, (2) identify important stopover areas and habitat use patterns of birds along their migration routes, and (3) assess waterfowl response to wetland habitat management and restoration. These studies aid our understanding of how anthropogenic modification of the terrestrial landscape (e.g., urbanization, habitat management), natural geographic features, and weather (e.g., hurricanes) can affect the terrestrial distributions of flying animals.

Book chapter↗

USGS2024

How well do existing surveys track fish community performance measures in the St. Clair-Detroit River System?

The St. Clair-Detroit River System (SCDRS) connects Lake Huron to Lake Erie and provides important habitats for many fishes of economic and ecological importance. Portions of the SCDRS are designated as Great Lakes Areas of Concern and fish production and conservation may be compromised. Efforts to address beneficial use impairments have focused on restoring habitat for native fishes and improving aquatic ecosystem health. Considerable site-specific research and long-term, annual fish surveys have examined responses to habitat improvements. However, there is uncertainty surrounding whether individual studies and surveys can assess (1) population-level benefits of habitat enhancements and (2) whether management objectives are being met. To identify monitoring gaps and inform long-term monitoring program development, we compared outputs from SCDRS fish monitoring surveys (based on discussions with regional agencies) with performance measures specified in management plans (obtained through gray literature searches). Performance measures for harvested species aligned well with outputs of existing surveys. In contrast, at-risk fishes often had objectives and performance measures that reflected knowledge gaps and study needs. Although harvested species were well-monitored relative to specified performance measures, at-risk fishes were less reliably collected by existing surveys, except for lake sturgeon Acipenser fulvescens . Effective evaluation of restoration efforts for at-risk fishes may require additional survey efforts that target species-specific habitat use and life history characteristics.

Michigan↗

USGS2020

Loss of coastal islands along Florida’s Big Bend region: Implications for breeding American oystercatchers

Many coastal-dependent species have undergone large-scale population declines due to impacts from habitat loss, including American oystercatchers ( Haematopus palliatus ). Islands along the Big Bend region of Florida’s Gulf Coast provide important nesting habitat for oystercatchers, but reproductive success here is low and habitat degradation and loss are a major concern. To determine rates and characteristics of habitat loss, we quantified changes in island sizes within two major breeding areas of the Big Bend: the Barge Canal spoil islands and natural islands at Cedar Key. We digitized aerial photographs from the past ~ 40 years, measured area and shoreline retreat of nesting islands, and identified trends over time by fitting linear mixed effects models. The total area of the ten Barge Canal spoil islands decreased by 55% between 1979 and 2016. At Cedar Key, the total area of the six islands measured decreased by 39% between 1974 and 2016, 85% of which occurred after 1995, indicating an increase in erosion rates correlated with oyster reef declines. Changes in available nesting habitat varied between the Barge Canal and Cedar Key islands due to differences in physical attributes; however, all islands significantly decreased in size over time. Given the long life and high site fidelity of American oystercatchers, these islands may currently be acting as an ecological trap for this species. Climate change, sea-level rise, and loss of oyster reefs are likely to continue to drive oystercatcher habitat loss throughout their range; thus, creation and restoration of oyster reefs and nesting islands will become increasingly important.

Florida↗

USGS2026

Tidal forested wetlands can be incorporated into blue carbon conservation and restoration strategies

Purpose of Review Blue carbon is an important concept for environmental policy. Blue carbon strategies (conservation and restoration for carbon gain) have been primarily implemented with mangroves, though are likely to be suitable for other tidal forested wetlands. Here, we discuss the expanding definition of blue carbon encompassing all tidal forested wetlands, synthesize ecological and carbon sink knowledge of tidal forested wetlands, and reflect on key actions in mangrove blue carbon research and implementation that could be applied to other tidal forested wetlands. Recent Findings Conceptually, the blue carbon concept has now expanded beyond traditional coastal vegetated ecosystems to include all tidal wetlands, including tidal forested wetlands. Emerging data on carbon sequestration, emissions, and budgets from around the world now show that many tidal forested wetland ecosystems are carbon sinks at a magnitude similar to mangroves. At the global scale, mangroves have become incorporated into blue carbon strategies rapidly compared to other tidal forested wetlands, facilitated by agenda-setting papers, adequate data addressing concerns on emissions and permanence, the availability of global maps, a clear ecosystem definition, clear accounting and policy frameworks, and international stakeholders who acted as high profile ecosystem advocates, alongside long-term capacity building efforts. This provides a roadmap for implementation in other tidal forested wetlands. Summary Tidal forested wetlands other than mangroves have high potential for blue carbon management. Many tidal forested wetlands share biophysical similarities with mangroves, carbon stocks can be similar, and methane emissions are often no higher. An increasing evidence base, challenging assumptions around greenhouse gas fluxes, and robust engagement with policy actors and frameworks, could increase the use of blue carbon for tidal forested wetland conservation and restoration.

Current Forestry Reports↗

USGS2010

Valuing ecosystem services from wetlands restoration in the Mississippi Alluvial Valley

This study assesses the value of restoring forested wetlands via the U.S. government's Wetlands Reserve Program (WRP) in the Mississippi Alluvial Valley by quantifying and monetizing ecosystem services. The three focal services are greenhouse gas (GHG) mitigation, nitrogen mitigation, and waterfowl recreation. Site- and region-level measurements of these ecosystem services are combined with process models to quantify their production on agricultural land, which serves as the baseline, and on restored wetlands. We adjust and transform these measures into per-hectare, valuation-ready units and monetize them with prices from emerging ecosystem markets and the environmental economics literature. By valuing three of the many ecosystem services produced, we generate lower bound estimates for the total ecosystem value of the wetlands restoration. Social welfare value is found to be between $1435 and $1486/ha/year, with GHG mitigation valued in the range of $171 to $222, nitrogen mitigation at $1248, and waterfowl recreation at $16. Limited to existing markets, the estimate for annual market value is merely $70/ha, but when fully accounting for potential markets, this estimate rises to $1035/ha. The estimated social value surpasses the public expenditure or social cost of wetlands restoration in only 1 year, indicating that the return on public investment is very attractive for the WRP. Moreover, the potential market value is substantially greater than landowner opportunity costs, showing that payments to private landowners to restore wetlands could also be profitable for individual landowners. ?? 2009 Elsevier B.V.

Ecological Economics↗

USGS2017

Greenup and evapotranspiration following the Minute 319 pulse flow to Mexico: An analysis using Landsat 8 Normalized Difference Vegetation Index (NDVI) data

In the southwestern U.S., many riparian ecosystems have been altered by dams, water diversions, and other anthropogenic activities. This is particularly true of the Colorado River, where numerous dams and agricultural diversions have affected this water course, especially south of the U.S.–Mexico border. In the spring of 2014, 130 million cubic meters of water was released to the lower Colorado River Delta in Mexico. To understand the impact of this pulse flow release on vegetation in the delta’s riparian corridor, we analyzed a modified form of Landsat 8 Operational Land Imager (OLI) Normalized Difference Vegetation Index (NDVI*) data. We assessed greenup during the growing period and estimated actual evapotranspiration (ET a ) for the period prior to (yr. 2013) and following (i.e., yr. 2014 and 2015) the pulse flow. We found a significant increase in NDVI* from 2013 to 2014 (P < 0.05) and a decrease from 2014 to 2015; however, 2015 levels were still significantly higher than in 2013. ET a was also higher in 2014 vs. 2013, with an estimated 74.5 million cubic meters in 2013 and 88.9 in 2014. The most intense greening occurred in the zone of inundation but also extended into the non-flooded part of the riparian zone, indicating replenishment of groundwater. These findings suggest the peak response by vegetation to the flow lasted about one year, followed by a decrease in NDVI*. As a long term solution to the declining condition of vegetation, additional pulse releases are likely needed for restoration and survival of riparian plant communities in the Colorado River Delta.

Ecological Engineering↗

USGS2005

Assessing uncertainty in ecological systems using global sensitivity analyses: A case example of simulated wolf reintroduction effects on elk

Often landmark conservation decisions are made despite an incomplete knowledge of system behavior and inexact predictions of how complex ecosystems will respond to management actions. For example, predicting the feasibility and likely effects of restoring top-level carnivores such as the gray wolf ( Canis lupus ) to North American wilderness areas is hampered by incomplete knowledge of the predator-prey system processes and properties. In such cases, global sensitivity measures, such as Sobol’ indices, allow one to quantify the effect of these uncertainties on model predictions. Sobol’ indices are calculated by decomposing the variance in model predictions (due to parameter uncertainty) into main effects of model parameters and their higher order interactions. Model parameters with large sensitivity indices can then be identified for further study in order to improve predictive capabilities. Here, we illustrate the use of Sobol’ sensitivity indices to examine the effect of parameter uncertainty on the predicted decline of elk ( Cervus elaphus ) population sizes following a hypothetical reintroduction of wolves to Olympic National Park, Washington, USA. The strength of density dependence acting on survival of adult elk and magnitude of predation were the most influential factors controlling elk population size following a simulated wolf reintroduction. In particular, the form of density dependence in natural survival rates and the per-capita predation rate together accounted for over 90% of variation in simulated elk population trends. Additional research on wolf predation rates on elk and natural compensations in prey populations is needed to reliably predict the outcome of predator–prey system behavior following wolf reintroductions.

Ecological Modelling↗