D. Todd Jones-Farrand

Comparison of statistical and theoretical habitat models for conservation planning: the benefit of ensemble prediction

Selection of a modeling approach is an important step in the conservation planning process, but little guidance is available. We compared two statistical and three theoretical habitat modeling approaches representing those currently being used for avian conservation planning at landscape and regional scales: hierarchical spatial count (HSC), classification and regression tree (CRT), habitat suitability index (HSI), forest structure database (FS), and habitat association database (HA). We focused our comparison on models for five priority forest-breeding species in the Central Hardwoods Bird Conservation Region: Acadian Flycatcher, Cerulean Warbler, Prairie Warbler, Red-headed Woodpecker, and Worm-eating Warbler. Lacking complete knowledge on the distribution and abundance of each species with which we could illuminate differences between approaches and provide strong grounds for recommending one approach over another, we used two approaches to compare models: rank correlations among model outputs and comparison of spatial correspondence. In general, rank correlations were significantly positive among models for each species, indicating general agreement among the models. Worm-eating Warblers had the highest pairwise correlations, all of which were significant (P < 0.05). Red-headed Woodpeckers had the lowest agreement among models, suggesting greater uncertainty in the relative conservation value of areas within the region. We assessed model uncertainty by mapping the spatial congruence in priorities (i.e., top ranks) resulting from each model for each species and calculating the coefficient of variation across model ranks for each location. This allowed identification of areas more likely to be good targets of conservation effort for a species, those areas that were least likely, and those in between where uncertainty is higher and thus conservation action incorporates more risk. Based on our results, models developed independently for the same purpose (conservation planning for a particular species in a particular geography) yield different answers and thus different conservation strategies. We assert that using only one habitat model (even if validated) as the foundation of a conservation plan is risky. Using multiple models (i.e., ensemble prediction) can reduce uncertainty and increase efficacy of conservation action when models corroborate one another and increase understanding of the system when they do not.

Assessing Ecoregional‐Scale Habitat Suitability Index Models for Priority Landbirds

Abstract Emerging methods in habitat and wildlife population modeling promise new horizons in conservation but only if these methods provide robust population–habitat linkages. We used Breeding Bird Survey (BBS) data to verify and validate newly developed habitat suitability index (HSI) models for 40 priority landbird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. We considered a species’ HSI model verified if there was a significant rank correlation between mean predicted HSI score and mean observed BBS abundance across the 88 ecological subsections within these Bird Conservation Regions. When we included all subsections, correlations verified 37 models. Models for 3 species were unverified. Rank correlations for an additional 5 species were not significant when analyses included only subsections with BBS abundance >0. To validate models, we developed generalized linear models with mean observed BBS abundance as the response variable and mean HSI score and Bird Conservation Region as predictor variables. We considered verified models validated if the overall model was an improvement over an intercept-only null model and the coefficient on the HSI variable in the model was >0. Validation provided a more rigorous assessment of model performance than verification, and models for 12 species that we verified failed validation. Species whose models failed validation were either poorly sampled by BBS protocols or associated with woodland and shrubland habitats embedded within predominantly open landscapes. We validated models for 25 species. Habitat specialists and species reaching their highest densities in predominantly forested landscapes were more likely to have validated models. In their current form, validated models are useful for conservation planning of priority landbirds and offer both insight into limiting factors at ecoregional scales and a framework for monitoring priority landbird populations from readily available national data sets.

Central Hardwoods ecosystem vulnerability assessment and synthesis: a report from the Central Hardwoods Climate Change Response Framework project

The forests in the Central Hardwoods Region will be affected directly and indirectly by a changing climate over the next 100 years. This assessment evaluates the vulnerability of terrestrial ecosystems in the Central Hardwoods Region of Illinois, Indiana, and Missouri to a range of future climates. Information on current forest conditions, observed climate trends, projected climate changes, and impacts to forest ecosystems was considered in order to assess vulnerability to climate change. Mesic upland forests were determined to be the most vulnerable to projected changes in climate, whereas many systems adapted to fire and drought, such as open woodlands, savannas, and glades, were perceived as less vulnerable. Projected changes in climate and the associated ecosystem impacts and vulnerabilities will have important implications for economically valuable timber species, forest-dependent wildlife and plants, recreation, and long-range planning.

Historical Open Forest Ecosystems in the Missouri Ozarks: Reconstruction and Restoration Targets

Current forests no longer resemble historical open forest ecosystems in the eastern United States. In the absence of representative forest ecosystems under a continuous surface fire regime at a large scale, reconstruction of historical landscapes can provide a reference for restoration efforts. For initial expert-assigned vegetation phases ranging from prairie to forest across the Missouri Ozarks landscape, we reconstructed historical (1815 to 1850) forest densities, basal area, percent stocking or growing space, and canopy cover. After examination of structural means and ranges by initial expected vegetation phases, we classified vegetation phases based on percent stocking boundaries of 30–55% for open woodlands and 55–75% for closed woodlands (diameters ≥ 12.7 cm). We suggest that a percent stocking boundary of 10% may separate prairie and savannas, but we did not identify any large scale prairies in Missouri. We provided structure of each vegetation phase for restoration targets; mean historical densities of vegetation phases ranged from 81 trees/ha in savannas to 285 trees/ha in non-oak/non-pine forests (diameters ≥ 12.7 cm). Due to greater densities than expected and larger diameter trees than current forests, historical forests may have been primarily (about 65%) woodlands with nearly closed canopies, unlike the open canopies presumed during settlement in the Missouri Ozarks. However, a closed yet single canopy layer can transmit enough light to sustain an herbaceous ground cover, given an open midstory due to frequent surface fires. Restoration of open woodlands across all public lands is not practical, but restoration of lower density forests composed of drought-tolerant tree species should translate to management for changing climate.

Multiscale habitat suitability index models for priority landbirds in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions

Habitat Suitability Index (HSI) models were developed to assess habitat quality for 40 priority bird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. The models incorporated both site and landscape environmental variables from one of six nationally consistent datasets. Potential habitat was first defined from unique landform, landcover, and successional age class combinations. Species-specific environmental variables identified from the literature were used to refine initial habitat estimates. Models were verified by comparing subsection-level HSI scores and Breeding Bird Survey (BBS) abundance via Spearman rank correlation. Generalized linear models that predicted BBS abundance as a function of HSI were used to validate models.

Effects of Culling on Bison Demographics in Wind Cave National Park, South Dakota

Abstract We used a stochastic Leslie matrix model parameterized with demographic data from Wind Cave National Park to evaluate effects of four culling strategies on population growth rates and age and sex structure of bison (Bison bison Linnaeus). The four culling scenarios we modeled included removal of: (1) yearlings only; (2) calf/cow combination; (3) a herd-wide proportional cull (i.e., individuals taken in proportion to their availability); and (4) calves only. We also allowed either one, two, or three years to elapse between culls to mimic current management activities, and chose culling values for each scenario that would maintain a stable population (i.e., λ ≈ 1.00). In the absence of culling, our model projected a growth rate of 16% per year (λ= 1.16) (SD = 0.02) for the Wind Cave bison population. The modeled population was characterized by a unimodal age structure for bulls and cows and a 1:1 bull: cow ratio. Removal of 75% of the yearlings or 75% of the calves every year was needed to maintain abundance at current size. These culling strategies altered the age distribution from baseline conditions, resulting in nearly equal proportions of age classes 2–15. When yearling culling or calf removal was skipped one year or two consecutive years, the yearling or calf removal option resulted in positive population growth even in the presence of a 90% cull. Because these strategies nearly removed entire cohorts, corresponding gaps were introduced in the age structure. About 40% of calves and 20% of cows needed to be removed under the annual calf/cow cull to stabilize population growth, producing a unimodal age structure of cows. However, the proportion of bulls in the 2–16 age classes increased, and the proportion of males was nearly equal across the middle age classes. The proportional cull, regardless of time between culling operations, resulted in the most symmetric age structure for males and females. To achieve λ ≈ 1.00 under a proportional cull strategy, 16% of all animals would need to be removed annually, 33% every other year, or 50% once every three years. Sensitivity and elasticity analysis indicated that adult females (5–13 years old) were the most important group of bison affectingλ. These modeled effects, along with factors such as logistical constraints, costs, efficacy, viewing opportunities for tourists, genetics, behavior, and agency policies should be considered when managers choose among culling strategies. When considering historical predation and harvest by Native Americans, we hypothesize that the calf/cow combination cull would have most closely approximated natural bison demographics after the widespread availability of horses (Equus spp.) in the year 1735. Before 1735, we hypothesize that the proportional cull would most closely represent historic conditions, although even this option might not reproduce the variability inherent in historical bison dynamics. We discuss the possibility and management implications of variable culling that might more closely mimic historical influences on bison populations on the Northern Great Plains.