Search

The U.S. Fish and Wildlife Service recently revised the recovery plan (USFWS, 2011) and designated Critical Habitat (USFWS, 2012a) for the Northern Spotted Owl ( Strix occidentalis caurina ). The Critical Habitat designation was based in part on a map of relative habitat suitability that was developed by USFWS (2011, 2012b) for this purpose. Loehle et al. (2015) critiqued the U.S. Fish and Wildlife Service’s approach to modeling relative habitat suitability for the Northern Spotted Owl. Here, we respond to Loehle et al.’s assessment, and identify four major shortcomings within it. First, it mischaracterizes the literature on spotted owls and MaxEnt, the species distribution model used by the U.S. Fish and Wildlife Service. Second, it is predicated upon several logic errors that, when resolved, undermine Loehle et al.’s conclusions. Third, it fails to demonstrate that the nesting and roosting site location data used by the U.S. Fish and Wildlife Service is a biased sample. Lastly, Loehle et al.’s claims of significant flaws in analytical methods and ecological inference by the U.S. Fish and Wildlife Service are not convincing. We assert that the U.S. Fish and Wildlife Service’s Northern Spotted Owl relative habitat suitability model was in fact scientifically rigorous, and that it met the intended goals that the U.S. Fish and Wildlife Service articulated for their models. [ABSTRACT FROM AUTHOR]

Abstract: Managing forests for multiple objectives requires balancing timber and vegetation management objectives with needs of sensitive species. Especially challenging is how to retain the habitat elements for species that are typically associated with late-seral forests. We develop a regionally specific, multivariate model describing habitat selection that can be used – when linked to an institutional forest inventory program – to assess, monitor and forecast habitat conditions for a key wildlife species. We use the fisher (Martes pennanti) in northwestern California as our example and develop a predictive model for resting habitat that is created using data from the specific region where it will be used. We explore how this resting habitat model differs from a similar model developed for the Sierra Nevada and consider the implications for forest management. We developed the model using MaxEnt by comparing vegetation data at 99 randomly selected fisher resting structures on public and tribal lands in northwestern California with 883 Forest Inventory and Analysis (FIA) plots within the same ecoregion. A total of 58 alternative vegetation models were specified and the top 10 were nearly identical in their performance (Gain>1.08; Area Under the Curve [AUC]>0.89). We chose a five-variable model (canopy closure, tree age, total basal area, volume of “large” wood and basal area of hardwoods) because it included the fewest variables and included only those that could be affected by management. This model was similar to the Sierra Nevada model, but did not include topographic features (e.g., slope) nor did it include a variable representing the density of small trees. The absence of variables related to topography may make it easier for managers to affect positive change in resting habitat suitability since all variables can be influenced by management actions. Moreover, the model indicates that small trees appear to be less important (compared to southern Sierra Nevada) and therefore the probability of producing high-value resting habitat without higher fire risk is greater. We also created a spreadsheet that simplifies the process of generating habitat predictions from new data. Since metrics of stand structure and wildlife habitat are sensitive to sample design, collecting new data with FIA protocols will provide the most accurate estimates of predicted habitat with this model. Together, the Sierra Nevada and northwest California models provide managers in California a quantitative means to assess and monitor resting habitat suitability using current and future data that are part of an institutionally supported program to inventory forest vegetation. [Copyright &y& Elsevier]

Abstract: The fisher is warranted for protection under the Endangered Species Act in the western United States and, as such, it is especially important that conservation and management actions are based on sound scientific information. We developed a landscape-scale suitability model for interior northern California to predict the probability of detecting fishers and to identify areas of important fisher habitat. Previous models have been extrapolated to this region, but our model was developed from the results of strategically planned detection surveys within the study area. We used generalized additive modeling to create a model that best distinguished detection (n =55) from non-detection (n =90) locations on the basis of environmental covariates. Four models were averaged to create a final model including the following variables: Amount of Dense Forest, Percent Hardwood, Medium & Large Trees, Structurally Complex Forest, Adjusted Elevation, Insolation Index and Predicted Abundance of Mammalian Prey. This model was well calibrated and correctly classified fisher detections 83.6% of the time and absences (non-detections) 70.0%. Independent test data were classified less well; 76.2% and 53.0%, respectively, perhaps a result of differences in the spatial and temporal characteristics of the data used to build versus test the model. The model is the first comprehensive portrayal of the distribution and configuration of habitat suitability in this region and provides managers a tool to monitor habitat change over time and to plan vegetation treatments. It also represents an example for the development of similar models for dispersal-limited mammals with large area needs, as well as other species associated with late-successional forests in northern California. [ABSTRACT FROM AUTHOR]

Abstract: In the Pacific Northwest, USA, red-tree voles (Arborimus longicaudus) are of conservation and management interest owing to their apparent association with late-seral forests and the relatively small extent of such forests, largely a function of timber harvest, fire, and conversion of forests to non-forest uses during the past century. We created and evaluated a series of red-tree vole habitat association models, and applied the best model to evaluate tree vole habitat quality within and outside of reserves throughout most of their range in Oregon and northern California. We modeled presence and absence of tree vole nests across a gradient of biotic, abiotic, and spatial features; and within and outside of reserves. The best model included spatial coordinates, percent slope, basal area of trees with diameter at breast height (dbh) between 45 and 90cm, maximum tree dbh, and standard deviation of conifer dbh. Plots with tree vole nests contained many late-seral/old-growth forest attributes such as large diameter, older, and variably sized trees. Evaluation of the best model, including rigorous cross-validation, showed the model to be statistically robust and to have very good/excellent predictive ability. Reserves had significantly higher mean habitat quality than non-reserved lands, and reserves had much more high quality habitat than non-reserves. [Copyright &y& Elsevier]

Abstract: Protection of area-limited species is an important component of plans to conserve biodiversity, but the habitat needs of such species can be different and important habitats may not align with existing reserves. We used empirically derived landscape suitability models for the spotted owl and the fisher to evaluate the overlap in habitat suitability for these two old forest-associated predators in an area of northern California affected by the Northwest Forest Plan (NWFP), a bioregional conservation plan. The area includes designated Wilderness areas and new reserves (Late-Successional Reserves, LSRs) established under the NWFP. We used the site selection algorithm MARXAN to identify priority habitat areas for each species, and for both combined, and to compare these areas with reserves. Sites were selected under two constraints, to achieve a threshold proportion of total habitat value and to select new areas equal to the total current area in existing reserves. The rank correlation between predicted value for the two species was low (0.11), because areas of highest predicted habitat value were more widely distributed for the owl. This difference also meant that the sites selected to optimize habitat value were more aggregated for fishers than owls, resulting in greater overlap of owl habitat and current reserves. To capture 25%, 50% and 75% of total habitat value for the owl required 14.0%, 29.2%, and 47.3% of the planning units, respectively; capturing the same for the fisher required only 5.3%, 13.5%, and 27.2%. A combined owl-fisher scenario resulted in areas that overlapped only ∼50% of existing reserves. The current location of LSRs may not be the best solution to maintaining well-connected habitats for these area-limited species in northwestern California. Whether LSRs are a better solution to protecting the diversity of other lesser-known taxa (i.e., salamanders and mollusks) is the subject of related work. [Copyright &y& Elsevier]