Habitat models can be used to examine changes in bird populations under different land management scenarios (e.g., conservation plans or urbanization). By applying models to simulated futures, we can assess the potential impacts of threats and devise strategies to avert or mitigate population losses. Similarly, we can project and visualize the potential outcomes of different conservation strategies before time and money are spent putting habitat on the ground, and thereby be more strategic and efficient in the actions we do take.
Spreadsheet-based Simulation Decision Support Tool (SSimDST)
The CHJV recognized that there are potentially many landscape configurations that could be devised to meet our population objectives. However, developing even a small subset of these potential future landscapes and running as many as 40 HSI models to determine their value for each species would be a time- and computer-intensive process. Thus, we sought to develop a quick-assessment process that could identify the future landscapes most likely to produce the desired results. These “pre-screened” alternatives could then be developed and run in a Geographic Information System (GIS – data mapping software) for a more rigorous assessment. The result of this effort was the Spreadsheet-based Simulation Decision Support Tool (SSimDST). Now in its fourth version, SSimDST (a.k.a. the spreadsheet tool) combines the HSI models and the EPV model in an easy-to-use format. The tool allows users to input the acres of natural communities (as defined by the EPV model) they want to restore within a subsection of the CHBCR, and the tool (1) updates HSI values for those patches, (2) converts HSI values to abundances based on a density linkage, and (3) summarizes population changes at the subsection and BCR scales. SSimDST can also handle negative acreage values to simulate habitat fragmentation and loss.
SSimDST has been used to estimate the potential for the CHJV’s draft habitat objectives to meet our population objectives at the BCR scale. However, because the tool was developed to work at the scale of ecological subsections, it cannot be accurately applied to land use changes within smaller areas (e.g., a Wildlife Management Area). To overcome this hurdle, the CHJV contracted the development of a GIS interface for the tool. The idea behind the interface is to allow users to select particular areas (by hand or from an existing polygon layer) within the CHBCR and the interface will convert the existing land use to the appropriate restored community (based on the EPV model) and calculate the changes to populations. The interface is completed and currently undergoing testing to ensure it works on a variety of Windows operating systems and versions of ArcGIS. It should be available to partners by early 2013.
Landscape-based Population Viability Models
The mission of the CHJV is to sustain native bird populations. Up to this point, however, our conservation planning has focused on measures of abundance because information on population demographic parameters is much more difficult to obtain. Estimating the demographic response of populations to conservation actions is vital to our success at sustaining populations. To address this need, CHJV staff worked with cooperators at the University of Missouri to adapt viability models for use at landscape scales for three priority species: Wood Thrush, Worm-eating Warbler, and Prairie Warbler. This model combines the HSI models for each species and the Generalized Productivity Function with a dispersal model in a metapopulation modeling framework that includes density dependence and environmental stochasticity. Recently, the models were applied to the CHJV’s draft habitat restoration objectives as well as other potential conservation scenarios (i.e., afforestation to reduce fragmentation, and increased non-breeding survival resulting from fewer deadly collisions with communication towers). These simulations indicate that strategically placed restoration or afforestation efforts are more effective than opportunistic (random) efforts at sustaining populations. Different conservation approaches have different advantages, so a mix of approaches is likely needed to achieve our goals.
The CHJV is partnering with the Northern Institute of Applied Climate Science (NIACS), the USDA Forest Service’s Northern Research Experiment Station, the University of Missouri, and the Gulf Coastal Plains and Ozarks Landscape Conservation Cooperative to investigate the potential impact of climate change on forests, birds and other wildlife across the entire CHBCR. The project will use the forest process model LANDIS PRO to model scenarios based on different climate projections and management regimes to examine potential changes in tree species composition. Results from LANDIS PRO will feed into habitat suitability models for birds and other wildlife, as well as viability models for Wood Thrush and Prairie Warbler.