Geographic Threats to Validity

For my independent project to culminate this class, I will be working with Andy Atallah to replicate part of a wildlife corridor analysis. The original study evaluated the connectivity of Makuyuni Wildlife Corridor, a stretch of unprotected land between Tarangire National Park and Essmingor National Forest Reserve in Tanzania. We will be reproducing the first part of the study, a multifactor analysis model that approximates cost of movement through the corridor based on least cost pathway analysis. The study was originally conducted using the QGIS Model Builder, and we will be replicating the workflow in R. The output we are attempting to replicate is a map displaying the minimum cost of movement through each point in the study area.

There are several possible geographic threats to validity in a wildlife corridor analysis. The first is scale dependency. Species of different sizes and behavioral characteristics show on-the-ground movement patterns of different scales. If the spatial resolution of analysis does not align with the movement patterns of the species of interest, the study may not accurately represent movement costs. It will be important to confirm that the spatial resolution of the model is appropriate for the species of interest.

A second threat is space-time interactions. Wildlife movement patterns can change over time, especially over the course of a year due to seasonal variations. Corridor analyses that do not take into account temporal considerations may not capture these dynamics. If the data is available, a potential solution is to incorporate seasonal data that accounts for changing movement behaviors or landscape characteristics.

A final geographic threat to validity in this study is boundary distortion. We will need to create an artificially high cost surface around the boundary of the corridor area to prevent unrealistic low-cost pathways from forming around the edge of the study area.

It is important to consider geographic threats to validity prior to embarking on a reproduction study, so that these considerations can be addressed in the methodology early on in the process.

References:

• Schmitt, R. R. (1978). Threats to validity involving geographic space. Socio-Economic Planning Sciences, 12(4), 191–195. https://doi.org/10.1016/0038-0121(78)90044-7