Regional Conductance is one of a suite of products from the Nature’s Network project (naturesnetwork.org). Nature’s Network is a collaborative effort to identify shared priorities for conservation in the Northeast, considering the value of fish and wildlife species and the natural areas they inhabit.
This index is built to support the Terrestrial and Wetland Cores as a measure of the total potential ecological flow of animals and plants between cores from a few to ten kilometers away. It is the continuous surface of 30m cells that is the basis of the discrete Terrestrial Core-connectors. The conductance index of each cell depends on its ecological similarity to neighboring cells and the cores it falls between, and the proximity, size and quality of those cores.
You may refer to the detailed technical guide for more information about local and regional conductance.
This product is to be used in conjunction with the corresponding terrestrial core-based landscape design products included in the Terrestrial and Wetland Core-Connector Network. With the regional conductance index, you can identify places that present the greatest total potential amount of movement of plants and animals between cores to contribute to the ecological connectivity between the most important and intact areas distributed across the region. The regional conductance index depends on the ecological similarity of each cell to its neighboring cells, and thus is relevant to movement-limited organisms.
You might explore the Regional conductance, Northeast U.S. in combination with the following products also available as part of Nature’s Network:
Terrestrial and Aquatic Habitat Map (DSLland), Version 3.1 to reveal the underlying ecosystems that influence conductivity through the region
Terrestrial Core-connectors to see how that binary classification was derived from the continuous regional conductance layer.
Probability of Development (2030 or 2080) to focus on important areas for connectivity that are likely to be lost in the future if not protected.
The Secured Lands layer to determine whether areas representing the best connections between terrestrial cores remain unsecured from development, and thus could represent priorities for land protection.
Description and Derivation
The regional conductance index is influenced by three major factors: ecological similarity, that of of the focal cell to those in nearby cores, and that of the landscape between nearby cores; proximity of the nearby cores; and size and quality of the nearby cores. The index is derived as follows:
Conductance between each pair of terrestrial cores is assessed using random low-cost paths to connect random points in the same macrogroup within cores within a threshold distance. If no points in the same macrogroup exist in the other cell, that path is dropped. Paths between pairs of points honor the landscape resistance for the macrogroup of the focal cell, thus, paths move through similar ecological systems.
A measure of the functional length of each path is determined from the the physical distance in meters integrated with the functional distance, the sum of the resistance of the intervening landscape along the path, based on the point of origin.
Path functional distance is converted into path probability of connectivity using a Gaussian density function based on a 10km bandwidth. This results in a non-linear decay, such that path probability declines with functional distance first only slowly, and then rapidly as it increases further, eventually declining to zero. Any path with a functional distance greater than 20km is dropped.
The path probability of connectivity is multiplied by the mean values of the two cores. The value of the cores are the sum of the core area selection index (see metadata for Terrestrial cores), which represents both the size and quality of the cores. The resultant value is assigned to each cell in the path and then summed across all paths in the landscape to give the regional conductance index.
Known Issues and UncertaintiesAs with any project carried out across such a large area, the Terrestrial Core-connector Network is subject to limitations. The results by themselves are not a prescription for on-the-ground action; users are encouraged to verify, with field visits and site-specific knowledge, the value of any areas identified in the project. Known issues and uncertainties include the following:
Regional conductance is contingent upon the prior designation of terrestrial core areas, and thus is it only meaningful when referenced to those designated terrestrial cores. Thus, only the terrestrial cores and connector products corresponding to the entire Northeast stratified by HUC6 should be used with this version.
Interpreting the conductance values for cells within the cores in complicated by those cells’ role in facilitating flows between other cores, and thus should be avoided.
Regional conductance is a generic measure of ecological flow and does not reflect connectivity for any single species
Metadata for the Terrestrial Core-Connector Network, Northeast U.S. describes additional issues and limitations with identifying the terrestrial core areas, which are relevant for the regional conductance.
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Potential Metadata Source