Applying Circuit Theory for Corridor Expansion and Management at Regional Scales: Tiling, Pinch Points, and Omnidirectional Connectivity

In the paper

“animals are well known to dwell in or pass through non-optimal habitat [54], [55]”

What the sources say

• Supported

  The Introduction (page unavailable) says the matrix surrounding habitat fragments is usually not completely hostile and can provide resources that affect persistence and dispersal. The cross-habitat spillover section (page unavailable) describes organisms moving between natural and human-managed habitats, supporting the claim that animals can occupy or pass through less-suitable habitat. (LLM, conf=0.87)

  cites [54] T Tscharntke, 2012, Landscape moderation of biodiversity patterns and processes - eight hypotheses, Biological Reviews source
• Not checked yetcites [55] P Beier, 1992, A checklist for evaluating impacts to wildlife movement corridors, Wildlife Society Bulletin

In the paper

“To minimize border effects that could be formed by the tiling process [51], we created a buffer around each tile with the surrounding land cover data to form larger and overlapping calculation areas for processing in Circuitscape (Figure 2).”

What the sources say

• Supported

  The Results report that omitting a buffer overestimated landscape resistance relative to using a buffer of real data. The Discussion recommends buffers to reduce bias from map boundaries. The cited paper supports the rationale for buffering, while tiling describes the citing authors’ application of that rationale. (LLM, conf=0.91)

  cites [51] EL Koen, 2010, The effect of map boundary on estimates of landscape resistance to animal movement, PLoS One source

In the paper

“These strategies are in active development [57]–[59], and include the detection of barriers that impede movement [56].”

What the sources say

• ?Not checked — no full text of the sourcecites [57] SA Cushman, 2012, Evaluating the sufficiency of protected lands for maintaining wildlife population connectivity in the U.S. northern Rocky Mountains, Diversity and Distributions source
• ?Not checked — no full text of the sourcecites [58] NE Heller, 2009, Biodiversity management in the face of climate change: A review of 22 years of recommendations, Biological Conservation source
• ?Not checked — no full text of the sourcecites [59] BW Compton, 2007, A resistant-kernel model of connectivity for amphibians that breed in vernal pools, Conservation Biology source
• Supported

  The citation to this paper is attached to the detection of barriers, not to the separate statement that strategies are in active development. The Introduction defines barriers as landscape features that impede movement and describes detecting them as a restoration strategy. (LLM, conf=0.94)

  cites [56] BH McRae, 2012, Where to restore ecological connectivity? Detecting barriers and quantifying restoration benefits, PLoS ONE source

In the paper

“It has already been demonstrated that across long time scales at which genetic mutations can be measured, resistance distance is strongly correlated to the differences between populations [28], [29], [42].”

What the sources say

• ?Not checked — no full text of the sourcecites [28] BH McRae, 2008, Using circuit theory to model connectivity in ecology, evolution, and conservation, Ecology source
• Partly supported

  The Results tables report strong correlations between resistance distance and genetic differentiation in mahogany and wolverine populations (R² = 0.68–0.85 across the listed measures). The paper discusses gene flow over many generations, but does not establish the claim’s specific time-scale qualifier—that these are long time scales at which genetic mutations can be measured. (LLM, conf=0.85)

  cites [29] BH McRae, 2007, Circuit theory predicts gene flow in plant and animal populations, Proceedings of the National Academy of Sciences of the United States of America sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [42] SF Spear, 2010, Use of resistance surfaces for landscape genetic studies: considerations for parameterization and analysis, Molecular Ecology source

In the paper

“The omnidirectional connectivity mosaic (Figure 5b) both blends and enhances these shadowing effects in its representation of connectivity in all directions.”

In the paper

“Using either a larger tile size or larger buffer to create the Circuitscape calculation area served to produce mosaics with less prominent seams.”

• Also stated in: § Discussion · plain

  “Prominent seams, which in our opinion are detrimental to the assembly of these tiles into mosaics, can be greatly reduced by increasing the tile size or the buffer size used to create the Circuitscape calculation area.”

In the paper

“For example, in the city located in the northeast part of the image in the east-west directional flow (Figure 5c), the shadow is larger than the city itself and visible well beyond the city’s pixel limits.”

In the paper

“The choices of tile size and buffer size used to create the calculation area affected the prominence of seams in strongly predictable ways (Table 1).”

• Also stated in: § Conclusion · boosted

  “Seam prominence is highly dependent on choices of tile size and buffer size.”

In the paper

“The strength of each factor is of the same order of magnitude (Table 1), meaning that both factors can contribute substantially to reducing seam prominence.”

In the paper

“In general, current density is highest in forest pixels, indicating that given the resistance values and the spatial configuration of land covers in the study area, current flows through forest whenever possible.”

In the paper

“Shown prominently in mosaics are pinch points, narrow corridors where organisms appear to be required to traverse when moving through the landscape.”

In the paper

“the most similar results had the largest buffer sizes (500×500 tiles with a 200% buffer), the largest tile sizes (1000×1000 tiles with a 75% buffer, 1000×1000 tiles with a 50% buffer), or both (1000×1000 tiles with a 100% buffer).”

In the paper

“Although the processing in Circuitscape of calculation areas of 5000×5000 pixels demanded substantial memory (Appendix S3)”

In the paper

“Despite the substantial differences among tiling parameters, current density mosaics were quite similar, with the major differences among mosaics being the difference in seam prominence.”

• Also stated in: § Conclusion · plain

  “Across a wide range of choices of tile sizes and buffer size when creating the Circuitscape computation areas, mosaics were nearly identical, with the identifiable differences among mosaics being the prominence of seams at tile junctures.”

In the paper

“Tracing along the eastern edge of the current density mosaic (Figure 6b) shows the uneven distribution of current passing through forests, which is particularly low in and around the area delineated by the outer edges of the high-resistance city.”

In the paper

“depending on the size of the tiles and buffers used to create the calculation area (Figure 2) for this method, seam lines between tiles may remain visible when a mosaic is assembled for a study area.”

In the paper

“Somewhat surprisingly, preliminary testing for this study indicated that two directional runs appeared to capture the meaningful spatial variability in current density; incorporating additional directions did not result in discernibly different mosaics.”

In the paper

“The substantial variation in current density suggests that not all forest in this landscape is equally important for providing connectivity; rather, the Circuitscape algorithm indicates that a complex interplay of land-cover composition and configuration influences the contribution to landscape connectivity provided by a given area.”

In the paper

“An earlier report by Anderson et al. [47] outlined a tiling approach to produce a continuous map, based on circuit theory, of potential movement paths in multiple directions.”

What the sources say

• Not checked yetcites Anderson et al. [47] Anderson MG, Clark Melissa, Olivero Sheldon, Arlene (2012) Resilient sites for terrestrial conservation in the northeast and mid-atlantic region. The Nature Conservancy. 168 p.

In the paper

“Circuit theory connectivity models are generally seen to be robust to coarsening of input data [53], which can enable computation across very large areas at coarse pixel resolution [28], [57].”

What the sources say

• ?Not checked — no full text of the sourcecites [53] SA Cushman, 2010, Scale dependent inference in landscape genetics, Landscape Ecology source
• ?Not checked — no full text of the sourcecites [28] BH McRae, 2008, Using circuit theory to model connectivity in ecology, evolution, and conservation, Ecology source
• ?Not checked — no full text of the sourcecites [57] SA Cushman, 2012, Evaluating the sufficiency of protected lands for maintaining wildlife population connectivity in the U.S. northern Rocky Mountains, Diversity and Distributions source

In the paper

“We note that the digital designation of a given connectivity value does not imply certainty of where a given organism will travel.”

In the paper

“A large and growing number of studies employ network-based connectivity models, in which a landscape is represented as a set of high-quality habitat nodes, with links connecting pairs of nodes if movement is possible between them [12]–[17].”

What the sources say

• ?Not checked — no full text of the sourcecites [12] DL Urban, 2009, Graph models of habitat mosaics, Ecology Letters source
• ?Not checked — no full text of the sourcecites [13] S Saura, 2010, A common currency for the different ways in which patches and links can contribute to habitat availability and connectivity in the landscape, Ecography source
• ?Not checked — no full text of the sourcecites [14] A Zetterberg, 2010, Making graph theory operational for landscape ecological assessments, planning, and design, Landscape and Urban Planning source
• ?Not checked — no full text of the sourcecites [15] P Galpern, 2011, Patch-based graphs of landscape connectivity: A guide to construction, analysis and application for conservation, Biological Conservation source
• ?Not checked — no full text of the sourcecites [16] B Rayfield, 2011, Connectivity for conservation: a framework to classify network measures, Ecology source
• ?Not checked — no full text of the sourcecites [17] M-J Fortin, 2012, Spatial statistics, spatial regression, and graph theory in ecology, Spatial Statistics source

In the paper

“Network-based representations can be analyzed to derive meaningful connectivity statistics [22]–[25], though these are often dependent on an assumed graph-theoretic model (e.g., complete graph, minimum planar graph) [19] and are often computer resource-limited as larger areas are considered [26].”

What the sources say

• ?Not checked — no full text of the sourcecites [22] JM Calabrese, 2004, A comparison-shopper's guide to connectivity metrics, Frontiers in Ecology and the Environment source
• ?Not checked — no full text of the sourcecites [23] P Kindlmann, 2008, Connectivity measures: a review, Landscape Ecology source
• ?Not checked — no full text of the sourcecites [24] B Rayfield, 2010, The sensitivity of least-cost habitat graphs to relative cost surface values, Landscape Ecology source
• ?Not checked — no full text of the sourcecites [25] RJ Dyer, 2004, Population Graphs: the graph theoretic shape of genetic structure, Molecular Ecology source
• ?Not checked — no full text of the sourcecites [19] Dale MRT, Fortin MJ (2010) From graphs to spatial graphs. In: Futuyma DJ, Shafer HB, Simberloff D, editors. Annual Review of Ecology, Evolution, and Systematics. Palo Alto: Annual Reviews. 21–38. source
• ?Not checked — no full text of the sourcecites [26] A Moilanen, 2011, On the limitations of graph-theoretic connectivity in spatial ecology and conservation, Journal of Applied Ecology source

In the paper

“To understand potential variation in the connectivity mosaic resulting from the choice of tile size and Circuitscape calculation area, we systematically varied these choices with a full 3 by 4 factorial design (Appendix S1).”

In the paper

“Yet increasing the buffer size, or decreasing the tile size, has the effect of increasing either the processing cost of each tile, the number of tiles needed to cover a large area, or both.”

In the paper

“Because current density varies across a landscape according to the underlying land use/land cover patterns, no two adjacent rows or columns have exactly identical current density values.”

In the paper

“Mosaics were created without any smoothing or manipulations of current density values between the tiles.”

In the paper

“While this approach has been proven useful for estimating the resistance distance between particular areas or populations, it remains difficult to generalize from the point-to-point mode into maps showing landscape connectivity across large areas.”

In the paper

“To test the robustness of our omnidirectional connectivity mosaics, we produced current density mosaics using two other arbitrary oblique directions and explored similarity among the resulting mosaics.”

In the paper

“The mosaics indicate high-flow regions that can be integral to landscape connectivity, and can be difficult to identify in non-circuit software or through point-to-point calculations of resistance distance.”

In the paper

“Overall, the shadows of current flow cast by cities were linked not only to the size of the high-resistance areas, but also to their configuration and placement in the landscape.”

In the paper

“Especially prominent seams may not be rooted in real patterns of land-cover composition or configuration.”

In the paper

“Connectivity among forest patches can facilitate or constrain movements of abiotic and biotic components of forest ecosystems [5], [6].”

What the sources say

• ?Not checked — no full text of the sourcecites [5] Forman RTT (1995) Land mosaics: the ecology of landscapes and regions. New YorkNew YorkUSA: Cambridge University Press. 656 p. source
• ?Not checked — no full text of the sourcecites [6] ME Soulé, 2004, The role of connectivity in Australian conservation, Pacific Conservation Biology source

In the paper

“The ability to create arbitrarily large mosaics providing a comprehensive view of connectivity should be of considerable use to researchers and practitioners working over broad spatial areas in a variety of different domains.”