Bowman Jeff, Adey Elizabeth, Angoh Siow Y J, Baici Jennifer E, Brown Michael G C, Cordes Chad, Dupuis Arthur E, Newar Sasha L, Scott Laura M, Solmundson Kirsten
Ontario Ministry of Natural Resources and Forestry, Peterborough, Canada.
Trent University, Peterborough, Canada.
PeerJ. 2020 Aug 3;8:e9617. doi: 10.7717/peerj.9617. eCollection 2020.
Conservation practitioners are often interested in developing land use plans that increase landscape connectivity, which is defined as the degree to which the landscape facilitates or impedes movement among resource patches. Landscape connectivity is often estimated with a cost surface that indicates the varying costs experienced by an organism in moving across a landscape. True, or absolute costs are rarely known however, and therefore assigning costs to different landscape elements is often a challenge in creating cost surface maps. As such, we consider it important to understand the sensitivity of connectivity estimates to uncertainty in cost estimates.
We used simulated landscapes to test the sensitivity of current density estimates from circuit theory to varying relative cost values, fragmentation, and number of cost classes (i.e., thematic resolution). Current density is proportional to the probability of use during a random walk. Using Circuitscape software, we simulated electrical current between pairs of nodes to create current density maps. We then measured the correlation of the current density values across scenarios.
In general, we found that cost values were highly correlated across scenarios with different cost weights (mean correlation ranged from 0.87 to 0.92). Changing the spatial configuration of landscape elements by varying the degree of fragmentation reduced correlation in current density across maps. We also found that correlations were more variable when the range of cost values in a map was high.
The low sensitivity of current density estimates to relative cost weights suggests that the measure may be reliable for land use applications even when there is uncertainty about absolute cost values, provided that the user has the costs correctly ranked. This finding should facilitate the use of cost surfaces by conservation practitioners interested in estimating connectivity and planning linkages and corridors.
保护从业者通常对制定能提高景观连通性的土地利用规划感兴趣，景观连通性被定义为景观促进或阻碍资源斑块间移动的程度。景观连通性通常用成本表面来估计，该表面表明生物体在穿越景观时所经历的不同成本。然而，真实的或绝对成本很少为人所知，因此在创建成本表面地图时，为不同景观要素分配成本往往是一项挑战。因此，我们认为了解连通性估计对成本估计不确定性的敏感性很重要。
我们使用模拟景观来测试电路理论中当前密度估计对不同相对成本值、破碎化程度和成本类别数量（即主题分辨率）的敏感性。当前密度与随机游走期间的使用概率成正比。使用Circuitscape软件，我们模拟了节点对之间的电流以创建当前密度地图。然后我们测量了不同场景下当前密度值的相关性。
总体而言，我们发现不同成本权重的场景下成本值高度相关（平均相关性范围为0.87至0.92）。通过改变破碎化程度来改变景观要素的空间配置会降低地图间当前密度的相关性。我们还发现，当地图中成本值范围较大时，相关性变化更大。
当前密度估计对相对成本权重的低敏感性表明，即使在绝对成本值存在不确定性的情况下，只要用户正确排列了成本，该测量方法对于土地利用应用可能是可靠的。这一发现应有助于对估计连通性以及规划连接和廊道感兴趣的保护从业者使用成本表面。
