Structural connectivity at a national scale: Wildlife corridors in Tanzania

Wildlife corridors can help maintain landscape connectivity but novel methods must be developed to assess regional structural connectivity quickly and cheaply so as to determine where expensive and time-consuming surveys of functional connectivity should occur. We use least-cost methods, the most accurate and up-to-date land conversion dataset for East Africa, and interview data on wildlife corridors, to develop a single, consistent methodology to systematically assess wildlife corridors at a national scale using Tanzania as a case study. Our research aimed to answer the following questions; (i) which corridors may still remain open (i.e. structurally connected) at a national scale, (ii) which have been potentially severed by anthropogenic land conversion (e.g., agriculture and settlements), (iii) where are other remaining potential wildlife corridors located, and (iv) which protected areas with lower forms of protection (e.g., Forest Reserves and Wildlife Management Areas) may act as stepping-stones linking more than one National Park and/or Game Reserve. We identify a total of 52 structural connections between protected areas that are potentially open to wildlife movement, and in so doing add 23 to those initially identified by other methods in Tanzanian Government reports. We find that the vast majority of corridors noted in earlier reports as “likely to be severed” have actually not been cut structurally (21 of 24). Nonetheless, nearly a sixth of all the wildlife corridors identified in Tanzania in 2009 have potentially been separated by land conversion, and a third now pass across lands likely to be converted to human use in the near future. Our study uncovers two reserves with lower forms of protection (Uvinza Forest Reserve in the west and Wami-Mbiki Wildlife Management Area in the east) that act as apparently crucial stepping-stones between National Parks and/or Game Reserves and therefore require far more serious conservation support. Methods used in this study are readily applicable to other nations lacking detailed data on wildlife movements and plagued by inaccurate land cover datasets. Our results are the first step in identifying wildlife corridors at a regional scale and provide a springboard for ground-based follow-up conservation.

野生动物廊道（Wildlife corridors）有助于维持景观连通性（landscape connectivity），但仍需开发新方法以快速且低成本地评估区域结构连通性（structural connectivity），从而确定应在何处开展代价高昂且耗时的功能连通性（functional connectivity）实地调查。本研究以坦桑尼亚为案例区域，结合最小成本法（least-cost methods）、东非地区最精准且最新的土地转换数据集（land conversion dataset），以及野生动物廊道访谈数据，构建一套统一且一致的方法论，以在国家尺度上系统性评估野生动物廊道。
本研究旨在解答以下四类问题：(i) 国家尺度下尚有哪些廊道仍保持连通（即结构上连通）；(ii) 哪些廊道已可能因人为土地转换（如农业开发与定居活动）而被阻断；(iii) 其他尚存的潜在野生动物廊道分布于何处；(iv) 哪些低等级保护地（如森林保护区与野生动物管理区）可作为连接多处国家公园（National Park）及/或禁猎区（Game Reserve）的踏脚石（stepping-stones）。
本研究共识别出52条可支持野生动物迁徙的保护地间结构连通廊道，较坦桑尼亚政府报告中其他方法初步识别的廊道数量新增23条。研究发现，早期报告中标记为"大概率已被阻断"的廊道中，绝大多数（24条中的21条）实际上并未在结构上被切断。尽管如此，2009年坦桑尼亚境内已识别的野生动物廊道中，近六分之一已可能因土地转换而被分割，另有三分之一的廊道当前穿越了未来可能被开发为人类用地的区域。
本研究还发现两处低等级保护地——西部的乌文扎森林保护区（Uvinza Forest Reserve）与东部的瓦米-姆比基野生动物管理区（Wami-Mbiki Wildlife Management Area）——可作为连接国家公园及/或禁猎区的关键踏脚石，因此亟需获得更有力的保护支持。本研究采用的方法可轻松推广至缺乏野生动物迁徙详细数据、且土地覆被数据集精度不足的其他国家。本研究结果是区域尺度野生动物廊道识别的第一步，也为后续实地保护行动提供了重要铺垫。