使用InVEST對薩赫勒地區綠色長城計劃下棲息地質量變化與道路影響之研究

Abstract

土地荒漠化威脅著當地居民的生命安全和糧食安全甚劇，而薩赫勒地區的土地退化，尤其是草地和森林的退化更會限縮生動物棲息地。薩赫勒綠色長城計劃(Great Green Wall project, GGW)是一項以再造林為重點的泛非洲計劃，目的是遏制沙漠化向撒哈拉沙漠以南擴張，同時保護生態多樣性。GGW於2007年啟動，實施至今已有15年，持續投入數百億美元。在GGW進行的過程中，需要評估區域內土地利用變化對棲息地質量的影響如何，一方面顯示了GGW的成果，另一方面也為後續實施計劃的方向和戰略的調整提供更多的參考。此外，由於世界範圍內道路擴張速度快，使得道路對於棲息地質量的影響變得更加重要，而道路生態學的興起也意味著需要更多的研究去量化評估道路的影響。生態系統服務和權衡綜合評估模型(InVEST)可以評估多種自然資源對人類的服務，為後續的使用和管理提供重要的參考依據。本研究使用GGW計劃中初始11個成員國在2007-2020年期間的土地利用資料，結合2020年該地區的一級道路和鐵路的路網資料，使用InVEST中的棲息地質量模型評估該地區的棲息地質量高低隨時間的變化，同時使用Fragstats計算景觀指數來描述該地區景觀在空間上構型的變化並探討道路對於棲息地質量變化的影響。結果顯示雖然沙漠面積減少，但棲息地質量並沒有如預期一般提升，道路影響不如預期，農業和城市化的擴張對於當地棲息地質量影響越來越大，各國棲息地質量變化的主導因素不同。為後續GGW計劃工作重點提供參考。

The encroachment of land desertification poses an imminent threat to both the livelihood and food security of local inhabitants. Particularly pronounced is the land degradation within the Sahel region, where the decline of grasslands and forests constricts the available habitats for wildlife. The Great Green Wall project (GGW), a comprehensive pan-African initiative primarily centered on reforestation, strives to curtail the southward expansion of desertification emanating from the Sahara Desert. Concurrently, the project seeks to safeguard ecological diversity. Launched in 2007, GGW has undergone continuous implementation over a 15-year period, supported by substantial financial investments. In the course of GGW execution, it becomes imperative to assess the impact of regional land-use changes on habitat quality. Such an assessment serves a dual purpose: elucidating the accomplishments of GGW and furnishing valuable insights for the refinement of future plans and strategic adjustments. Furthermore, the rapid global expansion of road infrastructure emphasizes the importance of assessing the impact of road networks on habitat quality. The burgeoning field of road ecology underscores the need for comprehensive research to quantitatively assess and evaluate the ramifications of roads on ecosystems. The application of Ecosystem Services and Tradeoff Evaluation Models (InVEST) proves instrumental in comprehensively evaluating diverse natural resources' services to human populations, thereby offering indispensable references for subsequent utilization and management strategies. This study employs land-use data spanning the period from 2007 to 2020 for the initial 11 member countries of the GGW project. This dataset is amalgamated with comprehensive road and railway network data from the region for the year 2020. The InVEST habitat quality model is then employed to assess temporal variations in habitat quality. Simultaneously, Fragstats is utilized to calculate landscape indices, providing an in-depth depiction of spatial changes in the regional landscape configuration. The study also investigates the impact of roads on changes in habitat quality. Results indicate a reduction in desert area, although the anticipated improvement in habitat quality is not observed. Surprisingly, the impact of roads is less pronounced than initially expected. The escalating influences of agricultural expansion and urbanization are identified as increasingly significant factors affecting local habitat quality. Discernible variations in the dominant factors influencing changes in habitat quality are observed among the participating countries. These findings provide insightful information for guiding the future focus of the GGW project.