Quantifying rangeland condition in the Tarangire-Manyara ecosystem

The ecosystem supports numerous wildlife populations and pastoralist groups, but is being reduced due to a changing climate and fragmented due to anthropogenic pressure. These changes cause increased grazing pressure and greater competition for grazing areas among livestock and wildlife populations, resulting in environmental degradation of this important ecosystem. Land degradation and habitat change are global economic and natural resource issues, with tropical and subtropical savannas being crucial to wildlife and human populations. Rangeland degradation is attributed to changing climate and anthropogenic pressure, such as human population increases and overgrazing, which results in lower biodiversity, reduced livestock health, and poorer pastoralist communities. Assessing rangeland health at a local scale is necessary for stakeholders to make informed management decisions to respond to land degradation. The rangelands of northern Tanzania support numerous wildlife populations and pastoralist groups, but are being reduced due to a changing climate and fragmented due to anthropogenic pressure. These changes cause increased grazing pressure and greater competition for grazing areas among livestock and wildlife populations, resulting in environmental degradation of this important ecosystem. Identifying rangeland health is complex and can be defined and interpreted in numerous ways, with characteristics of degraded rangelands including reduced biological and economic productivity, including reduced ecological and hydrological function, lower biodiversity, and the presence of invasive species. Bush encroachment and loss of ground cover are the two primary forms of rangeland degradation in Northern Tanzania. Bush encroachment occurs more often in higher rainfall and higher nutrient areas, while loss of ground cover often occurs in drier, low nutrient areas. Both of these degradation types result in grasslands becoming unsuitable for both livestock and wild ungulates. Sustainable land use within the remaining grazing areas is fundamental for the health of wildlife and livestock and the pastoralist communities that rely on this ecosystem. A quantitative assessment of rangeland degradation across the Tarangire-Manyara ecosystem as a whole has not been conducted previously. This analysis aims to assess rangeland condition and the level of degradation across the ecosystem, using a combination of vegetation surveys and remotely sensed data. The study area includes the Tarangire-Manyara ecosystem, which spans across northern Tanzania. The analysis will provide information on the spatial extent and variation in degradation across the ecosystem, which will inform management decisions to respond to land degradation. The study used a combination of vegetation surveys and remotely sensed data to assess rangeland degradation. Vegetation surveys were conducted in 2016 and 2018 to quantify vegetation cover and rangeland degradation. Remotely sensed data, including MODIS surface reflectance data, were used to identify suitable habitat variables that can be used to assess rangeland degradation. The analysis highlighted areas of high invasive species, such as Ipomea species, in the Simanjiro grazing easements and to the south of Randilen WMA. Low rainfall areas in the north of the study area, such as around Lake Natron, were predicted to have the lowest amount of invasive species. The analysis also highlighted areas of bare ground, which are predicted to be generally low across all WMAs and National Parks and in the grasslands around Lake Natron. However, areas to the east of Tarangire National Park, north of Mto wa Mbu, and near Longido have higher bare ground degradation relative to other areas in the ecosystem. The additional 2018 data resulted in improved woody cover maps, particularly in Tarangire national park. Areas with dense woody cover are to the north-west of Longido, localized parts of Randilen WMA, Manyara Ranch, southern parts of Tarangire National Park, and throughout Makame WMA. The study highlights the importance of sustainable land use within the remaining grazing areas for the health of wildlife and livestock and the pastoralist communities that rely on this ecosystem. The successful conservation of wildlife populations and coexistence with pastoralists across the ecosystem are dependent on the quality of communal lands and continuation of the traditional pastoral system. The analysis provides information on the spatial extent and variation in degradation across the ecosystem, which will inform management decisions to respond to land degradation.