Gain and loss: Human and environmental wellbeing – drivers of Kilimanjaro’s decreasing biodiversity

PLOS One | https://doi.org/10.1371/journal.pone.0334184 October 29, 2025 18 / 23 The importance of nature conservation for the protection of biodiversity The study area includes three forest reserves south of Moshi, with only Rau forest largely intact, while the others face near-total destruction, highlighting the importance of effective management in conservation to mitigate population growth’s negative effects on biodiversity. Rau Forest Reserve is increasingly attracting tourists, providing economic incentives for nature conservation in an area rich in endemic species that are found nowhere else. The value of such reserves is clear from Fig 10, based on Hurskainen et al. [75]. In a 1300 km2 area on Kiliman- jaro’s southern foothills (mainly within the study area, Fig 1), only 29% maintained semi-natural vegetation, with just 3% as forests in 2012. Fig 10, right panel shows species richness at 1-hectare grids; cultivated ecosystems have low species numbers, especially in high-intensity land use types like sugar cane plantations and rice fields. In contrast, Rau Forest and Namalok, a private nature reserve (see below) exhibit high species richness (84–100 species per hectare). Additionally, the critical role of riparian areas in connecting lowlands and highlands as biodiversity “blood vessels” is evident. Another large nature reserve is Namalok. Located in the southern part of the study area (Fig 1), this reserve covers 46 km2 and is owned by the semi-private/state-owned sugarcane company TPC. Initial efforts to conserve this area began in

2005 and it was fenced off in 2010. Due to its remoteness, in 1976 78% was still covered by natural vegetation (riverine forests, savanna woodlands and alkaline grasslands) and by 2022 this had increased to 100%. In recent years, antelopes and zebras have been reintroduced and the reserve is now open to tourists. Conclusions The lack of plant abundance data in our approach limits the application of diversity indices such as Shannon and even- ness metrics. Instead, we focus on species richness, the simplest and most appropriate measure of diversity [76,77], but also on species composition. We therefore address a very significant aspect of biodiversity. Fig 10. Land use and related species richness on the southern foothills of Kilimanjaro. Left: LULC map (2012) of the southern foothills of Kiliman- jaro with Moshi in the centre (compiled from Hurskainen et al. 2019 [75]), right: Mean species richness at 1 ha grid. High land use intensity resulted in low diversity, whereas protected areas harboured a high biodiversity. For more details and location of the study area see Supplementary Information S1 Text and Fig 1. https://doi.org/10.1371/journal.pone.0334184.g010