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 9 / 23 The individuals in this manuscript have given written informed consent (as outlined in PLOS consent form) to publish these case details. Results Demography The population around Kilimanjaro is experiencing rapid growth (Fig 4), rising from about 50,000 to over 1.4 million between 1889 and 2022 with an annual growth rate of 2.6%, and of 1.7% between 1976 and 2022 ([37,41], National Bureau of Statistics 1978, 2002, 2022 [49]). Climate According to Otte et al (2016) consistently significant rainfall trends over the period 1973–2014 could not be found for the lowlands of Kilimanjaro. For the period 1974–2016 at the Kilimanjaro Airport there was a significant increase in mean temperature (GLS p < 0.001) with a mean annual increase of 0.027°C. Over this period there was no trend in maximum daily temperature, but a significant increase in daily minimum temperature (GLS p < 0.001) with a mean annual increase of 0.032°C. LULC changes The spatial distribution of LULC classes for the four analysed time steps are shown in Fig 5A–D and Table 3, and the extent of each class for the period between 1976 and 2022 in Fig 6A. Areas of natural ecosystem types, including forest, regeneration, and savanna, decreased from 90% in 1911 to 19% in 2022 (Fig 4). In 1911 the extend of savanna was nearly at its natural maximum of 75%, with only 2% having been converted to agriculture in the lowlands. In 1976, the

extent of savanna and agriculture were nearly identical, but agriculture then expanded to become the dominant LULC class. Fig 4. Human population growth, reduction of natural vegetation and increase of town area on Kilimanjaro. Human population growth during the last 133 years (red dots with polynomial regression of degree 2), starting in 1889 ([37,41], Bureau of Statistics 1968, 1998, 2003, 2013, 2022 [49]); reduction of natural vegetation (green dots with polynomial regression of degree 2) and increase of town area (black dots with exponential regres- sion); correlation (Pearson’s r) of natural vegetation vs population (1911−2022) −0.985, p < 0.01 and vs town area (1976−2022) −0.915, ns. https://doi.org/10.1371/journal.pone.0334184.g004