Mapping of biodiversity hubs and key ecosystem services as a tool for shaping optimal areas for conservation

hence the need to map them to help guide the most effective conservation investments [64]. We used WW, a fully distributed, process-based hydrological model, that utilizes remotely sensed and globally available datasets to support hydrological investigation and decision-mak- ing globally especially in data-poor environments. We’ve run the WW’s web browser-based interface (www.policysupport.org/waterword) at 1 sq.km resolution. All data required for model application in Rwanda as well as anywhere in the world are provided unless substituted by user’s data [70]. It is assumed that if a model is capable of reproducing current conditions based only on physical relationships, it is likely to continue to do so under scenario conditions where the physical relationships remain the same [71]. WW uses the metric human footprint on water quality as a proxy for water contamination [70]. Human footprint on water quality calculates the potential water quality in a grid cell, for each grid cell the human footprint index represents the percentage of total rainfall water coming from upstream that is influenced by sources of contamination. This means that the areas with extensive human activities such as agriculture or urban areas will leave a significant footprint on water downstream but can also be diluted by waters from PA or undisturbed areas. 3 Results 3.1 Biodiversity distribution by taxonomic group 3.1.1 Distribution of biodiversity-rich habitat. Important biodiversity hubs for different taxonomic groups are shown in (Fig 2). The diversity of plants, amphibians, reptiles, mam-

mals, and birds disproportionately span on most of the Rwandan territory, but various fish species are concentrated mainly in the southern lakes of Rwanda and in the lake Kivu and its numerous islands’ shores. An extreme poverty of biodiversity, in all taxonomic groups is very obvious in the central part of the country, the very region that holds the largest urban centers including the capital city Kigali, and Muhanga, Nyanza, Ruhango, Nyamata, and Rwamagana towns. The region is also characterized by intense anthropogenic activities and very rare rem- nants of natural habitat. Important biodiversity hubs are distributed from east to the west of Rwanda, strongly sub- jected to the altitude and general annual rainfall distribution, hence by the 4 local climatic regions of Rwanda. From the east to the west, the lower elevation averaged 1220 m in the swampy Akagera river valley lays the ‘East-Rwandan dry and hot lowland zone’ in which the annual rainfall �900 mm and the annual temperature averaged at 21˚C, is dominated by savannah habitats and is mainly conquered by large mammals most of which are protected in the ANP and others scattered through the surrounding districts in relatively small unprotected natural habitats such as Ibanda-Makera natural forest (Kirehe district), Karama natural forest (Bugesera district) and Mashoza natural forest (Ngoma district). Follows the interior highlands that consist of rolling hills and valleys over which the annual rainfall reaches 1200 mm is dis- tinctly higher than in the eastern territories and the annual temperature averaged at 19˚C

which makes local climatic conditions become the ‘Temperate zone of the central highlands’ [72]. The highest lands in the west culminates at Karisimbi (4507 m) one of the 5 volcanoes of Birunga mountains on the extreme north of the Congo-Nile divide, the chain of mountains of rugged beauty that runs on the north-south axis and forms part of the Congo-Nile divide. This region receives the highest annual rainfall fulfilling the conditions of ‘Rwandan humid moun- tain climate’ with rainfall >1600mm and the annual temperature averaged at 16˚C, which makes it home to the highest diversity of tropical plants, hence offering habitat to the most diverse fauna species in almost all taxonomic groups. This region holds the highest number of PA such as Nyungwe NP, Gishwati-Mukura NP, and Virunga NP but also the unprotected nat- ural forests like Busaga natural forest (Muhanga district), and Karehe-Gatuntu forest complex PLOS ONE How do old national parks cope with regenerating conservation mission? PLOS ONE | https://doi.org/10.1371/journal.pone.0253151 August 17, 2021 9 / 20