Addressing risks to biodiversity arising from a changing climate: The need for ecosystem restoration in the Tana River Basin, Kenya

abundant [8] but, for many, higher temperatures will lead to an increased extinction risk or need to be able to move to cooler areas. Many studies have already observed shifts in species’ ranges and attributed this to climate change [9, 10]. Mobile species, such as butterflies, may be more able to track changes in climate; less mobile species, including many plants, tend to lag behind [11]. This means that groups of plants and animals have varying levels of vulnerability. Significant risks to global biodiversity are likely even if global temperature rise is limited [12, 13] and the Paris Agreement goals of constraining warming to well below 2˚C are met, so understanding which areas and species are most at risk is vital. Research into the impacts of climate change on biodiversity rarely also considers the effects of projected future land use change which will occur alongside changes in global temperatures and weather patterns [14]. Land use and cover is constantly changing across the world, as a result of multiple drivers and impacts, which can contribute to both climate change and biodi- versity loss [15, 16]. The greatest global change in land use has been towards more agricultural land [17]. As settlements and agriculture expand, more land is converted from its natural state. In addition, road and rail networks dissect the landscape, splitting areas of similar vegetation into smaller fragments. Increasingly fragmented habitats will limit species’ abilities to respond to climate change through dispersal and tracking their preferred climates. Species that remain

in isolated habitat fragments will begin to experience other negative effects, including potential reductions in natural genetic variation within the population and even local extinctions [18]. Preserving biodiversity is not only important in order to save species but also for wider ecosys- tems and human society. Reductions in biodiversity will lead to losses of ecosystem function and services, which will have impacts on humans [19–21]. Many published studies on the effects of climate change on terrestrial biodiversity in Africa have focused on southern Africa [22–25] or Madagascar [26, 27]. Research into the implica- tions of climate change for terrestrial biodiversity of East African countries is more limited. Previous studies focusing on Kenya have largely only considered single species, such as Grevy’s Zebra [28] and Rothschild’s Giraffe [29]. The biodiversity of Kenya is already under threat from a myriad of sources, including ecosystem degradation, water scarcity and habitat frag- mentation [30]. Most threats will be exacerbated by climate change and socio-economic devel- opment (through the changes in land and resource use). East Africa is also a region where the global climate models (GCMs) disagree on the possible changes to precipitation; with some GCMs projecting reductions in rainfall while many project increases [31, 32]. This uncertainty increases the difficulty in planning adaptation in this region. For example, there is a significant amount of work on how GCMs may misrepresent the rains in East Africa [33, 34].

Kenya’s Tana River Basin has previously attracted scientific interest, including studies on the impacts of dam construction [35], the ecological importance of the lower section of the basin [36] as well as more recent investigations into the impacts of climate change on the hydrology of the area [37, 38]. The Government of Kenya (GoK) has outlined significant devel- opment targets and infrastructure investments for hydropower, domestic water provision and irrigation in the region as part of their national development blueprint, the Vision 2030 [39]. The Tana River Basin already plays a vital role in the country’s economy; supplying 80% of Nairobi’s drinking water and around 70% of Kenya’s hydropower energy through its dams and is likely to become even more important if the Vision 2030 is realised. GoK’s Vision 2030 [37] also aims to ensure that ‘all wildlife ecosystems are fully protected’ and that wildlife corri- dors are secured. The basin is a biodiversity hotspot: it contains 15 Key Biodiversity Areas [40], its delta ecosystem has been designated as a Ramsar wetland and it is within two WWF Priority Places, the East African Acacia Savannas and the East African Coastal Forests [41]. In order to achieve the aim of protecting ecosystems, the combined effects of land use and climate change on biodiversity must be established. PLOS ONE Risks to Kenya’s biodiversity from climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0254879 July 21, 2021 2 / 25 Competing interests: The authors have declared that no competing interests exist.