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

of these have the potential to provide equal benefit to biodiversity. PAs that involve local com- munities as stakeholders have been found to produce better conservation outcomes than nationally designated protected areas [72, 73]. Land must be managed sustainably, using appropriate rangeland strategies like the observance of carrying capacity and conservation of vegetation [53], to avoid land degradation from overgrazing. Implications of development plans for biodiversity Agricultural expansion (including irrigation) is a major feature of the National Spatial Plan. This also presents a significant threat to climate refugia as many areas earmarked for agricul- tural expansion have been shown to contain refugia for biodiversity. A significant proportion (29% of refugia with 2˚C warming, 23% of refugia with 4.5˚C warming) have already been con- verted to agriculture. As this part of the analysis was based on agricultural data from 2015, it is likely that additional areas have been converted since then; further limiting the proportion of projected refugia available for species in the future. Further losses to the area of refugia as a result of activities in the NSP would be damaging to the future of biodiversity within the basin. Projected refugia for both animals and plants over- lap with proposed irrigation areas, high- and medium-potential agricultural land and eco- nomic growth areas from the NSP. This may lead to trade-offs between agricultural or urban development and biodiversity protection in some regions of the basin. Reducing the activities

in the NSP (agricultural, irrigation and economic expansion areas) by 24% could remove the threat to refugia with 2˚C warming while reducing the activities by only 14% could remove the threat to areas that are still projected to contain refugia with 4.5˚C warming. There are also benefits to agriculture of retaining refugia alongside NSP activities, such as the importance of these natural areas for supporting pollinators and the subsequent increase in pollination ser- vices for crops. Detailed spatial planning at the local level should take these co-benefits into account, incorporating conservation areas into wider agricultural landscapes. Although it was not possible to quantify the effects, other elements of the National Spatial Plan will threaten biodiversity. The LAPSSET corridor railway line and dam construction may restrict the movement of species towards the higher elevations. The importance of facilitating movement has been clearly demonstrated in the results for birds and mammals. Building addi- tional dams along the upper reaches of the Tana River and its tributaries may prevent species from moving to more suitable climates. In addition, dam construction upstream will have effects on the whole ecosystem, including the PAs. Changes to land use and hydrological prop- erties of unprotected parts of ecosystems can alter the biodiversity and ecosystem functioning within PAs [74]. So, even if existing PAs are preserved within the larger agricultural or eco- nomic development areas, the effects of intensive land uses on the edge of the PAs may limit

their suitability for wildlife. However, the interactions between land use and climate and their combined effects on bio- diversity are very complex and cannot all be considered within this research. Understanding all of these possible interactions is an ongoing area of research [75]. From this analysis, it is clear that there will be hotspots of conflict between competing land uses within the Tana River Basin. The Upper Tana Basin is likely to be an area of trade-offs. As the climate warms, the land further upslope is likely to become more and more suitable for plants and animals. A large range of species will be forced to occupy this smaller space. The Mount Kenya National Park and Natural Forest and Aberdare National Park are important PA in the north of the basin that are projected refugia for plants and animals under high levels of warming. These refugia are most at risk as they are considered high potential agricultural land. Preventing expansion of agriculture in these areas (around 125 km2, less than 0.01% of PLOS ONE Risks to Kenya’s biodiversity from climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0254879 July 21, 2021 15 / 25