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

8.5 in the 2080s is a proxy for the 4.5˚C world. Under RCP8.5 conditions, precipitation across the Tana River Basin is projected to increase substantially compared to RCP2.6, particularly in the north of the basin where these cells are located [59, 60]. Amphibians are affected by limits on precipitation and water availability [61]. These cells are projected to be refugia with 4.5˚C warming due to the increase in precipitation projected in this area of the basin. When no taxo- nomic group is able to shift their range in response to warming, more cells are projected to act as refugia for animals than for plants. This shows that plants could be particularly vulnerable to the changes in climate. Changes to the plants of the Tana River Basin are likely to have com- pound effects on the animals that depend on them for food and shelter. The difference between the costs of conserving biodiversity and global spending on conservation [62] necessitates prioritisation of spending. Identifying likely climate refugia within the basin may assist with this prioritisation. Implications for PAs A key consideration is whether the PAs will be sufficient for protecting biodiversity in a chang- ing climate. These results show that, with higher temperatures, the current PAs within the Tana River Basin could be insufficient for protecting many species. PAs form the first defence for biodiversity against many human activities and are the cornerstone of in situ biodiversity conservation. There is evidence of biodiversity declines within protected areas around the

world [63, 64], but species are generally better protected inside PAs than outside in the wider landscape [65]. This study has shown that many of the PAs in the basin already have a signifi- cant proportion of land within them turned over to agriculture. At the national level, it has been estimated that, as of 2015, 7.2% of land within PAs in Kenya had been converted to anthropogenic uses [66]. Many PAs in East Africa were originally established as game reserves and converted to gov- ernment-owned national parks following independence [66, 67]. These PAs were designated to protect large mammal populations or particular charismatic species rather than truly con- serving the full biodiversity of the area. These PAs do not adequately cover the hotspots of ver- tebrate endemism [66], so it is somewhat unsurprising that they may be insufficient for protecting biodiversity in a changing climate. Maintaining connectivity within landscapes, particularly between conservation areas, is vital for reducing pressure on ecosystems and encouraging demographic links and gene flow [68]. This may involve the creation of new protected areas that better protect a greater range of species. However, several studies have noted that land available for the creation of new PAs in East Africa is extremely limited [66, 69], so restoring previously converted land is also likely to be necessary to better protect biodiversity. Alternatively, the land projected to contain refugia that has not previously been converted

to agricultural uses could be managed sustainably (i.e. not converted to urban or cropland through the NSP, or overgrazed) rather than gazetted as strict nature reserves as creating new strict PAs sometimes leads to additional problems, such as those arising from mismanagement, negative local attitudes towards conservation and fences creating additional barriers to move- ment, which will undermine their effectiveness for conservation [70]. In Kenya, threats to bio- diversity within PAs come from a range of activities, including increased poaching, human encroachment, over-exploitation of natural resources by communities living within the PA boundaries, negative impacts associated with the expansion of tourism after the area is pro- tected, and perimeter fencing interfering with wildlife movement [71]. However, the manage- ment of protected areas must consider the needs of different stakeholders as well as the ecological value of the sites. There are many ways in which an area can be protected and many PLOS ONE Risks to Kenya’s biodiversity from climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0254879 July 21, 2021 14 / 25