The management effectiveness of protected areas in Kenya

The global proliferation of protected areas (PAs) is an enduring means of combating biodiversity declines and was a commendable tool towards achieving Aichi Biodiversity Target 11 (Pimm et al. 2014; Ceballos et al. 2015; Saura et al. 2019; UNEP-WCMC and IUCN 2021b). Even so, the effectiveness of PAs in conserving biodiversity remains debated due to continued species declines and ecosystem degradations within them (Hockings et al. 2006; Craigie et al. 2010; Joppa et al. 2016). This has intensified realizations that merely designating new and/or expanding existing PAs does not guarantee the protection of ecosystems and species (Barnes 2015; Geldmann et al. 2019), rather, the PA management must be effective and equitable to guarantee meaningful long-term conservational success and viability. Evaluating such effectiveness remains integral to efforts towards curbing unnatural biodiversity declines (Coad et al. 2015).

With recent studies showing increasingly high proportions of wildlife occurring outside existing PAs and populations declining within PAs (Craigie et al. 2010; Ogutu et al. 2016), Kenya is among the countries where understanding whether and how PA management relate to biodiversity distributions and welfare is pertinent. The country boasts several PAs under different governance and designation types, denoting whether the government manages them through state-mandated bodies or whether they are managed privately by local communities, individuals, and for-/non-profit organizations (UNEP-WCMC and IUCN 2021a). The PAs managed by the state (SPAs) have a stricter approach due to policy frameworks and operational systems formalized through state laws while privately-managed PAs (PPAs) have a less strict approach with their operations and rights controlled by land tenure agreements with local communities, individuals, and the state (Carter et al. 2008). Different PA management and designation types also mirror variable political and community goodwill and funding surety (Ervin 2003; Carter et al. 2008; Stolton et al. 2017) which might lead to variable effectiveness of conservational success such as curbing poaching, deforestation, land encroachment, and pollution across PAs. In the process, nonrandomly variable ecological states and species diversity distribution patterns might emerge between PAs based on the management and designations differences (Geldmann et al. 2013). In particular, due to stricter implementation of restrictions against ecosystem degrading threats, SPAs likely maintain ideal habitats for most mammals, reciprocally translating to higher species richness and phylogenetic and functional diversity compared to PPAs (Wicander 2015; Munoz Brenes et al. 2018; Harris et al. 2019). Oberosler et al. (2020) observed that highly human-disturbed PAs had low species diversity and altered occurrence patterns compared to strictly managed PAs which were less disturbed. In contrast, the less strict restrictions to access by local communities in PPAs (Carter et al. 2008; Stolton et al. 2017) imply they might be less species-rich, especially for larger mammals that are more sensitive to humans (Riggio et al. 2018).

Across most sub-Saharan countries, the utilization of PAs for biodiversity conservation mainly targets large charismatic mammals which are fundamental to touristic attractions (a vital economic pillar in these countries), are a major attraction for donor funding, and significantly influence political and policy action (Maciejewski and Kerley 2014; Balmford et al. 2015; Muchapondwa and Stage 2015; Lindsey et al. 2020). The large mammals also serve as focal species, embodying the viability of species conservation in PAs due to their high sensitivity to human disturbance and extinction risk (Morrison et al. 2007; Caro 2010). Ecologically, most large mammals influence the functioning and integrity of ecosystems by driving the abundance, distribution, and diversity of other species (Soulé et al. 2005; Caro 2010). For instance, as top predators of large- and medium-sized herbivores, large carnivores drive herbivore population and distribution patterns while the feeding and movement of megafaunas such as elephants, rhinoceroses, and giraffes create new resources and habitats for other species (Duffy 2002; Lacher et al. 2019). Overall, the large and endangered mammals are good models for investigating distribution and diversity mechanisms in PAs concerning management and designation differences because they are globally endangered (Bowyer et al. 2019), surrogates of other wildlife’s populations, and are highly diverse in terms of ecology, taxonomy, traits, and behaviour (Safi et al. 2011; Ripple et al. 2014; Bogoni et al. 2018).

For effective conservation practices, the metrics employed in evaluating the prioritization of areas and species should not only capture species richness but also the phylogenetic and functional dimensions (Devictor et al. 2010). Because species richness oversimplifies community assembly processes that determine the total taxa ecosystems can naturally support (Veech 2018), the use of phylogenetic diversity and functional diversity as complementary biodiversity indices rose in the early 1990s (Devictor et al. 2010; Chao et al. 2014). Various phylogenetic diversity and functional diversity indices can be decoupled into contrasting attributes to meaningfully target conservation of evolutionary diversity and species ecosystem functions (Faith 2016; Mazel et al. 2017, 2018; Cadotte and Tucker 2018; Edie et al. 2018). Measuring biodiversity using multidimensional diversity attributes also enable the conservational application of less obvious but useful biodiversity metrics such as the ratio of species representation and uniqueness in a local pool relative to a regional or global pool (Pärtel et al. 2013).

In this study, we analyzed the representation of terrestrial mammal ranges in PAs and how different PA governance and designation types relate to distribution patterns of multiple diversity dimensions. We hypothesized that diversity indices are not significantly variable between PA designation and management categorizations for the combined species pool but significant for focal species groups (large carnivores, large herbivores, and endangered species). We mainly sought to answer three questions; (i) How are the ranges and diversity of terrestrial mammals in Kenya represented in PAs? (ii) Do PA management and designation differences influence terrestrial mammal diversity distributions? and (iii) How do state-managed PAs compare with privately-managed ones in the representation of terrestrial mammal ranges and diversity distributions, especially of focal species (large carnivores, large herbivores, and endangered species)?

We investigated how ranges of terrestrial mammals are represented in PAs in Kenya, whether PA management and designation types influence diversity distribution patterns, and how state-managed PAs compare with privately-managed ones in the species representation. Our results showed nearly all terrestrial mammals in Kenya represented in PAs. However, the relative proportion of the ranges overlapping PAs was low, in agreement with the spatial conservation prioritization analysis which showed significant expansion of current PAs was needed to achieve a one-third coverage of species ranges in the best-solution conservation areas. Differences in PA governance and designation types were not systematically nor significantly associated with diversity distribution trends, and while there were more unique species in SPAs than in PPAs, averaged diversity indices were comparable between categories. Following, we discuss these findings in detail.

To answer how ranges and diversity of terrestrial mammals in Kenya are represented in PAs, we found nearly all terrestrial mammals in Kenya were represented (ca. 98%) albeit the relative proportions of the ‘protected ranges’ were low. While this compares with studies such as Gonzalez-Maya et al. (2015) where nearly all of Costa Rica’s mammals were represented in PAs, it illustrates that evaluating species conservation status based on range overlap in PAs might overestimate their overall range protection statuses. Similarly, Tyrrell et al. (2020) found relatively lower proportions of Kenya’s terrestrial mammals were adequately conserved in PAs and Coad et al. (2019) found low range proportions of terrestrial mammals were sufficiently represented within PAs globally. The relative range proportions overlapping PAs declined further when considering only strict PAs as adequately protected (i.e., national parks and national reserves), which was also supported by the spatial conservation prioritization analysis that showed considerable expansion of conservation areas beyond the existing PAs needed to achieve a one-third range representation of focal species. De Alban et al. (2021) also found that expanding conservation areas beyond existing PAs in Myanmar was needed to achieve a 30% representation target of species ranges and habitats. Notably, however, the high number of species with ranges represented in PAs and the clumping of irreplaceable priority conservation areas around existing PAs (Fig. 2) presents an ideal conservation opportunity and backdrop for the use of PAs to protect species and habitats/ecoregions. Because there are currently no alternative wildlife conservation tools besides PAs, they are indispensable in Kenya’s wildlife conservation pursuits, offering species with refugial ecosystems (Joppa et al. 2016) and serving as stronghold of threatened species (Pacifici et al. 2020). Also, PAs represent the most practical approach to effectively control land-use competition for biodiversity conservation with humans (settlement and agriculture), which is particularly severe in tropical Africa (Food and Agriculture Organization 2020). The observed decreasing species richness with status year likely reflects deteriorating species diversity, population, and ecological conditions in Kenya’s PAs over time, in the process, driving wildlife onto unprotected human-dominated areas. While we did not target untangling the specific non-management and non-designation factors driving the observed diversity trends, the pattern of biogeographical regionalization and diversity distributions in PAs (Online Resource 2: ESM_6) correspond to Kenya’s eco-climatic zonation as patterned by topography, water bodies, precipitation, temperature, and evapotranspiration regimes (Western et al. 2015). This suggests that abiotic variables such as climate and geography might be stronger predictors of the diversity variances, as is common among African mammals (Kamilar 2009; Kamilar et al. 2015; Rowan et al. 2016) and mammal diversity patterns in the tropics (Stevens et al. 2003; Rapacciuolo et al. 2019).

We also asked whether PA management and designation categorizations influence the diversity and community structure of terrestrial mammals. Our results showed PA designation and governance differences accounted for very low proportions of diversity variances and were not systematically associated with diversity and distribution trends. This agrees with previous studies (Stolton et al. 2017; Maxwell et al. 2020) and suggests that governmental and non-governmental stakeholders in PA biodiversity conservation in Kenya have equal contributions and should collaborate closely to improve the efficiency of PAs as wildlife conservation tools. The stricter management approaches (as practised in National Parks and National Reserves) appear to not translate to better ecological conditions and higher species richness in individual PAs, in contrast with expectations (Riggio et al. 2019; Ayivor et al. 2020). Unlike the averaged indices, the higher count of unique species in SPAs compared to PPAs can be explained by the temporal trend of PA designations, where SPAs are dominantly older. In these older PAs, species have had adequate time to naturally assort into available niches and stabilize/adapt ecological functions, leading to richer and diverse assemblages. The distribution and assembling patterns of the uncharismatic small-sized that comprise a dominant majority of Kenya’s mammals should be ecologically more stable because they hardly influence biodiversity conservation pursuit in PAs (Asaad et al. 2017). As such, their higher diversity in older and larger compared to younger and smaller PAs plausibly reflect actual ecological interactions (Brashares et al. 2001). For this, the observed decrease in species richness with PA status year reflects deteriorations of PA ecological conditions over time, which might also explain the increase of wildlife populations occurring outside PAs (Ogutu et al. 2016) and the decline of wildlife populations inside PAs (Craigie et al. 2010). Overall, the differences in diversity variations between government versus private managements concur with Ferraro et al. (2013) where strict PA management was not better at delivering conservation objectives across several tropical countries (Bolivia, Costa Rica, Indonesia, and Thailand) but contrasts Riggio et al. (2019) and Oberosler et al. (2020) where stricter PA management enhanced the welfare of ecosystems and species ecology in Eastern Africa. Nation-wide PA level assessment of management effectiveness in Kenya is needed to resolve, with greater certainty, how designation and governance differences impact biodiversity conservation outcomes and species community ecology.

Thirdly, we asked how SPAs compare with PPAs in the representation of Kenya’s mammals, especially the focal species—large carnivores, large herbivores, and endangered species. We found more unique focal species represented in SPAs (national parks, national reserves, and forest reserves) compared to the PPAs, which is unsurprising because they are accorded greater conservation concern and are almost exclusively found in government-managed PAs (Craigie et al. 2010; Bowyer et al. 2019), with their populations actively monitored and occasionally manipulated, through, for instance, translocations. Also, several SPAs are biogeographically unique ecosystems for globally endangered and range-restricted mammals, such as the Mountain Bongo in Mt. Kenya and Aberdares, the Hirola in the Northern Rangeland Trust Coast PAs, the Sitatunga in the Lake Victoria Basin PAs, and the Giant ground pangolin whose extreme eastern distribution is represented in some of the Lake Victoria Basin PAs. The SPAs also have more extensive nationwide distribution compared to PPAs, with PAs such as the Malka Mari and Lake Turkana national parks which are located in very remote areas serving as critical protective islands and likely to host highly phylogenetically and functionally diverse mammal assemblages. Even so, several PPAs are exceptionally vital to regional conservation of Kenya’s threatened mammals, such as the Lewa and Ol Pejeta Conservancies (black rhinos, elephants, and Grevy’s zebra). Joint efforts between PPAs and SPAs, such as in the Tsavo Conservation Area, the Northern Rangelands Trust, and Mara North Conservancy are the lifeline of wildlife migratory routes and crucial buffers to human-wildlife conflicts, thus, critical for the persistence of the larger and threatened species (Munoz Brenes et al. 2018; Ferreira et al. 2020; Oberosler et al. 2020; Pacifici et al. 2020). Despite the shortfall in national coverage and connectivity between PAs, the current PA network has the potential to successfully guarantee effective conservation of mammal ranges since wildlife populations within protected ecosystems persist substantially stabler than in unprotected areas, even under changing climates and intensifying human disturbance (Hansen and DeFries 2007; Thomas and Gillingham 2015; Boakes et al. 2019). However, such success depends on extending conservation strategies beyond PAs onto unprotected areas and entrenching these approaches into national wildlife policy legislations for long-term sustainability (Tack et al. 2019; Tyrrell et al. 2020). To this end, the greatest challenge is the integration of communities adjacent to wildlife areas within ecologically sound and socially embraced management plans. As the Protected Planet Report 2020 (UNEP-WCMC and IUCN 2021b) highlighted, successful engagement of communities, individuals, and private organizations by committed governments was vital towards attaining a 17% global PA coverage. These government-private-community feedback frameworks of PAs-wildlife management constitute the backdrop of successful conservation target-setting beyond the Aichi Biodiversity Targets and should be embraced in Kenya. Conventionally, because SPAs have more explicit definitions, management regimes, and funding surety, regardless of their economic profitability, they are currently a more enduring model of biodiversity conservation (Riggio et al. 2019). However, increasingly declining conservation funding opportunities for both PPAs and SPAs continue to aggravate the management of PA challenges such as human-wildlife conflicts, illegal bushmeat hunting, and illegal logging, and keeping private interest in wildlife conservation (Lindsey et al. 2020; McElwee et al. 2020). This has forced wildlife and conservation stakeholders to embrace utilitarian initiatives that better sustain PAs’ flow of ecological benefits to humans and sustain their interests to protect natural resources (Guerry et al. 2015). Of the two primary sources of benefits and incentives for conservation in Africa—tourism and trophy hunting—the latter has remained controversial and an unpopular conservation funding source except for southern Africa (Lindsey et al. 2007), although the evidence suggests it is an important conservation tool when sustainably implemented (Lindsey et al. 2006; Dickman et al. 2019). Studies also show that the classical conservation approach of relying on touristic incomes and government support cannot sustain biodiversity conservation for many biodiversity-rich countries (Bang and Khadakkar 2020; Hockings et al. 2020; Lindsey et al. 2020; McElwee et al. 2020). While Kenya banned trophy hunting in 1977 aiming to curb poaching, its progress in wildlife conservation since then has been an underperformance compared to countries that integrated sustainable trophy hunting into conservational frameworks, such as Neighbouring Tanzania and the southern African countries—South Africa, Zimbabwe, and Botswana (Lindsey et al. 2006; Ogutu et al. 2016). Sustainable trophy hunting can also lead to improved food resources, increased litter size and survival through the density-dependent reproduction/survival responses (Bowyer et al. 2019).

The geographical trends in diversity distributions bear on the performance of PAs for wildlife protection. For one, the central, western, and southwestern Kenya PAs which had the highest taxonomic, phylogenetic, and functional richness of terrestrial mammals are also surrounded by populous and intensively farmed buffer zones (Republic of Kenya 2015), implying that curbing human encroachment onto wildlife areas can be challenging. The human constraints on PA peripheries commonly drive wildlife emigration from PAs onto the settlement and farmed areas (Hansen and DeFries 2007; Hansen et al. 2011; Veldhuis et al. 2019), resulting in cyclic human-wildlife conflicts (Ogutu et al. 2016; Ojwang’ et al. 2017; Mukeka et al. 2019), which is an indication of ineffective PA biodiversity conservation performance. The suitability of these regions as priority conservation areas was downplayed by the Marxan analysis which, despite the high mammal diversities, mostly excluded them from the best solution reserve systems (Fig. 2). In these areas, PA managements should exploit existing provisions for maintaining interconnectivity (Watts et al. 2017; Saura et al. 2019) by building on the findings of studies such as Ojwang’ et al. (2017) where key wildlife migration corridors were observed to connect PA networks with non-protected ecosystems based on temporal variability in habitat suitability. Sustaining the connectivity of PA and non-PA lands based on wildlife habitat use can also benefit from nationally harmonized land ownership legislation that incentivizes increased private participation (Saura et al. 2018, 2019), as a more integrative, effective, and equitable conservation approach (Muchapondwa and Stage 2015; Tack et al. 2019). The species whose ranges did not overlap any PA had distributions that spanned the extremes of Kenya’s national boundary, with primary ranges in neighbouring countries (Tanzania, Uganda, South Sudan, Ethiopia, and Somalia). Their representation in PA systems can be attained through transboundary collaborations in PA design and management and national responsibility species initiatives towards maximizing ecological connectivity and representativeness (area-based conservation measures). Such transboundary conservation initiatives are increasingly recognized as critical components of biodiversity conservation in PAs (Schmeller et al. 2014; Venter et al. 2014; Kark et al. 2015; Saura et al. 2018; Kukkala et al. 2019; Maxwell et al. 2020) but are currently hardly adopted in East Africa. While we used the representation of species ranges in PAs, the approach can be prone to misestimations of PA and range coverages. Therefore, our results should be interpreted with the necessary caution. Kenya currently lacks nationwide standardized information on the protected biodiversity in PAs, even for the charismatic large mammals; for this, managements should direct more concerted efforts towards PA-level biodiversity inventories that can inform better-targeted conservation interventions and, thus, better outcomes.

Protected areas are vital biodiversity conservation tools despite debates concerning their effectiveness in combating species declines and ecosystem degradations. And as the 2020 Protected Planet Report (UNEP-WCMC and IUCN 2021b) underscored, biodiversity conservation success beyond Aichi Biodiversity Target 11 can only be achieved through effective PA management and just governance. Here, our analysis of the effectiveness of PA management in Kenya based on how differences in governance and designation types associate with terrestrial mammal ranges and diversity distributions provides some novel insights. While nearly all the terrestrial mammals in Kenya were represented in at least a PA, the relative proportions of the represented ranges were low, such that achieving a one third range coverage of focal species’ ranges in a best-solution reserve system, for instance, needed substantial expansion of conservation areas beyond current PA extents. Differences in governance and designation were not systematically associated with diversity variances, and while there were more unique species in state-managed PAs compared to privately-managed PAs, averaged diversity coefficients were comparable. These findings illustrate that, in Kenya, and as applicable across other countries, governmental and non-governmental stakeholders contribute similarly to wildlife conservation in PAs. The persistence of terrestrial mammals in PAs, therefore, depends upon clearly defined collaboration schemes between SPAs and PPAs managements in the appraisal of conservation performance and challenges. This would ensure that all PAs sustainably persist as protective ecosystems for mammals through, for instance, buffering PPAs of operational crises arising from unprecedented challenges to their profit-based conservation approaches (Bang and Khadakkar 2020; Lindsey et al. 2020; McElwee et al. 2020). Such collaboration also aligns with the trend of shifting wildlife conservation in Africa from classical exclusive state-management regimes to broader governances where several stakeholders are involved in the planning and execution of policies (Muchapondwa and Stage 2015).