Water and wildlife in the Serengeti-Mara ecosystem

Surface water is a key resource for wildlife conservation and its spatial and temporal distribution is important in understanding the distribution and composition of large herbivore assemblages in savannah ecosystems. Unprecedented continual decline in surface water availability in these ecosystems pose a threat to ungulates abundance and landscape use. But how changes in surface water will affect large herbivores has inadequately been investigated. Here we quantified drivers of changes in surface water in the Serengeti-Mara ecosystem and furthermore quantified changes in surface water availability affect the distribution and composition of large herbivore communities. We studied how fire and livestock grazing affect surface water availability and subsequently wildlife landscape use. Furthermore, we quantified water requirements of savannah ungulates using six different functional traits related to water loss pathways. We found that between 1972 and 2018, human activities upstream and outside protected area have changed the recession time scale for Mara River while the lack of human activities in the Serengeti National Park has maintained the hydrological properties of the Mbalageti River. Furthermore, we observed a wide range of water requirements among ungulates with two major groups of water dependent and independent species. In addition, this study provides evidence that each functional trait can be independently used to predict water requirements and in particular proposes that minimum dung moisture content is an easy to measure index of water requirement. Importantly, we showed that water requirements add a new dimension of niche partitioning for grazing ungulates that is independent of body size

Assessment of Soil Quality along the Proposed Main Road through Ngorongoro and Northern Serengeti, Tanzania

A new road through northern Serengeti National Park is proposed to be built. The purpose of this study was to collect baseline data on soils along the route of the proposed road before its construction. The physicochemical properties were used to characterize the soil before the construction of the proposed road. Levels of soil macro-elements mainly potassium (K), calcium (Ca), magnesium (Mg) and sodium (Na), and physicochemical properties: electrical conductivity (EC), pH, organic carbon (OC), soil organic matter (SOM), total nitrogen (TN), cation exchange capacity (CEC), phosphorus (P), aluminium (Al) were determined. Also, heavy metals: cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni) and zinc (Zn) were analyzed. This study was done on the eastern (Ngorongoro District) and western (Serengeti District) segments of the proposed road. The ranges in average values obtained for the physicochemical parameters and metal concentrations in the soils were: 0.05–0.57 mS/m for EC, 6.5–7.9 for pH, 0.71–1.23% for OC, 0.30–0.74 g/kg for TN, 1.23–2.12% for SOM, 20.6–79.7 mg/kg for available P, 0.27–2.08 meq/100-g for available K, 9.89–30.3 meq/100-g for available Ca, 0.29–0.67 meq/100-g for available Mg, 0.06–1.35 meq/100-g for available Na, 11.04–33.12 meq/100-g for CEC, 46702.9–63963.3 mg/kg for Al, BDL for Cd, 24.70–101.55 mg/kg for Cr, 27.31–34.96 mg/kg for Cu, 32390.8–42439 mg/kg for Fe, 18.06–22.19 mg/kg for Pb, 957.1–1458.9 mg/kg for Mn, BDL for Hg, 20.24–32.52 mg/kg for Ni and 96.09–124.14 mg/kg for Zn. These observed levels indicate that the soils before road construction are unpolluted, moderately fertile and within the specifications of good agricultural soil. On the western segment of the proposed road, the soil will need application of fertilizers for better agricultural usage. Keywords:    Physicochemical properties; soil quality; total nitrogen; macro-elements; heavy metals

Managing wetlands to solve the water crisis in the Katuma River ecosystem, Tanzania

The formerly perennial Katuma River in western Tanzania starts in a protected forest, it then flows through irrigated rice farms before reaching Lake Katavi, a floodplain wetland whose outflow regulates the river flow through the Katavi National Park (KNP) down to its outlet at Lake Rukwa, which has no outlet. In recent years, due to overexploitation of water for irrigation, the Katuma River dried out for up to four months per year and this greatly degraded the KNP ecosystem, the siltation of river lead to flooding of the adjacent areas during heavy rains, and the water level of Lake Rukwa has decreased by 4 m since 1992 while its fishery yield and water quality also deteriorated. In 2016, a total of 46 illegal weirs were removed from the Katuma River upstream of KNP. Following that, the river zero-flow periods were reduced by two months and Lake Rukwa water level rose by 1 m. We suggest that the construction of a low V-notch weir at the outlet of the Lake Katavi wetlands would further reduce the Katuma River zero-flow periods by an additional month, thus returning the river nearly to its former perennial status. The enforcement of regulations governing the construction of irrigation weirs is essential. These ecohydrology solutions do not eliminate the threats, but they amplify the opportunities for sustainable development at the basin scale. This example of active governance of water resources at the basin scale can be applied throughout Tanzania and in semi-arid East Africa in general

Are Tanzanian National Parks affected by the water crisis? Findings and ecohydrology solutions

Availability of water for wildlife in some of the National Parks in Tanzania has been hampered by several factors including the effect of climate change and anthropogenic factors due to the fact that most of the water catchments are outside the national parks. In order to ensure the survival of the National Parks, TANAPA, which is a Parastatal Organization mandated to manage the National Parks, has taken proactive initiatives and actions to tackle the water crisis in its National Parks, principally the Serengeti, Tarangire, Ruaha, Katavi, Rubondo, Saadani, Arusha and Kilimanjaro National Parks. These initiatives and actions have followed the ecohydrology guidelines for water management and they varied from Park to Park according to the local conditions. There are limits to what TANAPA can achieve by itself to save its National Parks from the water crisis, because TANAPA has no control on activities outside the Parks. For those water issues TANAPA has communicated its findings and recommendations to the government and stakeholders, and the resolution, or otherwise, of these issues requires state governance as well as in some cases cooperation between the East African countries

Fire regulates the abundance of alien plant species around roads and settlements in the Serengeti National Park

A large portion of East African ecosystems are officially protected, yet increasing wildlife tourism and infrastructural development are exposing these areas to invasion by alien plant species. To date there has been little quantification of alien plant species in the Serengeti National Park, Tanzania. In this study, we aimed to: (1) establish a list of common alien plant species; (2) quantify the frequencies of alien species near roads and settlements (i.e. tourist lodges and a campsite), and (3) estimate the abundance (plant cover) of alien plant species in relation to source activities (i.e. gardening) and park management (i.e. fire). In total, we detected 15 alien plant species in our surveys with an 80% probability of encountering an alien species within the first 50 m from a road or settlement. Overall, we found no difference in the presence of alien species near roads or settlements, but did find a significant decline in species presence with distance from these sources. Cumulative fire frequency was the most important factor influencing the abundance of alien species with the highest alien plant cover in areas with infrequent or no fires over the last 13 years. There was no difference in alien plant cover in relation to other commonly cited source activities, which may be due to the stronger influence of fire. Although the abundance of the majority of alien plant species was negatively related to fire, some species, notably Tagetes minuta, had higher cover with more frequent fires. Our results contradict findings from other African savannahs that suggest fire promotes invasive species and this is likely due to the species-specific interactions with fire. In the Serengeti, fire will be difficult to use as a management tool due to variable species response. Thus, we highlight that other management approaches such as physical removal and biological control agents can be implemented; however future work with these techniques should also consider the interaction of alien plant species with fire

Restoring the perennial Great Ruaha River using ecohydrology, engineering and governance methods in Tanzania

The Great Ruaha River (GRR) in Tanzania was perennial before 1993. Its source, the Usangu wetlands, was also perennial. Since then, the GRR has started drying out during the dry season, with a trend towards earlier and longer periods of drying. This drying process degrades the surrounding ecosystems along the entire length of the GRR, including the Ruaha National Park (RNP) and impacts human livelihoods throughout its course; it also impairs the economy of Tanzania through reduced hydropower generation at the Mtera and Kidatu power plants. The Usangu wetlands dried up in 2000, 2002 and 2005 during the dry season and its areal extent has been shrinking. Intensive livestock grazing and both dry and wet season irrigated agriculture in the Usangu wetlands, were the main reasons for this water crisis. In 2006, the Government of Tanzania moved to address the crisis by removing livestock from the Usangu wetlands, attempting to regulate water use in the GRR catchment and expanding the RNP to include the Usangu wetlands

Data from: Quantifying water requirements of African ungulates through a combination of functional traits

Climate and land use change modify surface water availability in African savannas. Surface water is a key resource for both wildlife and livestock and its spatial and temporal distribution is important for understanding the composition of large herbivore assemblages in savannas. Yet, the extent to which ungulate species differ in their water requirements remains poorly quantified. Here, we infer the water requirements of 48 African ungulates by combining six different functional traits related to physiological adaptations to reduce water loss, namely minimum dung moisture, relative dung pellet size, relative surface area of the distal colon, urine osmolality, relative medullary thickness and evaporation rate. In addition, we investigated how these differences in water requirements relate to differences in dietary water intake. We observed strong correlations between traits related to water loss through dung, urine and evaporation, suggesting that ungulates minimize water loss through multiple pathways simultaneously, which suggests that each trait can thus be used independently to predict water requirements. Furthermore, we found that browsers and grazers had similar water requirements, but browsers are expected to be less dependent on surface water because they acquire more water through their diet. We conclude that these key functional traits are a useful way to determine differences in water requirements and an important tool for predicting changes in herbivore community assembly resulting from changes in surface water availability