Saadani National Park Research Articles

Locating elephant corridors between Saadani National Park and the Wami-Mbiki Wildlife Management Area, Tanzania

Although more than 40% of Tanzania mainland is managed for nature conservation, protected areas are increasingly becoming isolated because of rapid habitat degradation in the matrix in between. Knowledge on corridors connecting the protected areas is urgently needed. We assessed the area between Saadani National Park and Wami-Mbiki Wildlife Management Area, combining interviews about wildlife occurrences from 20 villages in the area with least-cost landscape modelling with African elephants (Loxodonta africana) as the focal species. The interviews suggested that, in contrast to earlier assumptions, migration of elephants or the presence of one or more independent elephant populations still exists in the unprotected area between Saadani and Wami-Mbiki. A combination of the interview results and multiple least-cost models showed three corridors in the area. The corridor along the Wami river is the most important one, the area between Miono and Mandera was identified as an impeding zone. Management decisions on the wildlife corridors to be protected will require further in-depth research in the three specified corridor zones. Apart from providing insights into elephant movement ecology, the approach may be useful for localizing corridors elsewhere in eastern Africa. Resume Alors que plus de 40% de la superficie de la Tanzanie sont geres dans un but de conservation de la nature, les aires protegees y sont de plus en plus isolees a cause de la degradation rapide des habitats dans la matrice qui les relie. Il faut d'urgence etudier les corridors qui relient entre elles les aires protegees. Nous avons etudie la zone situee entre le PN de Saadani et l'Aire de gestion de la faune sauvage de Wami-Mbiki, combinant des interviews au sujet de la presence de la faune sauvage dans 20 villages de cette zone avec une modelisation a moindre cout du paysage, en utilisant les elephants (Loxodonta africana) comme espece focale. Les interviews ont suggere que, contrairement a des hypotheses precedentes, la migration des elephants existerait encore ou qu'il y aurait encore une ou plusieurs populations independantes presentes dans la partie non protegee comprise entre ces deux aires protegees. Les resultats des interviews et les multiples modeles a moindre cout ont revele l'existence de trois corridors dans la region. Celui qui se trouve le long de la riviere Wami est le plus important, et il apparait que la zone comprise entre Miono et Mandera constituerait une barriere. Les decisions en matiere de gestion des corridors de faune sauvage exigeront d'autres etudes plus approfondies dans les trois corridors identifies. Cette approche ne donnera pas seulement un apercu de l'ecologie des deplacements des elephants, mais elle pourrait aussi etre utile pour localiser d'autres corridors ailleurs en Afrique de l'Est.

Population, health, and environment situational analysis for the Saadani National Park Area, Tanzania

This study provides a snapshot of the population, health, and environment situation and practices in the villages surrounding the Saadani National Park (SANAPA) and demonstrates the utility of a transdisciplinary systems perspective to evaluate population–health–environment linkages (PHE). Analyzing survey data from eight villages, this paper shows that in the SANAPA area, livelihoods are highly dependent on natural resources, but both agriculture and fisheries are experiencing a decline in productivity and profitability. Population stressors include a high population momentum, early marriages, teenage pregnancies, and migration. Women bear a heavy workload, while having little or no say in decision-making. The public health situation is severe with health facilities few and far in-between; lack of access to clean water and safe sanitation; and many households suffering from diarrhea, malaria, pneumonia, skin diseases, and HIV/AIDS. Environmental protection arrangements are in place in all sites, however, the awareness of protected areas and their benefits is low and many feel helpless in protecting the environment. Climate change—increasing periods of drought and irregular rainfall—contribute to food insecurity and health problems. The interconnectedness between these stressors reinforces the need for an integrated approach to addressing coastal conservation and community development in the SANAPA area.

The effect of a protected area on the tradeoffs between short-run and long-run benefits from mangrove ecosystems

Protected areas are used to sustain biodiversity and ecosystem services. However, protected areas can create tradeoffs spatially and temporally among ecosystem services, which can affect the welfare of dependent local communities. This study examines the effect of a protected area on the tradeoff between two extractive ecosystem services from mangrove forests: cutting mangroves (fuelwood) and harvesting the shrimp and fish that thrive if mangroves are not cut. We demonstrate the effect in the context of Saadani National Park (SANAPA) in Tanzania, where enforcement of prohibition of mangrove harvesting was strengthened to preserve biodiversity. Remote sensing data of mangrove cover over time are integrated with georeferenced household survey data in an econometric framework to identify the causal effect of mangrove protection on income components directly linked to mangrove ecosystem services. Our findings suggest that many households experienced an immediate loss in the consumption of mangrove firewood, with the loss most prevalent in richer households. However, all wealth classes appear to benefit from long-term sustainability gains in shrimping and fishing that result from mangrove protection. On average, we find that a 10% increase in the mangrove cover within SANAPA boundaries in a 5-km(2) radius of the subvillage increases shrimping income by approximately twofold. The creation of SANAPA shifted the future trajectory of the area from one in which mangroves were experiencing uncontrolled cutting to one in which mangrove conservation is providing gains in income for the local villages as a result of the preservation of nursery habitat and biodiversity.

Structure and biomass along an Acacia zanzibarica woodland-savanna gradient in a former ranching area in coastal Tanzania

Questions: What factors influence the density, size and growth form of trees in secondary Acacia zanzibarica woodlands on a former humid savanna rangeland? How does tree density relate to variation in tree foliage and spines, and woody and grass biomass? Location: Tropical coastal Tanzania (former Mkwaja Ranch, now in Saadani National Park). Methods: We surveyed 97 circular plots (4-m radius) representing a gradient from open savanna to dense woodland. Within each plot, we measured all trees and estimated the biomass of spines. Foliage biomass of tree and grass layers was estimated on three occasions, twice during the wet season and once in the dry season. Soil samples were taken from each plot and analysed for texture and nutrient content. Interrelationships among various variables were investigated using linear multiple regression and mixed effects models. Results: Tree densities were highest on more nutrient-rich, heavy soils. Spinescence was highest on trees in open savanna. Biomass of tree foliage in the wet season was best explained by numbers of ant nests and tree live-wood ratio. Foliage biomass in the dry season was less than half that in the wet season and best predicted by grass biomass. Variables related to biomass of the grass layer were strongly influenced by fire; living grass biomass also decreased with increasing tree density. Conclusions: A. zanzibarica is a tree with a high water demand, and the association with heavy soils is probably due to greater availability of water on these sites. Establishment of A. zanzibarica woodlands significantly reduced grazing resources at Mkwaja Ranch. Under post-ranching conditions, however, fires and soil conditions predominate. The woodlands may, therefore, represent a transient state of woody density in a still resilient humid savanna.

Tree dieback and regeneration in secondary Acacia zanzibarica woodlands on an abandoned cattle ranch in coastal Tanzania

Questions: Bush encroachment is a major problem when African savanna ecosystems are used for cattle ranching. How do secondary woodlands develop after ranching is abandoned? What are the patterns and rates of tree mortality and regeneration? Location: Mkwaja Ranch (now part of Saadani National Park) in coastal Tanzania. Methods: Ninety-seven circular plots (4-m radius) were set in secondary Acacia zanzibarica woodland along a gradient of tree density. Variables relating to tree and grass layers and soil characteristics of plots were recorded. Seedlings were counted twice in the wet seasons, and resprouts once. Tree flowering and pod production were assessed during the fruiting season, while survival of trees initially present was recorded after 12 and 32 months. Interrelationships among variables were investigated using multiple linear regression, binary logistic regression and mixed effects models. Results: After 32 months, over one-third of trees in plots had died. Most died after fire, especially on heavy soils, and mortality was significantly related to the tree live biomass ratio and soil conditions. Seed production was very low, especially in denser stands. Numbers of seedlings correlated with soil and grass variables but not with seed rain. Half of trees killed above-ground produced coppice shoots from the base; in contrast, root suckering was independent of topkill. By the end of the study, no seedlings survived and no resprouts emerged above the grass layer. Conclusions: A. zanzibarica woodlands at Mkwaja Ranch were able to develop because of ranching, and can only persist under intensive grazing. The woodlands do not represent a successional stage towards forest and will probably revert to predominantly grassland vegetation within 10–20 years unless grazing pressure from wild ungulates increases considerably and/or fire regimes change.

N and P Cycling in Tanzanian Humid Savanna: Influence of Herbivores, Fire, and N2-Fixation

Availabilities of nitrogen (N) and phosphorus (P) have a strong influence on plant growth and the species composition of savannas, but it is not clear how these availabilities depend on factors such as fire, N2-fixation, and activities of wild herbivores and cattle. We quantified soil N and P availabilities in various ways (extractable pools, mineralization, resin adsorption) along vegetation gradients within a recently abandoned cattle ranch and a former game reserve in Tanzania (both areas now part of the Saadani National Park). We also assessed annual N and P balances to evaluate how long-term availabilities of N and P are affected by large herbivores, symbiotic N2-fixation, and fire. The results show that cattle ranching led to a spatial re-distribution of nutrients, with the local accumulation of P being stronger and more persistent than that of N. In the former game reserve, intensively grazed patches of short grass tended to have elevated soil N and P availabilities; however, because quantities of nutrients removed through grazing exceeded returns in dung and urine, the nutrient balances of these patches were negative. In dense Acacia stands, N2-fixation increased N availability and caused a net annual N input. Fire was the major cause for nutrient losses from tallgrass savanna, and estimated N inputs from the atmosphere and symbiotic N2-fixation were insufficient to compensate for these losses. Our results call into question the common assumption that N budgets in annually burned savanna are balanced; rather, these ecosystems are a mosaic of patches with both N enrichment and impoverishment, which vary according to the vegetation type.

Shifts in native ungulate communities on a former cattle ranch in Tanzania

AbstractWhen an area is brought under protection, current animal populations and their habitat preferences need to be assessed to predict population trends and future habitat availability. Using data from walking transects, we estimated the size of native ungulate populations on an abandoned cattle ranch in a coastal savannah in Tanzania, now included in the new Saadani National Park. Data were analysed with distance sampling and conventional strip transect techniques and were compared with results of previous wildlife counts. Few individuals of mainly browsing species were present in former cattle grazing areas exhibiting high bush‐encroachment while a ten times higher biomass of browsers and grazers was found in the cattle‐unmodified savannah. Population sizes of some species increased twofold between 1991 and 2001 within the entire area but neither population size nor species richness increased in the abandoned rangeland during our 3‐year study period from 2001 to 2003. We conclude that the former ranch has potential for future recolonization by wild ungulates. Resettlement will take place gradually with ‘pioneer‐species’ facilitating the entry of more demanding species. Habitat restoration through wildlife can be observed and quantified on Mkwaja Ranch which will be of importance for future management of native ungulates reclaiming abandoned rangeland.