Multiple anthropogenic pressures challenge the effectiveness of protected areas in western Tanzania

This research article was published by John Wiley & Sons, Inc. in 2022Despite being key conservation instruments, the ecological effectiveness of protected areas (PAs) is contested. To assess the ecological effectiveness of PAs in the Katavi-Rukwa Ecosystem (KRE) in western Tanzania, we investigated temporal changes in land-use and population densities of six large mammal target species (elephant, buffalo, giraffe, zebra, topi, and hartebeest) across areas with different conservation category, ranging from unprotected to strictly protected. During six survey periods between 1991 and 2018, we analyzed data from remote sensing and aerial wildlife surveys to derive (i) spatiotemporal patterns of cropland cover in relation to protection category; (ii) population densities of the six-target species; and (iii) distribution of these species across protection category, land-use and environmental variables. During the surveyed period, cropland increased from 3.4 % to 9.6 % on unprotected land and from ≤0.05 % to <1 % on protected land. Wildlife densities of most, but not all target species declined across the entire landscape, yet the onset of the observed wildlife declines occurred several years before the onset of cropland expansion. Logistic regression models indicated that target species preferred the national park over less strictly PAs and areas distant to cropland. As our data do not support a direct link between land-use change and wildlife densities, additional factors may explain the apparent ecosystem-wide decline in wildlife. To bolster wildlife conservation in the KRE, we recommended proactive strategies to reduce direct threats to wildlife and cropland expansion toward wildlife dispersal areas and migratory corridors

Land Use and Environmental Gradients Influence on Riparian Woody Plant Diversity and Structure in Lake Manyara Watershed Ecosystem, Tanzania

This research article was published in Open Journal of Ecology, Volume 13, 2023.Riparian vegetations are important in supporting ecological connectivity between aquatic and terrestrial ecosystems. The structure and species composition of riparian woody plants have been subjected to multiple forces with varying degree of influences. This study examined the influence of land use and environmental gradient to the structure and composition of the riparian woody plants in northern Tanzania. A total of 270 plots were surveyed for woody plant species in the riparian ecosystems and later analysed to determine the influence of land use categories (homegarden, crop field, woodlot, open canopy forest, and closed canopy forest) and environmental variables (temperature, precipitation, elevation and slope) to the species richness, abundance, and stand parameters. Basal area was higher in woodlots, homegardens and crop fields than in the open and closed canopy forests; and as expected the reverse was true for the number of stocking density. Correlation among stand parameters with environmental variables varied significantly. Species richness and species abundance were negatively correlated to precipitation, temperature and elevation, while stocking density and basal area were positively correlated to precipitation. The study recommends continual retentions of trees on farm, further promoting of agroforestry interventions and sustainable utilization of woody plants in open and close canopy forests

Forests, Farms, and Fallows: The Dynamics of Tree Cover Transition in the Southern Part of the Uluguru Mountains, Tanzania

This research article was published by MDPI, 2021Forests and woodlands remain under threat in tropical Africa due to excessive exploitation and inadequate management interventions, and the isolated success stories of tree retention and tree cover transition on African agricultural land are less well documented. In this study, we characterize the status of tree cover in a landscape that contains forest patches, fallows, and farms in the southern part of Uluguru Mountains. We aimed to unveil the practices of traditional tree fallow system which is socially acceptable in local settings and how it provides a buffering effects to minimize forest disturbances and thus represents an important step towards tree cover transition. We assessed land cover dynamics for the period of 1995 to 2020 and compared tree stocking for forest patches, fallows, and farms. We found that tree biomass carbon stocks were 56 ± 5 t/ha in forest patches, 33 ± 7 t/ha in fallows, and 9 ± 2 t/ha on farms. In terms of land cover, farms shrank at intensifying rates over time for the entire assessment period of 1995–2020. Forest cover decreased from 1995–2014, with the reduction rate slowing from 2007–2014 and the trend reversing from 2014–2020, such that forest cover showed a net increase across the entire study period. Fallow consistently and progressively increased from 1995–2020. We conclude that traditional tree fallows in the study site remain a significant element of land management practice among communities, and there appears to be a trend towards intensified tree-based farming. The gains in fallowed land represent an embracing of a traditional land management system that supports rotational and alternate uses of cropping space as well as providing a buffering effect to limit over-exploitation of forests. In order to maximize tree cover and carbon stocks in the farm landscape, this well-known traditional tree fallow system can be further optimized through the incorporation of additional innovations

Effects of climate change on potential geographical distribution of Prunus africana (African cherry) in the Eastern Arc Mountain Forests of Tanzania

The aim of this study was to model the impacts of climate change on potential geographical distribution of Prunus africana in the Eastern Arc Mountains of Tanzania. Maximum Entropy modelling was used to construct species distribution maps for P. africana to determine relative contribution, and effects of climate change on the potential geographical distribution of P. africana based on climatic scenarios. Species presence data were used as a dependent variable, while climate, soil, and topographic data were used as predictor variables. The current distribution model was evaluated with the Area Under the Curve (AUC) analysis. The results indicate that the distribution of P. africana could be modelled with a test AUC that is significantly better than random. The average test AUC value was 0.97. This indicates high performance of the model. Results of the contribution of predictor variables reveal that the current distribution of P. africana was highly affected by climatic variables. Environmental variables show the highest prediction contribution include maximum temperature warmest month (27.2%), elevation (11.4%) and rainfall driest month (11.3%). Results for potential geographical distribution based on current climatic conditions reveal that there is suitable habitats for P. africana almost in all Eastern Arc Mount (EAM) forests. Moreover, current distribution maps depict areas with high elevations as having very high potential habitat suitability values. Future distribution maps depict both gains and losses in range for P. africana under all climate scenarios. Representative Concentration Pathways (RCP) 8.5 scenario records larger loss in range for P. Africana compared to RCP 4.5 in the Mid-century 2041-2070 (2055) and Late-century 2071-2100 (2085) in the EAM forests. Among the EAM forests Udzungwa, Rubeho, West Usambara, Ukagaru, Uluguru and Ukagaru forests will lose much more suitable habitats for P. africana. This implies that most of the areas currently predicted in EAM forests as suitable will not be suitable in the future. Therefore, under changing climate, P. africana might expand or contract their suitable habitats, which will have implications on management and conservation of this species within the EAM forests. Advisor: Dr. Genesis T. Yengoh Master degree project 30 credits in Geographical Information Sciences, 2018 Department of Physical Geography and Ecosystems Sciences, Lund University. LUMA-GIS thesis nr 89Determining distribution and status of species in the context of climate change allow conservationists to assess contemporary and future ranges for plant species in the protected areas. Climate change data are important predictor variables for determining plant species habitat, but is rarely used in Tanzania when modelling current and future distribution of plant species. Prunus africana is a tree that is important for its pharmaceutical uses. In this study, I used species distribution modelling techniques to construct species distribution maps for Prunus africana. The goal of this was to determine relative contribution of Prunus africana and the effects of climate change on its distribution based on Inter-governmental Panel on Climate Change scenarios (Business as usual and Green economy scenarios). For the modelling, presence records for Prunus africana, were used as a dependent variable, while climate, soil, and topographic data which determines the growth of this species were used as predictor variables. I found that the geographical distribution of Prunus africana is highly affected by climatic variables such as maximum temperature warmest month and rainfall driest month followed by elevation and soils. Current distribution maps show that areas with high elevations in the study area are the ones with suitable habitat for Prunus africana. Future distribution maps show both habitat gains and losses for Prunus africana under both the business as usual, and green economy scenarios in the study area. The business as usual scenario records larger loss of suitable habitat for Prunus africana compared to green economy scenario in the Mid-century and Late-century. Therefore, under changing climate, some species like Prunus africana might expand or contract their suitable habitats, which will have implications on management and conservation of such species in Tanzania. Advisor: Dr. Genesis T. Yengoh Master degree project 30 credits in Geographical Information Sciences, 2018 Original title: Effects of Climate Change on Potential Geographical Distribution of Prunus africana (African cherry) in the Eastern Arc Mountain Forests of Tanzania Department of Physical Geography and Ecosystems Sciences, Lund University. LUMA-GIS thesis nr 8

Predicting suitable habitats of the African cherry (Prunus africana) under climate change in Tanzania

Prunus africana is a fast-growing, evergreen canopy tree with several medicinal, household, and agroforestry uses, as well as ecological value for over 22 countries in sub-Saharan Africa. This species is under immense pressure from human activity, compounding its vulnerability to the effects of climate change. Predicting suitable habitats for P. africana under changing climate is essential for conservation monitoring and planning. This study intends to predict the impact of climate change on the suitable habitats for the vulnerable P. africana in Tanzania. We used maximum entropy modeling to predict future habitat distribution based on the representative concentration pathways scenario 4.5 and 8.5 for the mid-century 2050 and late-century 2070. Species occurrence records and environmental variables were used as a dependent variable and predictor variables respectively. The model performance was excellent with the area under curve (AUC) and true skill statistics (TSS) values of 0.96 and 0.85 respectively. The mean annual temperature (51.7%) and terrain ruggedness. index (31.6%) are the most important variables in predicting the current and future habitat distribution for P. africana. Our results show a decrease in suitable habitats for P. africana under all future representative concentration pathways scenario when compared with current distributions. These results have policy implications for over 22 countries of sub-Saharan Africa that are facing problems associated with the sustainability of this species. Institutional, policy, and conservation management approaches are proposed to support sustainable practices in favor of P. africana

Tree Species Density and Basal Area in Image Forest Reserve, Tanzania

A research article was submitted to East African Journal of Forestry and Agroforestry, Volume 5, Issue 1, 2022Abstract The tree species density and basal area form structural and functional variables of healthy forest ecosystems. Tree density and basal area are among useful parameters for management of natural forest resources. A study was carried out in Image Forest Reserve (IFR) in 2019 to determine tree species density and basal area. A total of 170 plots measuring 20 m x 40 m were set along the land cover types at an interval of 250 m from each other. Trees with a diameter at breast height (DBH - cm) ≥ 5 cm were measured for their DBH at a height of 1.3 m from ground level and used to calculate the basal area (BA) (m2). The tree individuals were used to calculate the density (D). The largest basal area was recorded from forest cover (13 279 m2 ha-1), followed by woodland (4394.09 m2 ha-1), and wooded grassland was the least). The minimum BA was recorded from woodland, while the largest was from forest (6.881 m2 ha-1). In all land cover types the DBH class (cm) >40 cm had the largest BA. Woodland had the highest density of all other land cover types, followed by forest and wooded grassland was the least. The maximum density was recorded from woodland followed by forest and wooded grassland Ospina, R., & Marmolejo-Ramos, F. (2019). Performance of some estimators of relative variability. Frontiers in Applied Mathematics and Statistics, 5, 43. Ruffo, C. K. (1991). A report on the identification of species for Image Forest Inventory, Iringa Region. Tanzania Forestry Institute. Tenzin, J., Tenzin, K., & Hasenauer, H. (2017). Individual tree basal area increment models for United Republic of Tanzania (2013). Kilolo District Council Socio-economic Profile. The Statistics for Development. The Ministry of Finance, National Bureau of Statistics of Tanzania Report. pp. 2-10. Zilliox, C., & Gosselin, F. (2014). Tree species diversity and abundance as indicators of understory diversity in French mountain forests: Variations of the relationship in geographical and ecological space. Forest Ecology and Management, 321, 105-116. PDF icon Download Articl

Modelling elephant corridors over two decades reveals opportunities for conserving connectivity across a large protected area network

A research article was published by PLOS ONE October 13, 2023Protected area (PA) connectivity is pivotal for the persistence of wide-ranging wildlife species, but is challenged by habitat loss and fragmentation. We analyzed habitat suitability and connectivity for the African elephant (Loxodonta africana) across PAs in south-western Tanzania in 2000, 2010, and 2019. We quantified land-use changes through remote sensing data; estimated habitat suitability through aerial survey data, remotely sensed variables and ensemble species distribution models; modelled least-cost corridors; identified the relative importance of each corridor for the connectivity of the PA network and potential bottlenecks over time through circuit theory; and validated corridors through local ecological knowledge and ground wildlife surveys. From 2000 to 2019, cropland increased from 7% to 13% in the region, with an average expansion of 634 km2 per year. Distance from cropland influenced elephant distribution models the most. Despite cropland expansion, the locations of the modelled elephant corridors (n = 10) remained similar throughout the survey period. Based on local ecological knowledge, nine of the modelled corridors were active, whereas one modelled corridor had been inactive since the 1970s. Based on circuit theory, we prioritize three corridors for PA connectivity. Key indicators of corridor quality varied over time, whereas elephant movement through some corridors appears to have become costlier over time. Our results suggest that, over the past two decades, functional connectivity across the surveyed landscape has largely persisted. Beyond providing crucial information for spatial prioritization of conservation actions, our approach highlights the importance of modeling functional connectivity over time and verifying corridor models with ground-truthed dat

Assessing protected area effectiveness in western Tanzania: Insights from repeated line transect surveys

A research article was submitted to The African Journal of Ecology Volume 61, Issue 3 September 2023In many parts of East Africa, wildlife populations have declined over the past decades. Given these trends, site-based studies are needed to assess how protected areas with differing management strategies enable the effective conservation of wildlife populations. In Tanzania, game reserves are managed for tourist hunting, while national parks are managed for non-consumptive wildlife-based tourism. To assess the relative performance of these management strategies, we here focus on two areas: Rukwa Game Reserve (RGR) and Katavi National Park (KNP). Based on systematically designed line distance surveys in 2004 and 2021, we compared densities and group sizes of large mammal populations (African elephant, giraffe, buffalo, zebra, topi, and hartebeest) over time. Contrary to published ecosystem-wide declines observed in numerous species which considered earlier baselines, we did not detect significant population declines between 2004 and 2021. While these new results showing apparent stable populations do not invalidate earlier studies on wildlife declines, they could indicate a stabilisation phase after declines. This highlights the importance of considering appropriate temporal baselines and historical contexts when assessing conservation effectiveness

Attributes of 10 corridors mapped between PAs in south-western Tanzania.

Corridors are sorted by decreasing centrality scores to demonstrate their importance in keeping the protected areas network connected.</p