Land use/land cover dynamics driven changes in woody species diversity and ecosystem services value in tropical rainforest frontier: A 20-year history.

Land use/land cover (LULC) change is a prominent problem in tropical forests. However, the fundamental question of how much woody species diversity was lost and ecosystem services value (ESV) changed in response to LULC conversion has rarely been studied. Therefore, the objective of this study was to assess the impact of LULC change on woody species diversity and ecosystem service value in the last two decades in the tropical rainforest frontier taking the case of Sheka Forest Biosphere Reserve (SFBR), Southwest Ethiopia. Supervised image classification with a maximum likelihood approach was employed and 90 quadrants were laid for the woody species inventory. Diversity indices and descriptive statistics were computed and the non-parametric test (Kruskal-Wallis) was used to test the effect of LULC change on woody species diversity. The benefit transfer method was used to estimate the monetary value of ecosystem services adopting coefficients from empirical studies. The woody species richness, diversity, and evenness varied (X2 = 71.887, p < 0.05) across LULC types. The highest diversity was observed in the forest followed by cropland, coffee plantation, homegarden, and tea plantation. The estimated total ecosystem service value (ESV) was reduced by 21.56% from 309.11 million US$ in 1999 to 242.47 million US$ in 2020. Transition to mono-crop like tea plantations to maximize income not only altered native woody species but also induced the expansion of exotic species and reduced ESV, indicating a detrimental impact of LULC change on ecosystem integrity and stability in the future. Although LULC conversion destruct woody species diversity, cropland, coffee plantation and the homegardens were the refuge for some endemic and conservation priority species. Further, addressing contemporary challenges of LULC conversion through introducing mechanisms such as payment for ecosystem services that increase the economic and livelihood benefits of natural forests to local communities is important. Effective conservation and sustainable use approaches in which such species are systematically integrated into land use practices have to be planned and implemented. This could contribute to strengthening the conservation effectiveness of the SFBR of UNESCO and serve as a showcase for such conservation areas around the globe. The LULC challenges, particularly those emanating from local livelihood needs, could impede our efforts to conserve biodiversity, jeopardize the reliability of future projections, and have an impact on the conservation of threatened ecosystems, if it is not adequately addressed in time.

Modelling the distribution of Oxytenanthera abyssinica (A. Richard) under changing climate: implications for future dryland ecosystem restoration.

Bamboo is the world's most widely exploited plant resource, with significant socio-economic and cultural values. In most parts of Africa, the population is in jeopardy due to the high pressure from human and natural forces. Of these, Oxytenanthera abyssinica (A. Richard) is among the threatened bamboo species. Furthermore, the effect of climate change on the distribution of bamboo has not yet been adequately studied. Therefore, this study aims to model and map the current and future distribution of O. abyssinica in Africa under four representative concentration pathways (RCPs), such as RCP2.6, RCP4.5, RCP6, and RCP8.5. The future projections were done for the years 2050 and 2070 using SDM ensemble approaches. To model the current and future distribution of O. abyssinica in Africa, 737 presence data were collected from various sources. For this study, a total of eight (8) temperature and precipitation-related variables were used as inputs to the Species Distribution Model (SDM). Finally, the model performance was assessed based on the area under the curve (AUC) and true skills statistics (TSS) measures of statistics. Our results showed an upsurge in the distribution of O. abyssinica across the study area for the low and moderate suitability classes for the climatic conditions considered in this study. However, a steady shrinkage in the habitat was found for the higher suitability classes. The model indicated climatic-related factors such as precipitation during the cold and warm quarters (57.8%), followed by mean temperature during the coldest quarter, isothermality (41.9%) and topographic factors such as elevation and slope (31.6%) were identified as the main limiting factors for the growth of O. abyssinica. Precipitation and temperature during the dry period, on the other hand, had the least impact on the growth of O. abyssinica. Except for RCP2.6, the majority of south-western African countries and the Sahel region remain the most climatically stable ecosystems for O. abyssinica growth under the three climatic scenarios RCP45, RCP6 and RCP8.5. Our results revealed a steady increase in the future suitable habitat for O. abyssinica all over the continent under the considered climatic scenarios. Therefore, to support the future restoration of dryland ecosystems, countries should scheme a restoration policy that allows the sustainable utilization of O. abyssinica tree species. The future policy direction for biodiversity conservation and management should encourage the use of O. abyssinica as a major plant species for improving the livelihoods of people living in dryland areas.

Predicting the current and future suitable habitats for endemic and endangered Ethiopian wolf using MaxEnt model.

The Ethiopian wolf, endemic to Ethiopia, is the most endangered species in the world. As flagship species, a wide range of studies has been conducted on the Ethiopian wolf. However, there is scanty information about the impact of climate change on this globally important species. Thus, this study aimed to predict the current and future suitable habitats of the species based on four Representative Concentration Pathway scenarios of IPCC for the years 2050 and 2070 by using the MaxEnt model. A total of 479 species occurrence records were obtained from the field survey and Global Biodiversity Information Facility. The 19 bioclimatic variables and altitude were downloaded from worldclim and extracted for the study area using GIS software. The Pearson correlation analysis was employed to detect correlation among variables and maintained 10 variables. The prediction potential of the model was evaluated and found excellent to predict the distribution of the species. The result depicted that suitable habitats for Ethiopian wolves will be badly affected by climate change. Currently, about 9.4% of the total landmass of Ethiopia is suitable for wolves. However, it will be lost in the forthcoming couple of decade under all scenarios of global climate change. Consequently, the Ethiopian wolf is highly suspected to be extinct globally in the mid of 21st century, unless corrective measures are done in time. Therefore, enhancing the adaptive capacity of species as well as genetic resource preservation and captive breeding is advisable.

Present and future climatic suitability for dengue fever in Africa.

The number of dengue fever incidence and its distribution has increased considerably in recent years in Africa. However, due to inadequate research at the continental level, there is a limited understanding regarding the current and future spatial distribution of the main vector, the mosquitoAedes aegypti, and the associated dengue risk due to climate change. To fill this gap we used reported dengue fever incidences, the presence of Ae. aegypti, and bioclimatic variables in a species distribution model to assess the current and future (2050 and 2070) climatically suitable areas. High temperatures and with high moisture levels are climatically suitable for the distribution of Ae. aegypti related to dengue fever. Under the current climate scenario indicated that 15.2% of the continent is highly suitable for dengue fever outbreaks. We predict that climatically suitable areas for Ae. aegypti related to dengue fever incidences in eastern, central and western part of Africa will increase in the future and will expand further towards higher elevations. Our projections provide evidence for the changing continental threat of vector-borne diseases and can guide public health policy decisions in Africa to better prepare for and respond to future changes in dengue fever risk.

Impacts of climate change on current and future invasion of Prosopis juliflora in Ethiopia: environmental and socio-economic implications.

Prosopis juliflora is a serious invader, causing great ecological and economic damage in Ethiopia. Thus, it is imperative to examine potential invasion dynamics of P. juliflora at national level under climate change scenario to better influence decision making processes on the management of this invasive species. We derived a consensus model from five modeling approaches to examine the current and future (2050 and 2070) climatic suitability for P. juliflora under two climate scenarios (RCP4.5 and RCP8.5) in Ethiopia. Under the current climatic scenario, 94.8% of the country was non-suitable for P. juliflora establishment and invasion while 0.4% (4.56 million ha) was highly suitable. In 2050, highly suitable area for P. juliflora is expected to increase by 55.6% and 63.6%, while moderately suitable area is projected to increase by 33.3% and 42.9% under RCP4.5 and RCP8.5 climate scenarios, respectively. Compared to the current climatic condition, in 2070, highly suitable area for the species is projected to increase by 73.3% (3.43 million ha) and 80.0% (3.65 million ha) under RCP4.5 and RCP8.5 scenario, respectively. With the current cover, this invasive species had already caused significant impact on rangelands in many parts of the country. Its further expansion would worsen the problem, leading to great environmental and economic damage, thereby threatening the livelihood of the community. Negative environmental and economical impacts caused by the species will be high if preventive and effective management measures are not earnestly taken, and it becomes one of the major challenges for the 21st century pastoralism and their livelihoods. We recommend a national effort be organized towards combating P. juliflora expansion to new areas, especially in regions and protected area predicted as frontiers of potential expansion.

Effect of host diversity and species assemblage composition on bovine tuberculosis (bTB) risk in Ethiopian cattle.

Current theories on diversity-disease relationships describe host species diversity and species identity as important factors influencing disease risk, either diluting or amplifying disease prevalence in a community. Whereas the simple term 'diversity' embodies a set of animal community characteristics, it is not clear how different measures of species diversity are correlated with disease risk. We therefore tested the effects of species richness, Pielou's evenness and Shannon's diversity on bovine tuberculosis (bTB) risk in cattle in the Afar Region and Awash National Park between November 2013 and April 2015. We also analysed the identity effect of a particular species and the effect of host habitat use overlap on bTB risk. We used the comparative intradermal tuberculin test to assess the number of bTB-infected cattle. Our results suggested a dilution effect through species evenness. We found that the identity effect of greater kudu - a maintenance host - confounded the dilution effect of species diversity on bTB risk. bTB infection was positively correlated with habitat use overlap between greater kudu and cattle. Different diversity indices have to be considered together for assessing diversity-disease relationships, for understanding the underlying causal mechanisms. We posit that unpacking diversity metrics is also relevant for formulating disease control strategies to manage cattle in ecosystems characterized by seasonally limited resources and intense wildlife-livestock interactions.

Disease transmission in animal transfer networks.

Infectious diseases transmission is strongly determined by who contacts whom. Bovine tuberculosis (bTB) caused by Mycobacterium bovis is a worldwide burden for animal populations. One of the major transmission mechanism between herd is the transfer of infectious animal. In East Africa, pastoralists may receive or bestow livestock to create and strengthen social relationships. Here, we used a network approach to examine the relative importance of such cattle transfer in the transmission of bTB. First, a total of 2550 cattle from 102 herds were tested using the comparative intradermal tuberculin test to assess the presence of bTB infected cattle in the herd. A herd was considered bTB positive if it had at least one tuberculin reactor animal. Next, we calculated the centrality of each herd in the cattle transfer network using four established measures of social network centralization: degree, betweenness, closeness and fragmentation. The relationships between the network centrality measures and bTB infection were examined using generalized linear mixed models (GLMM). We found that a herd's in-degree in the social network was positively correlated with the risk of being infected with bTB (b=4.2, 95%CI=2.1-5.7; p<0.001). A herd that was close to many others (i.e., had a higher closeness index) had a larger chance of acquiring bTB infection (b=2.1, 95%CI=1.4-2.8; p<0.001). Betweenness centrality was also positively associated with the presence of bTB infection. There was a negative relationship between the fragmentation index and bTB infection (b=-2.7, 95%CI=-4.9-1.3; p<0.001). The study clearly demonstrated that the extent to which a herd is connected within a network has significant implications for its probability of being infected. Further, the results are in accordance with our expectation that connectivity and the probability that a herd will transmit the disease to other herds in the network are related.