Understanding the causes of bush encroachment in Africa: The key to effective management of savanna grasslands

Kgosikoma, Olaotswe Ernest; Mogotsi, K.

doi:10.17138/tgft(1)215-219

Cited by 28 publications

(23 citation statements)

References 23 publications

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“…The substantial losses of G. senegalensis in 2015 and the observed regrowth are part of natural cycles in a non-equilibrium ecosystem [13,38] and we have affirmed these rainfall controlled dynamics. On the other hand, shrub encroachment and the loss of herbaceous vegetation in southern Africa is considered an undesired effect for livestock farmers [33,39], the situation in Sahel with less rainfall and infertile soils is however different, and the valuation of the effects of gains and losses in woody cover need to be carefully assessed. Moreover, the spreading of single species leads to a poor biodiversity.…”

Section: Discussionmentioning

confidence: 99%

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Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

et al. 2017

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Abstract:The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall) led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014-2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of "greening" or "degradation". While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

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Section: Discussionmentioning

confidence: 99%

“…2017, 9, 39 3 of 21 product of the complex interactions between climate, biology, geomorphology, soils, fauna, fire, and human activity over time (see Figures A1-A6 and Table 1). Soils play an important role in defining the contrasting character of the western and eastern parts of the study region.…”

Section: Introductionmentioning

confidence: 99%

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

et al. 2017

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“…It has previously been observed that when bush encroachment occurs, high-quality grass species often disappear, leaving behind hardy and less palatable grasses. Further, bush encroachment could occur due to the removal of keystone species and/or the removal of grasses that often help with maintaining the balance of tree-grass interactions [72,73].…”

Section: Tsetse Prevalence and Distribution Patternsmentioning

confidence: 99%

Tsetse Invasion as an Emerging Threat to Socioecological Resilience of Pastoral Communities in Karamoja, Uganda

et al. 2020

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Over 70% of Uganda is infested by the tsetse fly, which has negative effects on human and livestock health. From colonial to post-independent Uganda, the Government of Uganda has worked to eradicate the tsetse menace. Despite these efforts, recent veterinary reports from the Karamoja sub-region have indicated widespread tsetse invasion. This study investigated the potential impact of tsetse invasion on the socioecological resilience of pastoral communities in the Karamoja sub-region. Results indicated that tsetse invasion is spreading from north to south of Karamoja. The tsetse transmission route emerging from southern Karamoja is perceived to be a continuation of the tsetse belt from West Pokot, Kenya. Cases of livestock deaths, livestock abortions, decreased milk yields, restricted access to prime grazing lands, heightened human-wildlife conflicts and disruption on crop cultivation have been reported. A computed socioecological resilience index in the study area was positive but low. Owing to the transboundary characteristics of tsetse invasions and sources and the associated documented effects, an urgent, strategic and system-wide intervention should be undertaken to control the tsetse invasion in this sub-region. software, J.O. and J.P.M.; validation, A.E., J.O., J.P.M. and B.B.; formal analysis, A.E., J.O. and J.P.M.; investigation, A.E. and J.O.; resources, A.E.; data curation, J.O., J.P.M. and A.S.; writing-original draft preparation, A.E.; writing-review and editing, A.E., J.O., B.B., and A.S.; visualization, A.E., J.O., B.B. and A.S.; supervision, J.J.N.; project administration, A.E.; funding acquisition, A.E. and J.J.N. All authors have read and agreed to the published version of the manuscript.

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“…The increase in woody species in former grass dominated landscapes is often perceived as negative as it reduces the ability of savanna ecosystems to provide goods and services (De Wit et al 2001;Lesoli et al 2013). For instance woody encroachment results in loss of biodiversity, reduction in capacity of rangelands to support livestock and wildlife, reduced surface stream flows, increase in fire hazards as well as soil erosion (Moleele 2002;Wigley et al 2009;Kgosikoma and Mogotsi 2013;Lesoli et al 2013;O'Connor et al 2014;Kgosikoma et al 2012). In view of the potential negative effects of woody encroachment on savanna ecosystem and projected increase in the bioclimatically suitable area, monitoring and management efforts could target these woody encroachment ''hotspots''.…”

Section: Bioclimatic Variables Of Importancementioning

confidence: 99%

Spatial distribution ofVachellia karrooin Zimbabwean savannas (southern Africa) under a changing climate

Shekede

Murwira

Masocha

et al. 2018

Ecological Research

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Climate change projections in southern Africa show a drier and a warmer future climate. It is not yet clear how these changes are going to affect the suitable habitat of bush encroacher woody species in southern African savannas. Maximum Entropy niche modelling technique was used to test the extent to which climate change is likely to affect the suitable habitat of Vachellia karroo in Zimbabwe based on six Global Climate Models (GCMs) from Coupled Model Intercomparison Project Phase 5 (CMIP5) and two Representative Concentration Pathways (RCPs) for the 2070s. An overlay analysis was then performed in a Geographic Information System based on the current and future bioclimatically suitable areas for the respective GCMs and RCPs. This was done to determine the potential effect of climate change on the focal species. Results show that temperature related variables are more important in explaining the spatial distribution of V. karroo than precipitation related variables. In addition, results indicate an overall increase in the modelled suitable habitat for V. karroo by the 2070s across the GCMs and RCPs considered in this study. Specifically, the suitable habitat of V. Karroo is projected to increase by a maximum of 57,594 km2 signifying a 69% increase from the current suitable habitat (83,674 km2). The suitable areas are projected to increase in eastern, western and south eastern parts of Zimbabwe. These results imply that improved understanding of the response of woody species to a changing climate is important for managing bush encroachment in savanna ecosystems.

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Understanding the causes of bush encroachment in Africa: The key to effective management of savanna grasslands

Cited by 28 publications

References 23 publications

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

Tsetse Invasion as an Emerging Threat to Socioecological Resilience of Pastoral Communities in Karamoja, Uganda

Spatial distribution ofVachellia karrooin Zimbabwean savannas (southern Africa) under a changing climate

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