Browsing by Author "Gilvear, David"

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Building Climate Change Adaptation and Resilience through Soil Organic Carbon Restoration in Sub-Saharan Rural Communities: Challenges and Opportunities
(MDPI, 2021-10-02) Taylor, Alex; Wynants, Maarten; Kelly, Claire; Mtei, Kelvin; Mkilema, Francis; Ndakidemi, Patrick; Nasseri, Mona; Kalnins, Alice; Patrick, Aloyce; Gilvear, David; Blake, William
Soil organic carbon (SOC) is widely recognised as pivotal in soil function, exerting important controls on soil structure, moisture retention, nutrient cycling and biodiversity, which in turn underpins a range of provisioning, supporting and regulatory ecosystem services. SOC stocks in sub-Saharan Africa (SSA) are threatened by changes in land practice and climatic factors, which destabilises the soil system and resilience to continued climate change. Here, we provide a review of the role of SOC in overall soil health and the challenges and opportunities associated with maintaining and building SOC stocks in SSA. As an exemplar national case, we focus on Tanzania where we provide context under research for the “Jali Ardhi” (Care for the Land) Project. The review details (i) the role of SOC in soil systems; (ii) sustainable land management (SLM) techniques for maintaining and building SOC; (iii) barriers (environmental, economic and social) to SLM implementation; and (iv) opportunities for overcoming barriers to SLM adoption. We provide evidence for the importance of site-specific characterisation of the biophysicochemical and socio-economic context for effective climate adaptation. In particular, we highlight the importance of SOC pools for soil function and the need for practitioners to consider the type of biomass returns to the soil to achieve healthy, balanced systems. In line with the need for local-scale site characterisation we discuss the use of established survey protocols alongside opportunities to complement these with recent technologies, such as rapid in situ scanning tools and aerial surveys. We discuss how these tools can be used to improve soil health assessments and develop critical understanding of landscape connectivity and the management of shared resources under co-design strategies
Connectivity between land, water, and people: integrating process concepts and assessment evidence across disciplines for co-design of soil erosion solutions
(Authorea, 2020-04-20) Blake, William; Kelly, Claire; Wynants, Mona; Patrick, Aloyce; Lewin, Shaun; Lawson, Joseph; Nasolwa, Emmanuel; Page, Annabel; Nasseri, Mona; Marks, Carey; Gilvear, David; Mtei, Kelvin; Munishi, Linus; Ndakidemi, Patrick
Soil resources in East Africa are being rapidly depleted by erosion, threatening food-, water- and livelihood security in the region. Here we demonstrate how integration of evidence from natural and social sciences has supported community-led change in land management in an agro-pastoral community in northern Tanzania impacted by soil erosion. Drone survey data and geospatial analysis of erosion extent and risk, supported by communication of ‘process’ and ‘structural’ hydrological connectivity, was integrated with local environmental knowledge within participatory community workshops. Rill density data were compared between cultivated plots that had been converted from pastoral land recently and more established plots where slow-forming terrace boundaries were more established. Slope length and connectivity between plots were key factors in development of rill networks. At the two extremes, recently converted land had a rill density ca 14 times greater than equivalent established slow forming terraces. Direction of cultivation, regardless of plot boundary orientation with contours, also enhanced rill development. Evidence of this critical time window of hillslope-scale rill erosion risk during early phases of slow-forming terrace development successfully underpinned and catalysed a community-led tree planting and grass seed sowing programme to mitigate soil erosion by water. This was grounded in an implicit community understanding of the need for effective governance mechanisms at both community and District levels, to enable community-led actions to be implemented effectively. The study demonstrates the wide-reaching impact of integrated and interdisciplinary ‘upslope-downslope’ thinking to tackle global soil erosion challenges.
Determining tributary sources of increased sedimentation in East-African Rift Lakes.
(Elsevier B.V., 2020-05-15) Wynants, Maarten; Millward, Geoffrey; Patrick, Aloyce; Taylor, Alex; Brendonck, Luc; Gilvear, David; Boeckx, Pascal; Blake, William; Munishi, Linus; Mtei, Kelvin; Ndakidemi, Patrick
Temporal and spatial sediment dynamics in an East-African Rift Lake (Lake Manyara, Tanzania), and its river inputs, have been evaluated via a combination of sediment tracing and radioactive dating. Changes in sedimentation rates were assessed using radioactive dating of sediment cores in combination with geochemical profile analysis of allogenic and autogenic elements. Geochemical fingerprinting of riverine and lake sediment was integrated within a Bayesian mixing model framework, including spatial factors, to establish which tributary sources were the main contributors to recent lake sedimentation. The novel application of Bayesian source attribution on sediment cores and subsequent integration with sedimentation data permitted the coupling of changes in the rate of lake sedimentation with variations in sediment delivery from the tributaries. These complimentary evidence bases demonstrated that Lake Manyara has experienced an overall upward trajectory in sedimentation rates over the last 120 years with distinct maxima between 0.80 and 0.85 g cm yr in the 1960s and between 0.84 and 1.81 g cm yr in 2010. Increased sedimentation rates are largely a result of a complex interaction between increased upstream sediment delivery following changes in land cover and natural rainfall fluctuations. Modelling results identified two specific tributaries as responsible for elevated sedimentation rates, contributing 58% and 38% of the recently deposited lake sediment. However, the effects of sedimentation were shown to be spatially distinct given the domination of different tributaries in various areas of Lake Manyara. The application of source-tracing techniques constrained sedimentation problems in Lake Manyara to specific tributary sources and established a link between upstream land degradation and downstream ecosystem health. This novel application provides a solid foundation for targeted land and water management strategies to safeguard water security and environmental health in Lake Manyara and has potential application to fill knowledge gaps on sediment dynamics in other East-African Rift Lakes.
Drivers of increased soil erosion in East Africa’s agro-pastoral systems: changing interactions between the social, economic and natural domains
(Springer, 2019-06-08) Wynants, Maarten; Kelly, Claire; Mtei, Kelvin; Munishi, Linus; Patrick, Aloyce; Rabinovich, Anna; Nasseri, Mona; Gilvear, David; Roberts, Neil; Boeckx, Pascal; Wilson, Geoff; Blake, William; Ndakidemi, Patrick
Increased soil erosion is one of the main drivers of land degradation in East Africa’s agricultural and pastoral landscapes. This wicked problem is rooted in historic disruptions to co-adapted agro-pastoral systems. Introduction of agricultural growth policies by centralised governance resulted in temporal and spatial scale mismatches with the complex and dynamic East African environment, which subsequently contributed to soil exhaustion, declining fertility and increased soil erosion. Coercive policies of land use, privatisation, sedentarisation, exclusion and marginalisation led to a gradual erosion of the indigenous social and economic structures. Combined with the inability of the new nation-states to provide many of the services necessary for (re)developing the social and economic domains, many communities are lacking key components enabling sustainable adaptation to changing internal and external shocks and pressures. Exemplary is the absence of growth in agricultural productivity and livelihood options outside of agriculture, which prohibits the absorption of an increasing population and pushes communities towards overexploitation of natural resources. This further increases social and economic pressures on ecosystems, locking agro-pastoral systems in a downward spiral of degradation. For the development and implementation of sustainable land management plans to be sustainable, authorities need to take the complex drivers of increased soil erosion into consideration. Examples from sustainable intensification responses to the demands of population increase, demonstrate that the integrity of locally adapted systems needs to be protected, but not isolated, from external pressures. Communities have to increase productivity and diversify their economy by building upon, not abandoning, existing linkages between the social, economic and natural domains. Locally adapted management practices need to be integrated in regional, national and supra-national institutions. A nested political and economic framework, wherein local communities are able to access agricultural technologies and state services, is a key prerequisite towards regional development of sustainable agro-pastoral systems that safeguard soil health, food and livelihood security.
Drivers of increased soil erosion in East Africa’s agro-pastoral systems: changing interactions between the social, economic and natural domains
(Springer Berlin Heidelberg, 19-06-18) Wynants, Maarten; Kelly, Claire; Mtei, Kelvin; Munishi, Linus; Patrick, Aloyce; Rabinovich, Anna; Nasseri, Mona; Gilvear, David; Roberts, Neil; Boeckx, Pascal; Wilson, Geoff; Blake, William; Ndakidemi, Patrick
Increased soil erosion is one of the main drivers of land degradation in East Africa’s agricultural and pastoral landscapes. This wicked problem is rooted in historic disruptions to co-adapted agro-pastoral systems. Introduction of agricultural growth policies by centralised governance resulted in temporal and spatial scale mismatches with the complex and dynamic East African environment, which subsequently contributed to soil exhaustion, declining fertility and increased soil erosion. Coercive policies of land use, privatisation, sedentarisation, exclusion and marginalisation led to a gradual erosion of the indigenous social and economic structures. Combined with the inability of the new nation-states to provide many of the services necessary for (re)developing the social and economic domains, many communities are lacking key components enabling sustainable adaptation to changing internal and external shocks and pressures. Exemplary is the absence of growth in agricultural productivity and livelihood options outside of agriculture, which prohibits the absorption of an increasing population and pushes communities towards overexploitation of natural resources. This further increases social and economic pressures on ecosystems, locking agro-pastoral systems in a downward spiral of degradation. For the development and implementation of sustainable land management plans to be sustainable, authorities need to take the complex drivers of increased soil erosion into consideration. Examples from sustainable intensification responses to the demands of population increase, demonstrate that the integrity of locally adapted systems needs to be protected, but not isolated, from external pressures. Communities have to increase productivity and diversify their economy by building upon, not abandoning, existing linkages between the social, economic and natural domains. Locally adapted management practices need to be integrated in regional, national and supra-national institutions. A nested political and economic framework, wherein local communities are able to access agricultural technologies and state services, is a key prerequisite towards regional development of sustainable agro-pastoral systems that safeguard soil health, food and livelihood security.
Integrating land-water-people connectivity concepts across disciplines for co-design of soil erosion solutions
(John Wiley & Sons, Inc., 2020-10-02) Blake, William; Kelly, Claire; Wynants, Maarten; Patrick, Aloyce; Lewin, Shaun; Lawson, Joseph; Nasolwa, Emmanuel; Page, Annabel; Nasseri, Mona; Marks, Carey; Gilvear, David; Mtei, Kelvin; Munishi, Linus; Ndakidemi, Patrick
Soil resources in East Africa are being rapidly depleted by erosion, threatening food, water and livelihood security in the region. Here we demonstrate how the integration of evidence from natural and social sciences has supported a community-led change in land management in an agro-pastoral community in northern Tanzania. Geospatial analysis of erosion risk and extent (based on a drone survey across a 3.6 km2 sub-catchment) revealed that recently converted land had ca 12-times greater rill density than established slow-forming terraced plots (987 ± 840 m2 ha−1 vs. 79 ± 110 m2 ha−1). Slope length and connectivity between plots were key factors in the development of rill networks rather than slope per se wherein slope length was augmented by weak boundaries between newly formed plots. Erosion evidence, supported by communication of 'process' and 'structural' hydrological connectivity, was integrated with local environmental knowledge within participatory community workshops. Demonstration of the critical time window of hillslope-scale rill erosion risk during early phases of slow-forming terrace development catalysed a community-led tree planting and grass seed sowing programme to mitigate soil erosion by water. This was grounded in an implicit farmer understanding of the need for effective governance mechanisms at both community and District levels, to enable community-led actions to be implemented effectively. The study demonstrates the wide-reaching impact of integrated and interdisciplinary 'upslope-downslope' thinking to tackle global soil erosion challenges.
‘Mind the Gap’: Reconnecting Local Actions and Multi-Level Policies to Bridge the Governance Gap. An Example of Soil Erosion Action from East Africa
(MDPI, 2020-09-25) Kelly, Claire; Wynants, Maarten; Munishi, Linus; Nasseri, Mona; Patrick, Aloyce; Mtei, Kelvin; Mkilema, Francis; Rabinovich, Anna; Gilvear, David; Wilson, Geoff; Blake, William; Ndakidemi, Patrick
Achieving change to address soil erosion has been a global yet elusive goal for decades. Efforts to implement effective solutions have often fallen short due to a lack of sustained, context-appropriate and multi-disciplinary engagement with the problem. Issues include prevalence of short-term funding for ‘quick-fix’ solutions; a lack of nuanced understandings of institutional, socio-economic or cultural drivers of erosion problems; little community engagement in design and testing solutions; and, critically, a lack of traction in integrating locally designed solutions into policy and institutional processes. This paper focusses on the latter issue of local action for policy integration, drawing on experiences from a Tanzanian context to highlight the practical and institutional disjuncts that exist; and the governance challenges that can hamper efforts to address and build resilience to soil erosion. By understanding context-specific governance processes, and joining them with realistic, locally designed actions, positive change has occurred, strengthening local-regional resilience to complex and seemingly intractable soil erosion challenges.
Soil erosion and sediment transport in Tanzania: Part I – sediment source tracing in three neighbouring river catchments
(Earth Surface Processes and Landforms, 2021-12) Wynants, Maarten; Munishi, Linus; Mtei, Kelvin; Bodé, Samuel; Patrick, Aloyce; Taylor, Alex; Gilvear, David; Ndakidemi, Patrick; Blake, William; Boeckx, Pascal
Water bodies in Tanzania are experiencing increased siltation, which is threatening water quality, ecosystem health, and livelihood security in the region. This phenomenon is caused by increasing rates of upstream soil erosion and downstream sediment transport. However, a lack of knowledge on the contributions from different catchment zones, land-use types, and dominant erosion processes, to the transported sediment is undermining the mitigation of soil degradation at the source of the problem. In this context, complementary sediment source tracing techniques were applied in three Tanzanian river systems to further the understanding of the complex dynamics of soil erosion and sediment transport in the region. Analysis of the geochemical and biochemical fingerprints revealed a highly complex and variable soil system that could be grouped in distinct classes. These soil classes were unmixed against riverine sediment fingerprints using the Bayesian MixSIAR model, yielding proportionate source contributions for each catchment. This sediment source tracing indicated that hillslope erosion on the open rangelands and maize croplands in the mid-zone contributed over 75% of the transported sediment load in all three river systems during the sampling time-period. By integrating geochemical and biochemical fingerprints in sediment source tracing techniques, this study demonstrated links between land use, soil erosion and downstream sediment transport in Tanzania. This evidence can guide land managers in designing targeted interventions that safeguard both soil health and water quality
Soil erosion in East Africa: an interdisciplinary approach to realising pastoral land management change
(IOP Publishing Ltd, 2018-12-03) Blake, William; Rabinovich, Anna; Wynants, Maarten; Kelly, Claire; Nasseri, Mona; Ngondya, Issakwisa; Patrick, Aloyce; Mtei, Kelvin; Munishi, Linus; Boeckx, Pascal; Navas, Ana; Smith, Hugh; Gilvear, David; Wilson, Geoff; Roberts, Neil; Ndakidemi, Patrick
Implementation of socially acceptable and environmentally desirable solutions to soil erosion challenges is often limited by (1) fundamental gaps between the evidence bases of different disciplines and (2) an implementation gap between science-based recommendations, policy makers and practitioners.Wepresent an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places in degraded pastoral land in the East African Rift System. In a northern Tanzanian case study site, hydrological and sedimentary evidence shows that, over the past two decades, severe drought and increased livestock have reduced grass cover, leading to surface crusting, loss of soil aggregate stability, and lower infiltration capacity. Infiltration excess overland flow has driven (a) sheet wash erosion, (b) incision along convergence pathways and livestock tracks, and (c) gully development, leading to increased hydrological connectivity. Stakeholder interviews in associated sedenterising Maasai communities identified significant barriers to adoption of soil conservation measures, despite local awareness of problems. Barriers were rooted in specific pathways of vulnerability, such as a strong cattle-based cultural identity, weak governance structures, and a lack of resources and motivation for community action to protect shared land. At the same time, opportunities for overcoming such barriers exist, through openness to change and appetite for education and participatory decision-making. Guided by specialist knowledge from natural and social sciences, we used a participatory approach that enabled practitioners to start co-designing potential solutions, increasing their sense of efficacy and willingness to change practice. This approach, tested in East Africa, provides a valuable conceptual model around which other soil erosion challenges in the Global South might be addressed.