Browsing by Author "Taylor, Alex"

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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
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.
Novel use of portable gamma sensors to rapidly assess soil status and recovery in degraded East African agro-pastoral land
(Copernicus Publications, 2024-05-01) Blake, Will; Amasi, Aloyce; Kelly, Claire; Lewin, Shaun; Mkilema, Francis; Msale, Furaha; Mtei, Kelvin; Munishi, Linus; Nasseri, Mona; Ndakidemi, Patrick; Taylor, Alex
Soil resources in East African agro-pastoral lands are being rapidly depleted by erosion, threatening food, water and livelihood security. Here we explore the utility of innovation in portable gamma sensors to rapidly assess soil health via proxy measurement of soil organic matter (SOM) providing visual information that enables local communities to take action to mitigate land degradation before it reaches a critical tipping point. This study is grounded in the outcomes of an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places. The work has shown that limitations to delivering socially acceptable and environmentally desirable solutions can be addressed by (1) closing fundamental gaps between the evidence bases of different disciplines and indigenous knowledge and (2) addressing, through participatory action, the implementation gap between science-based recommendations, policy makers and practitioners. Key adaptations implemented in the study region include new bylaws to enforce altered grazing regimes, grassland recovery and tree planting. Against this context, we report a first trial of a portable gamma spectrometer to rapidly assess spatial variability in soil health using total and radionuclide-specific gamma emissions from naturally occurring radioisotopes as a proxy for soil organic matter. A Medusa MS-700 portable gamma spectrometer was deployed on foot across a landscape of known variability in soil health status encompassing a spectrum of impact from severely gullied soil/subsoil, heavily grazed surface soil, recovered grazed soil (ca 3 years exclusion of livestock) and conservation agriculture plots. In-situ field results showed a clear gradient in raw total gamma count rate with sample areas in each zone at 1200 ± 100, 980 ± 70, 814 ± 60 and 720 ± 60 counts per second across the above four areas respectively. Correlations between radioisotope-specific gamma spectrometer data and organic matter (range 15 ± 2 to 30 ± 3 g kg-1 from degraded land to conservation agriculture) were evaluated to explore the dominant control on sensor response. Further comparisons are made to major and minor element geochemistry. Feedback from local Maasai community members who participated in the research further underpins the value of the sensor as a qualitative assessment tool e.g. using visual colour coding in the live data feed in the field. Quantitative comparison of sensor and laboratory data will permit development of protocols for airborne (drone) gamma spectrometry that offers community scale evaluation of grazing pressure on soil health to inform livestock future exclusion policy in common land prone to soil erosion.
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
Soils, Science and Community ActioN (SoilSCAN): a citizen science tool to empower community-led land management change in East Africa
(IOPscience, 2022-08-02) Kelly, Claire; Wynants, Maarten; Patrick, Aloyce; Taylor, Alex; Mkilema, Francis; Nasseri, Mona; Lewin, Shaun; Munishi, Linus; Mtei, Kelvin; Ndakidemi, Patrick; Blake, William
Pastoralist communities worldwide face complex challenges regarding food and feed productivity. Primary production systems are under stress, nutritional choices are changing and the relationship between development and agriculture is undergoing profound transformation. Under increasing pressure from climate and land use change, East African agro-pastoral systems are approaching a tipping point in terms of land degradation. There is an urgent need for evidence-led sustainable land management interventions to reverse degradation of natural resources that support food and water security. A key barrier, however, is a lack of high spatial resolution soil health data wherein collecting such information for each individual community is beyond their means. In this context, we tested whether bridging such data gaps could be achieved through a coordinated programme at the boundary between participation and citizen science. Key outputs included a community-led trial of a hand-held soil scanner, which highlighted a range of positive benefits and practical challenges in using this technology in this context, with identification of some potential solutions; and a targeted soil organic matter and nutrient status dataset in a small catchment-based community setting. The results show that if the practical challenges can be resolved, use of portable soil scanner technology has the potential to fill key knowledge gaps and thereby improve resilience to the threat of land degradation through locally responsive farmer and community decision-making.