Restoration of riparian habitats on sugarcane plantations for bird diversity, bird – regulated ecosystem services and climate change mitigation and adaptation in rural tropical landscapes, Tanzania

The growth of the agricultural sector in the rural tropics, is seen as crucial to improve food security and reduce poverty of millions of rural households (1-2). In Sub-Saharan Africa, agricultural growth corridors have seen rapid, coordinated investments in transport infrastructure, e.g. the Tanzania Agricultural Growth Corridor SAGCOT linking Malawi, Zambia, Democratic Republic of Congo, and Tanzania (3). How to implement this growth without risking large scale negative ecological and social impacts remains contested (6). The agricultural growth poses a pervasive threat to natural capital (here: forests, water, soil) and ecosystem restoration that aims to reverse biodiversity loss (4) and enhance climate change mitigation and adaptation of local communities (5). Riparian zones, i.e. natural non-converted habitat, actively restored natural habitat, or unmanaged areas, are an important conservation tool used to maintain biodiversity and ecosystem functions in tropical agricultural landscapes (7). Riparian zones benefit hydrology, water quality, biodiversity. However, large uncertainties remain on their effects on habitat connectivity for wildlife, crop pollination and pest control and carbon storage and emissions reduction and how their functions are mediated by width and quality (composition, structure) of the restored riparian habitat (8). Scientific evidence used to inform policies on riparian zones is dominated by ecological values at the expense of ecological disvalues (e.g. impacts on abundance of pests and crop yields), cultural values and socio-economic needs. The evidence base is particularly poor for agricultural landscapes in Sub-Saharan Africa.

With this research, we now want to urgently close the knowledge gaps. The focus of this PhD project is on the Kilombero Valley in Tanzania as a case study, from which upscaling to wider regions may be possible. The aim is to work with our partner, Illovo Sugar, to integrate across ecological and socio-economic evidence to inform the restoration and management of riparian zones on land used for sugarcane production, including small-holder and industry farmed land. The industry plantation fully supports our work with access to plantation land and facilities.

The three main objectives are: (O1) to identify variables that allow stakeholders, in particular industry, to determine what to restore in riparian zones (vegetation composition, water health) to maximise benefits to carbon storage, water quality and bird diversity/pest control functions. (O2) to evaluate where to restore to maximise benefits whilst minimising trade-offs against disservices such as less land and increased pest pressure (zonation, matching based on biophysical and socio-economic parameters) and (O3) establish best practice guiding how to restore (practicalities, co-design).

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The PhD candidate will implement a systematic literature review on restoration of riparian zones in rural tropical landscapes, globally. This will allow the candidate to establish variables to consider for their fieldwork, to identify evidence and evidence gaps that urgently need closing in relation to stated objectives, and to identify existing expertise in practical restoration of riparian zones.

For the fieldwork, the candidate will work with the supervisory team and partners in the case study landscape (Illovo Sugar, Sokoine University of Agriculture, Reforest Africa, TANAPA, IUCN Sustain) to implement tasks addressing the three objectives for the case study. This includes implementing surveys in remaining riparian zones along a degradation gradient for vegetation composition and width (working with a local botanist to identify plant species). We anticipate 20 transect walks of 500 m each along the main rivers and 20 along creeks on private (industry, small-holder farms) and government protected land. The PhD candidate will measure riverbank stability, water quality, and flows along the transect at 100 m intervals and additionally at 20 random points in farmed land with no riparian habitat. Bioclimatic niche modelling will be used to determine the climate suitability of riparian vegetation now and in the future.

The candidate will implement bird surveys along the transects and into the farmed land to establish the function of riparian zones for maintaining birds and to establish the role of these birds as potential pests, pest controls or pollinators. The candidate will work with local partners in focus groups, informed by expertise on riparian restoration, to develop best practice guidelines for restoration of riparian zones.

Project Timeline

Year 1

Months 1-2: Discussion of project objectives with the supervisor team and partners in Tanzania. Developing the field plan. Months 3-5: Application for research permits in Tanzania. Developing the protocol for the systematic literature review following PICO standards. Registration and publication of the protocol. Months 6-11: Implementation of the review and planning of fieldwork. Chapters 1 and 2 drafts ready for submission.

Year 2

Months 13 – 19: Fieldwork in the case study landscape in Tanzania. Months 20 – 24: Processing of data to create project database for subsequent analyses. First visualisation of results (bird diversity, water quality and riparian habitats) and draft for chapter 3.

Year 3

Months 25 – 31: Development of restoration protocol and focus groups discussions. Write up of results on process of riparian restoration. Finalising chapter 3 for submission. Months 32 – 36: Finalisation of draft for chapter 4.

Year 3.5

Months 37-42: Finalisation of dissertation and submission. Feedback to partners in the landscape.

& Skills

The successful candidate will receive training in evidence synthesis and data visualisation, advanced spatial analyses including predictive mapping and modelling, fieldwork design and implementation in rural tropical countries and socio-ecological methods and frameworks used in conservation science.

The candidate will be placed in the TROPS lab, situated with the Modelling, Evidence, and Policy RG, benefitting from interaction with a dynamic group of researchers working in tropical and UK landscapes to generate evidence for policy- and decision-making on pressing global challenges, including climate change mitigation through agroforestry, disease risk, human wildlife conflict, and biodiversity loss in changing landscapes.

References & further reading

(1) Pfeifer et al. 2022 A systems approach framework for evaluating tree restoration interventions for wellbeing and ecological outcomes in rural tropical landscapes. Philosophical Transactions of the Royal Society B. In Press.*
(2) Milheiras et al. 2022 Agroecological practices increase farmers’ well-being in an agricultural growth corridor in Tanzania. Agronomy for Sustainable Development 42:1-14
(3) Buseth 2017 The green economy in Tanzania: From global discourses to institutionalization. Geoforum 86: 42-52
(4) Kehoe et al. 2017 Biodiversity at risk under future cropland expansion and intensification. Nature Ecology and Evolution 1: 1129-1135
(5) Lewis et al. 2019 Restoring natural forests is the best way to remove atmospheric carbon. Nature 568: 25-28
(6) Fleischman et al. 2022 Restoration prioritization must be informed by marginalized people. Nature 607: E5-E6 *
(7) Lind et al. 2019 Towards ecologically functional riparian zones: A meta-analysis to develop guidelines for protecting ecosystem functions and biodiversity in agricultural landscapes. Journal of Environmental Management 249: 109391
(8) Luke et al. 2019 Riparian buffers in tropical agriculture: Scientific support, effectiveness and directions for policy. Journal of Applied Ecology 56: 85-92

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