IAP-25-135

Healing and Harm: invasive species, medicinal plant use, and community-based conservation in South Africa

The Soutpansberg Mountains, situated in northern Limpopo, South Africa, represent one of the country’s most biodiverse regions, recognised as a key biodiversity hotspot within the Vhembe Biosphere Reserve. This mountain range supports a wide array of ecosystems, from savanna to mistbelt forest, providing habitats for numerous endemic and medicinally important plant species. However, the ecological integrity of this landscape is increasingly threatened by multiple stressors including biological invasions, particularly by alien plant species that disrupt native vegetation dynamics, water availability, and ecosystem services.

Among these invasive species, Opuntia stricta (the prickly pear cactus) poses a growing challenge. Originally introduced for agricultural and ornamental purposes, it has spread widely across South Africa. The encroachment of O. stricta and other invasive plants threatens not only native vegetation and wildlife but also the diversity and availability of medicinal plants that local communities rely on for traditional healthcare. Additionally, overharvesting of medicinal plants further exacerbates biodiversity loss and ecological imbalance. These stressors are likely exacerbated by changes in climate across the region which may facilitate invasions and impact native plant phenology. Although extensive research exists on medicinal plants and invasive species in southern Africa, significant gaps remain at their intersection, particularly in understanding how biological invasions interact with human harvesting practices to shape biodiversity outcomes in culturally important landscapes.

The Leshiba Wilderness Reserve, located on the western Soutpansberg slopes, provides an ideal context for addressing the intersection of multiple stressors on endemic and medicinally important plant species. Here, O. stricta and other invasive plants are expanding. Although these species have not yet invaded prolifically, their established populations in surrounding areas, changes to habitat use and climate indicate the potential for future expansion. Yet, the ecological pathways of invasion, their impacts on medicinal plants, and the socio-economic drivers of medical plant overharvesting remain poorly understood.

This PhD will integrate ecological, ethnobotanical, and spatial approaches to investigate how invasive species and human use, under changing climatic conditions, influence medicinal and ecologically significant plant populations. The research will compare patterns of invasive plant encroachment and medicinal plant use across different parts of the Soutpansberg, spanning protected and unprotected areas, and sites with and without active management strategies. The aim of this project is to understand the ecological and social processes driving early-stage invasions and medicinal plant harvesting across this landscape, and to identify how varying management practices affect biodiversity outcomes. The project will co-develop community-based strategies that enhance the conservation of medicinal plants, prevent invasive species spread, and strengthen ecosystem resilience in the Soutpansberg.

Specifically, the project objectives are to:
1) Identify the pathways of invasion and early impacts of invasive plant establishment on medicinal plants.
2) Map invasion risk and identify areas where ecological vulnerability and human use of medicinal plants overlap.
3) Assess the ecological sustainability of current medicinal plant harvesting practices.
4) Analyse the socio-economic context of harvesting and community perceptions of invasion risk.
5) Co-develop, with local stakeholders, an adaptive management framework linking invasive species prevention, habitat restoration, and sustainable use of medicinal plants.

The project will be carried out in collaboration with Leshiba Wilderness and Wild Comm, with advice provided by The South African National Biodiversity Institute (SANBI). Therefore, the student will be working in partnership with these colleagues in South Africa when designing and conducting field data collection. The study will employ a mixed-methods approach combining ecological fieldwork, spatial analysis, and ethnobotanical research.

Methods:
1) The student will identify priority sites for assessment in protected and unprotected areas undergoing various management practices
2) Field work will involve mapping key topographical features and cataloguing flora present using botanical survey methodology and identifying ecologically important and medicinal species
2) To understand potential pathways of invasion into the key sites, surrounding areas will be assessed for invasive plant population density and proximity to the reserve.
3) One of main drivers of medicinal plant loss is overharvesting. Therefore, the student will conduct walking interviews and participatory workshops to identify drivers and mitigation measures to overharvesting.
4) Co-creation workshops with stakeholders will be held to design an adaptive management framework linking invasive species prevention, habitat management, and sustainable use of medicinal plants.

Year 1

Literature review as a systematic map to assess the effect of invasive plants on medicinal plant species (months 1-4); Satellite imagery downloads and drone flight course (months 5-6); prepping for fieldwork, mapping site features, plant inventory data downloads (months 7-8); designing surveys and citizen jury protocol (month 9-10); Botanical ID course (month 11); Environmental data collection and plant surveys in the field (months 12-15)

Year 2

Environmental data collection and plant surveys in the field (months 12-15); Invasive species assessments in surrounding areas (16-17); walking interviews and participatory workshops (18-20); mapping species distributions (month 21); Data management and modelling method assessment (months 21-23), attend BES invasive species conference (month 24)

Year 3

Data analyses, writing up results (months 25-30); Writing thesis chapters, attendance at an international conference (months 31-36)

Year 3.5

Writing publications and thesis submission (months 37-42)

The student will receive training from an interdisciplinary supervisory team,
particularly in some of the key NERC most wanted skills:

*Fieldwork: the large fieldwork element of this PhD means the student will be exposed to a variety of sampling and experimental techniques in the field
*Taxonomic Identification: to create an inventory of flora the student will receive species ID training.
*Data management and modelling: the student will have the opportunity to learn an array of modelling methods best suited to their data.
*Translating research into practice: As the output of this PhD will be integral to management of invasive species and conservation of medicinal plants, the student will receive training in science communication to multiple audiences (e.g. policy makers, non-governmental organisations (NGOs) and the wider public).

The student will also participate in IAPETUS training and events. A training budget is included for any external training required by the student