The potential effect of climate change on tropical agroforestry systems; a study of Mt Kilimanjaro's Homegardens

Abstract

Rainfed subsistence farmers in the tropics depending on natural resources for their crop production and wellbeing are highly vulnerable to climate change. Unless suitable adaptation measures are swiftly implemented, the wellbeing of these farmers could decline under climate change. Agroforestry, the integration and/or retention of trees within agricultural land, offers a potential adaptation solution through their various ecosystem services. However, whether and how agroforestry systems could themselves be impacted by climate change is currently not well understood.
A systematic review of literature focusing on the tropics found that 1) the effects of climate change on tropical agroforestry systems remains an understudied research field, especially the effects on farmers, 2) based on the limited evidence climate change mostly negatively impacts tropical agroforestry systems, and 3), the current supporting evidence-based is not highly reliable. Following these review findings, this thesis empirically assesses how homegardens – a type of tropical agroforestry system – could be affected by climate change by using climate analogue analysis along Mt Kilimanjaro’s climate gradient, covering its ‘midland’ and ‘highland’ agroecological zones. The midland’s climate represents a potential warmer and drier future climate under climate change, while the highland’s climate represents the present climate conditions.
To guide the thesis research, an interdisciplinary framework was developed using literature, existing frameworks, and qualitative fieldwork. The potential impacts of climate change on the homegarden’s tree-soil-crop ecological interactions supporting farmers’ banana production (farmers’ main food and cash crop), is then examined using structural equation modelling. The thesis then fully operationalises the conceptual framework through a mixed-methods study which examines variation and changes in provisioning ecosystem services and subsistence farmers’ wellbeing under different climate conditions to infer the potential impacts of climate change. The key findings from each chapter are then synthesised using causal loop diagrams to outline how climate change could affect homegardens as a social-ecological system.
Overall, this thesis finds that climate change could negatively impact on the ecosystem services from homegardens underpinning subsistence farmers’ wellbeing. As such, farmers’ wellbeing may also decline, which could positively feedback into their crop production system and exacerbate declines in ecosystem services. This thesis concludes that decision-makers should consider the potential future climate scenarios for areas where agroforestry adaptation measures are being considered, as well as the availability of additional farmland that could be used to supplement farmers’ crop production to reduce their climate vulnerability.

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Identifiers

ORCID for Kelvin Peh: orcid.org/0000-0002-2921-1341

ORCID for Craig Hutton: orcid.org/0000-0002-5896-756X

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