Butterfly diversity and land manager decision-making in critically endangered South African renosterveld
by Emmeline Topp
Date of Examination:2020-07-16
Date of issue:2022-07-11
Advisor:Dr. Jacqueline Prof Loos
Referee:Prof. Dr. Teja Tscharntke
Referee:Prof. Dr. Berta Martin-Lopez
Referee:Prof. Dr. Tobias Plieninger
Persistent Address:
http://dx.doi.org/10.53846/goediss-9349
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Abstract
English
Addressing global biodiversity loss requires understanding complex human-nature relations. This is imperative in global biodiversity hotspots, areas that contain exceptional endemism and have lost significant amounts of natural habitat due to anthropogenic activities. In these areas, this understanding can be advanced through the assessment of both ecological and social components of the landscape. One such area is the Cape Floristic Region (CFR), which contains one of the most critically endangered ecosystems in South Africa: renosterveld. Renosterveld is a native fire-prone shrub-scrub ecosystem that has been extensively transformed to commercial agriculture in South Africa’s Western Cape. Remaining renosterveld fragments are mostly in private ownership on areas which cannot be cultivated. These fragments foster remarkable biodiversity, primarily endemic plant diversity, but also insect diversity, including butterfly communities. This interdisciplinary thesis focuses on both ecological aspects, specifically butterfly diversity, and social aspects, including the decision-making context and climate change adaptation by land managers, of the agricultural landscape containing remnant renosterveld. This thesis consists of six chapters including an introductory framework chapter and five original scientific manuscripts. In an introductory chapter (Chapter 1), I first introduce the thematic setting of the thesis, the study region, research questions and disciplinary approaches, along with more detailed chapter syntheses. I then provide a systematic literature analysis of renosterveld ecology and conservation (Chapter 2), where I synthesize renosterveld ecology and identify threats, barriers and recommendations for conservation. In the following two chapters, I present empirical studies into butterfly and vegetation responses to local and landscape variables in remaining renosterveld fragments among intensively managed agricultural land. In Chapter 3, I find that flower species richness and microhabitat type impact butterfly species richness and abundance, and that fragment size is a key determinant of butterfly species richness across the landscape. In Chapter 4, I find that fire is a key driver of renosterveld vegetation and butterfly abundance, while landscape context is important for butterfly species richness. In Chapters 5 and 6, I present empirical studies into the decision-making context for land managers of renosterveld and land manager perceptions and adaptation toward climate change in this landscape. Through interviews with renosterveld land managers and application of the Intergovernmental Panel for Biodiversity and Ecosystem Services’ conceptual framework, I identify different decision-making contexts for renosterveld and associated nature’s contributions to people (Chapter 5). I also ascertain different external and internal influences on climate change adaptation among farmers in the CFR, including institutional factors and cognitive biases (Chapter 6). In summary, the results of my thesis shed light on some of the complex ecological and social processes at play in remnant renosterveld. Within the renosterveld remnants themselves, local environmental drivers such as floral resource availability and landscape level drivers such as fire and fragment size influence butterfly communities. Management for renosterveld plant conservation, including prescribed burns, may benefit renosterveld butterfly conservation through regeneration of plant diversity and removal of dominant shrub from otherwise unmanaged remnants. Land managers express a multitude of values related to renosterveld, including intrinsic, instrumental and relational values. Together with perceived rules and held knowledge, these values create the social decision-making context for renosterveld. Renosterveld is perceived by land managers to provide regulating, material and non-material nature’s contributions to people, including place-specific benefits such as flower collecting. Farmers with renosterveld on their properties perceive different levels of risk associated with climate change, and adaptation strategies differ between wheat and wine grape farmers. In a landscape where most remaining fragments of biodiversity-rich renosterveld vegetation are privately owned, my thesis provides important evidence for insect diversity in these remaining fragments, and reveals the social context and priorities for land managers as well as their perceptions of renosterveld, which can support the safeguarding of renosterveld in the future.
Keywords: social-ecological systems; nature's contributions to people; fragmentation; lepidoptera; agricultural intensification; landscape values