Understanding Social Ecological Regime Shifts: The case of woody encroachment in South Africa.Author(s): Luvuno, L.
Link to CST author(s): Dr Linda Luvuno
Full reference: Luvuno, L. 2019. Understanding Social Ecological Regime Shifts: The case of woody encroachment in South Africa. Stellenbosch University thesis.
Humanity has been very successful in modifying the planet to meet the demands of a rapidly growing human population. As human activities have grown in magnitude, they have become increasingly interlinked with ecosystem dynamics, creating social-ecological systems (SES). Increased human impacts on ecosystems are also leading to an increased occurrence of regime shifts: large, persistent changes in the structure and function of ecosystems and SES that often have substantive impacts on the suite of ecosystem services provided by these systems, and on the well-being of people who live in them. As global changes accelerate, better understanding the drivers, impacts and risks of regime shifts has become a key need. This knowledge has important implications for the formulation of management strategies that aim to either maintain existing desirable regimes, restore previous regimes where a regime shift has occurred, or facilitate transformation to new regimes in the novel planetary conditions we face. A prevalent regime shift in savannas worldwide is woody encroachment. Woody encroachment is a shift from a grassy savanna to a persistently woody savanna, and has direct implications for a variety of ecosystem services such as livestock grazing, and people’s livelihoods that depend on these services. Much of the work on woody encroachment has focused on the direct drivers of the process, such as the role of fire or grazing in inhibiting or promoting encroachment. However, less is understood about how underlying social processes may impact these drivers, how ecological changes may feedback to affect some of these underlying social processes, how to monitor woody encroachment as a regime shift and how encroachment impacts ecosystem services and human well-being. This dissertation consists of four research chapters in journal format. The first is a synthesis of the ecological drivers and the social processes and drivers of woody encroachment based on the published literature, synthesized using causal loop diagrams and a published regime shift analysis framework. The remainder of the papers focus on woody encroachment in the Hlabisa district of South Africa. The second paper used Landsat TM imagery to quantify the extent of woody encroachment from 1990 to 2016 under contrasting land uses, specifically state-owned conservation land and communal land largely used for subsistence agriculture. The third paper builds on paper 2 and used spatial autocorrelation and the sequential t-tests analysis for regime shifts (STARS) to explore whether the changes observed in the remote sensing data conform to the statistical properties of a regime shift. The fourth paper used semi-structured interviews to investigate how different land users in the Hlabisa area (state conservation game reserve, private game reserves and local communities) are impacted by woody encroachment. Paper 1 provides a broader social-ecological understanding of woody encroachment. This review highlighted the link between increased human populations (locally and globally) and woody encroachment, and suggests key management options based on the key feedback loops identified. Paper 2 and 3 highlight the value of multi-temporal remote sensing data to monitor the extent of woody encroachment and collect time series data that could be used in the detection of regime shifts and early warning indicator of these shifts. Paper 2 found that Hlabisa experienced significant increases in tree cover between 1990 and 2016, under both the conservation and communal land uses, suggesting that the changes may be largely driven by global drivers rather than local land use practices. Paper 3 shows that these tree cover changes constituted a regime shift, confirmed through the results of STARS and spatial autocorrelation. This paper also suggests that these approaches offer a method that could be used to monitor woody encroachment regime shifts. Paper 4 reveals that all interviewed land users perceived woody encroachment to be increasing in the area. Community members and private game reserve managers mostly reported negative impacts of woody encroachment, with mixed reports from the state reserve managers. This paper also showed that private reserve managers are the most active in undertaking actions to counter encroachment. This research can inform policy and management practices. The dissertation emphasises the importance of understanding the social and ecological interactions that underlie woody encroachment, including the worldviews of land users and managers. With the looming impacts of global warming, and possible technological advances that can change how people live and view the systems in which they live, it is important for SES managers to adopt a complex adaptive systems approach that considers possible feedbacks, drivers at local to global scales, approaching system thresholds, livelihood impacts, as well as the potential for novel planetary conditions.