The Dynamics and Resilience of Coral Reefs

Abstract

A major goal in ecosystem management is to prevent shifts to undesirable states, and there is widespread interest in understanding, mapping, and quantifying resilience to support management decisions. With rapid changes taking place on coral reefs, managers and scientists are faced with a challenging task in prioritising interventions that help strengthen reef resilience. Resilience-based management (RBM) of coral reefs requires in-depth knowledge on the various components and feedback mechanisms of the ecosystem, and uses resilience theory to inform decisions. To date, there are mechanistic models that analyse and forecast the future of reefs, but being data intensive and requiring specialist knowledge, are not applicable to managers in most locations with limited data and analytical training. Hence, there is a need to develop approaches to acquire insights on resilience using monitoring data.The global decline of reefs to varying extents, underscores the importance of understanding how biophysical factors influence and shape reef community dynamics. Multiple environmental factors affect reef functioning, either positively or negatively, and the diversity and complexity of responses make it difficult to predict future reef trajectories. My thesis addresses the need to improve retrospective analyses of time-series monitoring data to suit management goals, such as resilience, by focusing on the data collection and analytical components of long-term monitoring programmes. In this thesis, I trialled two state-of-the-art methods to extract useful ecological information and identified drivers of coral reef trajectories from long-term monitoring data collected in the Great Barrier Reef, arguably one of the most comprehensive coral reef monitoring dataset in the world.In Chapter 1, I provide a theoretical overview of the issues related to resilience and identify the quantification approaches found within the coral reef field. By examining the current state of knowledge, a simple framework of resilience-related concepts is developed, followed by an analysis of approaches used to quantify reef resilience and vulnerability. Seven broad quantification approaches were identified under the three principle concepts of (1) ecological resilience (ecological resilience, precariousness and current attractor), (2) engineering resilience (short-term recovery rate and long-term reef performance), and (3) vulnerability (absolute and relative vulnerability) respectively.iii Resilience-based management (RBM) is a new approach to reef management that is being adopted by governmental institutions globally. However, there are no quantitative studies on how this has changed coral reef monitoring and assessment. In Chapter 2, I conducted a critical evaluation of how RBM has changed the way we monitor our reefs. Through a comparison of metrics used in conventional programmes with those developed specifically for resilience assessments, I show that resilience metrics are much more diverse and have a strong focus on ecological processe...