Reef‐to‐ridge ecological perspectives of high‐energy storm events in northeast Australia

Abstract

Tropical cyclones (TCs) are the dominant high-energy storm (HES) events affecting marine, coastal, and terrestrial ecosystems in northeast Australia. My study provides the first synthetic analysis of ecological effects of TCs on key ecosystems along a reef-to-ridge gradient in the region. This gradient includes outer and mid-shelf, and nearshore coral reefs, seagrass communities, mangrove forests, and lowland, and upland rain forests. Firstly, I synthesize published research on ecological effects of HES events on natural ecosystems along the reef-to-ridge gradient, with a particular focus on evaluating their ecological resistance and resilience to HES events. Secondly, utilizing two case studies, I compare and contrast the large-scale wind energy effects of two severe tropical cyclones (TC Larry and TC Yasi) on natural ecosystems along their respective reef-to-ridge gradients, with a focus on damage patterns and early stages of recovery for key ecosystems. Finally, I consider the likely effects of climate change on future HES events, and how these may affect the resistance and resilience of ecosystems along the reef-to-ridge gradient. Damage patterns for ecosystems along the reef-to-ridge gradient for both TCs were largely determined by distance from the TC track, side of track, shelf position in the case of reefs, topography in the case of forests, forest type, and forest integrity (contiguous vs. fragmented). Major structural damage to coral reefs and contiguous rain forests after both TCs was patchy, suggesting some degree of larger-scale resistance of these ecosystems to HES events. In the case of littoral forests, small forest remnants, regrowth forests, and riparian forests much lower levels of resistance to high-energy winds were observed, due to patch size and edge effects. Apart from mangroves, most intact ecosystems along the reef-to-ridge gradient have shown early stages of recovery. However, small forests remnants and riparian forests in the agricultural matrix had lower levels of recovery compared with areas of contiguous forest. Anthropogenic climate change may reduce the resistance and resilience of ecosystems along the reef-to-ridge gradient to cope with future HES events, due to increased wind and wave energy, higher storm surges, higher intensity rainfall, and larger river plume events.