Forty-five years of change on low wooded islands, Great Barrier Reef

Abstract

During the 1928-29 Expedition, centred at Low Isles, Spender mapped the ‘low wooded islands’ or ‘island-reefs’ of Low Isles and Three Isles in detail, and additional information was published by Steers, T. A. Stephenson and others. From this work, two different models of the evolution of low wooded islands were proposed, Spender holding that the islands were in a state of equilibrium resulting from their location on the reef, Steers that they could be placed in an evolutionary sequence. Moorhouse described the results of cyclones at Low Isles in 1931 and 1934, and Fairbridge & Teichert reconsidered the general issues following aerial reconnaissance and a brief visit to Low Isles in 1945. Subsequently, aspects of change since 1928-29 have been studied at Low Isles by W. Stephenson, Endean & Bennett in 1954 and by W. Macnae in 1965. Maps produced since 1929, however, have all been based on Spender’s surveys. In 1973, Low Isles and Three Isles were remapped in detail, and a direct comparison can now be made over an interval of 45 years. This shows changes in island topography, and substantial alteration in the size and location of shingle ramparts which has affected conditions for coral growth on reef flats. Mangroves have extended greatly at Low Isles, but not at all at Three Isles. The implications of these findings for the general models of Steers and Spender will be discussed and related to the Holocene history of the Great Barrier Reefs.

Recent Developments on a Nearshore, Terrigenous-Influenced Reef: Low Isles Reef, Australia

“…1 : 6000 ( Figure 2) from 1928 (photo mosaic, GBRE), 1945 (oblique photographs. Royal Australian Air Force for FAIR-BRIDGE and TEICHERT, 1947TEICHERT, , 1948TEICHERT, ), 1982TEICHERT, , 1991TEICHERT, , 1996TEICHERT, , and 2001 (Australian Beach Protection Authority); (2) 1: 5000-scale maps of the Low Isles Reef surface IFAIKBRIDGE and TEICHERT, 1947;MOORHOUSE, 1936;SPENDER, 1930;STOD-DART et al, 1978); and (3} surface photographs and other data provided in reports (BELL and ELMETRI, 1995;FAIRBRIDGE andTEICHERT, 1947, 1948;GBRE, 1928-29;MOORHOUSE, 1933MOORHOUSE, , 1936STEPHENSON, ENDEAN, and BENNETF, 1958;STODDART et al, 1978;YONGE, 1930). Historical cyclone data for the area (Table 1) are compiled from the Australian Bureau of Meteorology (ABOM) and historical accounts for Low Isles Reef (MOORHOUSE, 1936;STEPHENSON, ENDEAN, and BENNETT, 1958).…”

“…As noted hy STODDART et al (1978), the pattern of expansion in the area originally mapped as the mangrove park corresponds to subtle variations in reef flat topography. Much of the mangrove park area lays an average of 1.2-1.5 m above datum, somewhat higher than the remainder of the reef flat (SPENDER, 1930).…”

The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific

“…At inter-annual to decadal timescales studies have also identified changes in island size and position on reefs (Taylor, 1924;Stoddart et al, 1978;Flood, 1986;Aston, 1995). Umbgrove (1947) and Verstappen (1954) were the first to develop a causal relationship between climate and reef island behaviour invoking medium-term (decadal) shifts in prevailing wind direction and strength and its influence on wave energy as a control on morphological adjustment of islands in Djakarta Bay, Indonesia.…”

Tsunami as agents of geomorphic change in mid-ocean reef islands

“…They are morphologically sensitive to changes in boundary conditions (sea level, waves and currents) at a range of timescales. For example, reef islands are considered prone to widespread destruction in response to future sea-level rise (Dickinson, 1999;Kahn et al, 2002), and have been shown to morphologically adjust to climate variations at interdecadal (Taylor, 1924;Umbgrove, 1947;Verstappen, 1954;Stoddart et al, 1978;Flood, 1986) and seasonal timescales (Hopley, 1981;Kench and Brander, 2006). Extreme natural events can also alter reef island geomorphology and the character and distribution of sediments.…”