Cay - Development and Stability

Development and Stability

A range of physical, biological and chemical influences determines the ongoing development or erosion of cay environments. These influences include: the extent of reef surface sand accumulations, changes in ocean waves, currents, tides, sea levels and weather conditions, the shape of the underlying reef, the types and abundance of carbonate producing biota and other organisms such as binders, bioeroders and bioturbators (creatures which bind, erode and mix sediments) living in surrounding reef ecosystems (Harney and Fletcher 2003, Hart and Kench 2007).

Significant changes in cays and their surrounding ecosystems can result from natural phenomena such as severe El Niño Southern Oscillation (ENSO) cycles. Also, tropical cyclones can help build or destroy these islands (Scoffin 1993, Woodroffe 2003).

There is much debate and concern over the future stability of cays in the face of growing human populations and pressures on reef ecosystems, and predicted climate changes and sea level rise (Kench and Cowell 2003, Hart 2003). There is also debate around whether these islands are relict features which effectively stopped expanding two thousand years ago during the late Holocene or, as recent research suggests, they are currently still growing with significant new additions of reef sediments (Woodroffe et al. 2007).

Understanding the potential for change in the sediment sources and supply of cay beaches with environmental change is an important key to predicting their present and future stability. Despite, or perhaps because of all the debate around the future of cays, there is consensus that these island environments are very complex and somewhat fragile.