Cay

[7][8][9][10] Over time, soil and vegetation may develop on a cay surface, assisted by the deposition of sea bird guano.

A range of physical, biological and chemical influences determines the ongoing development or erosion of cay environments.

These influences include: Significant changes in cays and their surrounding ecosystems can result from natural phenomena such as severe El Niño–Southern Oscillation (ENSO) cycles.

[13][14] 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.

[15][16] There is also debate around whether these islands are relict features that effectively stopped expanding two thousand years ago during the late Holocene or, as recent research suggests, they are still growing, with significant new accumulation of reef sediments.