Indicator: CO-76 Examples of the impact of climate variability on selected coastal and marine species, habitats or ecosystems


Some species and habitat types may be particularly susceptible to changes of climate, and may provide sentinel indicators for more widespread or less readily detectable changes. Coral bleaching is a particularly visible impact that can be caused by thermal change. Mangrove incursion into terrestrial rainforest or saltmarsh in tropical areas may also be indicative of the pressure of changing climate on ecosystems.

Coral bleaching

Coral bleaching is the whitening of coral colonies due to the loss of symbiotic zooxanthellae from the tissues of polyps. This loss exposes the white calcium carbonate skeletons of the coral colony. Corals naturally lose less than 0.1% of their zooxanthellae during processes of regulation and replacement (Brown and Ogden, 1993). However, adverse changes in a coral's environment can cause an increase in the number of zooxanthellae lost. There are a number of stresses or environmental changes that may cause bleaching including disease, excess shade, increased levels of ultraviolet radiation, sedimentation, pollution, salinity changes, and increased temperatures. Australia is particularly at risk of coral bleaching events.

NOAA provides monthly global data on sea surface temperature variations in areas at potential risk of coral bleaching due to changes in sea surface temperature. See Current Operational Coral Bleaching HotSpots for the year 2006  for details of current operational coral bleaching hotspots for the year 2006.

AIMS has undertaken some analysis of the NOAA coral bleaching data at: Coral bleaching Thermal stress indices 

The data show a distinct correlation between thermal stress and known coral bleaching events in 1997-98.

Further information: Reef Futures 2003, Coral Bleaching, CRC Reef Research Centre: Coral Bleaching 


Data from remote sensing are now available on the extent of mangroves across the Australian continent, and can be monitored in future for changes in extent of these important habitat species. While it may be expected that some loss of extent will occur as a result of habitat removal and modification due to the coastal extension of human settlements, changes in mangrove extent in some places may be directly attributable to climate change.


In south-eastern Tasmania, there are changes in the distribution of kelps, changes in the distribution of sea urchins, and problems with the salmon culture industry that can be related to climate change and, potentially, to other human influences (Edgar et al. 2005, Pittock 2003). These may be associated with the warm East Australia Current moving further south more frequently (Thresher et al. 2004). For example, the dominant mainland sea urchin (Centrostephanus rodgersii) has extended its range southward along the east coast of Tasmania. Concomitantly, macro-algal (kelp) communities have declined.

What the data mean

There have been declines that appear to be directly related to climate change in corals and kelps. Mangrove data have not yet been analysed for trends.

Issues for which this is an indicator and why

Coasts and Oceans - Contributions and pressures between the coasts and oceans and the atmosphere - Climate and carbon dioxide 

Coral bleaching, mangrove incursion into rain forest and salt marsh, and a range of other changes in the population, distribution and condition of selected species, groups of species and habitats may be indicative of the pressure of climate change and climate variability on ecosystems.

Other indicators for this issue:

Biodiversity - Pressures on biodiversity - Climate variability 

Changes in distribution and population of species due to climatic change have implications for biodiversity.

Other indicators for this issue:

Further Information