Coles et al., 2007:

"Results from the DPI&F monitoring programs indicate that at the scale of the GBRWHA, seagrass meadows were in a “healthy” state and have been relatively stable over the past 20 years. However within this overall “stability”, seagrasses have fluctuated, most often as a response to climate and at smaller localized scales there have been some acute event related changes. These fluctuations do not appear to represent long term trends in a particular direction - they are simply fluctuations.

Percent cover from the Seagrass-Watch data set when all sites are combined shows since 1998 a flat trend for inter-tidal coastal seagrass at around a 20% cover level, a decline in recent years in estuary inter-tidal and an increase in percent cover for reef platform seagrasses. The changes that have occurred are likely to be related to exposure at low tide and temperature and drying effects and are unlikely to be long term effects. Similarly across locations where fine scale mapping and monitoring is conducted, there have been decreases in intertidal seagrasses and increases in subtidal seagrasses during dry and hot drought years. The reverse occurred during periods of higher rainfall. Within these overall trends there are some location specific exceptions. Whitehaven Beach shows a marked decline related to anchor damage and a Lyngbya outbreak. This decline at one of Queensland’s premier beaches has been flagged as an issue of concern.

There have also been some gains in area such as at Green Island and Hinchinbrook Island but at least part of that change can be explained by improved technique. In the 20 years we have moved from position fixing errors of nautical miles to GPS fixes of 5-10 m accuracy. There are some notable species changes. Syringodium isoetifolium has colonised Green Island near Cairns since the mid 1980s. Pioneer Bay in the Mackay/Whitsunday region is becoming more Zostera dominated. But these are likely to be normal succession events.

There have been some losses to clamation projects through the coastal development permit process. Townsville Strand and developments at Airlie Beach are examples. The area lost in these developments is approximately 20 ha. This compares with an estimated area of seagrass of between 5 and 6 thousand square kilometres of coastal seagrass and a vastly greater area of deep water seagrass. It is important however to limit clamation of tidal and sub-tidal habitats for coastal development as this continuing trend is always results in a loss, never again and over long temporal periods the losses are cumulative."

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Citation and/or URL

Coles, R., McKenzie, L., Rasheed, M., Mellors, J., Taylor, H., Dew, K., McKenna, S., Sankey, T., Carter, A. & Grech, A. 2007, Status and trends of seagrass habitats in the Great Barrier Reef World Heritage Area: report to the Marine and Tropical Sciences Research Facility, Reef and Rainforest Research Centre on behalf of the Australian Government’s Marine and Tropical Sciences Research Facility., Cairns, Australia

Spatial Coverage

Reef-wide

Temporal Coverage

 Since 1985

Update Frequency

 Ongoing monitoring

Other Information

 None