GREAT BARRIER REEF
// Outlook Report 2014
9.3.3 Sources, scale and timing
The identified threats to the Region’s ecosystem and heritage values arise from a number of sources and are highly variable in both scale and timeframe. A better understanding of the individual threats is gained by linking them to their likely causes — the influencing factors identified in Chapter 6, including each of the direct uses — and by grouping them according to the likely timing and extent of their effect (Figure 9.3). Some of the threats identified as highest risk are affecting the ecosystem and heritage values at a broad, often Region-wide, scale and are happening now (for example, the very high risk threats of sea temperature increase and nutrients and sediments from land-based run-off). Of the very high risk threats, ocean acidification and sea level rise are predicted to show major effects over a longer timeframe (within 10 to 20 years, see Section 6.3), although their effects are already beginning to be documented. The risks associated with a changing climate are likely to increase in the future due to emissions trajectories and an unavoidable lag effect where future change is locked in by past emissions. The threats that are more localised in their effects are generally rated as having a lower risk and are generally associated with direct use of the Region. Nevertheless, some risks associated with some threats remain high at local or regional scale, as is the case for pesticide run-off.9
The highest risk threats are on a Region-wide scale; most are already having an impact.
Coral bleaching is one of the effects of increases in sea temperature
9.3.4 Highest risk threats
Based on assessments of the 41 identified threats (Figure 9.1 and Figure 9.2), 10 threats present a very high risk to the Region’s ecosystem and heritage values. A further eight and nine threats present a high risk to the Region’s ecosystem and heritage values, respectively. The threats assessed as very high and high risk (grouped by influencing factor) are: • climate change — sea temperature increase; altered weather patterns; ocean acidification; and sea level rise • coastal development — clearing and modifying coastal habitats; artificial barriers to flow; and disposal and resuspension of dredge material • land-based run-off — nutrients from run-off (including its links to outbreak of crown-of-thorns starfish); sediments from run-off; pesticides from run-off; and marine debris • direct use — illegal fishing, collecting and poaching; incidental catch of species of conservation concern; marine debris; incompatible uses (assessed for heritage values only); effects on discarded catch; retained take (extraction) of predators; disposal and resuspension of dredge material; and retained take (extraction) from unidentified or unprotected spawning aggregations. Outbreaks of disease, both naturally occurring and introduced, are also assessed as a high risk. Such outbreaks are likely to be an indicator of overall stress in the natural system from the accumulation of impacts arising from many influencing factors. The lack of understanding of the extent and location of many heritage values (for example wrecks and archaeological sites) means that the risks to heritage values associated with dredging, disposal of dredge material and damage to the seafloor in non-reef areas may be underestimated. A direct interaction with relevant activities may cause significant or permanent damage to sites of particular cultural or historical importance. Assessment processes required during permitting of these activities mitigate this risk, but only for identified values.
The highest risk threats arise from climate change, coastal development, landbased run-off and some aspects of direct use.