Geoscience Reference
In-Depth Information
ecosystems into a Four Degree World will result in their rapid loss, with a serious
reduction or elimination of the services that marine ecosystems provide to the
GDP and people of Australia and its regional neighbours.
What will this mean for Australia and its regional neighbours?
Marine resources that Australia and its regional neighbours enjoy will not be
viable in a world that has an average global temperature of 4°C or more. In this
world, coral reefs such as the Great Barrier Reef are likely not be dominated
by corals and will have little resemblance to coral reefs. Regional fisheries will
have collapsed as habitat degrades and ocean fisheries are transformed (Bell et
al., 2011). There is a significant risk that the carbonate scaffolding and archi-
tecture of coral reefs, critically important to biodiversity, fish stocks and coastal
protection, will begin to erode as calcification and the ability of coral reefs to
maintain themselves against physical and biological erosion is vastly reduced.
This will have potentially serious effects on the valuable resources represented
by GBR fisheries and tourism (Hoegh-Guldberg and Hoegh-Guldberg, 2008).
Erosion and inundation of coastal areas will put increasing pressure on coastal
ecosystems such as mangroves, seagrass and salt marsh. Many of these systems
represent important fisheries habitat and their reduction is likely to have
significant impacts on the viability of key fisheries. A similar conclusion can be
reached for Australia's regional neighbours if marine resources and services are
similarly impacted by climate change and ocean acidification (Hoegh-Guldberg,
2000; Burke et al. 2002; Hoegh-Guldberg et al., 2009; McLeod et al., 2010; Bell
et al., 2013).
Similarly, the migration of fish stocks away from where they are found today
presents major challenges for future fishing efforts. Changes to reproductive
timing and the potential mismatch between food resources in the larval stages of
many marine organisms could have profound effects on the energy flow through
marine ecosystems, resonating to higher trophic levels in Australia's marine
ecosystems. At the same time, the migration of organisms to higher latitudes will
potentially increase the risk of encounters with new diseases and novel predators
or prey species. The widespread ecosystem changes being inflicted on Tasmanian
coastal kelp forests by the invasive species, Centrostephanus rodgersii (described
above) illustrate how just one change can have such major impacts on entire
ecosystems and industries. A startling insight into a Four Degree World was given
by the 2010/2011 marine 'heat wave' along 2,000km of the Western Australian
coast, when water temperatures reached 4°C above normal for over 10 weeks
(Wernberg et al., 2011). Widespread die-offs of fish, seaweeds and invertebrates
(e.g. abalone) occurred and many tropical species were reported off the southern
west coast and eastwards towards the Great Australian Bight, including whale
sharks and manta rays that were sighted off Albany. Several fisheries and liveli-
hoods were negatively impacted and adaptation responses were put in place to
maximize recovery, e.g. the abalone fishery in the northern region was shut and
abalone where bought in from unaffected areas to aid stock recovery.
 
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