Threats & Challenges
The world’s marine ecosystems are experiencing a devastating decline in health – 70% of coral reefs are either lost or threatened, only 10% big predatory fish populations like tuna and sharks remain, and accelerating biodiversity loss in threatening the oceans capacity to provide vital ecosystem services such as seafood production and maintaing water quality.
Sometimes in remote, beautiful Tasmania we feel untouched by these pressures, but our marine wildlife and ecosystems also face significant challenges to their health and resilience. Some of the pressures on the marine environment include:
Climate change is having huge impacts on our marine environment, from warming waters, ocean acidification and damaging storm events. In Tasmania we are already experiencing a sea temperature increase three times greater than the global average. This will push some of our native species out of their cool comfort zones and allow other warmer species to invade, changing the ecosystem balance. Ocean acidification will also make it difficult for shelled species like our much-loved rock lobster to form their shells, or the foundation of the oceans food chains, plankton, to survive. This could have catastrophic impacts on the capacity of our oceans to provide us with food as growth rates change, species alter their location in order to reproduce and feed, and the entire food web is upset in the process — that includes us!
Coastal development and land based pollution puts pressure on some of our most sensitive marine environments — estuaries and coasts — through increased nutrients, chemicals, and changing habitats. These are the breeding grounds and nurseries for fish, birds and other species. Their impacts are keenly felt right through the lifecycle and food chains of many species. Over 500 ‘dead zones’ around the world are sucking the oxygen out of the oceans, making it impossible for marine life to survive. The Derwent Estuary in Tasmania is an example of intensive pollution that has required millions of dollars and years of effort to restore, and remains problematic with toxicity levels of some fish still too high to be eaten safely.
Decades of intensive commercial fishing can reduce the populations of targeted fish to very low levels, and have unintended effects on by-catch species. This can degrade habitat and reduce the health of ecosystems by having flow-on affects on other species that rely on them for food or as predators. This challenge isexacerbated by the largely unstudied impacts of recreational fishing, which for some species in some areas, is considered large. In Tasmania, our key fisheries of scallop, abalone and rock lobster were historically over-fished and are still working to bring back populations to sustainable levels.
Introduced and invading species can put ecosystems out of balance and reduce their overall health and resilience to other pressures by overriding native populations and destroying habitats. In Tasmania one of the most notable invading species is the long-spined urchin Centrostephanus rodgersii. This urchin has been wiping out kelp forests and habitats that are critical to healthy ecosystems, economically important species such as rock lobster and abalone, and tourism ventures.
For detailed information and reading suggestions go to our fact sheet: Threats to Tasmania’s Marine Environment.