In 2007, the IPCC stated “warming of the climate system is unequivocal, based on evidence from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level” (IPCC 2007).
The Greenhouse Effect
The ‘greenhouse effect’ is one of many physical, chemical and biological natural processes that shape Earth’s climate. The greenhouse effect plays a major part in creating our warm environment around the Earth’s surface. The atmosphere, consisting primarily of nitrogen (78%) and oxygen (21%), is essentially transparent to incoming (shortwave) solar radiation and to the longwave radiation emitted from the Earth’s surface. Around 30% of the incoming solar radiation is reflected back to space by clouds, aerosols (small particles in the atmosphere) and light coloured regions of the Earth (e.g., covered by snow, ice or desert) and the rest is absorbed by the Earth’s surface and, to a lesser extent, the atmosphere and re-emitted as longwave radiation (see Le Treut et al. 2007 for more detailed explanation; Figure 1). Other constituents of the atmosphere, such as water vapour, carbon dioxide (CO2) and trace gases like methane and nitrous oxide, are largely transparent to the incoming solar radiation but absorb and re-emit longwave radiation.
Australian ocean territory is huge, with a coastline of almost 60,000 km from tropical waters of northern Australia to cool temperate waters of Tasmania. Australia has sovereign rights over around 8.1 million km2 of ocean (excluding Australian Antarctic Territory) and greater than its land area. The Australian mainland is bounded by East Australian Current on the east coast and the Leeuwin Current on the west. These major currents carry warm-water into southern regions and have considerable influence on our marine flora and fauna. To the south, the southern ocean flows from west to east, and connects the Indian, Pacific and Atlantic Oceans.
Australian marine waters
Australia claims the third largest exclusive economic zone in the world, with sovereign rights over around 8.1 million square kilometers of ocean (excluding the Australian Antarctic Territory), greater than its land area of around 7.7 million km2. Australia has a coastline of almost 60,000 km that spans from the tropical waters of northern Australia to the cool-temperate waters of Tasmania.
Australia has highly diverse and unique marine flora and fauna, ranging from spectacular coral reefs in the tropics to giant kelp forests in Tasmanian waters. The species diversity in Australia’s northern waters is very high because it is a continuation of the Indo-Pacific biodiversity hot spot. Although Australian temperate waters have lower species diversity than northern tropical waters, they harbour more endemic species due to their long history of geographic isolation (over geological time) from other temperate regions. Australian waters contain ecosystems that are of international importance, The best-known example internationally being the Great Barrier Reef.
Australia’s marine biodiversity underpins considerable economic wealth, for fisheries and aquaculture amounting to a gross value of $A2.2 billion (2007-08) annually. Marine life also provides invaluable ecosystem services including coastal defence against damaging waves and storms, processing of pollution, oxygen production and greenhouse gas regulation.
Climate variability and change are likely to cause several fundamental changes to plant and animal life in our oceans: (i) changes in distribution and abundance; (ii) faster physiology, earlier timing of life history events such as breeding, and some species moving beyond their thermal tolerances; and (iii) changes in community structure and function (including general productivity). Of particular concern is that impacts of climate change, in conjunction with other human stresses such as fishing, eutrophication and species introductions, could shift coastal ecosystems beyond tipping points and thrust them into entirely new states that no longer function in the same way, and may not provide the ecosystem goods and services that we have become accustomed to.
Responding to climate change requires two platforms: mitigation of impact, through reduction of greenhouse gas emissions; and adaptation to climate change while mitigation gradually occurs. Some of the considerations regarding adaptation options for the natural marine environment are described here. While a range of stakeholders must also adapt to these changes, the focus of this report card is on adaptation options to assist species to cope with climate change.
Natural systems are likely to have limited capacity to adjust to the rate of climate change and its consequences. Increasing the adaptive capacity of species and biological systems increases the coping range before major change occurs. Climate change is just one of several pressures on our marine ecosystems. Other pressures include coastal development, fisheries, tourism, marine pollution, and increased terrestrial pollutant runoff, managing these will help increase the adaptive capacity of our marine biodiversity.