In Brief | Antarctic environment
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities
Australian State of the Environment Committee, Authors
(2011 Australian State of the Environment Committee), 2011
This is a summary of Australia state of the environment 2011, which is an independent report presented to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities by the State of the Environment 2011 Committee
The Antarctic environment is showing clear signs of climate change, which is likely to have profound effects on Antarctic species and ecosystems.
The East Antarctic Ice Sheet is losing ice at its coastal fringes—about 60 billion tonnes each year since 2006. The loss is occurring at an increasing rate and may contribute significantly to sea level rise. The upper layers of the Southern Ocean have warmed by 0.2°C since the 1950s. This rate of warming is faster than elsewhere in the world.
The ozone hole has largely protected East Antarctica from global warming.
Over the past half–century, western Antarctic surface temperatures have shown general warming trends with significant regional patterns. The Antarctic Peninsula is warming faster than anywhere else on Earth. In East Antarctica, the lower stratosphere has cooled and changed the atmospheric circulation through the loss of stratospheric ozone. A recovery of the ozone hole will reverse these processes and significantly increase the warming trend in East Antarctica.
The terrestrial ecosystems are changing, especially where snow fall is replaced by rain.
Retreating glaciers (particularly in the subantarctic), higher ambient temperatures and precipitation as rain rather than snow make the terrestrial environment more accessible to plant and microbial communities. A warmer climate and increased availability of liquid water enables their populations to expand and nonnative species to become established.
Antarctic vertebrates are highly specialised to survive in the Antarctic. Whether they can adapt to new conditions due to climate change is currently unknown.
Environmental changes cascade through ecosystems. In the Antarctic Peninsula region, an apparent decrease in the abundance of Antarctic krill has been attributed to the reduction in winter sea ice coverage. This in turn has caused a decrease in Adélie and chinstrap penguin populations. As the rate of environmental change increases, it may exceed the rate at which Antarctic vertebrates can adapt. Warmer waters also enable alien species to extend their range southward. Invading species are likely to outcompete, and perhaps replace, native species. It is likely that some native species will not survive the coming decades.
Increased acidification of the Southern Ocean can affect the base of Antarctic food webs.
Dissolved carbon dioxide acidifies the ocean and reduces the availability of carbonate ions that calcium carbonate shell-making organisms require for calcification, diminishing the ability of these organisms to form shells. Increasing ocean acidity due to increased levels of carbon dioxide is already affecting calcifying organisms—the shells of planktonic organisms known as foraminifera, which are food for many other organisms, are now about one-third lighter compared with pre–industrial times. These types of changes, which affect the base of the food web, can potentially change the dynamics of the Southern Ocean ecosystem significantly.
The pressure of human activities on Antarctica and the Southern Ocean is increasing.
The Protocol on Environmental Protection to the Antarctic Treaty commits signatories to comprehensive protection of the Antarctic environment. Australia has ratified the protocol by establishing legislation to enforce procedures that reduce the impacts of Australians visiting Antarctica and has taken practical steps to reduce the impacts of past activities, such as the clean–up of abandoned waste disposal sites. However, the human footprint in the region is gradually increasing. New stations are still being built; tourism to the continent continues to grow, particularly to the Antarctic Peninsula near South America; and, with a growing world population, commercial fishing activities are likely to increase.
Antarctica is showing clear signs of climate change. The physical and chemical components of the Antarctic environment are changing at an increasing rate. The most rapidly changing region is West Antarctica, particularly around the Antarctic Peninsula, where temperatures have risen by 5°C over the past five decades. Until recently, the environmental variables were thought to be more stable in East Antarctica. However, there is compelling evidence that change is occurring there as well, and while it is currently at a slower rate than in West Antarctica, the rate of change is expected to increase over the coming decades. The complex Antarctic food web is based on vast numbers of marine microorganisms, including bacteria, phytoplankton and zooplankton. Changes to the marine environment, including ocean acidification, will have a significant impact on these organisms, and since they are at the base of the food web, these changes will have profound effects throughout Antarctic ecosystems.
Climate change and warming conditions are also supporting the movement of alien species into the region, where they may outcompete endemic species. For example, there is already evidence that king crabs are expanding their range and are moving south, where they will be a new predator for the local soft–shelled and no–shelled invertebrates. Many subantarctic islands already harbour alien plant species, which often thrive and outcompete endemic species. Many also carry the legacy of introduced vertebrates, such as rabbits or pigs that were released during the sealing years as food sources onto the islands. Rats and mice also abound and can cause havoc among seabird colonies.
Some populations of seals and penguins that were slaughtered in huge numbers in the late 19th and early 20th century have recovered while others, especially the seabirds, still suffer great losses in commercial fishing operations. Most whale species that visit the Southern Ocean are still on the Red List of Threatened Species of the International Union for Conservation of Nature.
Antarctica, as the only continent without a native human population, has been subjected to less pressure from human activities than other continents. However, human presence on the continent still has an effect. Australia operates four permanently occupied Antarctic bases. About 4000 people work on the continent each year, and 53 650 people (including crew) visited Antarctica in 2010–11. Most human activities and environmental impacts are concentrated in the very limited ice–free areas, which impacts species that use these limited areas as important growth and breeding sites. The scale and intensity of human activities continues to increase, with new stations being constructed and tourism growing annually, particularly around the Antarctic Peninsula. Disturbance of habitat and wildlife, the introduction of invasive plants and pollution are all risks linked to human presence. Commercial fishing in the region places pressure on marine species, and the bycatch in illegal, unregulated and unreported fisheries is a significant threat. The extraction of marine resources will not only continue but will intensify in the future. Human activities far away also have an effect on Antarctica. Pollution elsewhere on our planet finds its way even to Antarctica: traces of DDT and its derivatives were discovered in the shells of Adélie penguin eggs in the mid–1960s.
What is most likely to have the most lasting impact in the region is the increasing amount of carbon dioxide produced by human activities across the planet. The Southern Ocean is absorbing vast quantities of carbon dioxide, leading to a change in the ocean's chemistry that has the potential to affect organisms and their lifecycles in a variety of ways. Increased atmospheric carbon dioxide is also producing climate change in the region. The changes will affect the marine and terrestrial ecosystems of the region, probably profoundly, in the coming decades.
Extreme weather events are likely to increase in frequency and perhaps in intensity as the planet warms. Antarctica is known for its high winds and intense storms. However, in certain regions, rain is now occasionally falling where previously it would only snow. These events are also changing the Antarctic environment and may have a long–term effect on biodiversity.
There is still insufficient understanding about how various factors may interact. For example, recent research has discovered a link between the ozone hole and the rate of warming in East Antarctica. While the ozone hole exists, clouds forming as part of the processes that create the thinning of ozone appear to shield the continent from warming. Predictions are that a recovery of the ozone layer will significantly increase the rate of warming.
Antarctic management is of international concern and is primarily regulated through the Antarctic Treaty and the Convention on the Conservation of Antarctic Marine Living Resources. Australia is committed to protecting Antarctica and adhering to all environmental protection measures through the Antarctic Treaty System, and leads efforts in the convention. Australia also plays a significant role in combating illegal, unregulated and unreported fishing in the Southern Ocean. Australia is developing ways to minimise the effects of our Antarctic activities; for example, by cleaning up historical waste tip sites, and developing procedures for remediation of oil spills and protocols to reduce the likelihood of accidental introduction of non-native species.
Research ensures that management of activities is based on sound scientific principles and the best available scientific knowledge. Australia's research in Antarctica and the Southern Ocean contributes to understanding how environmental systems function and how global climate change affects the Antarctic environment. While climate change cannot be mitigated through the management of activities in Antarctica, Australian research is helping to inform strategies to maximise the effectiveness of management of the Antarctic environment and ecosystems. It will also be important to understand the wider implications of Antarctic changes, as the atmospheric and oceanographic processes of Antarctica are important drivers for the weather in the Southern Hemisphere.
At the moment, Antarctica is still in a comparatively good condition. However, the pressures on the continent and the surrounding ocean will increase. Numerous climate change processes are now under way that are likely to alter the physical Antarctic environment in our lifetime. The rate at which the physical environment of the region is changing appears to be faster than the rate at which organisms, especially those of a higher order, can adapt to the changes. Ecosystems and species populations will be affected. Organisms will have to adapt or they will disappear. Although many uncertainties still exist, some populations are already changing in size. Not all populations are decreasing but, in the long term, they may be outcompeted by species that can adapt to the changing ecosystems, or be replaced by species whose range is now extending from warmer climes into the Antarctic region. The most likely candidates to vanish are those that have adapted to narrow environmental limits, such as emperor penguins, and invertebrates that grow and develop slowly. New fisheries will open as species more adapted to warmer conditions than currently found in the Southern Ocean move south.
Climate change and the future of Antarctica remain topics of intense scientific research and debate as data analysis is still hampered by uncertainties and, in some areas, data deficiencies. Climate change is unlikely to be linear and various regions will be impacted on different scales, as the dissimilar developments in East and West Antarctica already demonstrate. Despite all uncertainties, the risks associated with climate change are significant and deserve our full attention.