7 Antarctic environment | 6 Risks to the Antarctic environment
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
At a glance
As in other regions, the key risks to the Antarctic environment are being brought about by human activities often far away, including global population and economic pressures, and the effects of climate change.
While management can mitigate many of the population and economic impacts, climate change will be the main and uncontrollable driver bringing about change.
It is clear that Earth's polar regions are likely to be affected severely by changing climate conditions.6 These changes represent the highest risk to the region, since they are unlikely to be mitigated by any management measures. The impacts of climate change on the Antarctic environment are detailed in Sections 2 and 3 of this chapter.
Population and economic growth are leading to other risks. Remaining fish stocks around the world are highly depleted and appear largely unable to recover. With a growing human population demanding a new source of protein, the pressure on the industry to catch krill is likely to increase. A rapidly expanding krill fishery will have a considerable environmental impact and is a risk, particularly if the fishery expands at a rate that outstrips the ability of CCAMLR to manage it. In the past, the fishing nations that are active in the Southern Ocean had never reached the catch limits set by CCAMLR. However, in the 2009-10 season, the fishery reached the 'trigger level' in one of the subareas in the South Atlantic and the fishery was closed for the first time. Newly developed technology has allowed the vessels to catch about 800 tonnes per day compared with about 400 tonnes landed by 'old style' vessels.31 This advanced fishing technology has contributed to the rise in the krill catch to 210 000 tonnes in 2009-10 and high catch rates may force the krill fleet to expand into new areas to avoid exceeding the existing catch limits.
The consequences of krill fishing continuously operating at the catch levels set by CCAMLR are as yet unknown. The impact of environmental changes on the krill population, such as ocean acidification,228 will also have to be taken into account in the process for calculating precautionary catch limits for Southern Ocean fisheries.
Acidification of the world's oceans is occurring due to several concurrent processes but there is still much uncertainty about how, for example, climate change affects these processes, such as the 'biological pump'. However, it is well established that levels of anthropogenic carbon dioxide are increasing in the atmosphere, transferring 1 million tons of carbon dioxide to the world's ocean per hour.229 For the Southern Ocean, the process of overturning circulation (where deep water upwells and releases carbon dioxide to the atmosphere; see Section 1.1 ) is particularly important. As the atmosphere warms, the warming of surface waters increases stratification and limits gas exchange of this upwelled water with the atmosphere. This in turn causes greater retention of carbon dioxide, allowing more time for respiration of organic matter by marine bacteria. All these processes increase acidification.229 An increasing number of studies are highlighting diverse and sometimes unexpected consequences on marine ecosystems:
- The effects of ocean acidification on the availability of nutrients and the ability of organisms to deposit and maintain exoskeletons of calcium carbonate is compromised. With less calcium in their shells they are lighter and less likely to sink into deeper waters. This reduces the flux of organic material to the deep ocean (the 'biological pump') and increases the amount of carbon dioxide that is respired in the upper water column.230 The overall effect of climate change on the biological pump is influenced by many competing pathways (e.g. photosynthesis, grazing, sinking and respiration); the outcome is currently uncertain but is likely to have severe biological impacts within decades and could dramatically affect the structure and function of marine ecosystems.27,80,196-199 Such changes would have profound effects on ecosystem services, including the productivity of fisheries and the efficiency of the Southern Ocean sink for atmospheric carbon dioxide. These changes are most pronounced in the polar regions where the acidity of the water is changing twice as fast as in warmer, tropical and subtropical regions.
- Growth and survival of fish populations could become impaired in an acidifying ocean. Tropical fish larvae that were exposed to increased levels of carbon dioxide changed their behaviour in a manner that made them five to nine times more prone to predation. Such an increase in mortality can be detrimental to the long-term survival of fish populations.231
- A decrease in the ocean's pH may affect the absorption of sound in the ocean, making the oceans noisier.229,232 Whether this will impact marine mammals - for example in their ability to communicate - is currently unclear.
Human activities are increasing on the Antarctic continent. The human footprint on Antarctica is small compared with the total size of the continent; however, the impacts are not evenly spread. Human activity and associated impacts are concentrated around stations and stations tend to be built on ice-free land close to the sea. This land is also important habitat for the plants and animals of Antarctica. In East Antarctica, most of the sites suitable for building stations are already occupied and one new station is under construction. Currently, 53 research stations house up to 4000 individuals during summer and 1000 during winter.233
Through the Madrid Protocol's indefinite ban on mining activities in the Antarctic Treaty area, the Antarctic region is presently largely immune to the growing global demand for mineral resources. The Madrid Protocol and the Convention on the Conservation of Antarctic Marine Living Resources have so far been quite successful in managing human activities and reducing the impact of the human presence in the Antarctic region. However, as Tin et al.233 concluded when reviewing human impact on Antarctica, 'In the coming decades, the effectiveness of these regimes [the Madrid Protocol and the Convention on the Conservation of Antarctic Marine Living Resources] will be put to the test in the face of the continuing increase in intensity and diversity of human activities in Antarctica'.
Sea level rise through melt and ocean warming
Increased warming of atmosphere, leading to loss of ice cover and changes in sea ice seasonality
Reversal of ozone hole, reducing ultraviolet B radiation but increasing warming
Stronger winds and shift in oceanic fronts bringing warm water toward the ice shelf, leading to increased destabilisation of the ice
Changes in ecosystem structure
Increased illegal fishing, leading to impacts both on targeted and dependent species, as well as bycatch
Breakdown in food web productivity
Increased pollution (water and air)
Increase in commercial fishing activities, leading to impacts on targeted and dependent species
Lack of knowledge of interactions of processes, leading to poor management decisions
Increases in numbers of alien species with subsequent effects on native species and communities
Improved survival of pathogens with subsequent effects on native species and communities
More continental stations, intensifying pressures on local environments
Loss of biodiversity
Loss of keystone species as their physiological limits are exceeded
More extreme weather events due to climate change
Growth of tourism and the consequent increase in environmental impact (highly dependent on oil prices)
Collapse of the Antarctic Treaty System (in the foreseeable future)
Mineral exploitation, leading to disturbance or destruction of the environment
Increased noise levels in ocean due to acidification, potentially impacting the communications of marine mammals
Oil and gas exploration, potentially leading to disturbance or destruction of the environment