Major Environmental Concerns
Currently, the principal environmental concerns in Antarctica are related to changes occurring at the global level rather than at any originating from human activities within Antarctica itself. Those considered of most significance relate to depletion of the ozone layer and climate change. It is only in the recent past, however, that the Antarctic marine environment was subjected to uncontrolled, unsustainable, and profound disturbances by commercial exploitation of whale and seal stocks, leading to near-extinction of some species. While commercial exploitation is now prohibited, the impacts from this overexploitation are still evident in the marine ecosystem today. In comparison to these changes and the global changes noted, the environmental impacts of human activities occurring within Antarctica today are relatively minor and localized. Yet even these remain of concern because of the high scientific and aesthetic value to be derived by maintaining Antarctica as far as possible in a relatively undisturbed state.
More than 87 per cent of the earth's fresh water exists in a frozen state. The Antarctic ice sheet, together with the fresh-water ice shelves that extend from the edges of the sheet over the sea surface, contain more than 90 per cent of this frozen water (Meier, 1983). If all of this water melted, it would be equivalent to a sea level rise of some 60-72 meters (Drewry and Morris, 1992).
Small changes in the mass of large ice sheets have widely recognized implications for the global climate system and for sea level. The most up-to-date evaluation suggests that the Antarctic ice mass is decreasing (Jacobs and Hartmut, 1996), although further investigation is needed before a reliable statement can be made. The breaking away of icebergs from the edges of the ice sheet is the largest single cause of the reduction (Jacobs et al., 1992), followed by ice shelf melting (Jacobs and Hartmut, 1996).
Recent research on the Antarctic Peninsula has shown that steady ice shelf retreat has been occurring there over the past 50 years (Skvarca, 1993; Ward, 1995; Vaughan and Doake, 1996; Rott et al., 1996). Five northerly ice shelves on the Antarctic Peninsula have retreated dramatically during this period, perhaps in response to atmospheric warming (Vaughan and Doake, 1996). The recent dramatic collapse of the Larsen Ice Shelf implies that after an ice shelf retreats beyond a critical limit it may collapse rapidly (Rott et al., 1996). Ice shelves do appear to be sensitive indicators of climate change and, indeed, long-term warming trends on the Antarctic Peninsula are so large that they appear to be statistically significant (Stark, 1994; King, 1994).
Winter temperatures in the Antarctic fall so low that huge areas of sea are frozen over. This sea ice varies in extent from 4 million square kilometres in late summer (February) to almost five times that area in late winter (September) (Fullard et al., 1990). (See Figure 2.27.)These large seasonal fluctuations, together with the fluctuations in Arctic sea ice, play an important role in global climate by affecting exchanges of energy and water vapour (Wadhams, 1991).
An analysis of global ice cover between 1978 and 1994 detected no statistically significant change in Antarctic sea ice while Arctic sea ice seems to have decreased by 5.5 per cent (Johannessen et al., 1995). However, significant reductions in summer sea ice in the late 1980s and early 1990s in the Amundsen and Bellinghausen seas are consistent with a warming climate west of the Antarctic Peninsula (Jacobs and Comiso, 1993).
The Antarctic is globally distinct in terms of biodiversity, although it is inhabited by a relatively small number of different species. Among the fauna are 120 species of fish, 72 cephalopod (mainly squid) species, and about 50 species of birds, 35 of which breed in the region. What the Antarctic lacks in variety, however, it often makes up for in sheer numbers. There are estimated to be 200 million individual birds, 65 per cent of which are penguins.
There are diverse communities of benthic flora where the bottom of the ocean is too deep to be disturbed by ice. However, few plant species can exist on land in the Antarctic. The terrestrial flora is dominated by lower plants, including 350 identified species of lichen and a green algae that grows on snow and ice, giving the surface a red appearance. Only two species of flowering plant grow south of latitude 60°S.
The marine ecosystem, which contains most of the Antarctic flora and fauna, is characterized by short food chains from phytoplankton through krill to large mammals or birds. These short food chains make the Antarctic marine ecosystem very fragile and susceptible to disruption.
The krill, which occupy a central position in the food chain, are crucial to the stability and sustainability of the Antarctic ecosystem. Krill are tiny, shrimp-like crustaceans found in Antarctic waters. Some 85 species have been identified, the most numerous being Euphausia superba. They form the main food for five species of whale, three species of seals, and 20 fish species as well as squid and bird species. Estimates of the Antarctic krill stock range from 500 million to 750 million metric tons.
Krill attract a large number of whales to the region. As a result, Antarctic waters support a more extensive stock of whales than any other part of the world's oceans. The state of Antarctic whale stocks is of major concern after an extensive period of whale hunting by humans. With the exception of a very few species, there is considerable uncertainty over the numbers of whales of different species and in different geographical stocks. Because of this uncertainty, the International Whaling Commission (IWC), established by the 1946 International Convention for the Regulation of Whaling, only publishes data on species for which there is high statistical probability. Estimates for the late 1980s put the total number of blue whales in the Southern Hemisphere at around 460 and minke whales at around 760,000 (IWC, 1996). Seals, the other major mammalian group in the Antarctic, are estimated to number some 10 million individuals.
No estimates are currently available for Antarctic fish or cephalopod stocks.
Many pollutants originating in the industrial and populated areas of the world are transported to the Antarctic by atmospheric and ocean circulations. They include chlorofluorocarbons, which cause ozone depletion (discussed later in this section), radioactive debris from past atmospheric nuclear bomb tests and accidents, heavy metals, and hydrocarbons. At present, contamination levels are generally extremely low, and the area therefore presents an ideal laboratory for monitoring background pollution in studies on long-range transport of pollutants (Wolff, 1990 and 1995; Cripps and Priddle, 1991). In addition, because the ice preserves a historical record of the atmosphere, ice core studies can reveal global changes in trace gases and in some pollutants such as lead. Studies have indicated, for example, a 10- to 20-fold increase in lead concentrations from pre-industrial times to 1980, followed by subsequent decreases that can be linked to the increasing use of lead-reduced fuels around the world (Wolff, 1990 and 1992; Wolff and Suttie, 1994).
There have also been incidents of local accidental release of pollutants. A case in point was the release of 600,000 litres of diesel fuel into Arthur Harbour, Antarctic Peninsula, as the ship Bahia Paraiso sank in 1989 (Kennicutt and Sweet, 1992). Although isolated to date, such incidents could increase as travel to the Antarctic becomes more popular.
The discovery of the Antarctic ozone hole necessitated a major revision in theories of stratospheric chemistry. While stratospheric ozone loss had been predicted (Molina and Rowland, 1974), the magnitude of the ozone depletion over Antarctica, first identified in 1985 (Farman et al., 1985), was not. During 1978 to 1987, the ozone hole grew, both in depth (total ozone loss in a column) and in area. The growth was not linear but seemed to oscillate within a two-year period (Lait et al., 1989). The hole shrank dramatically in 1988, but in 1989-91 was as large as in 1987. The Antarctic ozone holes of 1992 and 1993 were the largest ever, although this was due in part to natural causes, specifically enhanced ozone-destruction by sulphate aerosols from Mount Pinatubo (WMO, 1995a).
In 1995, the ozone decline started earlier than in any previous year, while the rate of decline was the most rapid on record (WMO, 1995b). Measurements over the South Pole during September and October 1995 showed that there was nearly complete destruction of ozone at altitudes between 15 and 20 kilometres. At the same time, total ozone values over Antarctica were extremely low.
Increased surface solar UV-B, attributable to the depletion of stratospheric ozone, poses a threat to Antarctic ecosystems. UV-B is detrimental not only for primary terrestrial colonizers such as cyanobacteria and algae but also for lichens and mosses, higher plants, invertebrates, and marine organisms (Wynn-Williams, 1994). One study on productivity of phytoplankton in the marginal ice zone revealed an overall decrease of 6-12 per cent where phytoplankton were exposed to increased UV-B concentrations (Smith et al., 1992). While this overall loss is not large, the cumulative effect on the marine community is not yet known. In terms of ecological consequences, the displacement of UV-sensitive species by UV-tolerant ones is likely to be more important than a decline in overall productivity (McMinn et al., 1994).
The growth rates of several major ozone-depleting substances in the atmosphere have now slowed, demonstrating the expected impact of the 1987 Montreal Protocol and its subsequent amendments and adjustments (WMO, 1995a). (See also Box 2.4.) However, a substantial Antarctic ozone hole is expected to occur during every southern hemisphere spring for many more decades as stratospheric chlorine and bromine concentrations very slowly decline and begin to approach the levels of the late 1970s during the next century. Only if the restrictions controlling chlorine and bromine emissions are maintained can we expect the Antarctic ozone hole to disappear.
The Ozone Success StoryThe protection of the Earth's ozone layer is one of the most inspiring stories in the annals of international environmental diplomacy. The thinning of the protective ozone layer poses a great danger to the health and well-being of people and ecosystems around the world; it threatens human skin, eyes, and immune systems, damages plants and animals; and poses unknown hazards to the planet's climate. To halt this thinning, action against a range of highly diverse (and profitable) industrial chemicals is required, chemicals that have helped to bring what are now commonplace products into the homes of millions - refrigerators, aerosol sprays, insulating and furniture foams. The action has brought onto the global stage a vast array of players; scientists, industrialists, and diplomats, all working together in pursuit of a common goal - the protection of the ozone layer. It is a story of painstaking investigations, courageous decisions, hard-fought negotiations, and last minute compromises. And it is not yet over.
This success story of international environmental diplomacy was possible because science and industry, stimulated by the clear objectives of the Montreal Protocol, have been able to develop and commercialise alternatives to ozone-depleting chemicals. The 1995 Vienna meeting marked the end of the initial phase of the ozone regime, which concentrated on identifying ozone-depleting substances, agreeing on control measures, and phasing out substances in industrialized countries. Attention is now turning increasingly to issues of implementation in developing countries and countries with economies in transition, and to dealing with new emerging problems such as the first cases of non-compliance and the growth in illegal trade.