Human activities in Antarctica are very limited in comparison to other continents. There are no permanent populations living in Antarctica and neither industrial nor agricultural activities occur there. However, although the human presence is quite small compared with the overall size of the continent, human activities are concentrated on small ice-free areas adjacent to the coast, because they are easy to access by ship and they provide a stable surface for building. These ice-free areas are also home for most of the land-living plants and animals of Antarctica.The environmental impacts of human activities are concentrated in these areas, and impacts include disturbance to the landscape and contamination with pollutants.

Australia operates three permanently occupied research stations on the Antarctic continent (Casey, Davis and Mawson), as well as a station at Macquarie Island, and uses various ships and aircraft to transport people and goods to and from the stations.

Operational indicators

Under Article 17 of the Protocol on Environmental Protection to the Antarctic Treaty (Madrid Protocol), all parties are required to provide an annual report on steps taken to implement the protocol. To help monitor and manage the ways in which the Australian Antarctic program interacts with the Antarctic environment, the Australian Antarctic Division established a set of operational indicators. A number of these are discussed below. Annex III to the protocol outlines minimum requirements for waste disposal and waste management practices in the Antarctic, and this forms the basis of the division's waste management practices.

The operational indicators provide information about the actual or potential impacts of Australian Antarctic program operations on the Antarctic environment. The number of people present at or near the stations and on the ships is recorded monthly and reported annually (Figures 7.8 and 7.9). This provides a measure of the human pressure on the natural environment. Population sizes vary among the stations, between seasons (summer versus winter) and with year, depending on the research and building and maintenance requirements.

In the most recent decade, the winter populations on stations ranged from 14 at Macquarie Island to 25 at Davis Station. Since the rodent and rabbit eradication program began in 2010, the winter population has more than doubled at Macquarie Island. In 2011, there are 40 personnel on the island. Davis Station, where a variety of research, maintenance and building programs occur, has had the largest population over summer for many years, of up to 100 personnel.

The Australian Antarctic Division operates ships only from mid-October until April the following year. Winter travel by ship is impossible because of the extensive sea ice. Voyages have different purposes, such as deployment and retrieval of personnel, resupply of stations and marine science research. The ice breaker RSV Aurora Australis caters for all these purposes. However, supplying four stations in a timely manner with one vessel has proven to be a challenge. Hence, personnel may be deployed, for example, via tourist vessels that visit Macquarie Island. Occasionally, vessels larger than the Aurora Australis are chartered for a particular task, such as removal of waste (Box 7.7, p. 520).

Waste treatment and disposal

Waste treatment and disposal are a measure of human impact. The stations produce liquid waste comprising human waste, waste from kitchens and bathrooms, and limited volumes from workshops. Contamination of the latter is usually minimal as it is cleaned of oil before discharge into the sewage system. Wastewater effluent is discharged directly to the sea adjacent to the stations.

At Davis Station and Macquarie Island, sewage is macerated and released. Maceration is the minimum level of sewage treatment required under the Madrid Protocol. At Macquarie Island, sewage is discharged into a high-energy environment where the macerated particles are quickly diluted and dispersed. The wastewater treatment plant at Davis ceased to function and was removed in 2005. In the summers of 2009-10 and 2010-11, the Australian Antarctic Division investigated the potential impacts of sewage on the marine flora and fauna. Once available, the results of this research will inform decisions about future waste treatment options.

At Casey and Mawson stations, treatment plants process the sewage before it is released into the ocean. One of the measures used to assess waste treatment is the 'biological oxygen demand', which indicates how efficiently the stations' waste treatment plants remove organic matter from the sewage and how much organic matter is being released into the ocean. The quantities of suspended solids are also measured. Suspended solids indicate how efficiently the waste treatment plants break down organic matter, as well as the amount of organic matter that is released into the ocean as a result of human occupation (Figure 7.10).

In 1991, the parties to the Antarctic Treaty introduced the Madrid Protocol. Waste is minimised wherever possible; for example, by reducing packaging-goods delivered to Antarctica are contained in minimal packing, and substances such as washing powders and dishwashing liquids are biodegradable. Most rubbish and material no longer required are collected and returned to Australia (Figure 7.11) where they are reused, recycled or disposed of. Waste typically includes battery acid, laboratory chemicals, sewage sludge, paint, oil, paper, glass, aluminium, plastic (PET and HDPE), steel, copper, brass and building materials. Some waste, such as kitchen scraps and soiled food wrappers, is incinerated, resulting in exhaust emissions to the environment. For example, burns containing plastics generate hydrogen chloride; toxic gases, such as toluene, sulfur dioxide and chlorobenzene can also be generated. The ash may contain heavy metals.¹⁷² Australia aims to reduce the amount of materials incinerated on the stations, either by reducing the amounts of certain materials sent to the stations, or by diverting materials from incineration to reuse or recycling. Ash from the incinerators is returned to Australia. Data collected on waste levels enable the evaluation of the environmental impacts of operational and scientific activities, and the extent of community adoption and the economics of recycling.

Waste is returned by ship usually during the stations' resupply. How much waste is returned to Australia each year is highly variable and dependent upon the availability of cargo space on the ship. When necessary, vessels are hired especially for the purpose of returning waste; for example, in 2010-11 for the clean-up of the tip site in the Thala Valley (Box 7.7, p. 520).

Fuel usage

The quantity of fuel used by generator sets and boilers at all stations is recorded because the environmental impact of the emissions released from power generation and heating is proportional to the amount of fuel used in Antarctica. Special Antarctic blend (SAB), a light diesel fuel blended especially for cold climates, is used at the stations to power the stations' generator sets, to provide heat through boilers, and to run plant and equipment including the station incinerators and vehicles.

The quantity of fuel used to generate heat and electricity is a reflection of the efficiency of various electrical and heating systems and is also affected by energy saving strategies, the number of people on the station and the amount of heat and lighting required, which varies with ambient temperature and daylight hours. The need for electricity increases from summer to winter although fewer people occupy the stations (Figure 7.12), because current station designs mean that buildings are unable to be closed down during winter, even though some may be little used. A range of initiatives have been introduced to reduce fuel consumption wherever possible. The living areas are kept at 19 °C during the day and 16 °C at night. Those buildings that are connected to the general site services are kept warm using heat created by the generators in the powerhouse and only a few small buildings have their own electrical heating systems. Fuel-efficient 'cold pump' technology is being used for the long-term storage of perishable food. At Davis Station, air-to-air heat exchangers are used to pre-warm fresh air brought into buildings without introducing cold. At Mawson Station, two wind turbines were installed in 2003 to generate electricity (Box 7.6) and a 'smart grid' is being installed to regulate power use.

Fuel use by vehicles is also measured and reported. There are differences in vehicle use in summer and winter (Figure 7.13). During winter, vehicle use tends to be less than in summer-populations at the stations decrease to about 20 people or fewer and vehicles are generally not used in inclement weather. In summer, the station populations increase dramatically and with it maintenance, building and scientific activities. Since the introduction of the airlink, the fuel use at Casey Station has soared in summer and far exceeds fuel consumption at the other stations. Vehicles are required to prepare the ice runway and also to transport people between Wilkins runway (on the plateau behind Casey Station) and Casey Station. During winter, the fuel use at Casey Station is similar to that at the other continental stations. At Macquarie Island, vehicle use is largely limited to the station surroundings on the isthmus.

The quantity of fuel used by ships travelling to Australian Antarctic stations and on marine science voyages differs with variation in shipping demands between years. Marine gas oil (MGO) is a marine version of normal diesel and is used on the vessels to power the main engines and generator sets, to provide propulsion and general services to the vessels, such as power and heating. IFO 40 (RMC 10) is a light-grade fuel oil used by some of the Australian Antarctic Division vessels. This fuel is used for the main engines, and in some cases the generators.

Aircraft operations

In September 2005, the Australian Antarctic Airlink between Hobart and Casey Station was launched. The maintenance of the Wilkins Aerodrome requires about 10 000 litres of SAB per week (Figure 7.14). The Australian Antarctic Division uses an Airbus A319-115LR for transport between Australia and Antarctica. This airbus was selected in part because it has sufficient range for a return trip from Hobart to Antarctica without refueling in Antarctica. This avoids a range of potential environmental risks associated with the transport, handling and storage of large volumes of jet fuel. Two smaller, ski-equipped CASA 212-400s are used for intracontinental activities in summer. Each summer, there are also two to three single-engine Eurocopter AS-350 helicopters. When required, long-range helicopters (e.g. the Sikorsky S-76) join the fleet to support a variety of biological, glaciological, geological and operational programs. The helicopters also link Davis Station and the Davis Plateau ice airstrip some 20 nautical miles from the station, where the fixed-wing aircraft land when the sea ice runway no longer exists, and provide helicopter services from the icebreaker Aurora Australis.

Contaminated sites and pollution

In the AAT, contaminated sites are largely a relic of the past (before the Madrid Protocol in 1991) when nonburnable rubbish was dumped at various locations near the stations, or was disposed of by leaving it on the sea ice until it broke out. The old rubbish sites contain a variety of materials, including wood, assorted metals and batteries, and hydrocarbons such as fuel oils and lubricants. Because of past practices of dumping on the sea ice, this waste material is in both the terrestrial and nearshore marine environment. Some contaminants are known to be present in quantities that are hazardous to the environment and although they might be frozen in place for much of the year, they can be dispersed and transported away from the dump site into the surrounding environment; for example, by the flush of melt water that occurs each summer as the winter snows retreat. Studies have shown that hydrocarbons have accumulated in the sediment of bays near Casey Station.^176-177

The largest potential source of new pollution is the very large quantities of fuel that provide power for stations and vehicles. There is always the risk of oil spill when transporting or storing fuel and this is particularly so in Antarctica, where the climate makes all operations more difficult. Land-based fuel spills, some as large as 90 000 litres, have occurred either through mechanical failures or human error during refuelling or transfer from ship to shore (J Stark, Australian Antarctic Division, pers. comm., April 2011). Occasionally, fuel storage tanks have leaked during winter and the leaks have gone unnoticed until the summer melt reveals that they have drained their contents. Today, all tanks are bunded; that is, the tanks are surrounded by a secondary containment that restricts dispersion of fuel should a leak occur. Hence, the environmental damage is reduced or avoided altogether.

Before a site can be cleaned, it needs to be assessed to determine whether clean-up can be achieved without creating more environmental harm from the disturbance of the site. Chemicals present are identified and their concentrations determined. Currently, a number of tip sites and old fuel spill sites are at various stages of assessment and several fuel spills are being remediated (T Spedding, Australian Antarctic Division, pers. comm., April 2011). Research is also being carried out to determine the maximum possible concentrations of chemicals that will have no measurable impact on the environment-this type of information is commonly used elsewhere in the world as targets for remediation works but, until now, site-specific, risk-based remediation end points have not been available for the Antarctic environment.

Despite the large distances that separate Antarctica from the rest of the world, pollution generated elsewhere on Earth can also travel to Antarctica by air or water. Some persistent organic pollutants, such as the insecticide DDT, can be selectively transported to the polar regions through the process known as global distillation. This process occurs when volatile chemicals evaporate in the warmer places in which they are used and condense in colder places.

The persistent organic pollutants that reach Antarctica by long-distance transport are not yet known to be present in the region in sufficient quantities to cause environmental damage; however, these chemicals do not occur naturally and have toxic properties that can be hazardous to organisms. Antarctica provides an important site for monitoring global background levels of known contaminants that are controlled by the Stockholm Convention on Persistent Organic Pollutants, and also serves as an early warning of the global environmental build-up of new and emerging contaminants.