Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Dr Jann Williams, RMIT University, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06749 3
Biodiversity Issues and Challenges (continued)
Disturbance Regimes and Biodiversity (continued)
Impacts of pollution on biodiversity [BD Indicators 5 and 20]
The release of pollutants into the environment can kill organisms outright, change the biogeochemical conditions and processes occurring within a system and result in systemic changes that degrade habitats and make ecological processes dysfunctional. Biodiversity associated with sites intensively used by humans may be most at risk, although the non-point based effects of pollution on biodiversity such as downstream water pollution and downwind air pollution can be significant. Urban stormwater may contain high levels of contaminants such as faecal bacteria, nutrients, chromium, cadmium, lead, nickel, hydrocarbons and chlorinated hydrocarbons. In rural areas, irrigation run-off from farming activities may sometimes contain insecticides, fertilisers and herbicides that have been applied to crops. This run-off may affect aquatic and marine organisms living in the catchment and its associated estuaries and in-shore marine ecosystems.
Sediments and nutrients from urban effluent and agricultural chemicals are known to be polluting the inshore reefs of the Great Barrier Reef World Heritage Area, killing coral, encouraging the growth of sessile algae and changing the energy balance and dynamics of marine ecosystems (Wachenfeld et al. 1998). Increased sediment loads lead to muddier systems with less light for bottom communities and disturbance to benthic fauna as a result of siltation. Sediment and nutrient delivery to the Great Barrier Reef from land-based discharges (sources) has increased four-fold in the last 140 years. For the central reef system, 39% of all nitrogen and 52% of all phosphorus originated from river inputs, while sewage discharges accounted for 2.3 and 7.7% of nitrogen and phosphorus, respectively (Figures 31 to 34).
Figure 31: Increase in the human population in the Great Barrier Reef catchment area, 1900 to 1990.
Source: Queensland Year Book (1998)
Figure 32: Increase in the use of nitrogen fertiliser in the Great Barrier Reef catchment area, 1910 to 1990.
Excess fertilisers can cause run-off that may affect aquatic and marine ecosystems living in the catchment and associated estuaries and in-shore marine systems.
Source: Pulsford (1996)
Figure 33: Decrease in the area of native vegetation in the lower Herbert Catchment in northern Queensland from pre-European times to 1996.
Source: Johnston et al. (1998)
Figure 34:Increase in the total area of sugar cane (Saccharum spp.) harvested in Queensland, 1870 to 1990.
Intensive land use such as sugar cane requires the broad-scale clearing of native vegetation and this activity can threaten or destroy biodiversity.
Source: Queensland year books, compiled from many different years
Soil loss that results in sedimentation and a reduction in water quality may also affect aquatic and marine biodiversity. Much of the estimated four-fold increase in sediment on to the Great Barrier Reef has occurred during the last 40 years. This loss results from land uses such as grazing, cropping and urban development that are being undertaken on an unsustainable basis (see Pollution sources on the Great Barrier Reef catchment). During cyclones, sediment plumes have been recorded at least 100 km offshore. Non-lethal sediment loads may become lethal if the nutrient levels are also elevated (Wachenfeld et al. 1998).
Potential effects of pollutants on ecosystems include changes in the abundance of species, interruption to energy and nutrient flows, modification of habitats, reduction in soil, water and air quality, and changes to the stability and resilience of ecosystems. Where species consumed by humans are affected by pollution, there is the potential for serious human health problems. The release of total nitrogen and phosphorus into the environment results in many changes including the likelihood of more frequent and intensive algal blooms in waterways. The dominant release of nitrogen across the Murray-Darling Basin is from unimproved pastures (45% of total aggregate emissions of nitrogen) and cropping (31%), while cropping provides the source of over 50% of phosphorus emissions.
Pollutants can act synergistically to cause uncertain long-term effects on biodiversity. Examples of these interactions can be observed in western Tasmania where acid run-off and acid rain has killed mountain vegetation and affected aquatic ecosystems (e.g. 'dead' sections of river systems such as the Queen and King Rivers). These effects are compounded by the cyclical nature of ecosystem processes, which disperse pollutants widely from their sources and may affect biodiversity at considerable distances in a variety of surprising ways. One reason that mining uranium in Australia remains controversial is the potential effect of these operations on unique environments such as the wetland ecosystems of Kakadu National Park. This is despite two decades of research and monitoring that has not revealed any significant environmental impact on the Park from uranium mining (see Uranium and biodiversity).
Uranium is a naturally occurring, radioactive element that is capable of nuclear fission and is used as a source of nuclear energy and for nuclear weapons. Naturally occurring isotopes of uranium have half lives ranging from 4.5 billion years to 250 000 years. About 99% of uranium is in the form of U-238, which has a half life of 4.5 billion years. Mine tailings contain uranium ore with the uranium removed - the remaining radionuclides have a half life of 77 000 years. Uranium and its decay products give off alpha, beta and gamma radiation. This radiation can cause lethal genetic mutations and kill living organisms.
Uranium is mined at three locations in Australia, including the Alligator Rivers Region of the Northern Territory in which lies Kakadu National Park. Surrounded by Kakadu, Ranger Uranium Mine has been operating for 20 years. Uranium mining is controversial from an environmental and biodiversity protection perspective because of the perception of potential accidents that could occur at all stages of the nuclear fuel cycle, including the storage and disposal of various levels of radioactive wastes. Most uranium mining occurs in remote areas of the country that are considered to be of value as wilderness. During the milling of uranium ore, the uranium is removed from the crushed rock and concentrated for transport, but other radioactive substances are left in the residue, which is referred to as tailings. Initially, about 85% of the original radioactivity present in the ore is discarded in the tailings. After several months, the level of radioactivity in the tailings decays to about 70% of that originally present in the ore. The tailings then decay with a half-life of around 77 000 years. Safe management of all stockpiles and mining wastes is essential to prevent release of contaminants and ensure proper protection of the environment.
Uranium mining has attracted considerable attention since 1996 as a result of proposals for new mines (e.g. 11 identified deposits in Western Australia) and the use of remote, arid regions of the country for storage of radioactive waste. For example, during January 2000, the Commonwealth Department of Industry, Science and Resources was conducting drilling and other investigations of six potential sites for storing radioactive waste around Woomera (SA). One concern is that if radioactive waste were to be held at these sites, it may leak into the underground water and find its way into aquatic ecosystems, mound springs and the terrestrial food chain.
The Jabiluka Uranium Mine, 25 km to the north of the Ranger mine in the region of the Kakadu World Heritage Area, is controversial. In October 1996, Energy Resources Australia (ERA) submitted a draft environmental impact statement (EIS) for mining uranium at the site. Following the completion of assessment of the EIS and a Public Environment Report for alternative development options at Jabiluka, the Minister for the Environment found that there did not appear to be any environmental issue that would prevent either alternative from proceeding. The Minister made environmental recommendations that were subsequently endorsed by the Minister for Resources and Energy. A principal requirement was that all mill tailings would be returned underground to the mine void and to specifically constructed stopes or silos instead of tailing pits as proposed by ERA.
During October and November 1998, a mission from the World Heritage Committee visited the region and site to assess any ascertained or potential threats to the World Heritage values of Kakadu National Park that might arise from the proposal. Wasson et al. (1998), among others, made a submission to the mission specifying environmental concerns arising from weaknesses in the mine design at the mine site (e.g. geomorphology, hydrology and biology). These concerns included the effect that severe weather events may have on the mine storage facilities, leaching of chemicals from the tailings into the ground water, catchment and surrounding wetlands, effects on the aquatic ecosystems of the region, and the effects of climate change given that the tailing storage must be viable for millennia. The mission reported to the World Heritage Committee noting severe ascertained and potential dangers to the cultural and natural values of Kakadu National Park posed by the proposal for uranium mining and milling at Jabiluka and recommended that the proposal should not proceed. Because the Australian authorities had not had sufficient time to respond to the report, the World Heritage Committee made no firm decision on the future status of Kakadu at the November 1998 meeting. The Committee requested that the Supervising Scientist conduct a full review of the areas of scientific uncertainty. The issues specified were hydrological modelling, prediction and effect of severe weather events, storage of uranium ore on the surface and the long-term storage of mine tailings. The Supervising Scientist's assessment of the Jabiluka project was submitted to the World Heritage Committee in April 1999. The overall conclusion drawn was that the natural World Heritage values of Kakadu National Park are not threatened by the development of the Jabiluka mine and that the degree of scientific certainty that applies to this assessment is very high (Johnston & Prendergast 1999).
An independent scientific panel (ISP) was convened by the International Council of Science Unions (ICSU) at the request of the World Heritage Committee to review the report by Johnston and Prendergast (1999). The ISP report was provided to the Supervising Scientist in May 1999. The Supervising Scientist provided a supplementary report to the World Heritage Centre addressing the issues raised in the ISP review. The World Heritage Committee met in July 1999 and resolved not to inscribe Kakadu as 'World Heritage in danger'. After further investigations, the World Heritage Committee met in November 2000 and decided that the mine and mill proposal at Jabiluka does not threaten the natural values of Kakadu National Park.
The National Pollutant Inventory [BD Indicator 20]
The Commonwealth government supports a National Pollutant Inventory (NPI), an Internet database designed to provide the community, industry and government with information on the types and amounts of selected chemicals being emitted to the environment.
Australian industrial facilities such as petroleum refineries, chemical manufacturing plants and sewerage treatment plants using more than a specified amount of the chemicals listed on the NPI reporting list are required to estimate and report emissions of these substances annually. The location of these facilities is maintained by the NPI and is largely tied to major human settlements (Figure 35).
Figure 35: National Pollutant Inventory (NPI) reporting facilities.
Source: The National Pollutant Inventory reporting facility as at 31 January 2001, Environment Australia
The NPI substance list, compiled by its Technical Advisory Panel, lists 20 substances most hazardous to humans and the environment (Table 37). Mining of coal and metal ores may lead to the production of acid run-off, which can severely pollute water bodies and kill many species.
|1,3 Butadiene (vinyl ethylene)|
|Arsenic and compounds|
|Cadmium and compounds|
|Chromium VI compounds|
|Lead and compounds|
|Oxides of nitrogen|
|Polycyclic aromatic hydrocarbons|
|Total nitrogen (in solution)|
|Xylenes (individual or mixed isomers)|
Source: Environment Australia.
Emission sources for an airshed typically include motor vehicles; solid fuel burning; agricultural-related burning, fuel reduction and bushfire controls; and domestic/commercial solvents and aerosols. Industrial discharges into Cockburn Sound in Western Australia have been associated with massive loss of seagrasses and substantial levels of contamination of sediments and fishes.
Research into the effects of pollution on biodiversity [BD Indicator 20]
The disappearance (perhaps extinction) of frog species in eastern Australia and, indeed globally, is of serious concern. One explanation is the direct and indirect affects of airborne pollutants.
Mann and Bidwell (1999) reviewed environmental toxicology in Australian frogs and noted that few such studies have been carried out on native fauna. They reported that the single largest group of potential chemical pollutants that Australian frogs might encounter are the various pesticides used in agriculture and pest management. Much of the recent work examining the effects of pesticides on amphibians has concentrated on the newer generations of pesticides such as pyrethroids, carbamates and organophosphates, although there has been a resurgence of interest in the older organochlorine insecticides such as DDT because of their persistence in ecosystems and food chains. In particular areas, biological agents such as the chytrid fungi, iridoviruses or predation could also be involved in the decline of frog diversity.
In coastal Queensland, Mortimer (1999) quantified the trace metals, metalloids and pesticide content in intertidal Burrowing Crabs (Australoplax tridentata) and the large Mud Crab (Scylla serrata). Estuaries between Cairns and Brisbane were sampled and residues of dieldrin were found at all locations, and heptachlor epoxide and DDT were recorded at most. Calculations of ambient exposures to organochlorines based on residues in crab tissues indicated that dieldrin exceeded national water quality guidelines for protection of aquatic ecosystems at all sampling locations, but exposure to DDT and its metabolites was below the threshold of concern. Use of DDT, dieldrin and heptachlor is banned in Australia.
The primary former uses of dieldrin included treating crops for the control of root fly larvae, locusts, crickets and grasshoppers; in building and industry to control termites; and to control disease vectors such as cockroaches, fleas and mosquito larvae. Use of dieldrin was progressively restricted from 1973 and banned in June 1994. Heptachlor was used as a soil treatment to control ants and grubs in sugar cane areas; the Banana Weevil Borer (Cosmopolites sordidus) in banana plantations; and to control termites in buildings and other structures. Agricultural use of heptachlor ceased in 1987, but it was still used for termite control in Queensland until June 1995. DDT was used extensively in agriculture to control both crop and livestock pests. It was also used for domestic control of fleas, lice, mites and lawn grubs. Domestic uses were banned in 1973, and agricultural use was progressively restricted until it was banned in 1987. Dieldrin, heptachlor and DDT are extremely hazardous to humans and biodiversity (Table 38).
|Compound||ANZECC water quality
|Corresponding maximum acceptable concentration in crab tissues (mg/kg lipid)||Measured concentration (range of mean values) in tissues (mg/kg lipid) of the Mud Crab (MC) and Burrowing Crab (BC)|
|DDE||14||59||0.029-2.8 (MC); 0.03-2.2 (BC)B|
|Dieldrin||2||0.035||0.026-1.4 (MC); 0.043-5.5 (BC)|
|Heptachlor epoxide||10 (parent compound)||0.0037||0.018-0.62 (MC); 0.042-2.25 (BC)|
AProtection of aquatic ecosystems (marine waters);BConcentration of total DDTs, which are mostly the metabolite DDE.
Source: after Mortimer (1999).
More than 22 million tonnes of oil is shipped in Australian waters each year as tanker cargo, including many ships that pass through or near sensitive marine environments such as the Great Barrier Reef. Although Australia has experienced relatively few oil spills compared with elsewhere in the world, several major incidents during the 1990s (e.g. 1991: Kirki, 17 900 t of oil; 1995: Iron Barron, 325 t; 1999: Laura D'Amato, 80 t) are a reminder of the need for suitable monitoring of shipping standards and transits and the need for a high quality emergency capability. The probability of one or more major spills from tankers could be as high as 37% in any five-year period, and 84% in 20 years (Bureau of Transport and Communications Economics 1999).
Since 1975, an international agreement known as the London Convention (formerly called the London Dumping Convention) has controlled sea dumping internationally. In order to ratify the London Convention, Australia enacted the Environment Protection (Impact of Sea Dumping) Act 1981 which prevents the dumping of some wastes and provides for the regulated dumping of other substances in waters off Australia and its External Territories such, as the AAT, Heard Island and McDonald Islands, Macquarie Island, Norfolk Island, Cocos (Keeling) Islands and Christmas Island. Most permits issued are for the creation of artificial reefs or for disposal of uncontaminated dredge spoil.
Container ship with a cargo of hazardous chemicals, stranded on the Great Barrier Reef.
Source: A Rogers, The Courier-Mail