Cool fact…
As the only volcanically active subantarctic islands, Heard Island and McDonald Islands have been said to provide a valuable open 'window into the earth'.


Lenticular clouds over Big ben
Lenticular clouds over Big ben. Photo by E. Woehler (Photo: Eric Woehler)

The terrestrial and marine environments of the Heard Island and McDonald Islands (HIMI) Marine Reserve are largely unmodified by human activities.

This has been due to the absence of a local human population, the low frequency of human visitation, care having been taken by visitors to avoid causing damage, and because of the minimal amount of commercial resource activity in the region to date.

This situation is not static and there are a number of actual and potential pressures on the values of the Reserve.

The HIMI Marine Reserve management plan and associated Code of Conduct include comprehensive measures to minimise the environmental impacts of human activities.

What is a pressure?

The term environmental pressure generally describes an aspect of a human activity that exerts influence on the condition of the environment.

Follow the links below for brief summaries of the main pressures on the HIMI Marine Reserve.

Alien species

The human introduction and spread of alien species is a significant threat to biodiversity worldwide and particularly in small, isolated ecosystems such as on islands. Alien species are capable of causing major alterations to the structure and function of both marine and terrestrial ecosystems.

At HIMI, an alien species is defined to be:

A species, subspecies or lower taxon that has been introduced to the HIMI Marine Reserve as a result of human activity in or around the Reserve, or that has arrived in the Reserve by natural means from an area to which it was introduced as a result of human activity.

This means that an alien is a new species that arrives at HIMI having been directly transported there by human activities (in someone's pocket, or on equipment), or having arrived by natural processes (such as wind, seabirds) from a location to which it had been introduced by humans (e.g. from another subAntarctic island group).

A new species arriving at HIMI by natural means from another location where it grew naturally, it is not considered an alien.

There are currently no known alien species on McDonald Island and only four terrestrial species (two plants and two insects) considered as aliens on Heard Island, making HIMI one of the least biologically-disturbed regions on the planet.

While it is difficult to predict species introductions, a wide variety of terrestrial, freshwater and marine species could be introduced to HIMI. Rodents are considered to be the major alien species risk at HIMI, although invasive plant and invertebrate species would also have a huge impact on terrestrial ecosystems.

Other Southern Ocean islands have been exposed to a range of alien species, such as reindeer, cats, rabbits, grasses, insects and rodents. These species have caused significant impacts including the devastation of seabird breeding populations, modification of plant and invertebrate communities, general reductions in biodiversity and local extinctions.

On Australia's other subantarctic island, Macquarie Island, a five year effort was required to eradicate cats. Action has been successful kin 2011 to rid the island of rabbits and rats which had continued to have a heavy impact on the vegetation and nesting habitat of burrowing petrels and albatrosses.

The likelihood of aliens becoming established at HIMI is closely related to the number of individuals introduced and the number of human visits. Human activity at HIMI is expected to continue to slowly increase in line with interest in the region for science, tourism and fisheries.

The chances of alien species becoming established is also likely to increase as the climate in the HIMI region continues to warm.

Physical disturbance

Most of the HIMI Marine Reserve is free from obvious signs of human disturbance, which is rare among subAntarctic islands and is one of HIMI’s greatest values.

Physical disturbance could degrade this value by detracting from the natural visual and wilderness qualities of the HIMI environment, while also having direct adverse effects on landscape features, animal and plant species, habitats and ecosystems.

We may not notice a small track when travelling around our town or suburb, but in a pristine place such as HIMI, where there are no tracks, and relatively little other evidence of past human presence, the smallest physical damage can be obvious.

People moving over land by foot or vehicle, particularly coastal ice-free areas, can cause localised effects such as the compacting soil (affecting plant growth and re-establishment), the direct damage of vegetation (destroying invertebrate habitat), the damaging of sensitive geological features and the disturbance or destruction of cultural heritage sites. Souveniring is also an unacceptable practice, particularly relevant to cultural heritage items.

Physical disturbance may also result from the inappropriate placement of facilities (such as refuges, camping sites, monitoring equipment, survey markers) and from sampling undertaken as part of scientific research.

Wildlife disturbance

Animals in our neighbourhoods may have become used to the presence of humans, unlike the seals and birds at HIMI which live an isolated existence most of the time.

These animals live under very harsh conditions and any disturbance caused by humans getting too close or damaging their habitat can affect their chances of breeding and maintaining their populations.

At HIMI, wildlife colonies are concentrated in the ice-free coastal areas which are also the main areas of human activity. Where these activities and wildlife habitat overlap there is potential, albeit unintentional, for significant localised disturbance.

For example, excavations and the placement of facilities or equipment may collapse or contaminate burrows. Birds in flight may strike structures or guy wires, and the approach of humans either on foot or in a vehicle may also disturb wildlife.

Human activities can disturb all species, and to a varying extent. Different species have different sensitivities, which may also be dependent on their location, the time of year, and the stage of the breeding cycle. Typical reactions to disturbance may include the relocating of breeding habitat, their refraining from breeding, and the deserting of colonies or nests.

Disturbance can increase the mortality rate of young animals from predation, exposure, trampling or disorientation, which reinforces the need to apply caution at all times when around animals.

Marine mammals and seabirds are at risk of colliding with vessels while foraging or migrating in open waters, particularly if vessel sounds and lights attract the animals or mask important natural signals and communications.

Illegal fishing is also known to impact the HIMI region, through direct taking of fish, bycatch of fish, seabirds and seals, loss of fishing equipment and damage to benthic habitat.


Generally defined, pollution is the contamination of soil, water or the atmosphere by harmful substances.

Because the marine and terrestrial areas of HIMI are in a relatively natural state, the introduction of any harmful substances, or pollution, could significantly affect the environment.

Marine pollution

Under Australian law, all shipping is regulated to minimise the environmental impacts of discharged wastes and oil spills. Nevertheless, the potential for marine pollution at HIMI remains, including from debris which has drifted into the region from other parts of the Southern Ocean.

Marine pollution may result from shipping activities in the HIMI region, in the form of fuel or oil spills, sewage and waste water discharge, and from the disposal or loss of rubbish. Major fuel or oil spills would affect water quality and may kill marine animals (seals and penguins), flying birds and may damage critical habitats.

In the unlikely event of a major spill there would be limited capacity to respond except by the vessel causing the incident or another vessel if one is in the area. It is unlikely that most vessels could mount effective response action because of limited resources and hostile sea and weather conditions.

Floating debris is a major hazard. Marine mammals and seabirds attracted to the debris may become entangled, causing restricted mobility, infection, amputation, starvation, smothering or drowning.

Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris is listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). A threat abatement plan to address the issue is under preparation.

Terrestrial pollution

Terrestrial pollution (pollution on land) can also greatly affect the values of HIMI. Such pollution detracts from the scenic and wilderness qualities of the islands and has the potential to adversely affect plants and animals.

Potential sources of terrestrial pollution include human (toilet) waste and grey water (washing water). Disposal of these wastes on land may cause local impacts due to the increased nutrient input (although such impacts are likely to be minimal when compared to the nutrient input resulting from large wildlife colonies). Disposal of such wastes may also represent a disease risk to wildlife.

Spills of hazardous liquids, such as fuels and chemicals, may cause localised but long-lasting soil contamination, degradation of vegetation and invertebrates. Hazardous liquids may also cause harm to wildlife if ingested.

Wind-blown wastes degrade scenic landscape values and, particularly in the case of plastic, may injure, or kill wildlife.

Natural processes

The HIMI environment is highly dynamic, resulting from a range of powerful natural processes.

Biological pressures include the natural arrival and establishment of new species, and the increase or relocation of wildlife populations.

Geological and climatic processes such as volcanism, coastal erosion, glacial retreat and advance, and severe storms can directly alter the landscape, with consequent effects on the plant and animal species living at HIMI.

Volcanic activity at Heard Island could significantly affect plant and animal life on the island itself, and may also affect the benthic habitats adjacent to the island through landslides and deposits.

Natural disturbance to ice-free areas, and the creation of new ice-free areas, may result from landslips, glacial retreat or wildlife trampling.

Increases in wildlife populations (particularly fur seals or king penguins) may lead to trampling of vegetation, eutrophication of waterbodies, competition with other wildlife for breeding sites, disturbance to seabird nesting sites and impacts on the surrounding marine ecosystem through increased competition for food sources, as has been recorded at other subantarctic islands.

Cultural heritage items are susceptible to loss or degradation from natural processes, including from the effects of moisture, wind, wind blown sand and debris and direct disturbance by elephant seals and other wildlife. Coastal erosion also threatens cultural heritage sites, particularly those remaining from the sealing era, many of which were located close to the beaches adjacent to seal colonies.

This page was last modified on 28 February 2005.