Managing such a vast national park is a challenging business. We work hard to keep Kakadu healthy, controlling weeds and feral animals, using traditional burning to guard against wildfire, and constantly seeking the best information through monitoring and research partnerships.
You can help us keep Kakadu in good condition:
Reduce the risk of wildfire
- Make sure your cigarette butts and matches are out and put them in rubbish bins, not on the ground
- Use the fireplaces provided and, if none are provided, clearing the area around your campfire of any flammable material
- Always putting your fire out before you leave
Minimise the spread of weeds
- Check your vehicles, trailers and equipment for weeds before entering the park
- Keep to established roads and tracks, and don't enter quarantine areas
Let's keep Kakadu wild
- Don't feed the animals - it can harm their digestion and make them reliant on humans for food
- Secure rubbish and food scraps in the nearest bin, and keep your food stores safe in your car or an esky
This earth, I never damage.
I look after. Fire is nothing, just clean up.
When you burn, new grass coming up.
That means good animal soon,
might be goanna, possum, wallaby.
Burn him off, new grass coming up, new life all over
Bill Neidjie, Aboriginal traditional owner.
The role of fire has a major influence on the Australian environment and has shaped many of the plant communities we see today.
Before the arrival of non-Aboriginal people, Bininj/Mungguy managed their country with fire. Fires were lit all year round, although mostly in the early dry season. They were lit for many reasons: to make travelling easier; to flush out animals when hunting; to protect food resources such as yams from later fires; to clear around camp sites; to signal to others; and to fulfil spiritual and cultural obligations. These burning practices had the effect of promoting suitable habitats for a range of different plants and animals.
Fires lit by Bininj/Mungguy as they travelled to different parts of the country created a patchwork of burnt and unburnt areas.
With the arrival of non-Aboriginal people, the Bininj/Mungguy population decreased. Many people died of disease, others moved off their land to towns and settlements. With fewer people on the land, less burning was carried out so hot, late dry season wildfires became more common. These hot fires were often large and destructive, changing the distribution of plants and animals .
Each wet season monsoonal rains prompt rapid plant growth. During the dry season the vegetation dries out and large quantities of fuel accumulate. Since proclamation of the park, Bininj/Mungguy and park managers have worked together to reduce the number of hot fires at the end of the dry season.
In the fire-sensitive stone country burning is used to reduce the amount of fuel along creeks. Firebreaks burnt around fire-sensitive communities such as monsoon forest, sandstone heath and mature paperbark forest help to protect the communities from later, hot wildfires.
Early in the dry season firebreaks are also burnt around art sites, buildings, camping areas and other permanent structures. parts of the park boundary are burnt to reduce the risk of fires entering or leaving the park.
In the woodland areas traditional owners and park staff light many cool fires from the ground and the air in the early dry season. This creates a patchwork of burnt and unburnt areas, which breaks up the country, helping to prevent large, destructive wildfires later in the season.
As the floodplains dry out burning is done to reduce fuel loads. Bininj/Mungguy hunting goannas and turtles also light fires on the floodplains late in the dry season.
Research and monitoring are integral to fire management in Kakadu. Much research has already been done at Munmarlary and Kapalga; future research will look at the effects of burning in fire-sensitive communities and in the wet season. Continuing monitoring of the park's fire-management program and its effectiveness involves ground observation, photographic points that show the effect of burning over time, and satellite mapping of fire scars.
Weeds compete with native plants for light, moisture and nutrients and often do not provide appropriate food and shelter for native wildlife. Particularly invasive weeds reduce plant and animal diversity, change burning regimes, and alter the structure, function and species composition of natural ecosystems.
Kakadu remains one of the most weed free conservation areas in Australia. Only a small number of weeds found in the park are considered invasive: mimosa, salvinia, para grass, mission grass, gamba grass, candle bush, calopo, Gambia pea, golden shower, poinciana and coffee bush. Of these, mimosa, salvinia and para grass are given priority for control because of their potential to spread over large areas.
Mimosa (Mimosa pigra)
A Central American woody shrub that under ideal conditions grows up to 4 metres tall and is highly invasive. Large infestations are on the Adelaide River floodplain, the Daly, Finniss and Mary Rivers and on the East Alligator floodplain near Oenpelli.
Factors that contribute to mimosa's success are a lack of natural enemies, a rapid growth rate, production of large quantities of easily transported viable seed, and a tolerance of drought and flood. Unchecked, mimosa forms impenetrable thickets across floodplains.
In Kakadu the threat posed by mimosa was identified early, and prompt action has meant that the park is free of large mimosa infestations-it remains virtually an 'island in a sea of mimosa'. Controlling the plant takes considerable resources: since the 1980s four people have been employed full time in the park to locate and destroy mimosa by pulling out or mattocking small plants and applying herbicides to larger ones.
Salvinia (Salvinia molesta)
Water Hyacinth (Eichornia crassipes)
These noxious weeds were discovered in the Magela Creek system in 1983. The water hyacinth was successfully eradicated but salvinia spread rapidly into other tributaries of the East Alligator River and onto the Magela floodplain. Despite quarantining of the area and cooperation from the public, a new infestation was found in Nourlangie Creek in 1990. During the wet season salvinia is flushed out of Nourlangie Creek into the South Alligator River.
A biological control agent, the weevil Cyrtobagous salviniae, was introduced soon after salvinia's discovery. It effectively controls the weed most years. Towards the end of the dry season the weevil population rapidly decreases because most of the salvinia has been eaten. During a poor wet season, high nutrient levels cause the salvinia to grow faster than the weevil population can regenerate. This results in a blanket of salvinia over the water, but as the weevil numbers increase the salvinia is reduced later in the year.
With the help of the CSIRO Division of Entomology, a Management Plan has been developed to closely monitor the weevil's effect. Floating booms are also used to contain salvinia, and occasionally a low-impact herbicide is used to prevent excessive build-up of the weed and reduce the chance of it spreading further.
Para grass (Brachiaria mutica)
This grass was introduced to the area as pasture grass in the 1930s. Like mimosa, para grass can take over huge areas of floodplain, growing vigorously when grazing pressure is reduced and after burning. The grass is quickly filling in a number of Kakadu's wetlands and threatening wildlife habitats. Biological control is not an option at the moment since para grass is still being promoted as a valuable pasture grass for cattle outside the park. Control involves pulling out small infestations and using herbicides in larger areas.
Feral animals in Kakadu have been introduced by non-Aboriginal people. The animals were once either domesticated or native to another country and now live and breed in the park. Among the feral animals in Kakadu are Asian water buffalo, cattle, pigs, horses, donkeys, cats, dogs, rats, mice, house geckos and European bees. Cane toads were recorded in Kakadu for the first time in early 2001.
The management objective for feral animals in Kakadu is to limit, as far as possible, their adverse effects on the environment while taking into account the views and economic interests of traditional owners.
Buffalo in Kakadu
Asian water buffalo were introduced into northern Australian settlements between the 1820s and the 1840s, as work animals and for meat and hides. As these settlements were abandoned, the buffalo were released and quickly spread across the lowlands of the Alligator Rivers region.
By the 1960s buffalo numbers had reached enormous proportions and the damage they were causing was obvious. Buffalos cause damage in a number of ways. Their sheer size, weight and hard hooves compact the soil and inhibit plant growth, causing erosion. Their habit of wallowing erodes river banks and muddies the water, making it unsuitable for many aquatic plants and animals. They eat large volumes of grasses and other plants, competing directly with native wildlife. And as they move from one wetland area to another they create 'swim channels'. Where these channels intersect with tidal creeks, saltwater is able to move into freshwater swamps, often killing a number of plants and animals intolerant to saltwater.
Buffalo carry tuberculosis, which can be spread to domestic cattle. Because of the severe implications for the export meat industry, the Brucellosis and Tuberculosis Eradication Campaign was established nationwide to eradicate feral cattle and buffaloes from all areas. The Campaign provided funding to reduce buffalo numbers in the park.
The removal of buffalo from Kakadu National Park began in 1979. Of an estimated population of 20 000 buffalo, only a few hundred remain.
The difficult nature of the country and the consequent costs make total eradication almost impossible. The Brucellosis and Tuberculosis Eradication Campaign ceased at the end of 1997. As a result park staff have taken over responsibility for monitoring and controlling the buffalo numbers.
Since the reduction in buffalo numbers, degraded areas have recovered dramatically. There are fewer buffalo wallows, there is clear water in billabongs, there is less salt intrusion, and plants such as red water lilies, grasses and sedge plants - valuable food for native animals - are reappearing.
Other Feral Animals
Pigs cause damage to a broad range of Kakadu's habitats. They degrade the environment around springs and small rainforest patches, especially in the wet season. They also dig up areas in their search for food and compete directly with magpie geese and Aboriginal people for bulbs that grow along the wetland shores. The ground they expose is vulnerable to weed infestation-pigs are thought to be the main agents of spreading the weed mimosa through the park. Park staff control pigs close to known mimosa infestations on an opportunistic basis and feral pig control work is conducted regularly..
Horses are particularly common in the southern woodlands of the park. They spread weeds and damage waterholes by eroding soil and fouling the water. Recent control measures have reduced the number of horses along the Kakadu Highway.
Cats are present in low numbers throughout the park. Casual observations and research from southern Australia suggest that cats' hunting activity is having a detrimental effect on native wildlife. Cats are not allowed to be kept as pets in the township of Jabiru. They are shot by park staff each wet season along floodplain and creek margins. Again, this is done on an opportunistic basis.
Dogs that have become feral have some impact in that they interbreed with the dingo population in the park, changing the dingo gene pool. Jabiru residents are allowed to keep up to two dogs within the confines of the township and park residents can keep dogs at the discretion of the Director of National Parks.
Cane toads were found in Kakadu National Park on 12 March 2001. Cane toads are poisonous throughout most of their life cycle and current information suggests that they will have an initial impact on animals such as snakes, goannas and quolls, who will try to eat them. Evidence from other areas effected by Cane toads suggest numbers will stabilise after an initial period. No effective control measures are available. Cane toads in the park are likely to be one of the most pressing management problems facing Kakadu in the coming decade.