Conserving Kakadu

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.

 

Managing such a vast national park is a challenging business. The team at Kakadu National Park work hard to keep the park healthy, control weeds and feral animals, and use traditional burning to guard against wildfire.

Approved plant list for Kakadu residents

To protect Kakadu’s unique environment, it is important that all park residents take special care when buying plants and plant materials for their garden. We ask residents to avoid buying exotic plants which may go wild and take over from native plants and to take care not to allow garden weeds to spread. Gardening material brought into the park may also provide an entry pathway for exotic ants, plant viruses and other pathogens into Kakadu National Park.

Read more about approved plants...

Fire management

Fire has a major influence on the Australian environment and has shaped many of the plant communities we see today. Download Kakadu’s fire management plan.

Before the arrival of non-Aboriginal people, Bininj/Mungguy managed their country with fire.

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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.

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 Kakadu National Park was declared, Bininj/Mungguy and park managers have worked together to reduce the number of hot fires at the end of the dry season - it’s a great example of joint management.

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.

Weed management

Weeds compete with native plants for light, moisture and nutrients and don’t provide ideal food and shelter for native wildlife. This leads to a decline in plant and animal diversity, change in burning regimes, and alter the structure, function and species composition of natural ecosystems.

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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.

Significant resources have been committed to keep weeds under control. Each wet season Parks staff undertake weed control programs within the park and provide support to outstation residents with weed control activities.

Biological control techniques have been used to help control weeds such as salvinia and sida species. All known infestations of mimosa are being managed through regular monitoring and control activities and are considered to be under control.

Mimosa (Mimosa pigra)

Mimosa is a woody shrub from Central America. It can grow up to four metres tall and is considered highly invasive. There are large infestations on the Adelaide River floodplain, the Daly, Finniss and Mary Rivers and on the East Alligator floodplain near Oenpelli.

Mimosa thrives in Kakadu because there are no natural enemies, they grow quickly, produce large amounts of viable seed and are tolerant 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. 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) and 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 decreases.

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 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 manually pulling out small infestations and using herbicides in larger areas.

Estuarine crocodile management

Estuarine crocodile management in Kakadu is aimed at minimising the danger of crocodile attack while at the same time ensuring the protection of crocodile populations. Throughout the year park staff carry out crocodile surveys in all the major waterways to obtain data on distribution, numbers and size.

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If a particular crocodile's behaviour is thought to be a potential threat to people, the crocodile is either captured, tagged and released (a process that makes crocodiles wary of people) or given to an Aboriginal community for food.

The emphasis of Kakadu's crocodile management is to educate visitors about crocodiles and their dangers through brochures, signs and advice.

Feral animal management

Feral animals were introduced in to Kakadu 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.

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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. 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 grass and other plants, competing directly with native wildlife. As they move from one wetland area to another they create 'swim channels'. Where these channels intersect with tidal creeks, saltwater is able to flow 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 buffalo 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.

Pigs

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 then vulnerable to weed infestation—pigs are thought to be the main agents spreading the weed mimosa through the park. Feral pig control work is conducted by park staff regularly.

Horses

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

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.

Dogs

Dogs that have become feral have some impact in that they interbreed with the dingo population in the park, affecting 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

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 affected by cane toads suggest numbers may stabilise after an initial period. No effective control measures are currently available. Cane toads in the park are likely to be one of the most pressing management problems facing Kakadu in the future.