The building of the North Australia Railway line helped the mining camps, and places such as Burrundie and Pine Creek became permanent settlements. The mining camps and new settlements drew many Aboriginal people away from Kakadu. No Aboriginal people are known to have worked in the mines but their access to alcohol and other drugs had a huge impact.
Small-scale gold mining began at Imarlkba, near Barramundi Creek, and Mundogie Hill in the 1920s and at Moline (previously called Eureka and Northern Hercules mine), south of the Park, in the 1930s. The mines employed a few local Aboriginal people.
In 1953 uranium was discovered in the South Alligator River valley. Thirteen small but rich uranium mines operated in the following decade, at their peak in 1957 employing over 150 workers. No Aboriginal people were employed at any of these mines.
Early in the 1970s large uranium deposits were discovered at Ranger, Jabiluka and Koongarra. The Australian Government began an inquiry into land use in the Alligator Rivers region. The Ranger Uranium Environmental Inquiry (known as the Fox inquiry) recommended that mining begin at the Ranger site. It also said that Jabiluka and Koongarra sites should be developed, and that a town be built to support the mines.(Fox et al. 1976, 1977). The Ranger mine and the service town at Jabiru have had many impacts on Aboriginal people. Aboriginal people have different opinions about mining.
Kakadu is in the tropics, between 12° and 14° south of the Equator. The climate is monsoonal,
with two main seasons: the dry season and the rain season. The 'build up' describes the change between the dry and the rain. During the dry season (from April/May to September), there are dry southerly and easterly trade winds. Humidity is relatively low and rain is unusual. At Jabiru, the average maximum temperature for June-July is 32 °C. During the 'build up' (October to December) conditions can be extremely uncomfortable with high temperatures and high humidity. However, 'build up' storms are impressive and with many lightning strikes. At Jabiru the average maximum temperature for October is 37.5 °C.
The rain season (January to March/April) has warm temperatures and rain. Most of the rain is caused by monsoonal troughs formed over Southeast Asia. Sometimes tropical cyclones cause very heavy rain over small areas. At Jabiru, the average maximum temperature for January is 33 °C. Annual rainfall in Kakadu National Park ranges from 1,565 mm in Jabiru to 1,300 mm in the Mary River region.
The Aboriginal people, the Bininj/Mungguy, named as many as six seasons in the Kakadu region:
Periods of torrential rain and long dry spells mean that Kakadu can change its appearance according to the season, so is a place deserving of more than one visit.
Kakadu has more than 2000 plant species, because of the different geological areas, landforms and habitats. Kakadu is also said to be one of the most weed free national parks in the world.
The different geographical areas of Kakadu have their own specialised plants. The area called ‘the Stone Country’ has ‘resurrection grasses’ that are able to survive extreme heat, and dry conditions followed by periods of heavy rain. Monsoon forests often develop in the cool moist gorges found in the stone country. The southern hills and basins support several endemic plants that are only found in Kakadu such as "Eucalyptus koolpinensis" near Jarrangbarnmi (Koolpin Gorge). Lowland areas form a large proportion of Kakadu National Park and are mainly covered in eucalypt-dominated open woodland with the ground layer consisting of a large range of grasses including spear grass, sedges and wildflowers.
The floodplains, which are flooded for several months each year, feature sedges such as spike rush as well patches of freshwater mangroves (itchy tree), pandanus and paper bark trees (Melaleuca). Varieties of water lilies, such as the blue, yellow and white snowflake, are commonly found in these areas. Estuaries and tidal flats are populated with varieties of mangroves, in fact 39 of the 47 Northern Territory species of mangrove are found in Kakadu. These are important for preventing erosion of the coast. Mangroves serve as feeding and breeding grounds for many fish species including the barramundi.
On the tidal flats behind the mangroves, hardy succulents (samphire), grasses and sedges grow. Isolated pockets of monsoon forest grow along the coast and river banks. These forests contain several impressive trees, among them the banyan fig, which can be recognised by its large, spreading aerial roots, and the kapok tree, which has a spiny trunk, large, waxy red flowers and pods full of cotton-like material.
The different areas of Kakadu National Park support a huge number of animals, a number of which have adapted to particular habitats. Some animals in the Park are rare, endangered, vulnerable or endemic. Because of the extreme weather conditions experienced in the Park, many animals are active only at particular times of the day or night or at particular times of the year.
About 62 mammal species have been seen in the Park. Most of them live in the open forest and woodlands and are nocturnal, making it difficult to see them. Others, such as wallabies and kangaroos are active in the cooler parts of the day and are easier to see. The larger mammals are Dingos, Antilopine Kangaroos, Black Wallaroos, Agile Wallabys, and Short-eared Rock Wallabys. Smaller common mammals are northern quolls, brush-tailed phascogales, brown bandicoots, black-footed tree-rats, and black fruit bats. Dugongs are found in the coastal waters. However, recent surveys have shown smaller numbers of nearly all mammals throughout Kakadu. This includes once common and widespread species such as northern quolls.
Kakadu’s many habitats support more than 280 species of birds. This is about one-third of Australia’s bird species. Some birds range over a number of habitats, but many are found in only one environment.
To date, 123 species of reptiles have been found in Kakadu. Being cold blooded, these animals need heat from an external source such as the sun to control their body temperature. This is not to say that reptiles are active only during the day; in fact, few snakes can withstand Kakadu’s midday heat and most are active at night.
Two species of crocodile live in Kakadu: the Freshwater Crocodile ("Crocodylus johnstonii") and the Estuarine, or Saltwater Crocodile ("C. porosus"). Freshwater Crocodiles have a narrow snout and a single row of four large boney lumps called ‘scutes’ immediately behind the head. Estuarine Crocodiles do not have these scutes and their snout is broader. The maximum size for a ‘freshie’ is 3 metres, whereas a ‘saltie’ can exceed 6 metres.
Kakadu’s 25 frog species are extremely well adapted to the region’s climatic extremes. Many remain dormant during dry times. At the start of the wet season, when the billabongs and swamps start to fill with water, the night air is filled with the sounds of frogs such as the northern bullfrog and the marbled frog. As the water builds up, frogs and tadpoles have plenty of food, such as algae, vegetation, insects, dragonfly nymphs, and other tadpoles. Not all of Kakadu’s frogs are found in the wetlands: many live in the lowland forests.
Fifty-one species of freshwater fish have been found in Kakadu’s waterways; eight of them have a restricted distribution. In the Magela Creek system alone, 32 species have been found. In comparison, the Murray–Darling river system, the most extensive in Australia, now supports only 27 native fish species. Although introduced fish have been found in most Australian waterways, none have been recorded in the Park.