Earthshots: Satellite Images of Environmental Change

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» Wyperfeld National Park, Australia

These images show Wyperfeld National Park, Victoria, in southeastern Australia. The park is native shrubland—the Australian “bush”—and appears in the Landsat images as dark red. Grazing land appears pink, and cropland is a green-yellow pattern. Fires occur in the park almost every year, leaving huge fire scars: bright, bared earth that quickly regrows.

This area’s dry climate lies between wet coastal forest and interior desert. Within these images, the Wimmera River flows from the wetter south to the drier north, where it dies in a chain of lakes. In these Landsat images, the southernmost lake (Lake Hindmarsh) is always filled, the northernmost (Lake Agnes) is always dry, and the middle lake (Lake Albacutya) is wet in 1975 but dry thereafter, having last filled from 1974 to 1982.

Before European settlement, this region was near-forest—shrubs and small trees growing in varying density—with an understory of shrubs or grass. From the 1840s on, much of this bush was burned off to clear land for farming. Forested area (including shrubland) decreased in this region of Australia from an estimated 90% in 1869 to only 30–40% by 1987. Wheat yields in this region were high, so people tried farming even the areas with poorer or sandier soils. Crop failure in these sandy areas gave Wyperfeld the deceptive name “the Big Desert.” These sandy areas can be seen in the Landsat images as sand ridges in the park and as pink areas outside the parks, representing grazing land.

Map of the featured area.

By the late 1800s, some Australians were trying to preserve natural lands, including the nationally symbolic “bush.” The Forest Act of 1907 established forest reserves, some on abandoned homesteads, including part of Wyperfeld in 1909. After the Second World War, the increasingly mobile and urban population desired more parks. In the 1960s, the government proposed a partial development of the “Little Desert” (visible south of the “Big Desert”); in the backlash of public outcry the plan was canceled, the Little Desert National Park was greatly expanded, and a national conservation agency was created.

Wyperfeld National Park now covers 360,000 hectares, with its western half an official wilderness. The park is habitat for black-faced mallee kangaroo, desert hopping mice, 50 species of lizards and snakes, and 250 species of birds including parrots and eagles. Mallee fowl, a rare mound-nesting species almost extinct by the 1950s, also live in Wyperfeld’s vast shrubland.

Much of the park’s vegetation is mallee, a type of shrubland dominated by several sparse, tall varieties of eucalyptus. These eucalyptus have large underground tubers which sprout several stems after a fire, giving the mallee its distinctive look. The vegetation ranges in structure from short heath to tall, open woodlands but is commonly a thick, impenetrable scrub forest. Areas along the river are dominated by river red gum trees, which grow in the wetter soil there, and by black box trees, which grow in the slightly drier soil. These trees act as a natural record of floods, since they germinate in wet soil. The park also has stone-forming fungi, whose rootlike feeding-threads cement the sandy soil particles into underground “stones” of up to 20 pounds. These stones incorporate black rings of ash, forming a natural archive of fires.

Southeast Australia has a history of severe fire problems, with some historic deadly fires such as the Ash Wednesday fire of 1983, and lesser fires almost every year. The state of Victoria averages about 19 large fires (over 1,000 hectares) per year. These fires are often fast like grassfire but more intense. The winter rains that benefit wheat farming also aid the buildup of plant matter, which becomes highly combustible during the dry summers. Perhaps 60% of the fires in Wyperfeld are started by lightning, with the rest from various human accidents and purposes, including fuel reduction. Since the 1950s, Australians have systematically set controlled fires to reduce the risk of dangerous fires later. Wyperfeld staff currently set fuel-reduction fires along the park’s edges but fight all accidental fires, as required by law.

These fires kill individuals, but communities of living things survive. Studies elsewhere in Victoria indicate that 2–4 years after a fire, the forest floor is again littered with small twigs and leaves, the habitat for many small animals. There are more plant species in the area than before the fire, though frequent burning certainly can kill out some species. Forest studies show that different post-fire stages favor different species; mice do well right after a fire, for example, but some birds do better in long-unburned or intermediate areas. Now that habitat is restricted to “islands” of parkland, there is danger of an entire park being burned out, with no adjacent communities to recolonize the burned areas.

The Landsat images here show a stark change from unburned bush in 1975 to huge burn scars in the later images. The age of the scars can be estimated by their color; old scars are almost as darkly red as the bush, half-regrown scars are only pink, and the newest scars are very bright sand, or even black with ash.


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