World’s Soil Resources

of the country. The undulating and low relief landscapes also have saline and sodic soils. Large sedimentary
basins (e.g. Murray–Darling Basin) have moderately fertile soils although the current climate is highly variable.
The elevated tablelands adjacent to the Great Escarpment have significant areas of basalt and their
associated alluvial landscapes have some of Australia’s best soils for agriculture. Likewise, the dissected
landscapes to the east and south of the Great Escarpment where most Australians live are much younger. The
coastal river systems have fertile alluvial landscapes.
The remnants in New Caledonia, Papua New Guinea and New Zealand
The areas of the Australian Plate in New Caledonia, Papua New Guinea and New Zealand share ecosystems
with a common evolutionary origin (e.g. Antarctic flora including Araucaria and Nothofagus). They typically
have high levels of biodiversity although the above-ground systems are much better documented that those
in the soil. These remnant areas are on the more tectonically active fringes of the Australian Plate and they
have greater relief as a result.
Young active landscapes
New Zealand
The tectonically active landscapes of New Zealand can be broadly divided into the axis of high mountain
ranges, the basin and range provinces on either side of these ranges, the Taupo Volcanic Zone on the North
Island, and the lowlands and sedimentary basins. Only 15 percent of the land area is flat. The climate of the
country ranges from sub-tropical in the north to sub-Antarctic in the far south. Sixty percent of New Zealand
is >300 m above sea-level and there are about 3 000 mid-latitude mountain glaciers.
A climate sequence of Luvisols, dystric Cambisols and Podzols cover 69 percent of the country and are
derived from sedimentary rocks (greywacke, sandstone, siltstone and mudstone as colluvium, alluvium and
loess). Significant soils in the remaining areas include vitric Andosols derived from rhyolytic tephra (North
Island) and silandic Andosols, Nitisols and Ferralsols derived from andesitic tephra and basalt (mainly on the
North Island).
Papua New Guinea
Papua New Guinea has five major landscape regions (Löffler, 1977, 1979). The Southern Plains and Lowlands,
up to 400 km wide, are in the west of the country. Most of this region is less than 30 m above sea level and
includes the extensive alluvial plains of the Fly River. There are two mountainous regions that occupy the
majority of the country. The Central Ranges run the length of the mainland and have very high relief with many
peaks between 3 000 m and 4 000 m. The Northern Ranges run parallel and descend to a discontinuous
and narrow coastal plain. Between these ranges are the plains, lowlands and wetlands of the Inter-montane
Trough, many of which are associated with the Sepik River. The Islands Region is diverse and includes active
volcanoes (e.g. New Britain) particularly along the Northern Bismarck Island Arc. Fringing coral reefs and
raised coral limestone landforms are common in this tectonically active area.
Island landscapes and atolls
As noted earlier, most of the smaller islands in Melanesia, Micronesia and Polynesia are volcanic in origin.
Those with hilly or mountainous features were formed by the volcanoes themselves and they may have
fringing coral reefs, elevated coral platforms, or both. The low lying atoll islands have been formed by corals
growing on extinct seamounts or volcanoes that have eroded or subsided. Many of the atoll islands are only a
few meters above sea level and are therefore vulnerable to sea-level rise.
Status of the World’s Soil Resources | Main Report Regional Assessment of Soil Changes
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in the Southwest Pacific