The early settlers found the alluvial soils to be the most productive, but red-brown soils on upland slopes and in the state’s south-central Riverina region and black soils on the northern river plains also are exceptionally fertile. As a result of overgrazing, the clearing of trees and natural vegetation, and farming practices causing erosion, more than three-fourths of the soils in New South Wales suffer from degradation and gullying. Salinization is a major problem in the Murray-Darling basin, due to irrigation and the unwise removal of trees. The fertility of western soils cannot be fully exploited because of low rainfall and intense evapotranspiration.

Climate

New South Wales has a generally mild climate. The seasons are well-defined in the south, with a hot summer and cooler winter and spring and autumn transitions. Autumn begins in March, winter in June, spring in September, and summer in December. Seasonal variation is less apparent in the north, where summers are hot and wet and winters cooler and drier.

Precipitation in the state is highest with the orographic effect of the rise to the tablelands but generally declines northwestward. The Western Division, which consists of semiarid western plains, is recognized as an area of marked rainfall deficiency, and attempts have been made to rationalize land use there to minimize damage to the fragile environment. That portion of the state, roughly one-tenth of the total area, receives less than 10 inches (250 mm) of rainfall a year and lies beyond the westerly limit of wheat growing. About one-fifth receives between 10 and 15 inches (250 and 380 mm). The coastal districts have the most annual rainfall, varying from 35 inches (900 mm) in the south to 60 inches (1,500 mm) or more in the north.

Drought and flood are ever-present natural threats with which Australians live. Drought is closely related to the El Niño effect in Pacific Ocean waters.

The dry climate and abundant sunshine prevailing over the state present problems for the agriculturalist but make delightful living for those in the cities. It is rarely too hot in summer, though the north coast can be uncomfortably humid, and Sydney is without sunshine for an average of only 23 days a year. Inland it is both hotter in summer and colder in winter. Average temperatures range from about 75 to 84 °F (24 to 29 °C) in summer and from about 45 to 59 °F (7 to 15 °C) in winter. Temperatures over 100 °F (38 °C) are not uncommon in the summer months, and frost at night is common in winter on the tablelands and southern slopes. In the Snowy Mountains (Kosciuszko massif), heavy snow falls over an area larger than the Swiss Alps.

Plant and animal life

Except on the north coast, where remnants of subtropical rainforest survive, the vegetation is mainly xerophytic (adapted to frequent droughts). Clearing of the original forest that once covered most of the eastern third of New South Wales has gone on apace, often at a higher rate than in other Australian states, and environmental groups struggle to protect remnant stands. Dominant species are evergreen eucalypts (more than 600 species) and acacias. These take the form of scrub on the plains, where mulga, a species of acacia, is a valuable fodder tree, and there is also much damaged saltbush. Inedible spinifex grass grows in the northwest. Eucalypts are hardwoods suitable for chipping and construction, and there are only limited supplies of native softwoods such as cedar and hoop pine.

The rich birdlife includes many species of parrots and cockatoos, the flightless emu, the mound-building scrub birds, and mallee fowl. Lyrebirds are common in the coastal forests. Marsupials include koalas, wombats, kangaroos, wallabies, common and ring-tailed possums, bandicoots, and many others. Kangaroos and wallabies are plentiful, but, like many other species, face significant loss of habitat. The platypus may be common in quiet waterways, and the echidna, or spiny anteater, also survives, even in urban areas. Several species of poisonous snakes abound, including black, brown, and tiger snakes and the death adder; they are not aggressive, however, and loss of human life to snakebite is rare. There are two poisonous spiders, the red-back and the funnel-web. The best-known fish is the now-vulnerable Murray cod, found in the western rivers, which can grow to about 3 feet (1 metre) and reach weights of some 35 to 45 pounds (15 to 20 kg). Yabbies (crayfish) and other shellfish were an important part of the Aboriginal diet.

The environmental impact of European settlement on New South Wales has been enormous, and it is only now being recognized and to some extent remedied. It is believed that, since 1788, when the British began colonizing Australia, more than 35 plant species and a similar number of animal species—including more than two dozen mammals as well as various birds and frogs—have become extinct. In addition, several hundred plant and animal species are listed as threatened or endangered. One bright note was the discovery in 1994 of the Wollemi pine (Wollemia nobilis), one of the world’s oldest and rarest tree species, about 120 miles (200 km) northwest of Sydney.