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Proceedings of the Symposium on Dynamics and Management of Mediterranean-Type Ecosystems, June 22-26, San Diego, California

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Proceedings of the Symposium on Dynamics and Management of Mediterranean-Type Ecosystems, June 22-26, San Diego, California Vegetation Changes in Mediterranean Abstract: This paper reviews the vege- 1 tation of the mediterranean regions of Australia Since European Settlement Australia : as it was before European settlement less than 200 years ago, its degradation under agricultural practices with introduced plants and animals, and Marilyn D. Fox2 current and future land use. The main agencies of change have been clearing, grazing, fertilizing, altered fire regime and introduced species, both exotic plant species and introduced grazers. There have been extinctions (both total and local) while other native species have had their demographies and distributions altered. The Australian continent has only by an industrialized people and their recently been exposed to the effects of retinue of plants, animals and micro- the agricultural and industrial revolut- organisms. The Australian biota which ions. Its existence was known to navi- had evolved in isolation suddenly en- gators of the late sixteenth century, and countered the domesticated animals and in particular its northern and western crop plants of Europe. More tragically, coasts were charted through the early the aboriginal people suddenly encount- seventeenth century but with few record- ered the disease organisms of Europe, ed excursions ashore. these together with alcohol and the more direct measures of poisoning and shooting, The first European settlement was at decimated their populations in just a few Sydney in 1788, with the mediterranean decades. regions being settled later: on the Swan River (Perth) in Western Australia in Mediterranean Climate in Australia 1828 and in the Gulf of St. Vincent (Adelaide) in South Australia during 1836. The occurrence of mediterranean At the time of exploration and settlement climate in Australia has been interpreted the continent was home to an aboriginal differently by different authors. Those people who had been there for at least who have used the stricter interpretation 40,000 years. The dingo (Canis of Köppen's Cs type (Köppen 1936), of a familiaris dingo) was the only animal distinct summer half-year drought with associated with these hunter-gatherers appreciable rainfall during the winter and their only tools were spears, months, include Aschmann (1973) and woomeras (throwing sticks), boomerangs Milewski (1979). Specht and Moll (in and stone axes, plus their use of fire. press) extended this by including the Fire, then and now, was used to drive cool semiarid (BSk) type. Figure 1 shows large game into ambush, but more sign- the distributions of these types, as well ificantly it attracted game to the as that of the hot semiarid (BSh) type resulting soft regenerating growth which where this corresponds more closely with was also gathered by the women. The vegetation boundaries. The figure is Australian aborigine did not practise redrawn from Dick (1975, after Köppen agriculture; fire was the only agent used 1936). The mediterranean-type climate to modify the environment. (Csa, Csb and BSk) occurs over 8 percent of the continental area. With the coming of European man, a continent that had known only the The mediterranean regions are roughly sparsely dispersed aborigines was invaded the south-west of Western Australia and the eastern edge of the Great Australian Bight. Perth and Adelaide are the only 1Presented at the Symposium on centres of population in these regions. Dynamics and Management of Mediterranean To the north the mediterranean regions -Type Ecosystems, June 22-26, 1981, San are bounded by the arid (BW) zone while Diego, California. to the east the climate is humid with more evenly distributed rainfall (Cf). 2Ecologist, National Herbarium of New South Wales, Royal Botanic Gardens, Sydney, 2000, Australia. Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range 112 Experiment Station, Forest Service, U.S. Department of Agriculture; 1982. Figure 1-- The climates of temperate Australia after Koppen (1936) from a map by Dick (1975). The mediterr- anean climates (Cs) and cool semiarid (BSk) types are shown as well as the warm semiarid (BSh) type where this corresponds to vegetation boundaries THE ORIGINAL VEGETATION open forests on soils derived from granite and gneiss by karri (E. diversicolor), the The vegetation of the mediterranean drier open forests on soils from the regions of Australia is illustrated in ancient laterites by jarrah (E. marginata). Fig.2 (based on a map by Moore 1969). Woodlands are also usually dominated by This ranges from the impressive forests of eucalypts such as the black box south western Australia through the wood- (E. largiflorens) of south-western NSW, lands of characteristically "mallee" but may also be composed of acacias such eucalypts, to the heathlands and chenopod as mulga (A. aneura). shrublands. Given the uniformity of climate, the principal determinant of The eucalypt shrublands or mallee is vegetation structure is the nature and the form of vegetation most closely nutrient status of the substrate and associated with the mediterranean regions. absolute amount of precipitation. The These multistemmed, low (usually less than three major soil suites of southern 10m) eucalypts grow where the soil is Australia are the base-rich, nutrient-poor sandy but often overlies an alkaline clay and calcium-rich soils, and their relation- subsoil (Rossiter and Ozanne 1975). The ship to vegetation is reviewed by Specht understorey can vary from a chenopod and Moll (in press). synusium to one dominated by porcupine grass (Triodia irritans). Temperate sclerophyll forests grow in mediterranean regions of the south-west Much comparative work has been done on of Western Australia. These forests are the sclerophyllous low shrublands or dominated by eucalypts, the wetter tall heaths of Australia and other mediterranean Figure 2-- The vegetation of the mediterranean regions of Australia from a map by Moore (1969). The limit of the mediterr- anean-type climate (Csa, Csb and BSk) is shown as a heavy dashed line. 113 Figure 3-- Sources of alienation of the mediterranean regions of Australia. The distribution of the wheat belts and sheep grazing areas are shown and the limit of the mediterranean -type climate. The location of major conservation areas is also shown. regions (e.g. Specht and Moll in press). Figure 3 summarizes the major land Extending into the semiarid regions, this uses or sources of alienation within the is replaced by chenopod shrublands or mediterranean regions. Major conservation shrub steppe of Moore (1969). areas are also shown; these are usually national parks, however some are The arid zone extends to the coast at aboriginal reserves. the head of the Great Australian Bight and effectively divides the mediterranean The mediterranean regions correspond regions into western and eastern provinces. with the wheat belts and sheep grazing These are recognised as separate floristic areas so that generally the level of zones (Burbidge 1960), the south-western disturbance is high (Adamson and Fox, in temperate zone being the richest floristic press). In such areas the alienation is zone on the continent. compounded by the use of fertilizers, suppression of fire and an abundance of The vegetation of Western Australia introduced animals and plants. has recently been mapped by Beard (see Beard 1979 for a review). Satellite With the loss of habitat many native imagery was used to map the environments animals have become locally extinct. A (including vegetation) of South Australia small marsupial, the tammar wallaby (Laut et al 1977) and previously the (Macropus eugenii), which was once "the vegetation was described by Specht (1971). most plentiful and widely-distributed The mediterranean region of Victoria has wallaby in the south-west" (Thomas, 1888), received the sporadic attention of but "rapidly disappearing in the cultivated ecologists and botanists. It is mapped on districts" (Shortridge 1909) is "now Carnahan's (1976) map of the natural restricted to a few small scattered main- vegetation of Australia. The vegetation land colonies, and a number of islands" of western New South Wales was mapped by (Poole 1978). Beadle (1948) and Fox (1980) is currently mapping it at a larger scale. The effects of fertilizers on compos- ition and growth of heathlands in LAND USE IN MEDITERRANEAN REGIONS OF mediterranean South Australia have been AUSTRALIA demonstrated by Heddle and Specht (1975). Contamination of conservation areas, often Degree of Alienation islands in a sea of alienated land, is a major management problem. There is the In less than 200 years of European dual response of death or suppression of settlement the entire continent has been native species and invasion by exotic alienated to some extent. The degree of species adapted to the higher nutrient alienation ranges from clearing and levels. subsequent cultivation, altered nutrient levels, altered fire regime, to At present about ten percent of vascu- interaction with introduced animals and lar plants in Australia are exotics (Wace plants. 1973). The highest incidences of these 114 Figure 4-- Plant species at risk in the mediterranean regions of Australia (based on figures in Hartley and Leigh 1979). The total number of species considered at risk in each state is shown, as is the total for each subdivision, and the number considered to be endangered and vulnerable. are in the humid regions of the south- populations in the fifties. Today the east of Australia, with relatively few main control measures include poisoning, in the mediterranean
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