Keywords

1 Introduction

Australia (113°08′E–153°38′E, 10°41′S–43°38′S), has a terrestrial land area of almost 7.7 million km2, which includes the Australian continent mainland, the island of Tasmania, and numerous small islands. Australia is the driest inhabited continent in the world (Commonwealth of Australia 2012). The arid Australian climate can be attributed to the subtropical anticyclonic zone which covers the center of the continent; the Great Dividing Range which blocks water vapour from the east coast; and the West Australia Current, a cold current that significantly reduces precipitation in Western Australia. The climate in Australia is highly variable, with frequent drought events throughout the country. The climatic fluctuation and extreme climates in Australia are mainly driven by ocean currents, including the Indian Ocean Dipole and the El Niño–Southern Oscillation. Australia is dominated by drylands (aridity index < 0.65; 733.9 × 104 km2; 95.4% of terrestrial Australia), with water-sufficient areas existing only on Tasmania Island, in the eastern and northern coastal areas, and in the southwest corner. More than half of the country (65.2%) is composed of arid regions, followed by semiarid (25.5%), dry subhumid (4.7%), and humid (4.6%) regions, while hyper-arid areas are 0.007% of Australia area (Fig. 11.1). The arid Australian climate gives rise to a specialized and quite vulnerable terrestrial ecosystem which can be characterized by pervasive deserts and sparse grasslands. Approximately 80% of terrestrial Australia is classified as rangelands, where land use is dominated by extensive grazing of sheep and cattle (Feng et al. 2020; Foran et al. 2019).

Fig. 11.1
A heat map of Australia and a pie chart present the distribution of drylands. They indicate the following. Arid, 501.48. Semiarid, 196.28. Dry sub-humid, 36.12. Humid, 35.26. Hyper arid, 0.06. All values are 10 to the power of 4 kilometer squared.

Distribution of drylands in Australia. The standard global aridity index (AI, the ratio of long-term average annual precipitation to average annual potential evapotranspiration) map is from the Global Aridity and Potential Evapotranspiration (PET) Database v2 developed by the Consultative Group for International Agriculture Research-Consortium for Spatial Information (CGIAR-CSI) (Trabucco and Zomer 2019). AI ranges are 0–0.03, 0.03–0.2, 0.2–0.5, 0.65–0.65 and >0.65 for hyper-arid, arid, semiarid, dry subhumid, and humid regions, respectively

Full size image

In spite of the water-limited climate conditions and vulnerable terrestrial ecosystems, Australia has the highest average wealth, and the GDP per capita was approximately 5.74 × 104 US dollars in 2018. Australia has a population of nearly 26 million, equalling an average population density of 3.4 per km2. The population is highly concentrated in cities on the eastern seaboard. Population distribution pattern outside the main cities are of a few medium size towns and then many very small communities. Dryland social-ecological systems (SES) in Australia are threatened by the degradation of rangelands due to more arid climates and excessive grazing. Moreover, agricultural expansion, especially poor irrigation activities in areas with high potential evapotranspiration but limited rainfall, has led to dryland salinity, which is a key problem contributing to land degradation in southern Australia (Clarke et al. 2002; Lambers 2003). Human society in terms of population distribution, economic development, and the livelihoods of local communities, is greatly affected by water deficits and drought-induced ecosystem degradation. Therefore, in this chapter, we would like to provide an overview of the spatiotemporal dynamics of climate, ecosystems, and human society in Australia, especially during recent decades, and explore the relationships among these three key components. Multiple datasets on environmental conditions, vegetation cover, and human society or activities are analysed, and published studies are referenced.

2 Major Characteristics of Dryland Social-Ecological Systems in Australia

2.1 Climate Conditions

The mean annual temperature (MAT) is the lowest in the southeastern part of Australia, e.g., Tasmania Island. In tropical areas in northern Australia, the weather is perennially hot, whereas in the interior of the continent, which is covered by the arid anticyclone, summers are extremely hot, and winters are cool. Extreme temperatures influence vegetation, animals, and even humans (Cheng et al. 2018; Ebi et al. 2021; Hoffmann et al. 2019). Annual precipitation is the lowest in central Australia and high in northern Australia and some coastal regions. The precipitation seasonality declines from north to south in Australia and is higher on the southwestern coast than in the southeastern regions. For most parts of Australia, precipitation is the highest in summers and the lowest in winters. However, western and southern Australia showed the opposite pattern of seasonal precipitation variation. Therefore, over the southwest corner and Spencer Bay (including Kangaroo Island) located in southern Australia, where precipitation seasonality is large, typical Mediterranean climates are present. Mean annual solar radiation is generally higher in the north than in the south, but the seasonality of radiation increases with latitude. Desert areas receive higher radiation than relatively humid places (Fig. 11.2).

Fig. 11.2
6 heatmaps of Australia are labeled a to f. The precipitation seasonality, mean annual precipitation, temperature, and solar radiation are high over the northern regions, while temperature seasonality and solar radiation seasonality are high over the central, western, and Victoria regions, respectively.

Spatial patterns of temperature, precipitation and solar radiation and the seasonality in the drylands of Australia. The data are from the Australian Gridded Climate Data (AGCD), which are newly published by the Bureau of Meteorology Australia at the national computational infrastructure (NCI), as the successor of the Australian Water Availability Project (AWAP). The monthly precipitation data are available from 1900 until 2019 (Australian Bureau of Meteorology 2020b), whereas the monthly means of daily minimum and maximum air temperature data are available from 1910 to 2019 (Australian Bureau of Meteorology 2020a). Both temperature and precipitation data have a spatial resolution of 0.05°. Solar radiation data are from the updated Breathing Earth System Simulator (BESS)-RAD dataset from 2000 to 2019 and have a high accuracy (Ryu et al. 2018)

Full size image

The dryland climates in Australia (hereinafter ‘DRY AUS’) can be classified into 10 types (Fig. 11.3) according to the world map of the Köppen-Geiger climate classification (Kottek et al. 2006; Rubel et al. 2017). The central and western parts of Australia are dominated by a tropical desert climate (BWk), the northern coasts are hot year-round and dry in winter (Aw), most parts of the eastern coasts have warm and humid weather (Cfa and Cfb), and Mediterranean climates (Csa and Csb, warm and dry summers) dominate the southwest corner and some areas in southern Australia. The mean annual air temperature increases with the aridity level, but precipitation declines with the aridity level (Fig. 11.6a). The interrelationships among the interannual variations in solar radiation, temperature, and precipitation are all stronger in more arid regions (according to data from 2000 to 2019). Precipitation is negatively correlated with solar radiation (p < 0.01) in all regions. Temperature is positively correlated with radiation and negatively correlated with precipitation in all drylands in Australia, but these relationships are not significant in dry subhumid areas.

Fig. 11.3
A heatmap of Australia categorized the regions based on 10 different Koppen-Geiger climate classifications, namely, A w, B W k, B S k, C s b, C f a, B W h, B S h, C s a, C w a, and C f b. Most of the central and southern regions of Australia fall under B W h, while some northern regions fall under A w.

Köppen-Geiger climate classification in the drylands of Australia (In the symbol in the legend, the first letter indicates the main climates: A: equatorial; B: arid; C: warm temperate; the second letter indicates precipitation: W: desert; S: steppe; f: fully humid; s: summer dry; w: winter dry; and the third letter represents temperature: h: hot arid; k: cold arid; a: hot summer; b: warm summer)

Full size image

2.2 Soil and Topography

Australia has the lowest and flattest topography among all continents. However, eastern Australia is marked by the Great Dividing Range, which stretches more than 3500 km and has widths from 160 km to more than 300 km. The heights of the range are typically 300–1,600 m. The southern Great Dividing Range contains the highest place in mainland Australia: Mount Kosciuszko (2228 m above sea level). Except for eastern Australia, where the silt or clay fraction is relatively high in soils, sand dominates the surface soil in the drylands of Australia (Fig. 11.3). Soil organic carbon is high in the eastern coast and southwest corner of Australia but is quite low in the interior parts of the continent, especially in the desert areas (Fig. 11.4).

Fig. 11.4
2 heatmaps of Australia labeled a and b. A. Most of the western and central regions are dominated by sand, while the eastern and northern regions have silt and clay fractions. B. Higher soil organic carbon percent is noted in the eastern and south-western regions, while other regions have lower values.

Soil properties of drylands in Australia. a Soil texture and the fractions of sand, silt and clay; b spatial pattern of soil organic carbon. Soil properties are from the national soil attribute maps produced by the Soils and Landscape Grid Facility of Commonwealth Scientific and Industrial Research Organization (CSIRO) and soil map** (Odgers et al. 2015a, b; Viscarra Rossel et al. 2015). Bulk density, pH, available water capacity, total nitrogen, and total phosphorus of the soil layer (0–5 cm) are provided in this dataset (Viscarra Rossel et al. 2014)

Full size image

2.3 Land Use/Cover in Dryland Regions in Australia

Drylands in Australia are dominated by sparse and scattered grasses and shrubs (37.1%), followed by open shrublands (10.5%) and sparse trees (9.8%), all of which are typical ecosystem types in arid climates. Shrublands and grasslands are representatives of arid and semiarid regions in Australia and rarely exist in more humid places. On the other hand, closed forests mainly exist in humid and dry subhumid regions, while open forests can be found in semiarid, dry subhumid, and humid regions (see Fig. 11.5). Vegetation cover is much denser in more humid coastal areas. From the humid coasts to the dry interior lands, the ground cover changes from forest to grass and finally to bare ground (Fig. 11.6).

Fig. 11.5
2 parts. A. A map of Australia plots 22 different kinds of land use cover from 2002 to 2015. The open and closed trees are noted over the eastern and south western coasts. B. A stacked bar graph of land use cover type versus area. The shrubs and grasses, sparse and scattered, are highest in arid areas.

Land cover types in drylands in Australia: a most of the land cover in the drylands of Australia during 2002–2015; b annual mean total area of 22 land use cover types in different regions distinguished by aridity levels in Australia. Please note that the drylands of Australia, denoted by DRY AUS, consist of arid, semiarid, and dry subhumid regions. The data are from the National Dynamic Land Cover Dataset (NLCD) v2.1, published by the Australian Bureau of Agricultural and Resource Economics and Science (Lymburner et al. 2015)

Full size image
Fig. 11.6
2 heatmaps of Australia. A. The mean annual L A I value is high over the eastern and southwestern coastal regions, while lower values are noted over the interior regions. B. Most of the regions have short vegetation, with bare ground prevailing in the central region.

Vegetation cover in drylands in Australia. a Map of the mean annual leaf area index (LAI) during 2001–2018; b mean vegetation continuous fields in 1982–2016. The LAI data are from the Global Land Surface Satellite (GLASS) product suite (Liang et al. 2021; Tang et al. 2013; ** Indigenous and Western cross-cultural knowledge to support Indigenous cultural fire management. Ecol Manag Restor 23:75–82. https://doi.org/10.1111/emr.12532 " href="#ref-CR45" id="ref-link-section-d5585939e1772">2022; Nikolakis and Roberts 2020; Steffensen 2020).

The Murray-Darling Basin (MDB) is an example of a complex river system undergoing substantial water reform to balance the needs of human and the environment. The basin extends across 4 states in south-eastern Australia, occupying 14% of Australia’s total surface area. Much of the basin is semiarid and contains 50% of Australia’s irrigated agriculture. Multiple efforts, such as the 2007 Water Act and 2012 Murray–Darling Basin Plan (MDBP), were issued to sustainably optimize social and environmental outcomes in relation to water use in the basin (Bischoff-Mattson and Lynch 2017). The basin plan includes five parts (i.e., balancing/sharing, monitoring, review, revision, and adaptation) and guides all stakeholders to use water in a sustainable way (Productivity-Commission 2018). Most importantly, the MDBP manages the basin as one system, enabling the river systems to adapt to climate changes and continue to support all water stakeholders in the long term. Although crisis-driven management to some extent prevents ‘economic and environmental decline’, the Plan makes no direct allowance for climate change, setting the scene for a future crisis that will trigger further reform (Colloff and Pittock 2022; Pittock 2019).

Australia claims to be pursuing a ‘green growth’ model in response to the global economic crisis and climate change. An agroecological approach supports agricultural biodiversity while promoting sustainable livelihoods (Lanka et al. 2017). Indigenous people living in Australia’s tropical savanna landscapes are increasingly searching for income opportunities from environmental services or ecosystem services as an avenue for economic development and improvement of socioeconomic conditions (Greiner 2010). The sustainable livelihood in Australia can better cope with and recover from stresses and shocks and promote its capabilities and assets both now and in the future (Davies et al. 2008; Moran et al. 2018).

5.5 Social and Economic Development

Population ageing is probably the most important social problem for Australia in recent decades, since the proportion of the elderly population nearly doubled from 8.24% in 1970 to 16.21% in 2020 (Fig. 11.22a), and was still increasing at a high rate (0.29%/yr during 2010–2020), bringing about challenges to social and economic development (Kendig et al. 2016; O’Loughlin et al. 2017), 2.23 million women (17.2% of all women) for the ages over 65 years, more than men in the same age (1.96 million, which is 15.4% of all men), were now living in Australia. Spatially, the percentage of elderly people was generally higher in southern Australia than in northern Australia and is the highest on the southeast and southwest coasts (Fig. 11.22b). The elderly proportion was similar among regions with different aridity levels, but the proportions of children and juveniles in arid regions were lower, resulting in fewer youth labourers, especially 20–29-year-old people, than in other regions. Rapid growth of the Indigenous Population is expected, with population momentum, identification change, and mixed partnering and childbearing shown to contribute more to growth than above-replacement fertility and increasing life expectancy. Since 1971 the indigenous population of Australia has trebled. From 1991 to 1996 numbers grew by 33%. The future growth of Australia’s Indigenous Population is thus intimately connected to its interaction with the Non-Indigenous Population (Wilson 2016).

Fig. 11.22
2 parts. A. A line graph denotes that the elderly population percentage falls to about 8 in 1970, and it exhibits an upward trend. B. A map of Australia plots the percentage of people older than 65, with values ranging from 0.02 to 0.42. Some pockets of the southwest and southeast regions have the highest values.

Change in the population structure in the drylands of Australia: a temporal change in the proportion of the elderly (>65 years old) population in Australia; and b the percentage of people older than 65 in all local government areas in Australia in gridded 2020 population maps are from the Gridded Population of the World (GPW) v4 dataset from the Socioeconomic Data and Applications Center (SEDAC). The land area per pixel values were resampled from ~1 km resolution to 0.05°

Full size image

In Australia, the population is now generally moving out of Western Australia (WA) and the Northern Territory (NT) into eastern and southeastern Australia, including New South Wales (NSW), Victoria (Vic.), and Queensland (Qld). Therefore, the general direction of internal migration in Australia is from relatively arid regions to more humid regions.

The GDP in the drylands of Australia has more than doubled since 1990, increasing from US$ 3.3 × 1011 to US$ 7.0 × 1011 in 2015 (Fig. 11.23). The GDP increase rates were somewhat higher in the semiarid and dry subhumid regions (3.3% and 3.2%/yr) than in the arid regions (2.5%/yr).

Fig. 11.23
An area chart of G D P in 10 to the power of 10 U S dollars versus years. The values of arid are the lowest, and they are almost constant, while the values of semiarid and dry subhumid increase.

GDP changes from 1990 to 2015 in regions with different aridity levels in the drylands of Australia. The gridded GDP is from Kummu et al. (2018)

Full size image

According to nighttime lights (NTL), socioeconomic activities in dry humid areas in Australia remained relatively stable during 2000–2010 but rose rapidly later, indicating that urban development in the drylands of Australia significantly accelerated after 2010 (Fig. 11.24b) but remained unchanged in drier regions.

Fig. 11.24
A. A map of Australia plots the average nighttime light. Few spots over the southwest and southeast coast have the highest values, ranging from 5 to 56.3, while most of the interior region has 0 values. B. A multiline graph of mean nighttime light versus years. The highest plot values are for dry subhumid.

Nighttime lights (NTL) in the drylands of Australia: a spatial pattern of NTL averaged during 2000–2020; and b mean NTL changes from 2000 to 2020 in regions with different aridity levels in the drylands of Australia

Full size image

6 Summary and Conclusion

Dryland social-ecological systems in Australia are facing the accelerated warming and rapid socioeconomic developments since the twenty-first century, including population and GDP increases and urban development since the twenty-first century, but with great diversity in space. In terms of spatial variance, forests in the drylands of Australia have become denser since the twenty-first century, but shrubs may have degraded. This result is consistent with the NPV, or both the PV and NPV, which generally decreased in arid and semiarid regions and vice versa in dry subhumid areas. Increases in the LAI/NPP were concentrated in the relatively humid coastal areas of Australia, whereas in the arid interior part, the LAI/NPP generally declined. Precipitation changes dominated the variation in vegetation in the drylands of Australia (legacy effects exist), where short vegetation is more easily influenced by precipitation changes than trees. Reductions in fire have significant impacts on emission mitigation and air purification but may have adverse effects on endemic biodiversity. Fire management (i.e., proactive burning) is necessary both to conserve biodiversity and to reduce the negative impacts on socioeconomic systems (fight fire with fire). The roles of livestock grazing/fencing in biodiversity are heterogeneous. Both grazing and fencing can be useful management tools to achieve conservation objectives and can also be threats to biodiversity conservation. Australia has invested considerably in improving biodiversity since the late 1980s. Integration of policy makers, funding agencies, and the general public are essential for the next step of dryland social-ecological system conservation in Australia.