The Great Barrier Reef is the world's largest coral reef system, extending over 2,300 kilometres. It is home to over 5,000 species of mollusk, 1,500 species of fish, 400 species of coral and around 240 species of birds. It spreads over almost 4,000 individual reefs, 900 continental islands, 300 coral cays and 150 inshore mangrove islands.

In the last 30 years, climate change and many regional pressures have combined to cause ecosystem collapse across the reef, with shallower reefs worse off than deeper reefs. These pressures include five mass coral bleaching events since 1998, marine heatwaves, major tropical cyclones, freshwater floods from extreme high rainfall events, flood sediment and pollution, ocean acidification and crown of thorns starfish outbreaks.

Major feedback loops that compound the pressures are now establishing. From 1985–2017, the reef lost half of all coral cover due to five massive bleaching events, of which two were consecutive (2016, 2017). In 2017, 67% of corals died along a 700km stretch.

The reef provides around A$12 trillion of ecosystem services and over 64,000 jobs. The Australian and Queensland governments have committed billions into reef protection but there are significant challenges to overcome.

Australia’s tropical savannas sweep across more than 1 million square kilometres of northern Australia, from the western Kimberley region, WA, to the eastern edge of Queensland’s tropical coast. Savanna woodlands and forests have mainly gum trees over an understory of tall grasses and very ancient, poor soils.

These savannas are currently the least altered and unpolluted in the world, but they’re changing fast because of agriculture, mining and the effects of poor management decisions of the past. Land clearing has removed vegetation permanently, reducing food availability for wildlife. Climate change is adding further pressures as rains increase in the wet season, and dry seasons are becoming hotter and last longer.

Add in cat predation, the presence of cane toads, livestock encroachment and increasing bush fire frequency, and it becomes clear why Kakadu National Park is now a hot spot for mammal extinction.

Of particular urgency is the impact of a weed called giant African Gamba grass. It grows up to 4m in height and produces up to 74,000 seeds per square metre. This adds a huge fuel load for fires, which burn 12 times more intensely than native grass fires, with flames penetrating and killing tree canopy. Gamba grass fires are very expensive to fight, cause loss of livestock and agricultural assets, and diminish the financial viability of the low carbon farming initiative of “savanna burning”.

Damage to the savannas affects the cultural, spiritual and socioeconomic livelihoods of First Nations communities. Loss of ecosystem services, production and pastoral lands is around A$113 million per year.

In late 2015, nearly 40 million mangrove trees, representing around one million tons of carbon, died along 1,000 kilometres of the Gulf of Carpentaria. They succumbed to multiple pressures, including extremely high temperatures (39°C for 18 days), prolonged drought conditions, along with feral pigs, scrub fires and invasive weeds.

But most significant was the additive effect of severe El Niño conditions, which effectively pushed the sea away from the coast. This led to a short-term, extreme drop in mean sea level of around 20 centimetres, taking seawater away from mangrove roots.

Two severe tropical cyclones and damaging floods have since hampered its recovery. Continued tidal rafting of dead trunks is curtailing the establishment of seedlings and damaging remaining trees. And the decomposition of dead roots is probably affecting nursery habitat for fish and crustaceans.

The damage is expected to have lasting repercussions on the local economy and livelihoods of the region. The Gulf of Carpentaria fishing industry is worth A$30 million per year. First Nation people and recreational fishers also use the area. Ecosystem services from mangroves are worth around A$250,000 per hectare per year.

The wet tropics of North Queensland span around 450 kilometres, with rainforest covering around 1.85 million hectares. The region contains extraordinary diversity, with more than 3,000 plant species and over 60 vertebrate species found nowhere else on Earth. Although tropical rainforests make up only 0.1% of Australia’s landmass, they’re also home to over 50% of its ferns, butterflies and birds, and over 20% of freshwater fish, mammals, orchids, frogs and reptiles.

It’s for this reason and others, such as the significant First Nations cultural values, that the wet tropics are a World Heritage Area.

But they experience a range of pressures, many of which compound each other. These include habitat fragmentation, fringe livestock grazing, increased urbanisation, more frequent and severe fires and invasive plants and animals. Climate change poses perhaps the greatest threat overall.

Many of the region’s plants and animals live in discrete elevation bands: a “Goldilocks” combination of the right habitat and microclimate. As air temperatures increase and extremes in weather worsen, species’ areas of suitable habitat shrink. Some species have already moved to higher elevations and/or experienced striking local population declines. For example, in November 2018, a heatwave killed one-third of all spectacled flying foxes. And two possum species have disappeared from habitat under an altitude of 600 metres.

There have been four major storms or cyclones in 13 years. One event brought up to 2 m of rain, and the storm surge (seawater) inundated coastal rainforest. In 2006, one cyclone killed 35% of the regional cassowary populations, and cars and dogs killed many more as the birds left the destroyed forest.

The wet tropics are visited by around 5 million tourists per year, contributing over A$400 million to the region’s economy. In 2015, the wet tropics were valued at over A$5 billion per year, due to ecosystem services such as carbon sequestration, biodiversity protection, and soil and water resources.

The arid zone covers around 43% of Australia and is characterised by low lands, generally less than 300 metres in elevation, occasionally punctuated by a few big hills (higher than 1,000 metres). Vegetation ranges from woodlands, shrublands and grasslands to rangelands and desert dunes. There are isolated freshwater systems through the arid zone including waterholes and lakes, underground water, clay pans and springs fed by the Great Artesian Basin.

Widespread pastoral activities over the last 100 years have altered large areas of the arid zone from their pre-European states. Changes include major loss of habitats, reduction in small mammal populations, and livestock trampling of delicate biotic soil crusts (which maintain soil and dune stability and water infiltration).

There are more than 200 weed species. Some were planted for pasture, shade trees or to suppress dust, and dispersed by machinery, vehicles and floods. The most threatening is buffel grass. It has invaded extensive areas, wreaking havoc through degradation, habitat loss and biodiversity decline. Like Gamba grass in the north, in combination with extreme heatwaves, buffel grass has altered fire frequency and intensity. Hot fires now reach well into the tree canopy, killing the trees, as well as shrubs and native grasses.

Introduced feral animals include cattle, goats, camels, foxes, cats and pigs.

The arid zone rangelands are also economically important and contribute approximately A$4.4 billion per year to Australia's economy through tourism, pastoralism and agriculture combined.

Georgina gidgee is a keystone tree, a species that holds an ecosystem together, and dominates low open woodlands. It occurs naturally in small patches (up to 10 hectares) in the arid zone, growing mostly along watercourses and in clay depressions between spinifex grass dunes. Georgina gidgee woodlands are important hot spots for life, acting as refuges for native rodents, small marsupials, red kangaroos and bats. They provide permanent or temporary habitat for more than 80 bird species, and animals such as lizards and ants.

Georgina gidgee woodlands are heading for collapse due to a range of pressures including climate change, fire, overgrazing, wood collection, weeds, feral animals and changes in water flow. For example, harvesting for fence posts in the Brigalow Belt, Queensland, cleared 7.4 million ha of gidgee and associated ecosystems by 1998. What remains still suffers extensive loss through pastoral activities.

As mature trees are relatively long-lived (over 200 years), their recovery is slow. Without significant intervention, this ecosystem will turn into a desert.

The consequences of desertification include loss of shade for cattle, loss of water catchment surface for refilling the artesian basin, and loss of biodiversity and ecosystem function associated with their role in stabilising ancient dunes. Loss of vegetation also increases the number of giant, regional dust storms, which can travel all the way to the major cities in eastern Australia.

Ningaloo and adjacent reefs are within the World Heritage listed Ningaloo Coast, and comprise an ecosystem of immense biodiversity, and national and international ecological importance. It’s home to megafauna such as migrating whale sharks and whales, turtles, corals, and economically important habitat for fisheries.

The ecosystem is threatened by rising ocean temperatures, ocean acidification, and increasingly intense and severe weather events such as marine heatwaves and tropical cyclones. Coral bleaching events have been recorded from 1990 to 2019, causing substantial reef-wide death (such as around 80% loss of coral cover of Bundegi Reef).

Fish numbers have also decreased, especially in recreational fishing areas. Pressures from human use and water quality exacerbates these changes. And crown-of-thorns starfish and carnivorous snails hamper their recovery from bleaching.

The impacts of these combined global and local pressures are felt in tourism and commercial fisheries, which are worth around A$1.5 billion per year for the region.

Shark Bay, a World Heritage Area, is the home to one of world’s largest (4,300 square kilometres) and most diverse seagrass meadows. It’s a carbon storage hotspot, holding 350 million tons of carbon.

It supports an extensive food web, and diverse fauna including tiger sharks, and around 10% of the world’s dugongs, manta rays, dolphins, and green and loggerhead turtles. Southern right and humpback whales also use Shark Bay as a migratory staging post.

Over a background of chronic increases in seawater temperatures, Shark Bay experienced an unprecedented marine heatwave in the summer of 2010-11, lasting more than 10 weeks. Meanwhile, flooding from a tropical storm over the Gascoyne River catchment covered the bottom of the bay in up to 10 centimetres of mud. About a quarter of all sea grasses died, with limited recovery since.

This saw major decreases in dugongs (68% decrease), sea snakes (77% decrease). Populations of bottlenose dolphins, pied cormorants and green sea turtles decreased by 35–40%. Another marine heatwave hit in December 2019, and another is predicted for March 2021.

The failure of major seagrass recovery has led to the release of millions of tons of carbon dioxide as organic sediments breakdown. The ecosystem collapse caused major disruption to the local commercial fishing industry, when the scallop and crab commercial fishery had to close for five years.

The Murray-Darling Basin is Australia’s largest river system with 23 river valleys and over 77,000 kilometres of watercourses. The basin has more than 30,000 wetlands (400 wetlands are considered “high value” in Victoria alone) home to 46 species of native fish and 120 species of water birds. Some wetlands are recognised internationally as globally important.

The overall health of the river system is poor. Since European settlement, the river and tributaries have become highly regulated, with significant water diversion for agriculture and urban uses. These impacts have been exacerbated by increasing temperatures, declining average rainfall and severe droughts, further reducing water flows (by 40% since the mid-1990s).

Salinisation (saltier water), toxic algal blooms, hypoxia (low oxygen), introduced fish species, erosion, bushfire ash and nutrient runoff also contribute to declining water quality. Today, native fish populations are just 10% of pre-European numbers. Some 20 mass fish deaths, including of threatened species, have occurred since the 1960s.

The ecosystem is increasingly non-functional with decreasing freshwater biodiversity, and loss of ecosystem services and cultural values. The 2011 plan to improve the basin set a target to recover water for the environment, diverting it from irrigation. This was estimated to cost A$542 million annually, but the additional water has added A$3–8 billion worth of ecosystem services to the entire basin.

Despite the last drought ending, and rivers are flowing again, troubles are still emerging with recent reports of toxic algal blooms.

The Murray Darling Basin covers around 14% of Australia’s land area, comprising low-lying undulating areas, extensive plains and parts of the Great Dividing Range. The basin is Australia’s most important water catchment – forests and wetlands cover over 100 million hectares of floodplains and adjacent riverbank areas. The mighty river red gum is key to the health of these ecosystems that depend on frequent flooding (once every three years) for growth and reproduction.

Floodplain and riparian vegetation provide corridors and habitat for millions of animals, including water birds and 46 species of native fish. More than 2 million people live in the basin, and it’s home to 46 First Nations who care for at least 10,000 culturally significant places.

Over the last 200 years, humans have altered much of the basin, including the construction of weirs, irrigation channels, farm dams and municipal water reservoirs. All these changes affect the region’s water, and have significantly deteriorated riparian (bank-side) systems and populations of dependent species such as waterbirds.

Around 40% of the highly diverse ecosystems have been cleared or otherwise modified for logging and agricultural use. In 2008, an investigation of 1,600km of river estimated only 30% of the remaining river red gums were in good condition. Extraction of water for agriculture, including 1.8 million megalitres of groundwater, has increased soil salinity. The region is experiencing chronically raising temperatures, ongoing reductions in rainfall and increasingly long and severe droughts (2003–2009, 2017–2019).

Despite some restoration efforts, ecological collapse of riverine ecosystems continues. As tree deaths are becoming more widespread, forest canopy cover is reducing. Rivers flows and groundwater levels are decreasing, contributing to loss and degradation of habitat. Populations of birds, mammals and fish are shrinking. All these changes have flow-on impacts.

The basin is Australia’s main food bowl; 40% of food worth A$22 billion is produced annually. In addition, tourism contributes some A$8 billion each year. The droughts cut farm profits by 30%.

Montane alpine ash and subalpine snowgum forests occupy the highest forested areas of the Australian Alps. Alpine ash are giants and can grow over 90 metres tall, although trees over 40m are rare across most of the alps today.

Intense fires kill both snowgums and alpine ash. Climate change is increasing the frequency of fire through droughts, longer snow-free periods, tree stress and dry lightning in storms. This is amplified by positive feedback, where regrowth after prescribed burns or bushfire is much more flammable than long-unburnt forest. From 2000 to 2019, 84% of the entire alpine ash forests in NSW and Victoria were burned, some areas up to three times. Now, 70% of alpine ash are immature trees and over 75% of snow gums are at their most flammable age.

These forests are critical to the health of one of Australia’s most important water catchments. They also store large quantities of carbon, and surround high value utility and tourism infrastructure, such as Snowy Mountain power stations and ski resorts.

Increases in wildfire amplified by positive feedbacks place a heavy economic burden on these, as well as a health and safety impact on surrounding human populations.

The Great Southern Reef extends along 8,100 kilometres of coast, covering 71,000 square kilometres from Brisbane, around the south coast of Australia and Tasmania, to well north of Perth. It comprises a large number of rocky temperate reefs that support lush kelp forests, dominated by golden kelp and, in colder areas, giant kelp. Kelp supports high levels of biodiversity including other seaweeds, sponges, crustaceans, starfish, abalone, fish and rock-lobsters.

Different combinations of pressures cause kelp forest to degrade and collapse. These include coastal development, pollution, marine heatwaves, ocean acidification, and increased storm severity and frequency. For example, along 100 km of coastline reefs from Perth to Kalbarri, WA, most kelp forests have been lost and replaced with algal turfs. Giant kelp forests are now endangered.

The East Australian Current (thrust into popular culture via the film Finding Nemo) is frequently penetrating southward to Tasmania. This transports warm, nutrient- depleted waters, larvae of a NSW sea urchin and northern species of fish. The sea urchins severely damage the kelp forests, as does overfishing of large lobsters.

On conservatively estimates, the Great Southern Reef kelp forests generate at least A$10 billion per year in economic activity. Economic and social consequences of its decline include the collapse of the rock lobster, abalone and other fisheries, as well as impacts on Indigenous communities and decreases in tourism.

Forests and woodlands in south-west WA extend over 10,000 square kilometres. They include the northern jarrah forest, tuart forest and woodlands, and banksia woodlands. The woodlands experience a Mediterranean-type climate, with cool, wet winters and dry, hot summers.

Vulnerable parts of these forest ecosystems experienced substantial die-off during an acute drought associated with an extreme heat wave in 2010-2011. But warming and drying of the region has been chronic since the mid-1970s. Impact was locally severe with, for example, up to 60% of Menzies banksia dying in woodlands on the Swan Coastal Plains.

Die-off sites illustrate what can happen when these forests and woodlands don’t have enough water. If die-off occurs at larger scales, forest resources and ecosystem services (such as carbon storage and seed resources) are threatened. Increased fire is also a risk, with associated damage to property and widespread pollution from bushfire smoke, as was recently experienced in February 2021.

The Monaro tablelands of south-east NSW are characterised by mosaics of grassy woodlands, grasslands and forests. These provide important habitat for a range of threatened plants and animal species, including koalas, spotted-tail quolls and dusky wood swallows, as well as 15 other smaller marsupial species, 95 bird species, 14 species of reptiles and more.

Like most other temperate grasslands and grassy woodlands in Australia, the Monaro ecosystems have declined since Indigenous burning regimes were replaced with livestock and feral herbivore grazing, along with clearing, cultivation and non-native plant invasions.

Tragically, since 2005, ribbon gums that once dominated the rolling plains have died in great numbers. This is likely associated with the Millennium drought, ongoing drying conditions and heatwaves, and exacerbated by invertebrate pest outbreaks. More recently, the catastrophic Black Summer bushfires burned extensive areas across the Monaro.

Widespread tree deaths are not only a loss of habitat for mammals, birds, reptiles and invertebrates, but significantly impact the economy through lack of shelter for livestock during the Monaro’s harsh winters and hot summers. The impacts on the landscape’s aesthetic also affects human well-being.

The snowpatch herbfields, made up of dwarf grasses and alpine herbs, are one of the rarest and most restricted ecosystems in Australia. They occur only on steep, south-east-facing slopes of alpine and high treeless subalpine zones, where snow persists into the spring and summer growing seasons.

Over the past 50 years, climate change has caused warming of almost 1°C, and substantial decrease in snow amount and depth, cover and persistence in the Australian alpine area. Fire has also become a major force with increased frequency, dry lightning storms and extreme fire weather. And feral horses trample vegetation and cause soil erosion. These pressures, and others, are collapsing the snow patch herbfield, replacing them with larger shrubs and grasses or just eroded ground.

The collapse of the snow patch herbfields highlights the plight of the Australian alpine ecosystems in general. The alps are regional economic powerhouses; visitors to the Australian Alps generate over A$1.3 billion and the area employs almost 20,000 people.

The mountain ash ecosystem in the Central Highlands of Victoria supports the world’s tallest flowering plants. It’s among the world’s most carbon-dense forests, supporting an array of threatened forest-dependent species, and generating almost all of the water for the 5 million inhabitants of Melbourne (as well as communities and agriculturalists north of the Great Divide).

The mountain ash ecosystem is under enormous environmental pressure from widespread and recurrent wildfire, coupled with widespread clear-cut logging. Extensive old growth forests once dominated the ecosystem, but now just 1.16% of the ecosystem (1,886 hectares of 170,400 ha) is old growth. The widespread young forest is highly flammable and at extreme risk of reburning at high severity. This is especially due to increased temperatures and greater numbers of days marked as “extreme” on the forest fire danger index.

The collapse will have severe economic and social effects. The value of water from the ecosystem is 25.5 times greater than the value of the timber generated from the same ecosystem. The collapse of the ecosystem also poses an enormous threat for long-term carbon storage, biodiversity conservation and the billion-dollar tourism industry in regional Victoria.

The Tasmanian Wilderness World Heritage Area covers 15,800 square kilometres. One of its key values is the high concentration of ancient invertebrate animals and plants endemic to Tasmania (often called “palaeoendemics”). An iconic example is the genus Athrotaxis in the conifer family, which is considered one of the oldest surviving plant lineages on Earth — a living fossil.

There are two existing species of Athrotaxis: Pencil pines (Athrotaxis cupressoides) and king billy pines (Athrotaxi selaginoides). Both are very slow growing and can live for more than 1,000 years.

Like other palaeoendemics, Athrotaxis species can’t tolerate frequent or intense fire, and are restricted to fireproof landscapes. Around 30% of the range of king billy pines have been lost in the last 200 years, and half the pencil pines were burnt in the summer of 1960/61 by uncontrolled fires set by graziers to renew grasslands during an intense drought.

Climate change now threatens these and other palaeoendemic species through increased fire activity due to more dry lightning storms and drought. In January 2016, lightning storms ignited numerous fires that destroyed about 1% of the remaining pencil pines. These trees are unlikely to ever return. The loss of palaeo-endemics will profoundly diminish the region’s natural and cultural values.

Securing the survival of palaeoendemics under climate change requires costly management interventions. These include establishing fire breaks, targeted planned burning to reduce fuel surrounding the palaeoendemic refuges and active restoration programs. The Tasmanian Government and the University of Tasmania currently trial these measures.

The World Heritage sub-Antarctic Macquarie Island is home to unique alpine tundra. Cushion plants and bryophytes (such as mosses) dominate this treeless ecosystem. This uninhabited island ecosystem is one of the rarest on the planet, occurring on only eight other oceanic, sub-Antarctic islands. It’s home to many invertebrate species, and is the breeding ground of thousands of seabirds and marine mammals.

The ecosystem is rapidly collapsing due to mass die-off of cushion plants. Wind, rain and regional climate patterns all have changed in recent years, due to greenhouse gas increases and loss of ozone. There have also been increases in average wind speed, sunshine hours, and “evapotranspiration” (the sum of evaporation from the land surface plus transpiration from plants). Winter rainfall, cyclones, and a drier atmosphere also appear to have increased.

This has resulted in surface drying and raised surface evaporation of cushions and byrophytes in summer, leading to their death. With plants under such stress, an unknown disease has emerged that has now devastated much of this fragile ecosystem. And this has led to the ecosystem losing World Heritage values.

Antarctic vegetation is limited to the small ice-free areas covering less than 0.4% of the continent. Algae, cyanobacterial mats (dense “mats” of microbes), lichens and mosses dominate the flora, and there are no flowering plants. Moss beds only occur in areas where enough moisture is available during the short summer growing season. Some of the most extensive and well-developed vegetation in continental Antarctica support century old moss “forests” near Australia’s Casey Station. These lush, green moss turfs support the majority of invertebrates in the ecosystem.

From 2000 to 2013, the species composition in these Antarctic moss beds changed significantly. Moss species that can tolerate drier conditions expanded, while endemic moss, better adapted to frequent pulses of water from melted ice, declined. By 2008, half the mosses that had been green and healthy in 2003 suffered water stress, turning red or grey under drying conditions.

This drying is likely due to a combination of climate change and ozone thinning, making it windier and lowering temperatures around coastal East Antarctica in summer. This makes water less available during the growing season, and less water means less moss growth.

Historically, human activity associated with research stations has reduced local moss populations, but drying appears to be more widespread than just in the Casey region. Recovery has been limited, and in the summer of 2019-20, an Antarctic heatwave melted nearby snow banks and glaciers, causing flooding. Some grey mosses greened within a month. However, others that didn’t receive floodwater remained grey, stressed or dead.