What I do want to write about today is biodiversity and conservation in Australia, and the status of Australian wildlife in the society that has developed in the 227 years since January 26th 1788. Unfortunately I don’t think there is too much to celebrate. European settlement has dramatically altered the Australian landscape, with widespread habitat destruction, changes to land use and the decimation of native wildlife. Let us take mammals as an example: in the last 200 years almost half of all of the world’s mammal extinctions have happened in Australia, including the loss of the thylacine, the pig-footed bandicoot, and the toolache wallaby, amazing creatures that I am devastated I will never see. Today, many other Australian mammals remain at risk and many other remarkable Australian animals have also gone, like the northern and southern gastric brooding frogs (yes, they nurtured their young in their stomachs!), the Kangaroo Island emu, the paradise parrot and the Lake Pedder earthworm. Who knows how many other species have disappeared without ever being truly known, let alone appreciated. Unfortunately, it is highly likely that more will soon join them. Last year, Australian Geographic compiled a list of Australia’s critically endangered animals, including those listed by the IUCN and by the Australian Government. If you want to learn more about them, many are now profiled in a series of articles in The Conversation. The list of endangered plants is even longer. Even worse, it is not just individual species that have been affected, but whole ecosystems. Under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), 70 ecological communities in Australia are currently listed as threatened, including native grasslands, woodlands and forests.
This sorry tale raises many questions. How have we managed to stuff up so much, so quickly? What has changed since European settlement, to have had such a terrible impact on Australia? What is threatening Australian ecosystems today? What can we do to save the flora and fauna that remain?
I recently ran a straw poll amongst friends and colleagues, in real life and on Twitter. I asked “what do you think are the main threats to conservation in Australia”. I quickly received a range of responses (thanks to Alexander Dudley, Aaron Greenville, Chris Neff, Steve Leonard, Euan Ritchie, Manu Saunders, David Watson, @fudgeh0g, @diva_ex_machina and many others for contributing your thoughts) including: climate change, habitat destruction, human population growth, invasive species, land use changes, effects of mining and other big industries, public apathy, focus on economic growth, lack of resources and lack of political will to tackle conservation problems. Phew! Well that made for a depressing afternoon. To be honest the threats are so many, so intertwined and so variable that it is difficult for me to get my head around them all as a single concept. There is likely no such thing as “the single greatest threat to biodiversity conservation”. Apart from Homo sapiens perhaps…? Globally, habitat loss may be most to blame for the declines of species and ecosystems, but the causes of habitat loss are many and varied. At a local scale, threats to biodiversity vary with location, with taxonomic group (what is important for a wombat may not be for a beetle) and with habitat type. Officially, the Australian Government recognises 21 Listed Key Threatening Processes. These include the impacts of overexploitation, climate change, habitat loss, disease and introduced species.
It is impossible in one blog post to summarise all of the threats to wildlife conservation in Australia, so I thought that today I would draw on some examples that are most familiar to me, to try to illustrate this complexity. Still, this is a long post! The list below is far from comprehensive and far from even: there is a distinct bias towards vertebrates simply because that is what I am most familiar with. But if nothing else this Australia Day, I hope it will make you think about what Australian biodiversity might look like in another 227 years, and what you can do to help conserve our native species. And if you’re not Australian? Well, many of these processes will also be threatening plants and animals near you. The details may differ, but the trends do not…
- There is overwhelming evidence that the global climate is changing and there are several ways that changing climates may impact biodiversity. Many species have specific habitat requirements. Changes in average temperatures and rainfall patterns may lead to the disappearance of some of these habitats, along with their specialist species. For example, the mountain pygmy possum, Australia’s only hibernating marsupial, is restricted to alpine habitats. Higher temperatures in future are likely to reduce the depth of winter snow and the duration that snow remains on the ground in these areas, which will in turn impact on the mountain pygmy possum’s ability to obtain food and compete with other species.
- Severe weather events, such as tropical cyclones, are expected to become more common in future. More intense cyclones and their associated storm surges are likely to cause greater damage to lowland rainforests in tropical Queensland. One species likely to be affected is the endangered Southern cassowary, which will suffer food shortages and habitat fragmentation.
- Global sea levels are predicted to rise as a consequence of climate change, threatening to inundate low-lying coastal habitats. Shore-nesting birds and species that rely on coastal habitats for food and other resources will be most affected. For example, over 40% of the breeding habitat of the critically endangered orange bellied parrot is found in coastal areas below 10 metres elevation.
- The World Heritage listed Great Barrier Reef is the world’s largest coral reef ecosystem, home to an amazing diversity of marine life. Ocean acidification, caused by climate change, is a serious threat to the Great Barrier Reef. It causes coral bleaching and the breakdown of coral reef ecosystems .
- For many Australian reptiles, including crocodiles, turtles and many lizards, the sex of an individual is determined by the temperature at which its egg was incubated. Climate change is expected to alter average temperatures and temperature variability in many Australian climates, which could lead to imbalances in sex ratios for these reptiles. Some species may be able to adapt to new conditions by changing their nesting behaviour but they will remain dependent on the availability of suitable nesting sites.
- Extreme events associated with climate change, including storms, floods and fires, can provide opportunities for weeds to spread to new areas and to become established in ecosystems that were previously unaffected. For example, flammable introduced grasses, such as gamba grass, benefit from fires and are able to promote fires as their presence increases the availability of fuel. These grasses are able to replace native vegetation, such as eucalyptus woodland, with large tracts of highly flammable grassland.
- Fire regimes have changed dramatically in Australia since European settlement as a consequence of changes in human fire management, and climate change is likely to further exacerbate this. In some regions bushfires are hotter and more frequent, or occur at different times of year. These changes can adversely affect animal and plant species that are unable to recover between fire events. For example, changed fire regimes at Kakadu National Park are thought to be linked to small mammal declines, but the most appropriate fire management regime for these species remains poorly understood.
- When water is limited, human demand competes with the needs of the environment for access to this resource. For example, the Coorong, a Ramsar-listed Wetland of International Importance, receives its freshwater from the Murray-Darling system. At the downstream end of this system, the health of the Coorong is affected by human activities that remove water upstream. In recent decades the area has experienced a drought caused by the removal of much of the system’s water for irrigation and other human uses. This led to increased salinity and decreased biodiversity in the ecosystem and caused plants and animals to be less resilient to a subsequent severe weather-related drought.
- The infrastructure, including roads and port facilities, associated with mines and other resource extraction industries have serious potential to threaten biodiversity. For example, there are several planned and proposed port developments that have the potential to damage the Great Barrier Reef by dredging and dumping sediments and by increasing shipping traffic through the area, with an associated higher risk of pollution and accidents. In Western Australia, a new mine development approved in 2014 is expected to cause the loss of over 5,000 hectares of native vegetation and may disturb populations of protected species, including the Pilbara leaf-nosed bat.
- Development of natural environments for housing, industry and mining often leads to habitat destruction. One strategy used to mitigate the impacts of development on biodiversity is off-setting, where developers compensate for the loss of habitat through the protection of comparable habitat nearby. However, the effectiveness of off-setting remains poorly understood for many Australian habitats, and factors such as habitat fragmentation and variation in resource availability may mean the area of land that needs to be protected to ensure no net loss of biodiversity is actually much greater than the area that was developed.
- Coal seam gas extraction has the potential to damage Australian ecosystems through direct habitat loss, but, perhaps more worryingly, through the risks of pollution of groundwater systems and the habitats they supply.
- Australians enjoy eating seafood, and apparently we each eat around 25kgs per year. No doubt many people are enjoying prawns today at their Australia Day barbie. Relatively speaking Australian fisheries are well managed, but this does not mean that they are completely sustainable and moves to allow supertrawlers to fish in Australian waters pose even great threats of overexploitation and bycatch. Bycatch of seabirds during oceanic longline fishing is a particular threat to albatross and petrel species.
- Illegal trade in wildlife has the potential to seriously threaten some endangered species with small breeding populations, such as some reptiles and several species of black cockatoo. Unfortunately, there is high demand from international collectors for many of Australia’s unusual animals, providing lucrative incentives for criminal activity.
- Development of coastal habitats for housing and industry, including aquaculture, can impact many species. For example, shoreline development is one of the greatest threats to the persistence of mangroves, which provide habitat for many marine and terrestrial animals and plants, including commercially important fish and prawns.
- Agricultural and industrial activities near coastal areas can increase the runoff of nutrients and sediments into estuarine and ocean environments. Australia is home to the most diverse seagrass communities in the world and these play an important role as habitat for many aquatic species. Seagrass meadows are highly sensitive to reductions in the amount of available light and are threatened by any factors, such as sediment runoff and algal blooms caused by excess nutrient availability, that increase the turbidity of ocean waters.
- Since European settlement, approximately 13% of Australia’s native vegetation has been cleared, predominantly for agriculture, industry and housing. The scale of clearing has disproportionately affected some habitat types, for example it is estimated that 34% of Eucalyptus woodlands and 99% of temperate lowland grasslands have been destroyed. It is estimated that, in Queensland, around 100 million mammals, birds and reptiles died each year between 1997 and 1999 as a result of native vegetation removal. For habitat specialists, such land clearing can be catastrophic: the grassland earless dragon is restricted to native temperate grassland habitats and is threatened by the loss of almost all suitable habitat.
- Hollows in old and dead tree trunks provide important nest sites for many native vertebrates. Urban development of woodland areas often disproportionately affects hollow-bearing trees, as these may be considered dangerous to homes and infrastructure nearby. Meanwhile, the demand for forestry resources has led to the adoption of silvicultural practices that do not provide sufficient time for hollows to develop before trees are harvested. The endangered Leadbeater’s possum relies on the availability of suitable hollows for nest sites and is threatened by logging activity and bushfires that remove these.
- Light pollution from roads, houses, hotel and industrial developments can threaten marine turtle nesting success, by disorienting hatchlings and causing them to travel away from the sea when they leave the nest.
- Australia has become home to many invasive species. Among them, the red fox and the cat were surely two of the worst gifts ever bestowed upon Australia by European immigrants. Feral cats are likely the greatest current threat to Australian mammals, while foxes have been implicated in numerous declines and extinctions. Black rats most likely arrived in Australia on early ships from Europe. Unlike foxes and cats, their importance as invasive predators of native wildlife is not as well recognised, but they have been blamed for the declines of several invertebrates, birds and reptiles, especially on islands without larger predators to control them.
- Feral pigs are also predators of native Australian wildlife, but they may have greater impacts on biodiversity loss through their degradation of habitats and competition with native species. Introduced rabbits and goats are also environmental pests in Australia and contribute greatly to habitat degradation.
- Cane toads were introduced to Australia in the 1930s as a biological control agent. Unfortunately this effort backfired, and cane toads are now a listed threatening process in their own right! One of the reasons that cane toads are so destructive to native wildlife is that they are toxic to most predators that eat them: this has contributed to declines of several predators in northern Australia, including the northern quoll and goannas.
- Other introduced animals have the potential to become much greater threats in the future. The Indian myna bird and feral bees compete with native wildlife for tree hollow nest sites. The omnivorous red fire ant threatens both plants and animals, and the yellow crazy ant, which has already had a devastating impact on Christmas Island may become established elsewhere in Australia if we are not vigilant.
- Animals are not the only pests. There are 32 listed Weeds of National Significance in Australia, including horticultural plants that have escaped into natural habitats. For example, bitou bush aggressively out-competes native vegetation in coastal areas, while water hyacinth, one of the world’s worst weeds, chokes wetlands, obstructs waterways and provides habitat for mosquitoes.
- The fungus Phytophthora cinnamomi (also known as Phytophthora dieback) may be the biggest threat to biodiversity in much of western Australia, with over 40% of native plant species susceptible to infection.
- Myrtle rust is a new threat to hundreds of Australian plant species in the family Myrtaceae, which includes eucalypts, melaleucas and tea trees. It was first detected in Australia in 2010 and has the potential to become a serious problem for plant conservation.
- Chytridiomycosis is a disease that affects amphibians. It is caused by a highly virulent fungal pathogen, Batrachochytrium dendrobatidis, that has caused a global epidemic resulting in the declines or extinctions of at least 200 species worldwide. In Australia it has been implicated in the extinctions of four frog species and the declines of at least 10 others.
- Psittacine circoviral disease (PCD, also known as beak and feather disease) affects parrots and related species. It is often fatal to birds and is known to be able to infect several threatened species, including the orange bellied parrot and the swift parrot.
- Devil facial tumour disease (DFTD) is a contagious cancer that infects the Tasmanian devil. It is fatal to all animals that are infected and has now spread across much of Tasmania: devil sightings have declined by 80% on average since DFTD was first detected.