Biodiversity underpins a range of essential services to humans, including food production, air and water purification and climate stabilisation. Despite the efforts of many people, however, biodiversity continues to decline.
This is because a ‘extinction debt’ persists from past environmental degradation and current conservation actions are unlikely to reverse the trend.
Threats to Biodiversity
There are many threats to biodiversity in South Australia. Some are long-term pressures (e.g. climate change) that can affect species over large distances, but most of the threats are much closer to home. These local pressures include habitat loss and fragmentation; invasive species, including weeds, feral animals and predators; changing land management practices such as grazing and inappropriate fire regimes; changes to marine food webs and human impacts on marine and terrestrial breeding and feeding habitats; water quality (e.g. pollution from sediment runoff and pesticides); and direct human activities such as land clearing, invasive plant management and agricultural practices (Braby 2019).
The abundance and distribution of native animal species in rural South Australia are declining, particularly in the most-populated regions of the State. 12% of South Australian native animal species are threatened with extinction, with the greatest threat concentration in the Adelaide and Mount Lofty Ranges (Government of SA 2018). At a community level, the number of Threatened Ecological Communities in the State has increased since 2016 (see Figure 1 below). The most-threatened ecological communities are those with the highest probability of extinction and are found mainly in heavily modified landscapes for agriculture and urban development.
The State Government’s budget for the environment is not large, but it is important that the right priorities are set, and that all levels of government work together effectively to deliver improvements in biodiversity outcomes. This includes fostering biodiversity-friendly farming through initiatives such as Heritage Agreements and Landcare; removing policy barriers that limit conservation efforts; promoting biodiversity-friendly grazing and the use of natural resource management tools; and fostering a culture of stewardship on private properties.
In addition, the production of energy – electricity and transport fuels – is intimately linked to biodiversity outcomes in South Australia. From mining uranium and fracking natural gas, to vegetation clearing for wind farms and solar energy installations, to reducing emissions via coal and biofuels, the energy industry needs to recognise that it can have a positive impact on biodiversity through the use of technologies such as regenerative agriculture and bioenergy.
The invasive species (plants, animals and pathogens) that thrive in areas they don’t naturally occur are major threats to biodiversity. They can displace native species, compete for resources with them and degrade habitat. Invasive species often disrupt ecosystems, and are responsible for a wide range of impacts, from causing direct economic harm to threatening human health. Examples of invasive species in South Australia include cane toads, tamarisk, salt cedar, and the ice cream bean, Surinam cherry, and Arabian coffee (Coffea arabica).
A major threat to wildlife in rural South Australia is habitat loss and fragmentation. As a result of farming and development, the extent and quality of native vegetation has declined in many parts of the state since European colonisation. It is difficult for many native species to adapt or survive in agricultural landscapes, particularly on land with poor soils and shallow water tables. The decline of native vegetation also has a detrimental impact on the ecosystem services provided by the natural environment such as water filtration, carbon sequestration and soil stabilisation.
Intensive farming has contributed to the loss of biodiversity through changes in land use, soil management and fire regimes. However, there are some farmers who take a long-term view of the value of biodiversity, and protect and restore their land for the benefit of wildlife. There are also a growing number of people who are taking on the responsibility for biodiversity conservation on private property. These individuals and groups contribute significantly to the preservation of South Australia’s unique biodiversity through their work, efforts and financial contributions.
The energy sector is another important factor affecting biodiversity. It is essential to our society, yet its operation can have a negative impact on the environment. From mining uranium to fracking for gas, to vegetation clearing for wind turbines, to bird and bat deaths caused by electricity generation, the energy industry is an important driver of biodiversity loss in rural South Australia. A transition to a 100% renewable energy future could mitigate these effects, but it will require an enormous effort. Until then, we will need to carefully monitor the impacts of energy production on biodiversity in our landscapes.
As land is converted to pastures, crops, plantations and built areas, the ability of the natural habitat to support biodiversity is reduced. This is a problem not just for the animals and plants themselves, but also for the humans living in rural areas. Poor people usually suffer the most from the loss of natural resources, especially when they are dependent on the use of natural habitats.
In South Australia, land is increasingly used for agricultural production (Government of South Australia 2018). This means that the quality of the soil is changing, and this in turn affects biodiversity through direct human impacts. This is particularly the case with nutrient depletion, soil erosion, and the removal of native vegetation.
In addition to these direct impacts, the presence of invasive species reduces the diversity and functioning of natural ecosystems. For example, weedy plants such as African boxthorn Lycium ferocissimum and arum lily Zantedeschia aethiopica can out-compete native species for nutrients, whilst invasive pest animals like feral goats Capra hircus and dromedary camels Camelus dromedaries can damage agricultural and horticultural products through grazing pressure, herbivory and competition for food and water.
A range of measures could be taken to improve biodiversity outcomes on agricultural lands. One obvious course of action is to promote the development of biodiversity-friendly agriculture that spares native habitats. This includes a focus on ecological functions, such as pollination networks and predator-prey dynamics, rather than focusing solely on the restoration of historical biodiversity baselines (Frankham et al. 2014).
The development of landscape-scale models that can predict the impacts of a range of changes on the ecosystems in which we live is another important opportunity. These models could help us to better understand how the ecological communities of our state will change over time and allow us to plan for the future with greater confidence. Finally, boosting Government funding for the environment is critical to improving the effectiveness of environmental management in the countryside. The current level of Government funding is insufficient to protect biodiversity in the face of increasing human demand for the natural resource, and it is continuing to decline (Fig 3). Increasing this budget would allow us to more effectively target environmental management practices at the local scale to ensure the survival of the most threatened species.
Biodiversity – the variety of life on Earth – is essential to all natural ecosystems, as well as to human survival and wellbeing. This variety, represented by the genetic variation of organisms within a species and between species, is manifested in all living things and all the complex ecosystems they make up (Convention on Biological Diversity, Article 1b).
Human activity has caused a significant increase in the global rate of biodiversity loss, with the extinction rate now approximately 1000 times faster than would be expected from normal environmental fluctuations alone (Bradshaw et al., 2015). The elevated extinction rate is driven by a wide range of economic activities of the 7.5 billion-strong global human society, including direct exploitation of other species for food, clearing of forests and grasslands for agricultural production, spread of invasive species, pollution, and anthropogenic climate change.
Despite these challenges, the human impact on biodiversity can be slowed with better coordination and funding of conservation efforts. A doubling of current State Government investment in environmental protection and management would provide a substantial boost to the ability of South Australia to protect its threatened biodiversity (Fig. 2).
In addition to improving funding, it is important to recognise the importance of Indigenous peoples and their knowledge of and embeddedness in local ecosystems. This must be reflected in all conservation planning, decision making and activities.
South Australia has a good record of protecting its biodiversity, with large areas of land in the arid and semi-arid regions having been set aside as protected areas (Suppl. material 1). However, the condition of biodiversity in these areas is still declining compared with other parts of the State. In particular, the recovery of species richness and endemism in these arid regions is lagging behind other parts of the State.
In recent years, a large number of programs have been implemented to revegetate cleared land with native plants, especially in the arid and semi-arid areas. While such programs are a positive step, they must be carefully designed and managed to be effective. In particular, they should not rely on “biodiversity offsets” whereby the destruction of one habitat can be ‘offset’ by paying to restore another ecosystem (Bekessy et al., 2010; Maron et al., 2015).
To ensure the effectiveness of such programs it is also important to implement monitoring and adaptive management that demonstrates that the interventions are actually improving the resilience of the target species. This will require robust, scientifically sound monitoring and estimation of counterfactuals.