Outlook and impacts

Outlook

The coast is a zone of concentrated biodiversity, productivity and human impacts. Productive shallow waters and fertile soils give rise to a huge number of species and proliferation of life. However, human impacts generally increase with population density, and with 87% of Australia’s population living on the coast, the coastal environment faces intense pressure. Climate-related pressures are also increasing, with potentially devastating consequences to vast areas of coast.

Australian coasts are likely to continue to encounter significant and sustained pressures from population, industry and climate. In what is known as ‘coastal squeeze’, coasts are faced with pressures from both sides – land and sea – which narrow the range of available habitat for coastal biodiversity and, in some cases, squeeze species to extinction.

Pressures on the coast can be categorised as climate, population, industry or biologically driven. Population and industry pressures remain strong in Australia due to our predominantly coastal population, and include legacy issues from historical contamination and poor environmental management. It is, however, climate pressures that have received the most attention in recent years, due to greater understanding of future scenarios and the brutal impacts of extreme weather events such as storms, fires and floods on the coast.

According to assessments by academic experts, 2 pressures on the coastal environment (nutrient pollution and flow regimes) are considered to be improving, while 7 are stable and 10 are deteriorating. As climate change accelerates, our coastal population grows and industry expands into new territories, Australian coastal ecosystems face an uncertain future.

The relative impacts of climate-, population- and industry-driven pressures are shifting in balance, with extreme weather events becoming an increasingly dominant pressure and dwarfing some of the population-driven impacts that have previously held attention. Extreme events have inflicted major impacts since the 2016 state of the environment report, including heatwaves, floods and bushfires (see the Extreme events chapter). Since the 2016 report, we have witnessed the largest bushfires ever recorded in New South Wales and the degradation of large areas of mangroves in northern Australia.

A survey of 34 coastal local government areas (LGAs) (see Local Government Area survey) found that, overall, extreme weather events were considered to be the greatest threat to our coasts (Figure 1), as determined by a combination of impacts and trends. Coastal development and land use were perceived as the second-greatest threat, followed by erosion and inundation which are consequences of sea level rise.

On average, LGAs considered extreme weather events to be the pressure imposing the greatest impact on their local coast (Figure 2). This was followed by terrestrial invasive species – a concern shared by academic experts – coastal development and land use, and erosion and inundation. Very few of the pressures on the coast were considered by LGAs to be well managed, with the exception of cultural harvest.

As a consequence of pressures, two-thirds of the environmental components (environments, habitats and species) assessed by academic experts for this chapter are considered to be in poor condition at a national scale (Figure 3). Shorebird species are the most imperilled species group covered in this chapter, with 12 of 19 migratory species showing national-scale population decline in recent decades (Clemens et al. 2016). This decline appears to be primarily driven by destruction of their habitat overseas, such as land reclamation occurring in China. We should expect the extinction of some threatened species within the next decade unless urgent management intervention occurs (see the Biodiversity chapter).

In contrast, other coastal species are thriving and will potentially benefit from warmer conditions in the future. With no natural predators, crocodiles continue to grow in number in the Northern Territory. Other species and habitats are also doing well in some parts of Australia despite a poor national outlook, as reflected in the mixed gradings provided by Traditional Owners and local governments in local and regional assessments (Figure 3).

Australian society has undervalued certain ecologically important coastal habitats, such as saltmarshes, mangroves and dune vegetation, leading to their severe degradation. Because of their prime positioning close to the water and perceptions of low aesthetic appeal, these habitats have been deprioritised in favour of coastal development, and exploited or degraded by human activities. Historical losses of these habitats are yet to be rectified, though new impacts are less common and restoration efforts are underway.

Restoration projects exist for several key habitat-forming species, including seagrasses, mangroves, shellfish and algae. Most of these projects aim to advance knowledge of the principles for restoration and provide proof-of-concept, but are rarely conducted at spatial scales necessary for restoration of whole populations. They offer hope, however, that restoration can be achieved in the future with sufficient resources.

The redistribution of marine life is caused by both climate change and other human activities. There are numerous examples of climate change shifting the distributions of species southward – a trend almost certain to continue. We are likely to see species establish in new areas, such as mangroves expanding southward, and tropical marine species moving into temperate reefs.

Indigenous communities are raising concerns about the health of their sea Country. To take action, we must embrace diverse thinking and respect the wisdom that Indigenous knowledge holders have developed through their lived experiences with continuous adaptation to environmental change across their Country. Co-design processes must rapidly replace top-down hierarchies – in which government is at the top – with a willingness to work together on an agreed platform of decision-making that respects diverse knowledge and views. Improvements are being seen in bringing agencies to the table of Indigenous-led management. To keep building progress, it is important to acknowledge the collaborations and expanding efforts that have brought us to where we are now, and identify what can be catalysed for future advancement in coastal management.

We have been trying for some time to create change. It has to be imposed change, legislative change – we need to have that accountability. (Participant, Traditional Owner online yarning circle)

Impacts

The outlook for Australian coasts will have subsequent impacts on environmental and economic values, and human wellbeing.

Environmental and economic impacts

First, the good news. Management of some population- and industry-driven pressures on the coast is improving, such as measures to curb nutrient pollution and alterations to flow regimes. The populations of many iconic coastal species are doing well, such as dugongs, or very well, such as crocodiles. If these trends continue, we may make significant progress towards achieving several United Nations Sustainable Development Goals and reducing impacts on the coastal environment.

Now for the bad news. The growing threat of more frequent and severe extreme weather events is difficult to manage, at least in the short term, and has impacts that can dwarf those of population- and industry-related pressures. For example, the 2019–20 megafires and the mass dieback of mangroves in northern Australia undoubtedly resulted in staggering losses in biodiversity and ecosystem services, most of which are unmeasured. The cost of the 2019–20 megafires is estimated to exceed $100 billion − making it Australia’s most economically costly natural disaster to date.

Large-scale losses of coastal habitat-forming species, such as mangroves and seagrasses, as a result of either coastal development or extreme weather events, are particularly damaging to biodiversity and ecosystem services. Since European arrival we have lost approximately 47–78% of saltmarsh and mangrove extent and 20–26% of seagrass extent (Serrano et al. 2019), and in some areas, these habitats are now suffering mass climate-driven dieback (Duke 2017).

Losses of habitat-forming species impact not only the habitat formers themselves, but many other species that rely on them for habitat, food and other ecological services. This includes species on the Environment Protection and Biodiversity Conservation Act List of Threatened Fauna, such as dugongs, which feed on seagrasses and whose populations have been impacted by cyclone damage to seagrass meadows in south-eastern Queensland. It also includes numerous invertebrate species, many of which are undescribed but provide essential ecosystem services.

Loss of biodiversity also results in loss of ecosystem functions and services. Ecosystem functions include primary production, nutrient recycling and biological resistance to invasion by exotic species. Without proper ecosystem function, we may lose critical ecosystem services that benefit human society, such as clean water, food and stable coastal sediments. Importantly, coastal vegetation, and coral and shellfish reefs provide natural protection from storms and storm surges, so their removal leaves coastal land more vulnerable to extreme weather events and erosion.

Another key ecosystem service provided by coastal ecosystems is carbon storage, often referred to as blue carbon storage when associated with coastal and marine systems (Serrano et al. 2019). Australian saltmarsh, mangrove and seagrass habitats are globally important sources of blue carbon storage, and are estimated to hold 5–11% of blue carbon soil stocks worldwide, despite major historical losses. Conservation and restoration of these habitats can help Australia mitigate fossil fuel emissions while gaining beneficial ecosystem services, such as coastal fortification and habitat for biodiversity.

The redistribution of species due to climate-induced range shifts and exotic species invasions will impact biodiversity and ecosystem functioning into the future. As species move south, new biological interactions will occur. We will then be faced with deciding how such range expansions should be viewed and managed – either as natural processes that should be left uninterrupted, or as biological invasions requiring interventions to protect local species.

Figure 4 summarises scores for the condition, trend, outlook and management effectiveness of each topic, as assessed by local government areas (LGAs). Academics, Traditional Owners and LGAs all identified threatened species as being of high concern, because many continue to decline. Shorebirds were the species group of greatest concern to LGAs, reflecting national trends of decline in numerous shorebird populations.

The degradation of our coastal environment has economic consequences for coastal livelihoods and our $60 billion tourism industry, the seventh largest national tourism market globally. Coasts, especially features such as the Great Barrier Reef, are a strong focus for both domestic and international tourists visiting Australia.

There are staggering economic impacts associated with invasive species, which in 2011–12 cost Australia an estimated $13.6 billion (Hoffmann & Broadhurst 2016).

Human wellbeing

Human wellbeing is inextricably linked to the state of the environment – a connection well documented in the emerging field of ‘planetary health’ (Myers & Frumkin 2020). Experiencing and interacting with nature benefits both physical and mental health, and because 87% of Australians live on the coast, our wellbeing is closely tied to the health of our coastal environment.

The quality of the environment affects many components of wellbeing, including:

• health
• living standards
• community and social cohesion
• security and safety
• freedom, rights, recognition and self-determination
• cultural and spiritual fulfilment
• connection to Country and nature.

Each wellbeing component is related to assessments in this chapter (Table 1).