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The vast majority of Australians (87%) 50 kilometres of a coastline. The coast offers scenery, swimming and cooling from the sea.

But the problem is, coastlines as we know them are going to change. Sea-level rise is accelerating. As seas inch higher, storm surges can reach further inland and coastal erosion intensifies. Australia’s coasts are .

Low-lying areas are particularly vulnerable, such as Western Port Bay in Victoria.

So why aren’t we planning for what will happen? In this year’s federal budget funds were allocated to many long-term needs, such as submarines for defence (around a 20-year timeframe), the Inland Rail project for freight (around 15 years), Sunshine Coast rail link for transport (at least 10 years) and long term policies for green manufacturing. State budgets also make long-term commitments.

But there was nothing to prepare our coastal communities for the water. Sea level rise and storm surge are problems which get steadily worse. If we spend to avoid A$1 billion of damage in 2040, that’s the same as avoiding $4 billion in 2070 and $10 billion by 2100, according to the released last year by co-author Tom Kompas and colleagues.

The economic costs are known

If we don’t prepare, we risk damage to housing, the environment, towns and coastal and marine industries.

What does sea-level rise cost? The Kompas report found within 75 years, the projected sea-level rise of 0.82 metres coupled with 19% more storm surges would cause staggering economic loss in Victoria, to the tune of $442 billion, flooding 45,000 hectares of inhabited land and affecting almost every coastal community.

Overseas, the scale of the problem is staggering. Estimates for damage to coastal towns and cities in the European Union and United Kingdom are $1.4 trillion.

Why aren’t we taking this seriously?

It is good practice to strategically plan for known risks and needs. And we do make long-term plans in many areas. But so far, coastal adaptation is not one of them.

Because greenhouse gas emissions aren’t dropping as needed, we have already a certain level of sea-level rise. That’s because there’s a lag time between emitting gases, warming the atmosphere and oceans, and melting ice flowing into seas.

What does adaptation look like? We have six options:

1. Non-intervention: authorities deliberately let impacts occur. You might use this strategy if it would be too expensive or impossible to protect a coastal area, or if there are no people living there.

2. Avoid: make sure new houses, infrastructure and human uses for coastline are moved away from the area to be affected.

In Australia, local or state-wide sea-level planning benchmarks are used to denote areas where permanent development needs justification. Benchmarks and assessments differ markedly around the nation.

3. Nature-based methods: boost or restore natural systems able to reduce damage.

This method involves working to bring back or improve natural habitats such as , sand, shellfish reefs, mangroves, wetlands, saltmarshes, or seagrasses to build up sediment, adding height and natural ways to absorb some of the force of higher seas.

Many Australian states already have examples . In the EU, the REST-COAST program is many nature-based restoration projects, while the United States has many examples, such as .

4. Managed retreat: relocate away from the danger.

The community of Isle de Jean Charles in Louisiana was the first community globally to in a planned way. In Vietnam, farms and villages in Hue province have away from the sea.

While no Australian community has gone through a managed retreat due to sea level, the Summerlands estate on Phillip Island to protect Australia’s most famous penguin colony.

5. Accommodate: rebuild to reduce risk.

When disaster strikes, it makes sense to rebuild to reduce future risk. Australian authorities often use this technique . But there are no known examples of similar work on our coasts. In the US, areas of New Orleans to let future floodwaters escape rather than stay trapped for weeks, as they did after Hurricane Katrina.

6. Protect: build hard physical barriers to stop the water getting through.

Historically, building seawalls and dikes has been the first response authorities reach for. The problem is, these barriers are expensive to build and maintain, especially at the scale that will be needed.

Where to from here?

What will nudge authorities to start preparing in earnest? Time, for one. As sea-level rise accelerates, authorities will have to act.

But acting late is much more expensive than acting early. We need to avoid the , where catastrophe seems far enough away in time that we can delay acting.

What our policymakers need is the social license to act. The planned retreat of the Welsh town of Fairbourne because when the council’s plans became public, house values plummeted.

To be able to focus on coastal adaptation means so politicians are supported to make hard but necessary decisions in the interests of the next generation.

A national approach would help. Not everywhere can be protected. It makes sense to focus our efforts on places where many people live, or the special habitats we want to keep.

If we keep putting our heads in the sand, we’ll get soaked.

Acknowledgement: Alan Stokes of the Australian Coastal Councils Association contributed to this article

Anthony Boxshall an Enterprise Fellow at the University of Melbourne, the Chair of the Victorian Marine & Coastal Council, a Board member of Parks Victoria, and the Principal & Founder of Science into Action, a science impact company.

Anna Grage is a Visiting Research Fellow with the University of Adelaide, and a Board Member on the Victorian Marine and Coastal Council (VMaCC). The Kompas Report, as referred to in the article, was commissioned by VMaCC. Anna is also a Principal Consultant with Earth-Sea Planning.

The University of Melbourne and Tom Kompas received support and research funding from the Victorian Marine and Coastal Council, Life Saving Victoria, and the (then) Victorian Department of the Environment, Land, Water and Planning.