Above from left, Professor Stuart Kahn, Dr Ian Goodwin, and Professor Michelle Leishman.

What can scientists tell us about how climate change will affect coastlines and cities, asks Fran Molloy.

Most Australians live in cities and towns and even houses that were built a century ago, and that are no longer suitable for the climate of 2022, which is already hotter by one degree Celsius than in 1910.

What will our cities, our coastlines and our urban landscapes look like next century, when locked-in global climate change will push average temperatures up by at least another one to two degrees, no matter how soon we halt greenhouse emissions?

PROPERTIES

Karl Mallon, chief executive, Climate Valuation Climate risk and infrastructure analyst

Climate change poses huge threats to property, says Karl Mallon, who models the impact and cost of climate change on assets for large organisations. “Even properties in the middle of a city, not exposed to bushfires, not exposed to flooding and not exposed to sea level rise, will still be at risk and may be dangerous to be in during a heatwave,” he says.

Property in 2120 will have passive temperature controls (insulation) as well as active intervention, including safe zones for residents. “Cities and apartment blocks may have highly airconditioned areas, where people can take temporary refuge during extreme heatwaves,” Mallon says.

By 2120, properties must adapt to extremes, he says – building codes in flood-prone areas might require elevated living areas with parking underneath. “Properties could comprise resilient materials that can withstand ember attacks, and selfprotect with automatic sprinkler systems so people can leave safely – things we are just starting to do now will become universal.”

Mallon says that the scenario for people in 2100 depends on changes we make today.

“Will we live in a techno-utopian world where we planned well and have prepared for climate risks in our property sector? Or will we fail to do that work and leave people to live in inappropriate properties?”

SEA LEVEL RISE and COASTAL RETREAT - Ian Goodwin/Mitchell Harley

Australia’s coastline will see serious impacts from sea level rise –varying wildly from place to place, says Dr Ian Goodwin, a marine climatologist and Principal Scientist at ClimaLab advising governments and organisations on marine climate risks.

His work with paleoclimate and satellite data tracks sea levels during the last interglacial period, around 125,000 years ago, when global temperatures were about two degrees warmer than today, finding that while sea levels in some locations were six to eight metres higher than today – others experienced little change.

“Our notion of sea level rise is that it is universally linked to coastal erosion and coastal retreat, but in fact, it’s not a one-size fits all impact, and sediment supply from the continental shelf or river systems can leave sections of the coastline stable through rising seas because of that supply of sand,” he says.

Dr Mitchell Harley from the University of NSW has mapped Australian beaches using satellite photographs since the 1980s, and says most of Australia’s coastline has been stable over the past four decades, when sea levels rose around 10 centimetres.

“Beaches are surprisingly resilient and while they can be almost instantly depleted in extreme storms, most can recover relatively quickly too,” he says.

Climate change will bring a dramatic rise in extreme events along with more rapid sea level rise, he says – meaning significant coastal inundation in some (but not all) areas.

“Uncertainty is rife, but our current, rigid planning instruments make zoning almost impossible to change, creating an inflexible way to deal with coastal erosion where billions might be spent on ineffective defences,” he says.

Harley says that over the next century, it will be important to establish buffer zones to accommodate ongoing uncertainty around how coastlines respond to extreme storms and significant sea level rise.

Dr Mitchell Harley, above, is pushing for buffer zones to protect our coastlines from extreme storms and a rise in sea levels.

WATER SECURITY

Professor Stuart Khan

“Water scarcity will heighten, and Australia can expect extreme weather events to increase in both frequency and severity, meaning our water systems will need the ability to be resilient,” says Professor Stuart Khan, who is Professor of Civil and Environmental Engineering at the University of NSW. “There will be increased focus on ‘rainfall-independent water supplies,’ such as seawater desalination plants and underground aquifers to meet water shortages during droughts,” he says. Khan says that the key is good planning – and Victoria’s 50-year water plan includes urban water strategies that focus on the proportion of the city’s demand for water to be supplied through rainfall-independent sources, and desalination plants will play a growing role in water resilience for coastal cities. “The other big rainfall-independent supply which will play a growing role in inland cities, is recycling through advanced water treatment processes, which we can already do, and this almost becomes an infinite source of water because you can use the same water over and over and over again,” he says. “The key to this is having secure, cheap energy sources – renewables will play a vital role here.”

URBAN GREENSPACE - Professor Michelle Leishman

Plant ecologist Professor Michelle Leishman is Director of Macquarie University’s Smart Green Cities hub, creators of the ‘‘Which Plant Where’’ program guiding councils and landscapers on the plant species to best survive a harsher future climate. “Extreme heat and declining rainfall will affect green spaces and urban vegetation – particularly for inland suburbs and towns away from coastal breezes,” she says. “These locations will also rely on greenspace and shade to provide adaptation, cool the environment and make our cities more liveable,” she says. Leishman’s research uses government climate models and planning tools to test the plant species that can best tough out the likely future climate extremes like heatwaves and flooding. “We’re developing the evidence base, tools and resources for the urban forestry industry to plan over the next century,” she says. Leishman says that today’s planners also face environmental protections that are under constant siege due to rising land values, particularly in urban areas. “There’s constant conflict between the greater, long-term communal good from that urban greenspace versus an individual’s capacity to make short-term profits from developing land; finding the right balance can be a struggle.”

Fran Molloy

100 years of climate change: what to expect