Hot in the City: Our cities will only get hotter as development expands - and a lack of trees doesn't help

The fresh drone images, taken by The Courier, show the lack of vegetative cover provided in new housing estates, where homes are pushed up eave-to-eave on ever-shrinking blocks. Some are now being sold on allotments of 250m2 - less than the area of a tennis court, smaller blocks of land than were once provided to Housing Commission dwellings.

In some cases there is literally no room for a small garden let alone a tree; certainly not a shade tree of any size. While these are new estates and newly-planted trees are still in their infancy in many cases, the survival of those trees is not guaranteed.

The pictures demonstrate an overall failure on the part of planning regulations across Victoria to adequately address the removal and replacement of trees and vegetation, and of a need for changes in legislation and education to ensure developers, residents, councils and communities understand the vital importance of trees in preventing urban heat build-up.

Even the government's independent advisory body Infrastructure Victoria has called for reform to accelerate the replacement of trees. In its latest 30-year strategy, two draft recommendations are: a 30 per cent tree canopy coverage in new growth areas by mandating coverage during precinct development, with funding for relevant Victorian Government agencies and local government to plant, replace and maintain canopy trees; and immediate reform to the developer open space contribution scheme, providing direct funding to create interconnected open space networks and extend Melbourne's urban tree canopy.

The City of Ballarat has several tree management plans and an exceptional tree register, all covered under its 2019 Urban Forest Action Plan. The plan proposes to double Ballarat's tree canopy to 40 per cent by 2040, planting 2500 trees a year in public areas for the next decade.

Will this be enough to offset the heat island affect created by massive development and tree removal? The City's plan itself acknowledges that:

The number of trees and therefore canopy cover on land not owned or managed by council is yet unknown... Given the paucity of data on private trees it is unknown whether tree canopy over private property is increasing or decreasing over time. This information is required in order to develop appropriate actions to preserve existing tree stocks and encourage canopy cover on private lands.

But all tree planting is now a Catch-22 situation. As heat builds and temperatures rise in crowded development areas, those trees which have been planted are less likely to survive. According to research journal Nature Climate Change, it's likely in the next 60 years over 90 per cent of our eucalypt species - our hardiest trees - will lose 50 per cent of their distribution area as they succumb to increased temperatures of just three degrees. Those trees which do survive will need increased amounts of water and nurturing, making them more expensive to maintain.

Much of the land being developed in the west was scarcely-treed grass and farmland to begin with, but the massive buildup of asphalt and concrete requires new approaches to replacing even that vegetation, says RMIT's Sustainability and Urban Planning Associate Professor Joe Hurley. And it will have an effect on the rest of Ballarat, especially with summer north-westerly and westerly winds.

Professor Hurley is one of a number of contributors to a series of reports mapping vegetation cover and heat vulnerability in Melbourne and the regions. The reports, created for the Victorian Department of Environment, Land, Water and Planning (DELWP) were published in 2019 and 2020. He's also contributed to a series of academic papers on the impact of tree densification and tree loss in many journals.

He says while local governments across Australia are becoming more progressive in addressing urban forestry, strategies and programs, investment is still very focused on public land, rather than encouraging private residential planting as well.

"There are less barriers to action on (public) land; however, it makes up the minority of of land in our cities, the majority of it is private land," Professor Hurley says.

"The more recent developments, compared to 10 or 15 years ago, are actually doing a bit better on public land. But if you're talking about getting a reasonable canopy cover, that's not enough land. Even if you get all the electricity wires and pipes in the right spaces and footpaths and crossovers and all that, you're just not going to get there. So then there's the question of private land - and there's not really much effort going on there in new development at all."

"We also see a growing recognition and an appetite for action, to try and have stronger influence on private lands, which holds the balance of land and the balance of vegetation and trees in most urban areas. We're seeing losses particularly concentrated on private land. All the empirical work we've done looking at tree change over time shows the greatest losses on private land, and the reasons for that are quite complex."

One of the reasons is simply expense. Developers aren't tree-planting charities; they're in business to make money. Planting trees and making sure they survive is expensive, and it affects the bottom line.

"It costs money in terms of potential impacts on your floor area, in the simplicity of delivering a housing product, says Professor Hurley.

"So it's messy. If you're in the business of flipping land, putting houses on it and selling at the bottom into the market, it's messy. Like six-star housing, it's messy. Anything you're adding onto your business model is generally resisted. You're trying to maximize return on investment, often in situations where they're fairly highly leveraged themselves."

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Therein lies the problem, says Professor Hurley. Tree coverage and retention targets are great, but they deliver nothing without effective strategy; strategies require enforcement. When new homes are one of your two key sources of income, and developers are delivering those homes, councils are unlikely to bring developers to a regulatory heel.

"If you're not developing strategy to deliver on that target, and the monitoring and evaluation to check on your progress against your plans to deliver that target, then the target becomes pretty meaningless. So a target of 40 per cent cover increase (referring to the City of Ballarat's planned coverage target) - what I would like to see is how that's actually expressed in physical terms. For this increase, across the whole city based on average, that's probably works out okay. But where does that cover go?

"It sounds good. I'd like to see the thinking behind it. In many areas they (council) lack the agency and the authority to potentially have much impact, particularly when we're talking about private land, where the relationship with state planning and the broader economy of urban land development is the business end of that basic discussion. We can't just pile on local government.

"But we also don't want to ignore or understate the issue of the sentiments of individuals and households and communities with respect to trees. That is a worrying trend for a range of different reasons: a position where many households say 'I just don't want trees in my yard.'

"It's one of these things where people can understand the benefits, indeed want the benefits - but don't want the perceived lack of benefits to them directly. It's just one of those perverse things: 'I want the community benefits, but I don't want to be the one providing it, because of leaf litter, because of birds, because of roots impacting the infrastructure of my house, because I want to park my second car on the nature strip."

Professor Hurley insists he is not an opponent of urban densification, but a proponent of intelligent approaches to growth.

"Consolidation is not the evil here necessarily. There are plenty of ways to do urban development, consolidation, provide housing supply in ways that don't systematically erode existing vegetation, or systematically produce landscapes with very poor or little vegetation cover."

City of Ballarat CEO Evan King says the council's priority is to retain as much native vegetation as possible and to protect trees through planning legislation. He says 3750 trees have been planted by council on public land in the last two years, and a tender has been issued for another three years of that program. There are an additional 1400 trees planted in Sebastopol in a further council initiative. But is it enough to offset the trees being lost across Ballarat?

"Are there enough trees? We certainly want to encourage as much canopy covering in those (western development) areas as you possibly can," Mr King says.

"There are certainly more trees there now than there were, but obviously that has to offset the impacts of the development at the same stage, and I understand the argument that the development causes increased hate so the,impetus to try and plant as many trees as possible is really important. I think many people living there look after those trees and plant extra trees in their gardens.

"Really, there is an impetus to look after all areas of Ballarat to make sure that we're retaining the tree canopy as much as possible. And where that's not possible, we're making sure there are significant requirements for tree planting, as part of development."

Addressing the loss of vegetative cover through the destruction of private gardens for densified development is still a work in progress for the City of Ballarat. While community programs such as Food is Free encourage the reuse of small and disused space to grow foliage, the council said it is "continuing to work with the Department of Environment Land Water and Planning to monitor tree canopy coverage via satellite imagery, which gives the most accurate data."

Meanwhile the City is planning for a population of 160,000 in 2040 - just 18 years away. Whether future planning will incorporate a more aggressive approach to cutting heat growth will determine how liveable Ballarat will be.

So what is the 'urban heat island effect' or UHI?

Scientifically, it's straightforward. If you remove vegetation of any sort and replace it with concrete, asphalt and brick, those building materials will absorb solar radiation and return it to the environment as heat.

The more material, the greater the amount of heat returned. In Ballarat's hot summers, the winds prevail from the west and north-west, meaning heat is carried into the city from the expanses spreading out to the Wimmera. With little vegetation, homes are forced to rely on air-conditioning to cool, increasing the amount of heat fed back into the atmosphere.

In 1851, the first colonial experience of how savage that heat can be was experienced in the Black Thursday fires, which destroyed great swathes of the state from February 6, sweeping from the north towards Melbourne. Victoria's average summer temperature has increased by almost one degree since the 1950s, and is expected to increase by another one to almost three degrees by the 2050s, according to the CSIRO's Climate Science Centre.

Since 1970, the number of bushfires in the state has increased by 170 per cent.

UHI's are increasing in every Australian city, as pre-existing single homes are swallowed up for higher density housing. House and garden blocks are being consumed at an ever-increasing rate, pushed by population growth, itself pushed by state and federal policies which argues economic growth can only be stimulated by a larger population.

While new blocks shrink, increasing the profit margin for developers, the house sizes are growing - and the heat is rising.

In the last decade, of Australia's major cities only Hobart and Canberra managed to increase its tree canopy cover, and that by just one per cent, according to the Australian Conservation Foundation's Temperature check: Greening Australia's warming cities study conducted by Monash University.

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