The report found more than 70 per cent of Swan Coastal Plain vegetation had been cleared and the resulting overheating, together with climate change, was affecting public health. Metropolitan councils are employing environmental consultant Paul Barber to analyse tree canopy cover and land surface temperatures in their areas. Fortunately, experts found the "urban heat island effect" could be offset if planners took action. At the request of five Perth councils, environmental consultant Dr Paul Barber got to work. His consultancy, ArborCarbon, measured canopy cover throughout the councils and correlated those measurements with land surface temperatures measured through satellite data, airborne thermal monitoring and ground-based thermal imaging.

He said there was a strong correlation between canopy cover and heat. How your area scores on the tree front. Credit:University of Technology, Sydney "Some of those newer, developed suburbs with small blocks and big houses and not much space for trees... are as hot as, or close to, Perth Airport by midmorning in summer," Dr Barber said. "[They] can be up to six degrees warmer than some of your older, more established suburbs with high canopy cover - such as Wembley Downs and Subiaco." Chris Cornish is campaigning to stop mass tree-felling as a routine part of development. Credit:Emma Young

Some of Perth's hot spots included Piara Waters, Clarkson and Butler, which were less than half a degree below the hottest location - Perth Airport. Westminster was another hot suburb with a land surface temperature of 35.2 degree, less than a degree cooler than the airport. Dr Helen Brown says urban heat islands will affect society's most vulnerable. Suburbs such as Glen Forrest, Kalamunda and Subiaco were between four and six degrees cooler. Dr Barber, an adjunct associate professor at Murdoch University, is completing a study of the entire metropolitan area that will enable comparisons between, and within, all of Perth's local governments.

In the meantime, evidence collected in 2014 by Sydney's University of Technology - which ranked Australian urban councils' tree canopies - spelled bad news for people living in the Belmont, Fremantle and Canning areas. These councils scored lowest for tree cover in Perth, with around 10 per cent each. Kalamunda, Mundaring and Swan performed better (above 30 per cent) as did the western suburbs (20 to 30 per cent). But Dr Barber said development was causing some areas - including the western suburbs - to lose canopy cover rapidly. He said the removal of large trees was often justified by replacement with several smaller ones, but this showed a failure to understand the significance of canopy cover. "One large specimen may provide 100 square metres of canopy cover," Dr Barber said.

"Its replacement with three smaller advanced specimens, with a combined canopy cover of three metres, is just not adequate." He said many trees sourced from nurseries were currently stunted due to numerous factors, including unhealthy root systems and insufficient early soil volumes. A potential result was that many "replacement" trees would never grow large enough to replace the mature trees felled for development. He said canopy cover was becoming more of a concern for councils and several were developing urban forest strategies and plans, hence research into canopy cover and condition being necessary for benchmarking and target-setting. Dr Barber said dark surfaces such as bitumen and dark roofing on developments were not reflective and were very prone to absorbing and retaining heat. Tree shading would not only prolong the life of those surfaces, but also reduce the urban heat island effect. "We need to be smart about how we develop and design urban spaces, particularly in Perth which has many hours of sunshine," he said.

"We are starting to work closely with landscape architects, urban designers and planners... it's essential when you're planning urban areas that you consider vegetation as an asset that needs to be healthy for decades to come. "Perth is a very clean, green place and always has had clean air and water and a great climate – but that will change over time if we don't develop and plan wisely, consider sustainable development and manage our vegetation sustainably." Community groups, such as the Bayswater and Stirling Urban Tree Networks, have formed in an attempt to influence planning decisions and public attitudes around these issues. Others are pushing the point in their campaigns for election to local government - including Chris Cornish (City of Bayswater) and Ruffein Tshiamala (City of Stirling). Mr Cornish, already a councillor, wants to introduce laws which would force developers to submit the monetary value of trees they want to cut down as part of any planning proposal. A financial planner by trade, he said it was already possible to place a dollar value on trees using methods such as those already developed for legal and insurance purposes. He is campaigning for that to become common practice.

In 2014, he successfully influenced the City of Bayswater to resolve to increase its canopy from 13.2 per cent to 20 per cent by 2025 through an Urban Forest Strategy, now being drafted. The cities of Belmont and Armadale each published Urban Forest Strategies in June 2014. The City of Perth is developing its own plan, drawing on Dr Barber's research, and has also approved a policy to calculate the "amenity value" of the city's trees. Between 2011 and 2013, the City of Stirling lost 39 hectares of canopy cover. In late 2014, it introduced a target to increase its tree canopy from 12.5 per cent to 18 per cent by 2030. Chief executive Stuart Jardine cautioned that while the city can maintain and plant trees on land it has control over, gaps in planning legislation at the state level made it "very challenging" to prevent tree loss on private land.

Typical of challenges to public health and living costs, those likely to be worst affected by urban heat islands will be society's most vulnerable. Dr Helen Brown, of Curtin University, described urban heat islands as a kind of localised climate change caused by three factors in urban development - built materials trapping heat, urban machinery producing waste heat and the removal of trees (and their associated shading and cooling functions). She said the elderly, the very young and those who work outdoors were particularly vulnerable to heat stroke and other heat-related illnesses. The poor and the homeless were also at risk, as they had a reduced capacity to choose well-designed housing, or adapt their environment through luxuries such as airconditioning. Dr Brown stressed that planning decisions in Perth might not have much effect on global climate change, but they did have power over the urban heat island effect. The National Climate Change adaptation research facility has launched the Vulnerable Communities Network, which is working with the Australian Council of Social Services and University of Adelaide to get researchers, policymakers and community sector talking together.

A recent workshop in Perth discussed the community sector's future role in climate policy and responding to natural hazards such as heat. "The Vulnerable Communities Network is really focusing on a whole range of factors that make certain groups of the community vulnerable – people from low socio-economic backgrounds, people struggling with health problems, the aged population, women in domestic violence situations, for example," University of Adelaide School of Public Health research fellow Scott Hanson-Easey said. "People who are already struggling with economic problems are less able to adapt, they don't have the capacity to turn on their airconditioners, or don't even live in a home with functioning airconditioning, especially those in rental properties without much ability to negotiate with owners – those relationships can be tricky. "The type of housing they get into will often have antique insulation and they can't always easily move into or access cooler places such as shopping centres or local swimming pools." Dr Hanson-Easey's research is into communities of humanitarian refugees, who have come to Australia without the resources to adapt that people in established communities have.

"The kind of things I hear when I've spoken to people is that they're already struggling with lots of things, like racism, unemployment and lack of financial resources, and it's this that makes them particularly vulnerable to hazards," he said. "They also have problems with communication ... if they can join communities with well established networks and leaders they can draw on that support, but in emergencies they lack the usual information channels and are prone to being a bit 'left out of the loop'." Discussions from the workshop will inform an ACOSS report for the national facility that will outline the policy implications of climate change and urban heat for both the disadvantaged and the organisations that support them. Follow WAtoday on Twitter