The Urban Heat Island Effect

The following is a summary of a position statement by the Australian Institute of Landscape Architects titled, Cooling Cities – The Heat Island Effect.

It is now indisputable that average temperatures are on the increase, giving rise to elevated urban heat island, (UHI) effects. With now more than three quarters of our population living in urban areas, more people are becoming susceptible to health issues that can be directly related to the UHI.

On this 'heat map' of England, London, Liverpool, Manchester etc, are easy to locate!

 Simply put, an urban heat island is a city or other urban area that is significantly warmer than the surrounding areas due to human activities. UHI is caused by the presence of heat absorbing materials – concrete, asphalt, etc, the clearing of green spaces and in cities, the building of skyscrapers resulting heat trapping canyons.  

In 2013, research undertaken by Melbourne City Council determined that the average temperature in the CBD was 4°C higher than the surrounding suburbs. At night, because the heat absorbing materials then release their heat, the difference is as much as 12° higher.

Heat related deaths in Melbourne in 2013 totaled approximately 200. The state road toll for 2013 was 243! UHI effects increase the health risks particularly to the young and the elderly.

A report commissioned by the City of Melbourne concluded that “… the total impact of the UHI effect contributes a cost of approximately $300 million dollars …”

Drouin's tree cover is worth saving.

Among other conclusions, the AILA advocates for

# Greater protection of existing tree cover through increased value assessment of their worth.

# Commitment from all levels of government to annually increase tree canopy cover in urban areas.

# Greater awareness of the value in greening new and existing urban spaces.

Further reading links...

‘Melbourne city centre a death trap as heat-island effect takes its toll’ – The Age Jan17, 2014.

‘Beat the heat: western Sydney tackles the urban heat island effect’ – The Sydney Morning Herald Jan22, 2016.

‘Responding to the Urban Heat Island: A Review of the Potential of Green Infrastructure’ – Victorian Centre for Climate Change AdaptationResearch (1.38MB pdf).

The Engineer Who Loved Trees

Roy Everard Ross was the Shire Engineer and Building Surveyor for the Buln Buln Shire for 21 years from 1925 to 1946. On one of his trips overseas in the 1930s, he brought back from South Africa some seeds of the Cape Chestnut tree, Calodendrum capenses. The seeds were cultivated and the young trees were planted along the Princes Highway at the western entrance to Drouin.

Four trees were planted on the north side of the highway. One was moved as a mature tree in the late 1960s (to make way for a petrol station). It was replanted in Lampards Road outside what was to have been the new home for the Buln Buln Shire offices. The trees on the south side of the highway were planted from seed later in the 1960s.

These trees bear prolific pink flowers in summer, covering the entire crown of the tree making a spectacular display. They were on the State Register during the years of the Buln Buln Shire.

Interestingly R. E. Ross also became the Shire Engineer for Warragul and Narracan Shires, and was also the manager of the joint quarry committee. He moved to Melbourne in 1959 and went on to become a wealthy property investor and owner of Bayview Quarries.

Ross was passionate about trees and one of his great interests was conservation. As part of the R E Ross Trust, (external link), contributions to bodies such as The Trust for Nature has allowed for large tracts of private land to be purchased for public use.

Why a Tree Strategy for Drouin?

The development of the Drouin Precinct Structure Plan and the projected growth and expansion of the township of Drouin means that rapid change is coming to a once small town and community.

Development is continuing apace

Drouin has always been known for its trees both propagated and remnant. The town has been blessed with creative Directors of Parks and Gardens in its past as Buln Buln Shire. The variety of trees that have been planted throughout the town’s history and the layout of parks and reserves have been well planned with colour, shape, form and good design alongside the remnant trees. 

 

Alex Goudie Park - a sensitive mix of propagated and remnant trees

The Parks and Gardens men and women who worked for the Shire were inspired by these Directors and became passionate themselves about the trees and environment of the town in which they worked and lived.

Wood St

The result is that today we live in a town with beautiful trees in streets, parks, reserves, public spaces and private gardens. Drouin is known for its trees and is often referred to as ‘The Ficifolia Town’. However as development encroaches, all the trees of our town are under more risk than ever before.

Main South Rd - the attractive southern entrance to Drouin

Friends of Drouin’s Trees and the Baw Baw Significant Tree Strategy for Drouin were conceived in an effort to safeguard and perhaps enhance the wonderful tree cover that exists in the town.

 

Some old remnant giants - Hearn St

Further reading

1 Baw Baw Shire links page - Amendment C108 The Warragul and Drouin Precinct Structure Plans.

2 Metropolitan Planning Authourity a small 2 page PDF summary- The Warragul and Drouin Precinct StructurePlans.

3 The Age 16^th Aug 2014 Newspaper article from 2 years ago – Long term road map for growth in WestGippsland.

Trees and Air Pollution

Trees reduce the greenhouse effect by absorbing carbon dioxide (CO2), one of the principal ‘greenhouse gases’, and by shading our homes and offices.

During photosynthesis, trees absorb CO2 from the air and use it to help make other compounds essential for plant growth and oxygen is released back into the atmosphere.

By shading our homes and offices, trees reduce the amount of electricity needed for air conditioning. Most of our electricity is produced by burning coal, which produces carbon dioxide that is released into the atmosphere. A shady tree is both directly and indirectly reducing the amount of CO2 in the atmosphere.

 

Shady streets save money and help reduce atmospheric CO2

Carbon dioxide however, is not the principal air borne health risk of urban areas. CO2 is a problem gas in terms of climate change, but more health problems to residents are due to nitrous oxides and particulates from vehicle exhausts and factory emissions.

 

Trees help absorb vehicle emissions

Nitrous oxides and particulates in the air can have serious health effects especially for children and the elderly, including respiratory and cardiac problems and even premature mortality.

Softening building lines, absorbing industrial emissions, mitigating noise

Numerous worldwide studies have shown that well planted urban forests can filter large amounts of particulate matter from the air. A recent study indicated that the urban trees of London removed between 800 and 2000 tonnes of particulates from the air each year. Research in the United States concluded that the trees of New York saved an average of eight lives per year by absorbing particulates.

The nitrous oxides from car exhausts and other gases in the air are removed when the leaves of a tree absorb the air through their pores. In 2008, a team of researchers at Purdue University in Indiana, showed that trees were capable of absorbing the dangerous nitrous oxides and converting them into useful amino acids for other plants to use.

 

Quietly working away at keeping us healthy

Acid rain is a phenomenon caused by the oxides of sulphur and nitrogen reacting with the moisture in the air to produce rain drops that are acidic. When a tree absorbs nitrous oxides from the air it is helping to ameliorate the corrosive effect of acid rain in some regions.

Not just beautiful!

Trees can make urban areas healthier places in which to live.