North Newtown streetscape providing lots of shade

North Newtown streetscape providing lots of shade.  This is a normal streetscape for this area.

Compare with a street in Dulwich Hill that actually has many street trees

Compare with a street in Dulwich Hill that actually has many street trees

There is an interesting article in The Conversation written by Prof. Rod Keenan & Benjamin Preston, both from the University of Melbourne.

Some points in the article –

  • Victoria currently has an average of 9 days per year of temperatures above 35C.  No action on greenhouse emissions will likely result in an average of 21 days a year with temperatures above 35C by 2070.
  • “Combine that with increasing urban density, more hard surfaces & less greenery, & a larger, older & more multicultural population, & the potential impacts from heatwaves start to multiply rapidly.”   Think of the development already in Marrickville municipality & the huge amount of development to come.

The Authors suggest two ways to help mitigate this & I think these are applicable Australia-wide –

  1. Increasing the ‘green infrastructure’ by 10%.  Green infrastructure means street trees, parks, green roofs, green walls & retaining water.

I’d suggest 10% is the absolute minimum, but can you imagine the positive change if the Marrickville urban forest was increased by 10%.

The City of Melbourne is planning on increasing their urban forest canopy cover from 22% to 40%. The City of Sydney is aiming to increase their urban forest by 50% by 2030 (just 16-years away) to help lower the urban heat island effect.

  • 2. Education.

“Health awareness programs can promote related benefits such as improved air quality; planners can reduce the red tape involved in planting street trees; local governments can identify priority neighbourhoods for development, protect existing greenery, & implement water-sensitive urban design.” 

“Increasing green infrastructure will also require the use of private space – one major challenge will be to give private landowners the incentive to keep or install greenery & incorporate vegetation into building design.”

Although Sydney has not experienced a true heatwave this summer, it has been very hot.  Melbourne & Adelaide both experienced two heatwaves this January, baking over a number days.  On 16th January, Adelaide was given the title of ‘the hottest city in the world’ with a temperature of 44.2C, still short of the forecasted 46C.

An article on Care2 discusses the American city of Phoenix trying to cope with 100-degree nights.  “The city averages more than 100 days a year with temperatures reaching over 100 degrees. (37.7C)   In 2013, 115 days hit 100 degrees. In 2011, the city set a new record for days over 110 degrees (42.3C) with 33. That’s over one month of the year with scorching highs. This winter has so far been warmer than average.”

Temperatures are rising everywhere.  The urban heat island effect is increasing those temperatures, & importantly, not allowing the temperature to drop after the sun goes down.  Phoenix has “a shade plan for the built environment & also a plan to “frankly just plant more trees.”  See – http://bit.ly/LuA1xC

We need to start planting now in both private & public spaces if we are to ever hope to be able to cope with projected temperatures.  Sydney’s temperature is expected to be like living in Rockhampton in Subtropical Queensland.  See – http://bit.ly/1aLsaYf

Marrickville Council needs to decide how much to increase the urban forest & set & meet targets to achieve this.  The yearly budget allocation needs to be such to allow this to be achievable.   I have often wondered whether public trees & parks are lower down in the budget & whether these are seen as not as important as grey infrastructure.

Certainly we need to do what we can to keep the trees we have & this means treating them for diseases, fertilizing, mulching & pruning where necessary.

In my opinion, the community needs to help Council keep new trees alive by continuing to water trees once a week when Council has stopped water 12-weeks after planting.  It only takes a few hot days to lose a tree & if we look realistically, the bulk of our street trees are living in very harsh conditions.  Many are either hemmed in by concrete or in visibly dry & compacted soil.

I know there are many who will baulk at the idea of watering a public tree, but it is commonplace in many countries overseas.   The US for example, has a strong community involvement in public trees, whether planting them or looking after them.  Both the US & the UK have community ‘Tree Wardens’ looking after public trees.  These people are not tree experts.  They receive training by their Local Council to do the work they do.

Keeping that tree alive will help reduce your power bills as they help cool the air around your house.  Street trees clean up the air by removing particulate matter from vehicles, so better quality air comes into your home.  They also increase the value of your residence or business amongst many other benefits, so it stands to reason that taking care of the tree outside your property brings significant returns.  Better a living healthy tree, than a dead tree or a sapling that struggles to grow & may take many years to reach a decent size.

Older larger trees are far better at carbon sequestration than smaller trees – another reason why it makes sense to look after them.

You can read the full article here – http://bit.ly/1mQumNW

Tall shady street trees are the norm in Chippendale

Tall shady street trees are the norm in Chippendale

Canterbury Road - this section is mega-hot on a sunny day.

Canterbury Road – this section is mega-hot on a sunny day.

While there are street trees, this is still a hot street in Marrickville

While there are street trees, this is still a hot street in Marrickville

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