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The Conversation – “an independent source of information, analysis & commentary from the university & research sector” has published yet another fabulous article, this time about trees. The article was written by Gregory Moore – Doctor of Botany, University of Melbourne & published 30th January 2012.
“Greg Moore Senior Research Associate of Burnley College, University of Melbourne was Principal of Burnley from 1988 to 2007, & Head of the School of Resource Management at the University from 2002 to 2007. With a general interest in horticultural plant science, revegetation & ecology, Greg is particularly interested in arboriculture. He was inaugural president of the International Society of Arboriculture, Australian Chapter, & has been a member of the National Trust’s Register of Significant Trees since 1988 & chair since 1996. He has served the Board of Greening Australia (Victoria) since 1988 & chaired Treenet since 2005. He is on the board of Sustainable Gardening Australia & is a trustee of the Trust for Nature. He has written two books, contributed to three others & has published over 120 scientific papers & articles.”
‘The Conversation’ allows this article to be republished so here it is in full. The use of bold is my emphasis.
For a great return on investment, try trees
Perhaps it is a pity that so many Australians think of our parks, gardens, streetscapes & urban landscapes only in terms of their aesthetics. While green spaces are beautiful & decorative, these attributes can mask the many functions vegetation serves in cities, to the point where its economic, social & environmental benefits are overlooked. Yes, trees are beautiful; but more than that, they save our cities a lot of money.
Cities are biodiversity hot spots because of the variety of habitats available in public & private open space, including front & back yards. Urban landscapes & trees have been wonderful but silent assets in our cities for decades & even centuries.
They are major urban infrastructure assets. I often hear it said that; “There are better things to use water on than plants and gardens”, but I challenge you to name them. What else delivers so many benefits immediately: benefits that last centuries into the future, which prolong healthy lives & make cities both sustainable & livable?
At a time of climate change, it is worrying that both private and public open spaces are threatened by urban renewal & development that puts at risk long-term sustainability. In many of these developments there is insufficient open space – public or private – to plant large trees, & the opportunities for vegetation to ameliorate the heat island effect, lower wind speed, provide shade & reduce energy use are lost. This affects the economic viability of such developments, as well as its long term environmental sustainability. http://www.epa.gov/hiri/
The shade provided by trees drops temperatures by up to 8°C: there is real economic value in that. Shade can reduce air conditioner use by 12-15%, which also decreases carbon emissions from our largely brown-coal-generated electricity.
When 11 million trees were planted in the Los Angeles basin, it saved US$50 million per annum on air conditioning bills. Large trees were removed from school grounds in the name of safety after the Black Saturday fires, without thought of the shade they provided. Consequently, large shade sails had to be provided to protect students from excessive summer sun. http://bit.ly/AwLn4P
It is more difficult to place a value on reduced wind speeds (up to 10%) due to the presence of vegetation, or on protection that trees provide from hail. However, we do know that under climate change winds will be stronger & that severe storms will be more prevalent. Indeed, Victoria has already suffered the effects of several major wind & hail storm events over the past few years. http://bit.ly/sCl4kM
Urban vegetation also removes atmospheric pollutants. It was calculated that the vegetation of New York provided US$10 million of benefit in pollution removal in 1994. http://nrs.fs.fed.us/units/urban/local resources/downloads/Tree_Air_Qual.pdf Sadly there are few similar studies for Australian cities. However in the only study of its kind, economists found that each Adelaide street tree provides a minimum annual benefit of $200 per year & that it was an under-estimate of the real value. http://bit.ly/x5qRKd
Vegetation also holds & absorbs water during more intense rainfall events – unlike concrete & paved surfaces. The economic value of reducing localised flooding could be substantial.
Vegetated landscapes, especially those containing trees, improve human heath, extend life spans, reduce violence & vandalism, and lower blood pressure. http://www.treenet.org/images/stories/symposia/2009PDFs/2009%20people%20and%20trees%20providing%20benefits%20overcoming%20impediments%20dr%20jane%20tarran.pdf
Vegetation humidifies the air, easing breathing & reducing the need for medication in those with respiratory difficulties. In reducing the urban heat island effect, trees can also substantially reduce the excess deaths that occur, predominantly among the elderly, during heat waves. It is often forgotten that the fires of Black Saturday killed 172 people, but the heat wave surrounding it was responsible for 374 deaths. http://bit.ly/zkz1K9
There is ample evidence that treed landscapes foster both active & passive recreation. Green & leafy environments will be one of the vital strategic tools in dealing with children lacking exercise & becoming obese, encouraging an ageing population to exercise & curbing ever-increasing health costs. The human health benefits can save society a truck-load on medical & social infrastructure costs.
Melbourne is one of Victoria’s biodiversity hot spots. The parks, gardens, streets & front and backyards provide a very diverse range of plant species that generate a myriad of habitats & niches for wildlife. High density urban developments & inner city renewal make it virtually impossible to grow trees in places that were once green & leafy. We rarely ever see the real costs of such developments.
In the past decade tree populations in many Australian cities have declined, particularly with the loss of private open space. While the costs, damage & nuisance values attributed to trees are widely known, the benefits they provide are often subtle & under-appreciated.
Urban vegetation provides economic & ecological services to society. They are assets which warrant the expenditure of resources such as labour, energy & water. Such expenditure is not wasted: trees & urban landscapes provide far more economically & ecologically than they use. In any comprehensive & fair calculation urban trees & landscapes are worth more than they cost.
* data-tracker http://theconversation.edu.au/content/5050/tracker
This article was originally published at http://theconversation.edu.au Read the original article – http://theconversation.edu.au/for-a-great-return-on-investment-try-trees-5050
1. Professor Nigel Tapper of Monash University, a speaker addressing the National Tree Symposium at Adelaide University of Adelaide said urban trees actually save lives during heatwaves. Treenet Director David Lawry spoke about stormwater being diverted from the gutter to street trees. A test is being done in Unley Adelaide to measure its affectiveness. …the devices could deliver up to 400 litres of water directly to trees during moderate rain, resulting in healthier trees, more comfortable urban environments & less stormwater getting to waterways & the sea. To me it makes absolute sense to channel rainwater from the gutter into the area around the street tree. To achieve this is quite simple & only requires a remodeling of the kerb.
The National Tree Symposium also discovered that proposed changes by the South Australian government to significant tree regulations will leave a large amount of existing trees unprotected by the equivalent of a Significant Tree Register. http://www.adelaidenow.com.au/fears-of-an-open-season-on-adelaides-bigger-trees/story-e6frea6u-1225914516653
2. Darwin has a tree emergency on its hands with between 60-70 large Weeping Rosewood trees showing symptoms of fusarium wilt (a fungal disease not indigenous to Australia), which spreads by spores in the soil. If this is the case, Darwin could lose thousands of trees within the coming decade. http://www.ntnews.com.au/article/2010/09/04/176981_ntnews.html
3. The ACT’s Council, the Department of Territory & Municipal Services has been ordered to improve upon their policy & procedures of public tree removal by becoming more transparent & accountable to the community. 20 – 40% of the ACTs 630,000 park & street trees are expected to be axed within the next 20 years. I’d be very busy if I lived there. http://www.canberratimes.com.au/news/local/news/general/tree-change-residents-to-get-appeal-rights/1932556.aspx