Trees: the ultimate green investment?
Perhaps it is a pity that so many Australians think of our parks, gardens, streetscapes and urban landscapes only in terms of their aesthetics. While green spaces are beautiful and decorative, these attributes can mask the many functions vegetation serves in cities, to the point where its economic, social and 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 and private open space, including front and back yards. Urban landscapes and trees have been wonderful but silent assets in our cities for decades and 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 and make cities both sustainable and livable?
At a time of climate change, it is worrying that both private and public open spaces are threatened by urban renewal and 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, and the opportunities for vegetation to ameliorate the heat island effect, lower wind speed, provide shade and reduce energy use are lost. This affects the economic viability of such developments, as well as its long term environmental sustainability.
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.
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 and that severe storms will be more prevalent. Indeed, Victoria has already suffered the effects of several major wind and hail storm events over the past few years.
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. 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 and that it was an under-estimate of the real value.
Vegetation also holds and absorbs water during more intense rainfall events – unlike concrete and 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 and vandalism, and lower blood pressure. Vegetation humidifies the air, easing breathing and 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.
There is ample evidence that treed landscapes foster both active and passive recreation. Green and leafy environments will be one of the vital strategic tools in dealing with children lacking exercise and becoming obese, encouraging an ageing population to exercise and curbing ever-increasing health costs. The human health benefits can save society a truck-load on medical and social infrastructure costs.
Melbourne is one of Victoria’s biodiversity hot spots. The parks, gardens, streets and front and backyards provide a very diverse range of plant species that generate a myriad of habitats and niches for wildlife. High density urban developments and inner city renewal make it virtually impossible to grow trees in places that were once green and 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 and nuisance values attributed to trees are widely known, the benefits they provide are often subtle and under-appreciated.
Urban vegetation provides economic and ecological services to society. They are assets which warrant the expenditure of resources such as labour, energy and water. Such expenditure is not wasted: trees and urban landscapes provide far more economically and ecologically than they use. In any comprehensive and fair calculation urban trees and landscapes are worth more than they cost.
Gregory Moore is a Doctor of Botany at University of Melbourne
This article was originally published on The Conversation – theconversation.edu.au. Reproduced with permission.
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Vegitation
I didn't know begitaion could do all that, maybe I should fill my home with more plants.
James
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Not quite accidental
" Sadly there are few similar studies for Australian cities."
Actually it is likely to be quite deliberate. As we have systematically failed to assess the externalised costs of our activities on human health.
Even when these studies are done overseas, as with coal minng and combustion, we steadfastly refuse to acknowledge the true costs.
The role of "nature" in physical and mental health is now well documented overseas, and especially improtnat for children and the least well-off in society. In other words, excising "nature" from our cities damages the most vulnerable in society.
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Perhaps it is a pity that so
Perhaps it is a pity that so many Australians think of our parks, gardens, streetscapes and urban landscapes only in terms of their aesthetics. While green spaces are beautiful and decorative, these attributes can mask the many functions vegetation serves in cities, to the point where its economic, social. Thanks. Regards, croatian
Trees
We neen to replace ALL the trees cut down over the last 200 years to have any chance of controlling global warming.Any vacant space needs to be retreed.
Trees
Trees are priceless. However we must plany local mindigenous species generally, as many introduced non -natives and non local natives have become environmental local weeds which thrive and spread through local natural bushlands.
Lists are available online for fire retardant trees, food trees and plants, trees requiring less water, shade trees, etc. Houses including brick, burn down because people do not prepare and carry out their fire plans, not due to trees.
Cities can produce huge quantities of food from trees- mainly non indigenous but from a growing list of indigenous food plants.
In developing countries forests have been cleared of trees used for burning as fuel for cooking. This causes up to 45,000,000 deaths annually from soot. Time for solar cookers internationally (and in Australia) to save on fossil fuels.
Great to see how trees can provide good health and relaxation. Oh Yes. Plant more trees everywhere.
Trees and urban power lines
Power utilities need to pay for trimming and pruning trees growing under power lines in urban areas. House owners do not have the proper facilities to do that job. They also run the risk of electrocution. Affordability is another matter worthwhile of consideration.
No trees mean poverty.
I am sure we all greatly underestimate the value of trees. Many of our cities in Australia are actually also large forests with a very active eco-system. One of the best initiatives ever undertaken in Australia was the 1 Billion Tree programme. Trees can reduce sun damage to cars and human skins; they can keep pets cool and make waiting for a bus bearable. There seems to be a direct correlation between the well being of a nation and the number of trees per population. For example wealthier countries like Japan and Sweden have a far larger number of trees. Maybe the most striking example is between Haiti and the Dominican Republic. In Haiti, virtually ever forest has been destroyed and the country is on of the poorest in the world. On it border, the Dominican Republic managed to protect trees and large forests and with a similar environment to Haiti. In 1925 still 60% of Haiti was forested and today it is believed that 98% of these forests were cut down. The Dominican Republic on the other hand, large forest s protects the lowlands from flooding and provides much loved tourists destinations.
Trees
All very well but other than shade, moisture, happiness, comfort, perfume, biodiversity, oxygen - what have trees done for us? They drop leaves and hide spiders and trap basket balls.
You just can't beat green concrete but black bitumen is pretty good.
Trees belong in a tree museum where you charge people a dollar and a half just to see 'em (apology to big yellow taxi) We really don't know what we got til its gone.
Newcastle City Council don't agree
Laman Street, Newcastle, has been the site of a physical battle over Hills figs for several years. The total costs thus far are well over the million dollar mark and, despite there being no sign of illness or weakness in the remaining 20 trees, the council is deadlocked 50/50, all legal avenues have been exhausted and the anti-tree brigade are poised for a win. 2 dozen figs, planted 1931, 80 years old, condemned on the basis of emotion.
See: There's plenty available via Google, or go to http://www.dailytelegraph.com.au/news/sydney-nsw/protestors-storm-barric...
TREES
No argument with planting trees, I've planted over 5,000 ove 15 years, on 17 acres. However large trees do not have to be planted near buildings, and are a danger, as well as a nuisance, with leaves blocking down pipes. By all means plant trees, but encourage people to plant shrubs-nothing over 2 metres near houses. Without more evidence some of the claims seem pretty dodgy!