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1 .Good day, ladies and gentlemen.
2 .I have been asked today to talk to you about the urban landscape.
3 .There are two major areas that I'll focus on in my talk: how vegetation can have a significant effect on urban climate,and how we can better plan our cities using trees to provide a more comfortable environment for us to live in.
1 .Trees can have a significant impact on our cities.
2 .They can make a city, as a whole, a bit less windy or a bit more windy ,if that's what you want.
3 .They can make it a bit cooler if it's a hot summer day in an Australian city,or they can make it a bit more humid if it's a dry inland city.
4 .On the local scale - that is,in particular areas within the city - trees can make the local area more shady, cooler, more humid and much less windy.
5 .In fact trees and plantings of various kinds can be used to make city streets actually less dangerous in particular areas.
6 .How do trees do all that, you ask?
1 .Well, the main difference between a tree and a building is a tree has got an internal mechanism to keep the temperature regulated.
2 .It evaporates water through its leaves.
3 .And that means the temperature of the leaves is never very far from our own body temperature.
4 .The temperature of a building surface on a hot sunny day can easily be 20 degrees more than our temperature.
5 .Trees, on the other hand, remain cooler than buildings because they sweat.
6 .This means that they can humidify the air and cool it - a property which can be exploited to improve the local climate.
1 .Trees can also help break the force of winds.
2 .The reason that high buildings may keep it windier at ground level is that,as the wind goes higher and higher, it goes faster and faster.
3 .When the wind hits the building, it has to go somewhere.
4 .Some of it goes over the top and some goes around the sides of the building, forcing those high level winds down to ground level.
5 .That doesn't happen when you have trees.
6 .Trees filter the wind and considerably reduce it preventing those very large strong gusts that you so often find around tall buildings.
1 .Another problem in built-up areas is the traffic noise is intensified by tall buildings.
2 .By planting a belt of trees at the side of the road,you can make things a little quieter,but much of the vehicle noise still goes through the trees.
3 .Trees can also help reduce the amount of noise in the surroundings, although the effect is not as large as people like to think.
4 .Low-frequency noise, in particular, just goes through the trees as though they aren't there.
1 .Although trees can significantly improve the local climate, they do however take up a lot of space.
2 .There're root systems to consider and branches blocking the windows and so on.
3 .It may therefore be difficult to fit trees into the local landscape.
4 .There's not a great deal you can do if you have what we call a street canyon - a whole set of high-rises enclosed in a narrow street.
5 .Trees need water to grow.
6 .They also need some sunlight to grow and you need room to put them.
7 .If you have the chance of knocking buildings down and replacing them, then suddenly you can start looking at different ways to design the streets and to introduce...