17 June 2011

Bringing nature (back) into cities...

This article was prepared by postgraduate student Cynthia Resendiz as part of the ECOL 608 Research Methods in Ecology course.

“Canterbury plains are one of the worst examples of the loss of native plants in New Zealand...less than 0.5% of native vegetation remains on our plains”, New Zealand’s Spellerberg, a Lincoln University scientist, said in a blog interview in 2010. Trees that live in cities come from different parts of the world; however, not all trees are suitable for all environments. Each species has special requirements to grow successfully, but native trees are already adapted, and they are a good choice for urban spaces.

We need trees in cities. Trees, especially native species, have many functions and values, producing economic, social and environmental benefits. They can provide us with goods and services such as: improving air quality, recreation, saving energy, and ornamentation.

The kind of trees found in a city depends on public preferences, planning decisions and even historical reasons. There are many areas in cities reforested with new trees, but mainly using non-native trees. Particularly in New Zealand, due to the historical influence of the United Kingdom, urban trees are chiefly non-native, and often from the northern hemisphere.

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The use of exotic trees is becoming old-fashioned. There is a global tendency to plant native trees. For example cities such as Adelaide in Australia or Warrington New Town in United Kingdom are implementing programs to redress the loss of native vegetation.

Many scientific studies suggest that native trees are the best option for cities. One of these studies was published in Landscape Review by Ian Spellerberg in 2008. He highly recommends planting native trees and gives the following criteria for choosing trees:
• Besides an aesthetic and functional tree, we need to think carefully about why we need a tree and where it will be planted. We must have in mind that this is a long-term decision.
• The genetic origin of the plant is important, particularly when it is a indigenous tree. We should ask for native species grown from seeds from the local area (eco-sourcing).
• Try new species, especially trees indigenous to your area. These kinds of trees have low maintenance requirements. This is important because life in cities is busy and you should not have to worry about your tree. If you are living in Canterbury, the organizations Trees for Canterbury or Motukarara Conservation Nursery may help you to make your choice.
• Learn about possible nuisance factors. This involves safety and structural problems. Sometimes trees can cause health problems (i.e. allergies). Also the anatomy of the tree can bring problems to houses and people (e.g. root spread can damage pipes).
The diversity of species and ages of trees are important. It is recommended to have patches that include a mixture of them.

We should be proud of New Zealand’s natural heritage. Planting native trees contribute to conserve genetic resources that are exclusive from New Zealand. This will attract native wildlife, such as native birds, providing sources of food and habitat.

“I think New Zealand’s more precious natural heritage are native plants. Therefore, we should celebrate native plants by having a native only policy for urban areas” – Ian Spellerberg said in May 2011.

Given these points, the decision around planting a tree is very important and must be taken carefully, because it is an investment for the long term, which can bring us invaluable benefits. Your tree must be adaptable to urban conditions, otherwise we can get the opposite result, and the tree can bring us problems. Buying a tree seems simple, but it is an important decision that can contribute to nature conservation. Next time, look at the trees growing around you, and think about what kind of tree you would like to plant.

Kind regards John Maillard for the photo of Ian Spellerberg

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