The Cost of a Tiny Urban Forest

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In this episode I talk about the cost of planting a tiny forest, specifically a forest planted using the miyawaki method.

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The world is suffering from extreme floods and heatwaves, alongside continual and increasing biodiversity loss. The long-term impacts on the environment, the economy and our society are severe. Between 1990 and 2015 129 million hectares of forests were cut down or burned. This deforestation is responsible for an estimated 5 billions tons (17% of annual global carbon emissions).

Miyawaki Method

Essentially Miyawaki forests are densely planted native species of trees and plants on a plot that is around 100 square metres. At an early stage in the planting, because they are so tightly packed in, there is a lot of competition for light, space and water, which gets them to grow faster.

The soil at a site is analysed and improved. Up to 100 local species are selected to be planted. The site is monitored, watered and weeded for up to 3 years, after which it is self sustaining.

The Benefits of Tiny Forests

The Miyawaki method has been shown to grow up to 10 metres a year, with considerable benefits for carbon capture and recreating biodiversity where it has been lost.

The Miyawaki method is planned for carbon sequestration. Carbon sequestration is the removal of carbon from the air and storing it in leaves, branches, trunks, roots and soil.

Deforested areas take over 70 years to recover, and although the Miyawaki forests are likely to sequester less carbon, they take a lot less time to develop.

Temperature reduction – Miyawaki forests can also be planted in small, urban areas, with cities that are concretised becoming heat sinks. Just try being in a city like London or Rome in the middle of summer! Other benefits include air quality improvement, noise reduction, health and well-being, biodiversity balance, and soil stabilisation.

The first tiny forest in the UK planted by Whitney Council (Courtesy of Earthwatch UK)

The Cost of Tiny Forests

Care has to be taken to make sure that the planting of these forests does not result in trees cut down elsewhere as they are replaced using the method. Tree plantation (called afforestation) has previously been used for economic gain, minimising ecological diversity. They are used for the resources of Sitka spruce or palm oils.

Miyawaki planting in Bengaluru, India (Courtesy of The Economic Time s)

The urban land could also be in a bad state, so digging and preparing the site is costly. The density of planting means more saplings required than for a more dispersed site, adding another lot of cost.

There are criticisms of the method. They can be monotonous in their aesthetic, with all the trees being of the same age. It is a more expensive method of planting because it requires more seedlings to cover a certain area, but the rapidity of the forest growth and the minimal maintenance required recompense some of that expenditure.

Summary

As we look for technological solutions to our environmental problems, innovation in the methods applied to tree planting could lead us to solve several problems at once – biodiversity loss and attenuating flooding being other serious problems nature faces. As cities continue to grow, to become megacities, not only are green spaces important for our mental wellbeing, but they are going to be valuable in the fight against climate change.