14/03/14 - The hitchhikers guide to urban forestry

The seminar was presented by Tim Hall of the Woodland Trust Scotland (https://www.linkedin.com/pub/tim-hall/21/7a9/46). He opened the talk by giving a very simple, but enlightening definition of a tree: "A plant you can climb". As a fairly avid tree climber myself, this is a definition I will remember for a long time (not sure I fancy climbing a monkey puzzle tree though)!

He began the talk by giving some very simple, but highly revealing statistics. 50% of the global population of humans lived in urban areas in 2010. This is predicted to rise to 70% by 2050 [http://www.un.org/en/development/desa/population/publications/urbanization/urban-rural.shtml]. In Britain, 80% of the population live in urban areas. Considering the relatively recent development of urban areas globally, I found these figures astonishingly large. I wasn't surprised by the 80% in Britain, as we're a highly developed, small island, but the global figures were very interesting. It really highlights the extent to which we (humans) have developed the planet!

Urban Forests

Tim then went on to define what an urban forest is. The name was new to me, but the concept is simple when viewed from above. All the trees and plants in urban areas create a forest that is interwoven with the buildings and infrastructure. These trees aren't only found in parks and gardens, but also along streets, paths and even on buildings!

An urban forest.
[http://susty.com/urban-forest-benefits-trees-climate-change-atmospheric-carbon-sequestration-water-air-quality-wildlife-habitat-economic-health-lifestyle-environmental/]

Bosco Verticale - Milan. [http://webodysseum.com/art/bosco-verticale-urban-forest-buildings/]

Urban forests do also include woodlands within 1km of areas where 2000+ people are living. By this definition the woods along the Menai Strait and at the top of Roman camp count as urban forest. I find these woodlands interesting, but it's the benefits given by the trees and shrubs that are fully integrated with the urban environment that I found really interesting! 

Benefits

Tim outlined the major benefits that these urban trees provide

• Act as a windbreak - Streets act as wind funnels and the trees minimise this effect.
• Provide shade in summer - This provides a nice cool environment on the street and prevents the sun warming offices too much, thus reducing the need for air conditioning.
• Provide light in winter - The loss of leaves in the winter allows light to get to the offices so they heat up. This reduces the demand for internal heating.

Shade and light differences during the seasons

• Transpire 450L of water a day - This also reduces the need for air conditioning.
• Reduce urban heat effect - Urban areas can be up to 4*C warmer than the surrounding countryside. The transpiring urban trees cool the surrounding area and reduce this heating effect.
• Reduce rainfall impact - Urban areas are notoriously bad for rainfall run off. When large amounts of rain fall in a short period, floods can occur. Urban trees help to soak up excess water and reduce the chance of flooding and property damage.
• Health benefits 
• Clear air pollution - Photosynthesis and other chemical processes help remove pollutants from the air and improve the air quality for the inhabitants. 24,000 people die prematurely each year due to illnesses associated with air pollution. In Chicago the trees remove 10.8 tonnes of pollutant material from the air each day! These include CO2, CO, Sulphur dioxide.
• The UK has the worlds highest rate of child asthma (15%) - the highest rate of these are found in the lower socioeconomic areas where there are fewer trees. The link between the two has not been scientifically proven, but there is an interesting correlation between the two.
• Improve mental health - It has been shown that having trees in any area can improve and maintain good and stable mental health. This is particular important in areas where many people live and work in highly stressful, mentally draining environments.
• The "Branching Out" project in Scotland encourages people with mental health issues to get out into woodlands.This costs money to run, but it's believed to cost less than would otherwise be spent on medication for the participants.
• 1/6 people in the UK have a mental health issue during their lifetime. A planned increase in the density of urban forests is likely to help reduce this number.
• It has been shown that people are also more likely to walk to work if there are trees on their route. This also improves mental health and physical fitness.

Management

Tim's job involves the management and maintenance of Scottish urban forests. He says this is very challenging because although people enjoy having trees in their area, they don't want them to block light, spoil the view, have the roots break up the pavement, have the leaves block drains etc. People management seems to be the major part of the job!

Tree roots damage property including pavements and drives

The idea of urban forests is quite recent but is coming into the public mainstream more and more. Some universities even offer courses in urban forestry now! 

I think the concepts covered by Tim were all very interesting and it's great to know that planting of trees and vegetation is now a major governmental target. I'm likely to get involved in some sort of forest management in the future, and it would be great to take these skills into an urban environment. I don't think I'll ever get heavily involved in this kind of work. The prospect of having to deal with angry householders daily is not at all appealing, but I do think it's important to have trees in urban spaces!