Valuing Southwark’s Urban Forest

August 2020

An inventory of the trees in the London Borough of Southwark has revealed the huge economic value of the urban forest that is being managed by the tree officers there.

Tree officers are often recognised as ‘custodians of the urban forest’, managing the public tree estate for the common good.

The study, using i-Tree Eco, carried out by our Treeconomics team, discovered that the trees owned and managed by the London borough would have a replacement cost of over £165 million.

In addition, using Southwark’s own tree inventory, our team was able to calculate that the trees managed by the council remove over 21 tonnes of air-borne pollutants, valued at £135,000 plus each year, and store over 57,000 tonnes of carbon, valued at over £14 million per year.  They also divert over 35,000 cubic metres of storm water away from the local sewers each year, which is worth an estimated £21,183 in avoided stormwater treatment costs.  Furthermore, the benefits provided by these trees will grow as the trees do.

This study highlighted the many ecosystem services that trees provide.  However, the benefits linked to health and well-being cannot currently be measured using i-Tree; so the annual benefits figure of almost £400,000 is certainly an underestimation.

By valuing the benefits that its trees are providing, Southwark Council now has an evidence base with which to mitigate for development impacts, inform land use changes and, through planned intervention, avoid losses to its natural capital.  The results of the study will certainly help the council to make informed management decisions about its green infrastructure.

The urban forest is dynamic and needs to be annually replenished through strategic new tree planting.  As a follow up to the i-Tree Eco inventory project, Southwark then commissioned our team to create a Tree Planting Opportunity Map, to highlight areas with tree planting potential throughout the borough.  The mapping exercise showed that if, over time, all actual plantable space were to become tree covered, Southwark’s canopy cover could increase from 19.9% to 34.9%

Cllr Rebecca Lury, Cabinet Member for culture, leisure, equalities and communities, commented: “In Southwark, we are committed to nurturing our existing 82,000 trees, and planting more. As an inner London borough, we value the vital role that our trees play in helping to improve air quality, as well the other multiple benefits they offer to local communities and neighbourhoods.  We welcome Treeconomics and their expertise.  This commission will help us to further quantify the environmental benefits that Southwark’s trees provide to local people and better inform our current and future management, of Southwark’s urban forest.”

To view the Southwark reports, click here.