Following our last post featuring the publication of results of the London iTree Urban Forest Survey, this week’s post focuses on an in-depth analysis of the green assets of the Victoria in the Borough of Westminster, London highlighting the wide range of benefits (or ecosystem services0 green infrastructure provides in urban settings.
The Green Benefits in Victoria Business Improvement District Report – An analysis of the benefits of trees and other green assets in the Victoria Business Improvement District. The following is a summary of the full report.
Victoria, London Borough of Westminster, is a major transport hub, tourist destination and centre for business and commerce. Like many urban areas Victoria suffers from the effects of a high density built environment with an overall lack of natural features and this contributes to overheating in the summer through the urban heat island effect as well as surface water flooding, when the drainage system cannot accommodate the volume of water running off of hard surfaces. The Victoria Business Improvement District (BID) acts as a platform for business to take a lead in enhancing the overall urban environment of Victoria and to help shape the area for future development.
Trees intercept rainwater thus reducing the burden on the drainage system; they cool the air and provide invaluable shade on a sunny day, and, of immediate benefit to Victoria in the face of major redevelopment, they can contribute to cleaning the dust and pollution from the air we breathe. So clearly Victoria’s street trees and those in public and private green space have a central role in mitigating these environmental challenges and so contribute to making Victoria a better place to do business. The Victoria Business Improvement District considers trees to be a core component of the local infrastructure and has therefore commissioned the research presented in this report to provide a clearer understanding of the financial benefits of trees in a specific location so that we can say with confidence that our trees are saving the business community thousands of pounds per annum.
Green infrastructure can deliver benefits to urban areas. Trees in particular can provide a wide range of benefits (or ecosystem services) such as storing carbon, reducing the urban heat island effect and improving air quality. Understanding the structure, function and value of Victoria Business Improvement District’s green infrastructure can inform decisions that will improve human health and environmental quality. This report presents a baseline quantitative assessment of the air pollution, amenity, carbon storage and sequestration benefits of trees as well as the storm water and surface temperature benefits of existing green infrastructure in the Victoria BID.
This report also estimates the additional benefits that could be generated if the 5% canopy cover increase target set by the Mayor of London for Greater London, by 2025, and the potential green roofs and ground level green spaces investments identified by the BID are both realised in Victoria. This assessment was conducted using the i-Tree Eco model (also known as UFORE1 ), as developed by the U.S. Forest Service, Northern Research Station, Capital Asset Valuation for Amenity Trees (CAVAT) and tools within the Green Infrastructure Valuation Toolkit. It considers the impact of public and private trees as well as other types of green infrastructure assets including green roofs and gardens.
Existing trees, green spaces and other green infrastructure assets in Victoria divert up to 112,400 cubic metres of storm water runoffs away from the local sewer systems every year. This is worth between an estimated £20,638 and £29,006 in reduced CO2 emissions and energy savings every year. The total structural value of all trees in Victoria, (which does not constitute a benefit provided by the trees, but rather a replacement cost) currently stands at £2,103,276. The trees in Victoria remove a total of 1.2 tonnes of pollutants each year and store 847.08 tonnes of carbon. London plane currently dominates the treescape within Victoria BID, storing 59% of all carbon, filtering 67% of all pollutants and making up 29% of the tree population.
However the London planes represent an ageing population and in order to maintain the current level of tree benefits to Victoria BID more trees capable of attaining a larger stature will need to be planted. When implemented, the green infrastructure opportunities identified by Victoria BID have the potential to:
- Divert up to 67,500 additional cubic meters of storm water runoff every year, representing an estimated extra £12,392 in avoided CO2 emissions and £17,417 in energy savings annually. Future design choices – particularly in relation to green roofs – will have a determining impact on the scale of water management benefits realised.
- Reduce peak summer surface temperatures by up to 5.1˚C in the area surveyed. This will moderate local air temperatures, helping to ensure that the BID remains an attractive and comfortable environment for residents, visitors and workers alike. It will also reduce the need for air conditioning in office buildings, lowering energy costs and carbon emissions.
- The high CAVAT value of London plane in particular justifies the investment required to establish and maintain very large trees in the urban environment, yet equally points to the vulnerability arising when such a high proportion of value resides in a single species.
Public and private trees in the Victoria BID provide valuable benefits. Realising the Mayor’s target for increasing canopy cover together with the creation of additional green roofs and ground level green space would dramatically enhance the scale of ecosystem services the area enjoys. These conclusions highlight some key recommendations in order to ensure that benefits currently arising from the BID’s green infrastructure are sustained and future green investments fulfill their potential for generating returns:
- Conduct succession planting for London planes. The local tree resource is characterised by a good diversity of species, which makes it more resilient to pressures such as pests and diseases or climate change. However, most of the canopy area and therefore most of the benefits arising from the Victoria BID’s treescape are provided by London planes. Many of these trees are mature specimens, as has already been highlighted in previous studies (Kelly 2012). Provision should be made to ensure that adequate succession planting is carried out in order to maintain benefits at the current levels.
- Target private trees owners for awareness raising and best practice on tree management. Many of the BID’s trees are in the private realm and in the buffer area. Therefore, a reduction in privately owned trees will reduce this benefit. Strategies and policies that will serve to conserve this important resource (through education and community engagement for example) would be one way to address this.
- Focus on large canopy trees both for planting and maintenance. The amount of healthy leaf area equates directly to the provision of benefits (or ecosystem services). Canopy cover can be increased through new tree plantings. However, the most effective strategy for increasing average tree size and tree canopy is to preserve and manage the existing trees within the BID so that a good proportion can grow to maturity. Where new trees are planted the Westminster Trees and the Public Realm SPD (Westminster City Council 2009) recommends using the tree species with the largest canopy a site can accommodate. Ensuring this is well-enforced in the future will be key to maintaining tree benefits at their current level.
- Engage with Thames Water to ensure the benefits from proposed green investments can more directly reach BID members. Trees currently make a positive contribution to the management of storm water in Victoria. The proposed investment to increase canopy cover, create new ground level green spaces and dramatically extend the area of green roofs and will significantly alleviate the local drainage system. This will unarguably result in public benefits, by contributing to reducing the prevalence of flooding events which regularly damage and interfere with the local infrastructure. It will also reduce the amount of water that will need to be treated by the local water company, Thames Water, thus offering real savings. All efforts should be made to ensure local owners and occupiers in Victoria who, as part of their water bill, pay for the drainage of the area get access to their share of this saving. Thames Water grant a rebate to its customers on drainage fees based on pipe diameter rather than based on volume reduction. This doesn’t provide a strong incentive for green approaches such as those envisaged for Victoria. Direct engagement with Thames Water on this issue could result in an innovative pilot – offering a model that could be rolled out to other parts of London.
The Landscape Institute featured Greening for Growth in Victoria as a case study in their 2011 publication ‘Local Green Infrastructure: helping communities make the most of their landscape’
“ The Victoria BID is championing a sustainable green agenda for the area and is looking to become the leader in the development of sustainable business environments through the retrofitting of green infrastructure. We are working closely with public and private sector partners to achieve a positive change in the physical landscape in the area. The increase in green infrastructure will not only benefit the environment but also the workers, residents and visitors that come into Victoria every day.” Ruth Duston, Chief Executive Officer Victoria BID