Coventry Urban Forestry Strategy 2022 -2032

Our research and engagement with stakeholders has identified several long-term challenges that we need to address. However there are also new and emerging opportunities that we need to embrace over the coming years. These challenges and opportunities can be summarised as follows.

• Funding
• Planning
• Maintaining
• Protecting
• Promoting
• Sustaining  

Funding the urban forest

Historically the majority of funding for the urban forest in the UK comes from the public sector - 70% from local authorities and 15% from Central Government and the EU100.

Nationally, a reduction in central government grants to local authorities has led to a 10.5% decrease in spending on green spaces and the urban forest between 2010/11 and 2012/13101.

.Across Coventry, Lottery grants, WREN funding bids, ERDF and fundraising events have been successful in raising capital, but these opportunities aren’t sustainable, often one-off or small short-term grants and not for securing the long-term cost of management102. As a result, the lack of funding has consistently been raised as the main constraint for improving the urban forest and GI, both in its creation and maintenance. In the longer term, funding the urban forest will require longer term financial planning and securing investment in the urban forest asset from a range of sources. Now opportunities should focus on the following issues and opportunities.

• Planning gain: Investment in the long term strategic planning of the urban forest should seek to maximise planning gain via s106 agreements and the Community Infrastructure Levy (CIL). CIL was developed in 2017 in Coventry and will be a means of securing investment in the urban forest, but this demand must compete with other provisions for welfare and amenity.
• Regeneration and Business Improvement Districts (BIDs): Tree planting opportunities and retrofitting existing grey infrastructure arise through BIDs or economic regeneration whereby businesses, local government and agencies work together to deliver local business-led aspirations. The `Greening for Growth’ project (2010) in London’s Victoria BID identified the potential for 1.25ha of new GI, 1.7ha of enhancements to existing GI and suitable space for 25ha of green roofs103. Coventry’s BID104, which aims to ‘promote, develop and boost the city centre to make it a great place to work and visit’ could provide a sustainable option for contributing to the urban forest in the longer term.
• Investment in the urban forest: With a mass of evidence revealing the role of urban trees affecting the nation’s health and wellbeing, the current urban forestry budgets for creation, management and maintenance is a small leaf in the Autumn fall when compared to the costs that have been identified ed eating up the NHS and Social Care budgets which access to the urban forest could address as health savings. Coventry City Council is encouraging local residents to be more active in their daily lives by providing a new integrated healthy lifestyles services, called Healthy Lifestyles Coventry105.

Planning the urban forest

Planning and designing development within the context of the urban forest is vital.

To assist in planning urban forests, local authorities around the UK have adopted the principles behind `Trees in the Townscape – A Guide for Decision Makers’106 produced by the Trees and Design Action Group (TDAG) in 2012. The NPPF 2012 recommends all local authorities set out a strategic approach to the ‘creation, protection, enhancement and management of Green Infrastructure’ including urban forests but only a few local authorities have achieved embedding a `GI Approach’ into their local strategies. Birmingham, for example has included spatial plans of additional GI sites107.

CCAAP proposes a series of policies which touch Coventry’s urban forest, and which are supported by the Infrastructure Development Plan under ‘Physical, Social and Green Infrastructure’ now appended to the Local Plan. Policies relevant to this Strategy include:

• CC1 Development Strategy: ‘The city centre will continue to be developed and regenerated to ensure that it is a truly world class city centre, leading in design, sustainability and culture’. This will be delivered by the provision of a ‘connected public realm including public squares and green spaces, easily accessible through the creation of desirable and legible pedestrian routes’; and ‘providing an attractive and safe environment for pedestrians, cyclists and motorists’.
• CC8 Green and Blue Infrastructure: ‘A high quality and well-connected network of green and blue infrastructure assets has the potential to make the city centre a more attractive proposition for external investors and local people’. The retention of trees that contribute towards public amenity forms part of this aim.

 CCC has identified that new connected green spaces are required to maximise the cumulative benefits of GI and the urban forest. How these plans are delivered will be part of a revised ‘Green Spaces Strategy’ (2018). In addition, the ‘Warwickshire, Coventry and Solihull Green Infrastructure (2016)’ has been developed at a sub-regional level as an effective tool for planning and evidence base for planning policies and strategies.

As trees take more than a life time to mature, and the loss of mature tree stock have particular repercussions in the value of the urban forest, future planning for planting is essential to accommodate best practice and consider how best to deliver the multiple benefits of the urban forest. The following issues will need to be considered.

• Planning for tree planting: To ensure Coventry retains existing tree cover levels, planting needs to be continually assessed, opportunities scoped, designed effectively and tree planting undertaken in accordance with best practice. CCC will need to consider revisions to supplementary planning guidance and detailed technical notes.
• Working with developers: One of the most significant threats to our urban forest is new development and Coventry has a high demand on land resource. Effective partnerships and adopting innovation is key in successfully delivering environmentally sympathetic managed growth across Coventry’s already pressurised urban environment. The maintenance, development and conservation of Coventry’s tree stock is important in ensuring that Coventry remains a great place to work and live, supporting Coventry’s future.

Coventry’s Green Infrastructure Study (2008)108 suggested a set of GI standards for greater levels of sustainability within new developments, including:

• GI should be considered in the same manner as any other form of infrastructure servicing new development, and should be an essential component of all developments;
• New GI associated with development should connect into site level and local green space networks which should in turn connect into the city-wide network;
• All developments should include GI elements, including SuDS, urban trees and green roofs, which deliver multiple sustainable benefits to the urban environment through their natural processes.

The Planners at CCC frequently receive inadequate plans from developers, often with trees being retained which are unsuitable for the proposal or new buildings not considering the existing tree stock on the site. Communication is the key to convey to the developer that any planning guidance involving trees will be to the minimum standard as described in `BS 5837:2012 Trees in relation to design, demolition and construction – Recommendations’, which also describes minimum tree protection standards. A tree survey needs to be undertaken by the developer to BS5837: 2012 to understand the condition and habit of the trees on site and to be able to calculate the Root Protection Area (RPA) to ensure proper protection from indirect and direct damage.

Loadbearing on trees also needs to be taken into consideration by developers and Planners, including reference to BS1377: Part 9 Soils for civil engineering purposes, Department for Transport earthworks guidance109, and long term monitoring protocols110.

• Partnership working with private landowners: The greatest proportion of our urban forest is privately owned, and care of the tree obviously varies vastly. When dealing with enquiries from private landowners, CCC will refer them to the correct direction of advice and best practice from the industry. Policies and future actions will need to consider how CCC continues to engage with private landowners for the development of the urban forest.
• Enhancing biodiversity: Trees make up a significant and highly visible component of Coventry’s biodiversity, with Tree Protection Orders (TPOs) and listings designated for their biodiversity value. They include ancient semi-natural and secondary native woodland, wood pasture, parkland, scrub, and individual Ancient and Veteran Trees. Many priority species protected by the Wildlife and Countryside Act 1981 (as amended) including bats, common dormouse, barn owl and stag beetle are directly associated with certain tree species for habitats and food, such as Black Poplar, which is a biodiversity priority species. Many insects specialise in their feeding preference on just a few tree species, whilst others are generalists that benefit from multiple tree species. In England native Willows, Oaks and Birches support the most varied insect herbivore species; Beetles are better supported by Scots Pine. Generally non-native trees are associated with fewer species than native trees as they ‘have had less time to form associations with native organisms’111.

It can though be seen where tree diversity is limited in urban areas that some non-native trees such as Sycamore support a large quantity of biomass, providing a valuable food source for birds. Some native tree species form few insect herbivore associations due to a high level of tree defence mechanisms eg. Yew112. Pollinating insects hosted by trees provide essential ecosystem services in urban areas of Coventry by pollinating flowers and producing food. Trees offer an important source of pollen at particular times of year when other sources are unavailable.

The HBA has been undertaken by Warwickshire Wildlife Trust in partnership with the six Warwickshire local authorities including Coventry since 1995. Their remit is to survey every field and boundary to provide up-to-date biodiversity data, which is mapped in GIS. This process is continually ongoing, data is updated annually, making the HBA the longest continual survey of this kind, which is crucial as the data is used in decision making regarding the spatial planning and development control of the urban forest. Phase 1 Habitats Surveys provide data on urban forest change, land use pressures and feeds policy and decision making on GI, ecological connectivity and biodiversity off setting.

The Warwickshire Wildlife Sites Project is now part of the HBA Partnership, which is responsible for Local Wildlife Site selection which covers some of our urban forest. A detailed Phase 2 Habitat Survey is undertaken against a set of national criteria called the `Green Book’. The designation of Local Wildlife Sites is considered by a panel of experts which includes an officer from CCC.

The biodiversity value of urban trees when seen as a collective and in association with other elements of GI is a functioning ecosystem providing habitats for many species in hostile urban environments.

The UK Biodiversity Action Plan (UKBAP) established a native woodland habitat creation target of 134,500ha by 2015113. The new UKBAP habitat ‘Open Mosaic Habitat on Previously Developed Land’ is concentrated in urban and peri-urban areas, which is an important habitat for many rare or threatened and protected invertebrates, plants and birds on unique soil conditions. The urban forest can be planned to increase these populations. Some species harbouring within the urban forest are invasive and require careful management.

Important for planning Coventry’s urban forest, it is known that species population size is also directly linked to the size of available habitat area e.g. the biodiversity benefits of massing the urban forest was demonstrated by bird species richness114, and most 10-35 ha parks will contain all the birds recorded in any urban area of that region. Therefore, removal of an area of urban forest in Coventry or a line of street trees could impact on the movement of species, which use urban trees and GI as ‘stepping stones’ of habitat, enabling longer-distance movement for some species115. For instance, it has been demonstrated that managed roundabouts and road verges planted with suitable trees support a wide variety of plants and insects116. Warwickshire Wildlife Trust’s Lottery-funded ‘Dunsmore Living Landscape’117 scheme, seeks to restore important wildlife habitats and corridors in the areas lying between east Coventry, Rugby and north Leamington. In the future, policies and actions need to consider long term management plans for biodiversity within the urban forest. CCAAP Policy CC8 ‘Green and Blue Infrastructure’ recognises that there needs to be a strategic overview of greenspace to support local biodiversity networks, and that urban forestry is integral to this.

Planning for climate change

Extreme and more frequent weather events are expected in the future118, and infrastructure will need to resist these predicted changes, which is not considered extensively in current Local Development Plans.

The NPPF 2012, the UK Climate Change Risk Assessment 2012 and the subsequent National Adaptation Programme 2013 all recognise the role of urban GI and forest in climate change adaptation. The BiFOR: Birmingham Institute of Forest Research, is researching the evidence case for forests as part of One Planet Living, and is currently researching how forests will respond to the future prediction of CO2 increase119. This data will provide an important argument for enhancing our urban forest in Coventry. Even modest increases in tree canopy can reduce the urban heat island effect and build resilience to climate change through evapo-transpiration and shading, as well as improving air quality. An attractive urban forest, as promoted by CCAAP Policy CC1 Development Strategy ‘to provide an attractive and safe environment for pedestrians and cyclists’, can also encourage active travel which will further mitigate air pollution. The role trees play in alleviating the effects of climate change needs to be recognised and provision made available to plan for new tree planting. Well-informed decision making is therefore required on the design of buildings, infrastructure, open space provision and tree species selection in response to the effects of climate change. TDAG guidance needs to be integral to all decision making120.

Planning to alleviate air pollution

Street trees have been associated with a lower prevalence of asthma in children. Designated Natural Health Improvement Zones (NHIZ) is one of the initiatives endorsed in the `2011-15 Health Protection Agency Strategy’ to tackle this challenge. NHIZs are centred on those areas most affected by air pollution (Air Quality Management Areas), and, within these areas, trees and green walls planted facilitate the trapping of pollutants by foliage. CCAAP Policy CC1 aims to ‘combat poor air quality and other pollutants’ and urban forestry needs to be highlighted a key solution. Grey Friars Green has now been identified as an ‘Air Management Area’. CCAAP Policy CC8 regarding ‘Green and Blue Infrastructure’ recognises that a key source of pollution in Coventry is the city’s ring road, and ideas for “greening” the route, such as vertical planting schemes and tree planting, are currently being explored.

The urban forest in Coventry has a direct role to play in alleviating air pollution and specific technical guidance will need to be developed to address this increasingly concerning issue.

Maintaining the urban forest

CCC is continually looking at ways to effectively cost save through maintenance, in order to provide better value for money. With increasing financial constraints placed on CCC to manage the urban forest, the public and private sector both need to seriously consider investment targets.

Local community support or ‘buy-in’ to their urban forest assists in moderating long-term financial and managerial costs. But is maintenance of the urban forest essential to maximise its benefits? While well-maintained green spaces can improve mental health, overgrown vegetation can have a negative impact by increasing the fear of crime although these overgrown spaces may be better for biodiversity. Some infrastructure such as green roofs, walls and rain gardens require minimal maintenance once installed. For other types of infrastructure, such as green spaces, the cost of maintenance can be higher – through mowing, weeding and watering. These costs often fall to local authorities and have been the focus of budget cuts in recent years. GI includes a wide range of infrastructure types, so generalisations regarding the cost of implementation and maintenance are difficult to make. Maintenance may increase long-term jobs in the local community, but alternative sources of funding are required to cover these costs. Design that is sensitive to maintenance costs can improve the sustainability of a project by minimising this budget. The following issues and challenges for long term management and maintenance of the urban forest need to be considered.

Tree inspections and risk assessments

Inspections based on Visual Tree Assessment (VTA) form the basis of pro-active maintenance regimes for all CCC owned trees. CCC’s approach to tree inspection and hazard evaluation is set out in its Tree Risk Management of Parks, Open Spaces and Woodlands policy (TRM). GIS is used to collect and manage the tree data, in conjunction with a specific tree asset management system. In light of emerging case law, CCC will need to further consider specific policy and resource implications for cyclical visual tree inspections.

Tree pruning

Inappropriate or poor pruning of trees can have long term financial and safety impacts. CCC will not top or prune trees inappropriately. However, the programme of street tree pruning that pollards many trees in the highways across Coventry annually has to continue. This work is necessary for the City Council to satisfy its liabilities towards subsidence risk. In the long term, the City Council has an aspiration to replace all these trees with more suitable species that will see an end to this type of pruning.

Street trees

CCC takes responsibility of all the street trees on Coventry’s highways. Specific policies and procedures, including TRM for inspections and proactive maintenance will be adopted as part of this Strategy. Parks and public open space- All trees in the principal parks have been surveyed and recorded in the tree asset management system, with the resulting health and safety actions undertaken.

New planting

It is recognised that new trees require specific maintenance during the initial establishment phase to ensure that they thrive, and to avoid costly maintenance issues and health and safety concerns in the future. For street trees, this is becoming more of a challenge and it is important in these environments where trees have been removed due to highway operations that replacement planting is undertaken the following planting season to ensure continuity of tree heritage of that street. Clear policies and procedures need to be adopted to ensure the correct establishment of trees within the urban forest.

Woodland trees

CCC own and actively manage over 200ha of mature woodland within the city boundary. 100ha of these are ancient and semi-natural woodland or replanted ancient woodland sites. All CCC woodlands have Management Plans that are under review.

Protecting the urban forest

Our urban trees have to be tough to survive, in particular our street trees which have to fight for survival.

Coventry already has a range of protection measures for trees but we need to communicate the benefits of trees as well as enforcing legal protection. Challenges for future consideration will include the following issues.

Current policies

Policies for tree protection should embrace the lifecycle that an individual tree endures to thrive and survive, and the value it contributes to the urban forest as a whole. Our urban forest now shapes our local landscape character and is a legacy leftto us by Victorian, Edwardian and pre-war designers. Coventry’s Local Development Plan (LDP) recognises that trees make ‘a valuable contribution to the city’s green landscape’.

Policy GE3 ‘Biodiversity, Geological, Landscape and Archaeological Conservation’ states:

• Sites of Special Scientific Interest (SSSIs), Local Nature Reserves (LNRs), Ancient Woodlands, Local Wildlife and Geological Sites will be protected and enhanced. Proposals for development on other sites, having biodiversity or geological conservation value, will be permitted provided that they protect, enhance and/or restore habitat biodiversity.
• Biodiversity will be encouraged particularly in areas of deficiency, in areas of development and sustainable urban extensions, and along wildlife corridors. Opportunities will be sought to restore or recreate habitats, or enhance the linkage between them, as part of the strategic framework for green infrastructure. Protected Species, and species and habitats identified in the Local Biodiversity Action Plan (LBAP), will be protected and conserved through a buffer or movement to alternative habitat. Identify ed important landscape features, including Historic Environment assets, trees protected by preservation orders, individual and groups of ancient trees, ancient and newly-planted woodlands, ancient hedgerows and heritage assets of value to the locality, will be protected against loss or damage. In the case of archaeological remains, all practical measures must be taken for their assessment and recording in accordance with Policy HE2 [...] In order to restore good levels of biodiversity across the Warwickshire, Coventry and Solihull sub-region, it is important to have urban areas that are permeable for wildlife, with havens for wildlife through the city and connected corridors linking sites [...]

CCAAP Policy GE4 ‘Tree Protection’ states:

•  ‘Development proposals will be positively considered provided a) there is no unacceptable loss of, or damage to, existing trees or woodlands during or as a result of development, any loss should be supported by a tree survey; b) trees not to be retained as a result of the development are replaced with new trees as part of a well-designed landscape scheme, and c) existing trees worthy of retention are sympathetically incorporated into the overall design of the scheme including all necessary measures taken to ensure their continued protection and survival during construction’;
• ‘Development proposals that seek to remove trees that are subjection to protection, without justification, will not be permitted'.

Compensatory measures are identified in Policy GE4 to prevent the removal of trees as far as possible, but when loss is unavoidable ‘compensatory provision of new trees should be proposed as part of a well-designed landscape scheme or within other areas of green space within the local community. This will ideally be within 400m of the site [...] All replacement trees should be of an appropriate type and status to reflect those which have been lost’. If a tree is subject to protection as part of an Ancient Woodland or through a TPO, then trees should be ‘retained for the value they add to the visual amenity of the area’.

Current and future policies will need to be reviewed and adapted to meet future challenges.

Loss of trees

Sometimes for the right reasons, a tree does need to be felled. But when is loss unavoidable and who makes this decision? Many members of the public have raised this question after tree felling within the distinctive streetscapes of other UK urban areas. Planning Services at CCC are responsible for enforcing and monitoring statutory protection of trees on private land, and rely on the technical support of the Tree Preservation Officer, with assistance from the Urban Forestry Officers. With increasing pressures on our resources in Coventry, with house building, new infrastructure and attracting new business, a strong policy is required on enforcing protection and compensation, and an increase in awareness amongst professionals, residents and developers.

CCC’s LDP states that ‘in exceptional circumstances where the benefits of development are considered to outweigh the benefits of preserving the protected tree, development will be permitted subject to adequate compensatory provision being made’.

There are opportunities to provide suitable compensation measures when a tree is lost. Either replacement trees, or a financial contribution equivalent to the value of the removed tree(s). How this is calculated is using appropriate assessment provided by the draft`Trees & Development Guidelines for Coventry: Supplementary Planning Document (July 2018)’121 and agreed between the Developer and CCC using methods such as CAVAT calculating the value of a single tree.

Tree protection orders (TPOs)

CCC has a statutory duty to protect the urban forest by administering TPOs and designating Conservation Areas. This proactive use of TPOs as a tool to sustain the urban forest and protect from the urban pressures it faces, places a responsibility on the land owner to request permission from the Council prior to any tree works. Policy HE2 ‘Conservation and Heritage Assets’ states that ‘In order to sustain the historic character, sense of place, environmental quality and local distinctiveness of Coventry, development proposals will be supported where they conserve and, where appropriate enhance those aspects of the historic environment, which are recognised as being of special historic, archaeological, architectural, artistic, landscape or townscape significance’.

Ancient trees, veteran trees, and ancient woodlands

Although Ash is the most common tree species within Coventry, few really old Ashes exist; many by 150 years are hollow due to a decline in tree health and prone to wind-blow of their crowns. A significant number of Ancient Trees exist across Coventry. English Oak (Quercus robur) dominate the Ancient Tree listings, with 382 specimens (currently known) with girths of 5 metres-plus, judged to be at least 250 years old with many in the former historic Arden parkland or within ancient hedgerows.

Policy HE2 ‘Conservation and Heritage Assets’ states that ‘All development proposals should aim to sustain and reinforce the special character and conserve the following distinctive historic elements of Coventry [including] the wider Arden rural environment on the fringe of the city comprising field systems, ancient woodlands and commons developed over the centuries...’

Princethorpe Woodlands includes 20 woodlands, covers 618ha and represents more than 10% of the whole of Warwickshire’s ancient woodland. The Local BAP for Warwickshire, Coventry and Solihull identifies Princethorpe Woodlands as ‘the most significant cluster of ancient woodlands in Warwickshire’ which are connected by ecologically valuable networks of hedgerows. Princethorpe Woodlands is now part of a Lottery-funded Dunsmore Living Landscapes scheme122, which has the following aim: ‘to restore important wildlife habitats in the areas lying between east Coventry, Rugby and north Leamington and reconnect people with these special places’.

Future policies and actions will need to address the long term custodianship of Ancient and Veteran Trees and the Ancient Woodlands of Coventry.

Promoting the urban forest

How do you get the public and potential developers to become more aware about the importance of the urban forest in Coventry? Positive news stories are a challenge to gain the interest of the press, but aiming high in a strategic vision is something that Coventry needs to do. For example, CCC undertake social media campaigns regarding parks eg #loveparks but not specifically the urban forest, and deal with Twitter threads, humour and engagement in different ways. Coventry’s stories are amassed in a generic #LoveCoventry Twitter feed, as well as more recently #CityofCulture2021. Coventry’s successful City of Culture 2021 bid presents an opportunity to demonstrate Coventry’s culture and heritage, and the role that its urban forest plays in that.

The challenge we need to embrace is how CCC translate the community’s increasing awareness of the urban forest into a long-term, meaningful engagement at a local level, particularly with people’s time being even more pressurised. CTWN are proactive crucial groups of volunteers who are trained, act as the “eyes” for the Council, provide advice and undertake tree planting. However, it is important that they do not undertake work which is beyond their duties and liabilities. Tree Wardens work in partnership with the Council, the Tree Council and Conservation Volunteers to research and empower their local communities to take on practical projects relating to the urban forest. Several also sit on their respective Parish Councils or other organisations and can therefore be seen as the connection between the local authority and the Council, and a key voice for the urban forest.

As we have discussed, there is a wide range of bodies including universities, government agencies, the third sector, companies and other organisations with a focus on trees in urban landscapes working in Coventry, such as CTWN, WWT, The Woodland Trust, TDAG and Trees for Cities, who have knowledge, experience 31 Coventry: Urban Forest Future Coventry Urban Forestry Strategy Ancient Oak tree, Cannon Hill and expertise about urban trees which could be beneficial to CCC. There is also a wealth of evidence from research emerging all the time about the wider benefits of trees and GI, as referred to in this Strategy, which could be used to benefit and inform the way that CCC maintains, manages and develops Coventry’s urban forest.

CCC should utilise this knowledge and expertise in conjunction with that already in-house from directorates across the Council and delivery bodies to bring together a joint independent-led group which can be called on for advice and knowledge, which could be called the Coventry Urban Forest Group.

Promoting and raising the profile of the urban forest will be key to the successful implementation of the Strategy.

Sustaining the urban forest

A resilient and sustainable urban forest is based on various factors, such as a wide ranging tree size and species distribution, directed by rigorous management strategies and policy and planting more than felling. This is important to enable the urban forest to deliver the benefits described in the values sections outlined above. One of the prime objectives of Coventry’s urban forestry management should be to facilitate sustainability and resilience through population diversity. A healthy tree population, for example, can ensure more carbon is stored than released, as long as the amount sequestered by healthy trees is greater than the emission of carbon from the decomposition of dead trees.

For example, large mature trees offer unique ecological roles not offered by smaller and younger trees, therefore the optimum level of trees of this stature needs to be maintained, and thus protected. It is important to calculate the number of trees required to restock their mature neighbours to ensure the urban forest is inherently resilient. New planting must be in excess to take into account tree mortality of new stock.

For Coventry’s more mature tree stock, Biodiversity Management Action Plans for `Woodpasture’, `Old Parkland’ & `Veteran Trees’ have been written123; and ‘Ancient and other veteran trees: A guide to good management’124 is also full of information. Future policies and plans will need to consider the following challenges and opportunities  

Optimising the urban forest

“Ideal” tree populations have been adopted in certain cities such as Toronto to inform management of the urban forest with the aim of creating a resilient urban forest. Mapping the existing tree population structure and comparing it with “ideal” tree population structures can help identify the number and type of tree stock needed to fill the gap. This provides powerful data for policy and demonstrates the funding and resources required to achieve this optimum urban forest. But numbers of trees are not the only crunch data, as leaf area and tree canopy cover is the driving force behind tree benefits. When leaf area and tree canopy cover is calculated through an i-Tree type assessment and combined with abundance of a certain tree species a “dominance value” can be determined regarding the benefits they can bring. In London, for example, Apple trees are the “third most populous tree” but “ranked 8th for species importance”.

Diversity of tree species

Diversity in the urban forest has two main components: the number of species present plus the genetic diversity of the individual species present. Diversity of both native and non-native trees is crucial in reducing the potential impact from threats such as pests and diseases and climate change and enhances the capacity of the tree population to deliver ecosystem services. The selection of tree species will be crucial for long term diversity and this should form part of detailed technical advice promoted by CCC.

Planting more, felling less

As well as species diversity, the principle of planting more than felling or removal of trees needs to be endorsed. Systems will need to be adopted to determine metrics and targets for planting.

Pest and pathogens

Pest and diseases are a serious threat to the biosecurity of our urban forests. With an Ash dominant urban forest there are concerns about Chalara Dieback of Ash (Hymenoscyphus fraxineus) which has been identified in Coventry. The University of Birmingham through BiFOR is currently researching the resilience of trees to pests and diseases including resilience of imported diseases/pests and has found that climate change is altering the range of pests and diseases likely to affect the UK125. The outbreak of pests and diseases is supported by the importation of trees, particularly large landscape trees, and the increasing volume of packaging materials used in international trade. Tree populations dominated by a few species are more vulnerable to the threat with `Dutch Elm Disease’ for example, causing the death of approximately 30 million Elm trees in the UK.

CCC have recognised that action must be taken to limit pests and diseases as incidence, spread and severity of an outbreak varies according to tree health, management and young tree procurement policies, as well as the weather and tree species. Action plans which set out how to deal with largescale outbreaks of pests and diseases, such as Ash dieback, will need to meet with Government advice.

The Landscape Institute’s Technical Note 4 (2017)126, identifies the following main pests and diseases affecting the UK’s trees: Hymenoscyphus fraxineus (ash); Sweet chestnut blight; Bleeding canker (horse chestnut); Massaria (London plane); Phytophthora; Asian longhorn beetle; Oak processionary moth; Acute oak decline. There are other pests and diseases which have not yet arrived in the UK, but have the potential to do so, including Emerald ash borer; Xylella fastidiosa; Japanese beetle; and Citrus longhorn beetle.

Future policies and procedures will need to consider how pest and diseases are addressed and controlled in the future.

Managing different interests

Across Coventry we have significant swathes of mature urban forest. However these very same trees we have been demonstrating the value of can for some residents and businesses be a source of frustration. This generally happens when the particular tree significantly contributes to the local public realm and landscape character, but provides challenges to those nearby. Managing potential conflicts can be resolved through effective communication and proactive maintenance. In the future, promoting good management and the need for trees should be a priority.