Leading Arboricultural and Ecological Consultants

Trees - The key to Climate Proofing our Cities (Part 1) Review

Seminar XI

TREEWORK ENVIRONMENTAL PRACTICE SEMINAR XI, held at the Royal Geographical Society, Hyde Park, Kensington on 10th July 2008

Originally published in AA Newsletter issue 142 by Simon Richmond, Technical Officer, Arboricultural Association

Treework Environmental Practice have once again provided a comprehensive and thought provoking perspective on our attitude to trees. This conference, sponsored by the Forestry Commission, Barcham Trees, E Cosolis Ltd and Edenvale Young, in association with the Arboricultural Association and the Institute of Chartered Foresters, featured 13 invited speakers. Neville Fay of Treework Environmental Practice introduced the day along with Jeremy Barrell who has also been instrumental in creating and supporting this event and the day was then ably chaired by Professor Chris Baines, Broadcaster and Government Advisor on Environmental matters.

The conference was well attended by some 120 delegates and although it was, to some extent, preaching to the converted, there was such a wide range of stakeholders present and so many varying perspectives addressed, that most if not all went away feeling educated and in some cases, inspired by what they had heard and seen. The conference title that attracted delegates is one that we all have opinions about; what was impressive was the way in which each speaker’s specific approach and subject area provided us with another strand with which to learn, to appreciate the ‘larger picture’ and, as Chris Baines evangelistically encouraged us, to communicate: ‘If just one bright idea, project or innovation grows from this event, and that is communicated, we have sown the seeds of change’ (unashamedly paraphrased).

"Increasing trees and other green space by as little as 10% could effectively neutralise the projected increases in urban surface temperatures over the next 20-50 years".

Dr Richard Simmons, CEO of CABE Space, talked about the significance of Trees in Towns II and the recognition of trees’ contribution to promoting sustainable communities. It is obvious that Local Authorities have an important role to play in the future planning and management of our urban to play in the future planning and management of our urban environment; Tree in Towns is an essential tool in providing information and helping to offer a co-ordinated approach.

Dr Roland Ennos of Manchester Faculty of Life Science gave me a fascinating and entertaining description of studies carried out in Greater Manchester on the efficiency of ‘urban greenspace’ in reducing the effects of climate change. Dr Ennos concluded that increasing trees and other green space, including grass, by as little as 10% could effectively neutralise the projected increases in urban surface temperatures over the next 20 – 50 years. However, associated studies of projected changes to rainfall patterns over the next few decades, showed that, while trees in particular and green space in general certainly reduce the rate of run off and facilitate re-evaporation, etc, the overall effects of this mitigation are not so great. He suggests that, even with a 10% increase, by 2080 runoff would still be increased by up to 50%.

Jan Cermak, ‘tree eco-physiologist’ from Brno University, Czech Republic, discussed Climate and Hydrological Control. Jan has studied transpiration in a range of circumstances using different species, soil types and climate models. The relation of tree survival rates given differing soil conditions and the responding rooting structures to facilitate moisture availability were fascinating to see and once again, our understanding of the likely root architecture for a given tree in particular circumstances was challenged. ‘Trees’ development of the sinker roots and the water storage functions of roots. In association with their anchorage properties, was explained, and the need for further investigation of this area of arboricultural understanding was also emphasised.

MARTIN Kelly, chairman of the Trees and Design Action Group (TDAG), outlined the background and formation of TDAG including those organisations that had so far become members. A not for profit organisation, TDAG is an umbrella group that has a 10 point action plan to address a range of issues related to increasing the number and viability of our tree population.

Keith Sacre, Sales Director of Barcham Trees, commenced by introducing some of the statistics in relation to existing tree planting in Greater London, from Barcham’s own records, indicating that the population of recently planted trees should provide improving tree cover in the coming years. However, he went on to point out that the proportion of large canopy trees in relation to smaller species was very low and furthermore, the long term survival of these trees was poor. The problems with establishment success rates were examined and the audience was invited to rise to the challenges this presents us with. From the nursery perspective, Keith also described some of the research that has been conducted into survival rates of different planting stock.

The next speaker was Professor Helga Fassbinder, an urban planner and Editor in Chief of the International online ‘Biotope City Journal’ (www.biotope-city.net), who talked about the different approaches to ‘city greening’ from two European cities: Paris and Amsterdam. Paris has developed a centralised and systemised approach to the issue, coined as ‘vegitalisation de la ville’, with exhibition gardens in the city centre, green walls, pocket gardens, etc, supported by a comprehensive public relations strategy directed at all citizens. Amsterdam, by contrast, has a much more ‘home pun’ approach, with 14 independent and autonomous local boroughs. In general, the greening initiative is driven by the citizens, and broadly accepted by the authorities. In conclusion, Prof Fassbinder points out that, whatever way it is approached, the aim is the same, to increase and maintain the green infrastructure of our towns and cities. The way it is achieved will depend on the administrative structure and political and social-cultural circumstances locally.

Peter Thurman, of the Thurman Consultancy, took us through an entertaining and thought provoking whirlwind tour of the worst and best examples of tree planting and design schemes, looking at examples of how we address issues of unity and structure, scale, proportion and balance, time, space division and spatial definition, light and shade, colour, texture and form. He called upon the planners, architects, developers, local authorities and others involved in the decision making process to rise to the challenge and not be accused of ‘cynical tokenism’ in their tree planting design plans.

"The way it is achieved will depend on the administrative structure and political and socio-cultural circumstances locally".

John Young, Director of Edenvale Young Associates Ltd, brought an engineering perspective to the role of design and planning. The presentation centred on our understanding of how rain is intercepted in its journey from sky to sea and how trees and ‘green space’ are crucial in the natural alleviation of flooding risk. In particular, he introduced the concept of Sustainable Drainage Systems (SUDS) and the significance of trees helping to mitigate flash flooding.

James Urban, of Deeproot, USA, concentrated on soil structure – the key to tree establishment and survival. James highlighted the folly of our typical tree planting systems: We really cannot expect a semi mature rootballed tree, planted in a 1 m cubed planting pit dug out of compacted, structure-less soil, to survive at all, let alone to flourish. Yet, our urban environment is so often restricted by surrounding features both below and above ground that trees are commonly planted this way. James’s work has been pioneering new approaches to creating structured soils of sufficient volume to accommodate the growth of newly planted trees for a foreseeable future, incorporating the need for underground services, vehicle and pedestrian traffic and building development.

David Ball, Professor of Risk Management, Middlesex University, talked about our current concepts of risk in modern life and drew some interesting comparisons with other industry approaches to our ‘risk-averse society’. Starting with the basic principles of Health and Safety law in the UK, and the Health and Safety Executive’s view, David drew out how our perspectives are affected by corporate and local authority responses to the litigious climate. When applied to arboriculture, again the questions arises as to how current risk decisions are made and whether the process of risk assessment is objective when looked at in context, particularly the context of the vast range of benefits derived from trees.

Richard Nicholson, Arboricultural Consultant and Planning Expert, discussed the way in which planning applications are currently managed in relation to existing trees and to proposed planting of trees on development sites. Richard reminded us that ‘There are three ways of achieving the strategic objective of large trees within the built form: 1: Retain large trees on development sites; 2: Plant them; or 3: Designate what might be called ‘surrogate sites’ for tree retention or planting.’ Presenting a balanced approach to these options, Richard examined a range of examples of sites and situations to illustrate his points. In conclusion, he emphasised that the change that is now needed is around the interpretation of the current guidance by arboriculturists, particularly those working for local authorities, and applying a realistic, design based approach, in co-operation with the full range of professions involved in the development process.

Jim Smith, the London Tree and Woodland Framework (LTWF) Manager, outlined the threats to our tree stock and the implications of failure to respond to these. He then went on to describe how these challenges are being met, by listing some of the projects and initiatives that LTWF have been working on with various partners. Once again, it was emphasised that success in these areas relies on co-operation within the professional communities involved in managing our trees and an awareness raising culture so that the importance of trees is properly recognised.

Following a session of question and answers from the delegates to all speakers, the day was summed up by Neville Fay who drew together the key points from the day and the positive and constructive proposals that had been presented. Amazingly, to the organisers’ and chairman’s credit, the day finished precisely on time!