Sunday, October 26, 2014
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The LTOA - Caring for the Capital's Trees

Welcome to the LTOA website. The London Tree Officers Association (LTOA) constitutes the professional & technical voice for London's trees & woodlands. Its aim is to enhance the management of the Capital's trees. We hope that you find the LTOA website both interesting & informative. If you have any questions, comments or suggestions, please do not hesitate to contact us.


Open Source Canopy Cover Audit (OSCCA)

Do you know what percentage of your borough is covered by trees and woodlands? Do you know if it has changed significantly over the time or how it varies within different parts of your borough? Without knowing your existing tree cover, how will you plan and manage future tree planting?

To answer these and other questions, the LTOA would like all London boroughs to complete and return a baseline canopy cover survey. In order to achieve this, the LTOA with the support of the Greater London Authority, have devised a straightforward means of estimating tree canopy cover. The tools we have created are called ‘OSCCA’ (Open Source Canopy Cover Audit), and are available for anyone to use. OSCCA allows you to generate random points on aerial images of your borough, which can then be classified according to land cover, (trees, roads, water, etc). This quickly lets you build up a reliable tree canopy cover estimate.

There are two sets of guidance for OSCCA to help you to undertake your canopy cover survey. Which guidance you follow depends on the mapping system in use in your borough, either ArcGIS or MapInfo. If you are unsure which system you use then please speak to a colleague in your mapping team.

It is important that you check the licence arrangements for your aerial images with your colleagues in the mapping team, as some licence restrictions may prevent data (such as canopy cover), being derived from aerial imagery and made public. If you are in any doubt about the licence arrangements for your aerial photographs you can contact the Greater London Authority, who are able to make aerial images available to London boroughs to use in this project without this licence restriction.

Once it is set up, the canopy cover survey is quick and easy to complete. And when you have completed the survey you can:

  • Compare the percentage of trees and woodlands with other green infrastructure, or with the percentage of land covered by buildings or transport infrastructure for instance.
  • Use the survey results alongside other datasets (such as ward boundaries) to determine areas of low canopy cover to prioritise locations for new tree planting.
  • Assess the difference that recent tree planting has made to your canopy cover, by repeating the survey using past aerial images.
  • Record and monitor progress on meeting targets for canopy cover.
  • Take on more complex surveys – for example distinguishing between privately and publicly owned trees

To register your interest in carrying out a survey, and for any queries about OSCCA please contact the LTOA Canopy Cover Working Party via This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Please contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it if you are interested in using aerial imagery held by the GLA

Members of the Canopy Cover Working Party are:

  • Rupert Bentley-Walls (London Borough of Hackney)
  • David Houghton (London Borough of Camden)
  • Dave Lofthouse (London Borough of Merton)
  • Barbara Milne (City of Westminster)
  • Jonathan Robinson (London Borough of Hackney)
  • Matt Thomas (Greater London Authority)

The programme for MapInfo was created by Jonathan Robinson (London Borough of Hackney).

The guidance for using ArcGIS was devised by Matt Thomas and Rebecca Page (Greater London Authority).


What we know and don’t know about the physical benefits of trees and where are the gaps in research

Professor Roland Ennos, describes how the focus of this gap-fill research work undertaken in association with the Trees and Design Action Group (TDAG) and supported by Fund4Trees identifies the current state of knowledge of three key physical areas which can be influenced by the presence of trees. The research also highlights areas where more research could be beneficial. The target audience for this research paper are those involved in policy, management/protection, design and delivery of urban trees.

“We have focused on three key areas:

  • Carbon storage and sequestration: this has been researched and written up in the agreed format.
  • Cooling: this has been researched and split up into 3 separate benefits: local cooling of people; local cooling of buildings; and regional cooling and urban heat island reduction. We’ve finished all the text for this and just need a few diagrams and references.
  • Flooding: work has been begun in this area.

The other major issue to consider is reduction of pollution but this would require specific expertise in this area to investigate. As far as noise reduction is concerned, this is not something trees are actually good at, and reduction in wind is far too difficult to quantify. We propose to approach Landscape and Urban Planning about publishing our reviews.”

Martin Kelly, TDAG Chair and Land Planning Director at Capita Property and Infrastructure, commented that “this is a very important step for urban trees. As practitioners it is vital that we work with evidence based research in order to make appropriate long-term decisions which are what is required if we are to have an effective well-distributed urban forest for the future benefit of our towns and cities. TDAG thanks both Fund4Trees for financial support and Professor Ennos and Dr Asrafur Rahman for their expertise in making this important piece of work possible."


LTOA seminar on Tuesday 7 October 2014

At London Borough of Redbridge


9.30am - Tea and coffee

10:00am - Introduction from new LTOA chair Richard Edwards

10.05am - John Parker, LTOA working party chair, Surface materials around trees in the hard landscape

10.15am - Lars Schultz-Christensen, Arborist in Copenhagen, Tree Planting in Copenhagen

11:00am - David Houghton, Tree planting for subsidence

11.20am - Questions

11.30am - Short break

11.40am - Brian Crane, Brian Crane & Associates, Initial results from a long term study of the effects of root damage on street trees

12.25pm - Dave Lofthouse, LTOA working party chair, OSCCA (Open Source Canopy Cover Audit)

12.45pm - Questions

1.00pm - Lunch at local pub sponsored by Barcham Trees

Thank you to Christian Sheldon and LB Redbridge for hosting the meeting and for providing tea, coffee and biscuits and to Barcham Trees for the lunch.

Please note: this LTOA seminar is for LTOA members only. Please contact Becky if you want to attend: This e-mail address is being protected from spambots. You need JavaScript enabled to view it


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Join the LTOA

Members can attend, for free, the the LTOA meetings which are held four times a year and cover a wide range of tree related matters. Click here to find out how to become an associate member


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