Study aims to facilitate evidence-based decision making on species and nurture

Research to examine the benefits of urban trees

TDAG (the Trees and Design Action Group) intends to collect and review research undertaken on the physical benefits of urban trees, in order ‘to identify what is and what is not known about them, and how best to improve our knowledge’. 

Its Fund4Trees (F4Ts) study will culminate in a TDAG web resource for researchers, practitioners and the general public. The findings will be published in peer-reviewed journals, on the TDAG website, as a stand-alone report for TDAG, and will be publicised to the general public through the conventional and social media.
TDAG coordinator Sue James, describes the review as ‘an important step forward', and says that the outcome will be of value to all built-environment professionals.
The work will be carried out by Dr. Mohammad Rahman, whose PhD addressed the effect of tree species and cultivation on the cooling benefits of urban trees. It will be supervised by Professor Roland Ennos, an authority on the physical benefits of urban trees.
‘We are delighted to undertake this work,’ says Ennos. ‘A huge amount of thought and energy goes into research, but all too often the results simply don’t get through to the people who really need it – the practitioners. 
‘We aim to review the literature and let people know clearly and concisely what is known, and perhaps even more importantly, what is not known about the physical benefits of urban trees. This will also help researchers focus on important problems rather than repeating work that has already been done.’
The Fund4Trees research advisory committee recommended the project for funding. Its chair, F4Ts trustee Dr Gabriel Hemery, says there is a need to compile the very best existing evidence about the importance of urban trees, and to review quantitatively any benefits which arise. ‘We are aware that the identification of knowledge gaps is much-needed,’ he adds, ‘and these will help steer our own support for urban tree research in future as much as it will that of the wider research community’. 
According to TDAG chair Martin Kelly, it is vital that practitioners are aware of evidence based research, ‘in order to make long-lasting decisions and a starting point is to know what evidence there is’. 
Considerable research has been and continues to be carried out on the physical benefits of urban trees in the UK, the rest of Europe and beyond. However, according to TDAG, initial surveys of the literature suggest that, while some areas have already been well covered, the work has been carried out by many isolated groups of researchers ‘and consequently there has been no overall methodological framework, or even consistent physical basis for their investigations’. 
In addition, some of the benefits have only been modelled, not investigated by experiment, it claims, ‘while in many other cases only generic benefits of "typical" trees have been quantified with little investigation of the influence of tree species or cultivation techniques’. 
The result of this, says TDAG, is that, while there is a good deal of literature, it is often quite inaccessible to practitioners and the general public. ‘It is also hard to judge its quality and it rarely seems to tackle the questions they want to ask: which trees are best and how should they be grown to provide the greatest physical benefits, for example. The result is that some important areas of research continue to be neglected while in others research is needlessly replicated or carried out using flawed methodologies.’


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