Expert warns over paucity of tree data

Poor urban tree data could lead to negative impacts on budgets and biosecurity, respected urban forestry expert warns.

Johnston: urban forestry expert - image: HW
Johnston: urban forestry expert - image: HW

Lack of basic survey work on urban trees could have damaging implications for budgets and the fight against ash dieback, one of Britain's most respected urban forestry experts warned last week.

Dr Mark Johnston, who wrote the landmark Trees in Towns II report, told the PlantNetwork Urban Public Gardens Conference that the sector is dogged by poor data collection and lack of acknowledgement by the Government and landscape architects of the wider value of trees.

He said that when he wrote his report it was delayed by the Government and then published in electronic format only. He ended up self-publishing the book.

He found only 16 per cent of authorities had done a full survey of all their highway trees, while 30 per cent had not conducted any survey.

"Only 19 per cent have an accurate record of the percentage of their district covered by trees and woodland, yet that's the basis of any tree strategy," said the research fellow at Myerscough College. "How can you go forward if you don't know where you are now?"

Lack of firm data has biosecurity implications, he said. We do not know what percentage of the urban forest includes ash and whether the trees are Fraxinus excelsior or the various cultivars "because we haven't done the basic survey work".

But he said a few councils are trailblazers. Torbay Council used i-Tree software to work out that its urban forest cover is 11.8 per cent and that it absorbs 50 tonnes of pollution a year. But the killer statistic is how much the urban forest is worth: a total of £280m.

"These figures are very useful. Budgets are under increasing pressure and tree officers are losing their jobs up and down the country. If you can say our urban forest has a value of £280m and then someone proposes a budget cut of £50,000 you have a powerful tool.

"You can work out how much that will devalue the urban forest, say £15m, and ask: 'What's the sense of that?'" said Johnston.

Green infrastructure: vital role played by trees

"We talk about green infrastructure and ecosystems services. Many of those benefits such as carbon sequestration are performed by trees, especially large ones. But when you hear the Government or a landscape architect go on about green infrastructure, you never hear the word 'tree'. This is sad. There is no conflict between trees and green infrastructure - they are not competing concepts. If you look at US literature you will see the terms 'green infrastructure' and 'urban forest' together. It's the urban forest that performs many of those vital benefits."

Dr Mark Johnston, research fellow in arboriculture and urban forestry, Myerscough College

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