Gardens help towns and cities beat countryside for tree cover
A tree lined street in Camden, North London
In urban areas there are not only high-rise buildings and offices, but also a lot of trees in the land.
Two London boroughs - Camden and Croydon - were among the top 20 places in England and Wales with the highest tree cover, according to a research project.
Now largely rural areas had some of the least - including part of the Lake District and the Yorkshire Dales.
Garden trees increase the numbers in cities while agriculture explains some of the low rural rankings.
Bluesky International, an air survey company that carried out the work with the help of mapping specialist Esri UK, says they have discovered around 400 million trees to date - but there are more to be found.
A map of the upper and lower digits for tree populations in England and Wales. The locations in the lower 20 are mostly along the east coast. The top 20 places are concentrated in the southeast around Surrey.
Most of the trees are grouped in the south
In Camden and Croydon, almost a third of the borough is tree-covered. Croydon has several wooded areas and Camden includes Hampstead Heath and Primrose Hill.
However, with the data mapped, you can see the distinct pattern of tree-lined streets and trees in gardens that help increase the percentage.
A graphic showing the tree cover in Camden, North London. Camden has 30% trees.
Surrey Heath has the largest proportion of trees.
But the area "has seen quite a change lately," says John Tucker of the Woodland Trust.
"If you look back 60, 80, 100 years, much of this area was open heathland and would have been cultivated and grazed."
But when animal husbandry became less economical, the area returned to the forests.
A graphic showing tree cover in the south of England. The highest point is Surrey Heath. Many of the other places in the top 20 surround this area.
The lower areas are mainly rural
The location with the lowest tree cover is South Holland - an area of mostly farmland on The Wash in Lincolnshire.
It follows the neighboring Boston.
This part of the east coast to East Yorkshire is in the lower 20 areas.
"These areas were swept by trees for agriculture and have never recovered," says Dr. Paul Brindley, an expert in trees and planning in the Department of Landscape Architecture at Sheffield University.
A treeless landscape in South Holland, Lincolnshire
But perhaps more surprisingly, areas in the lower 20 parts of the Yorkshire Dales include National Park and an area of the Lake District.
Richmondshire and Craven between them cover a large part of the Yorkshire Dales but have only 6% tree population.
Eden, an area that includes Ullswater and parts of the North Pennine Area of Outstanding National Beauty, has only 7%.
A graph shows tree cover in Eden 7%, Craven 6% and Richmondshire 6%. They are all up north near the Pennines
After the Ice Age it would have been 80-90% trees, according to Peter Leeson of the Woodland Trust.
But the demand for wood throughout history has resulted in trees being felled and used for everything from wood fuel to building mines.
Many areas have also been cleared to make way for fields for animals to graze in, and sheep can have a secondary effect in eating new trees before they can settle.
View over the Northern Pennines
Dr. Brindley says knowing where the trees are is important as it can help assess their impact.
"It's not just that there is one thing that they benefit from - there is a wide range of benefits."
Studies show that green spaces and trees in particular can help improve people's health and well-being and promote biodiversity. Bees especially like trees.
They also play an important role in cooling our urban areas which, due to the number of buildings, people and vehicles, often generate more heat than the surrounding rural areas.
Cllr Adam Harrison, Camden Council cabinet member, believes trees play an important role in the well-being of the people in his district.
"They can improve air and water quality, reduce noise pollution, support wildlife, and are fantastic for improving mental and physical health," he says.
The data shows which areas benefit from having trees in such gardens in Sheffield
The 20 areas with the most tree cover:
Neath Port Talbot
Reigate and Banstead
Epsom and Ewell
The 20 areas with the least tree cover:
City of London
East Riding of Yorkshire
Isle of Anglesey
North East Lincolnshire
How was it done
The trees were recognized by machine learning. Bluesky International combines its own high resolution aerial imagery, terrain map, and surface map.
With these three sources of data and a machine learning algorithm, they can find out which objects are trees and which are not. From this they create their National Tree Map, which was mapped by Esri UK.
They think they have a good estimate of the tree cover in different parts of the country, but they cannot accurately calculate the number of trees in England and Wales.
* Tree cover maps by Irene de la Torre
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