20 February 2020
Planting urban trees to boost climate action and citizen wellbeing is a growing trend, but what does it take to get it right? France's greenest city, Angers, shows how it should be done
'He who plants a tree, plants hope', says the famous first line of an otherwise obscure 19th century poem. This sense of hope was certainly in the air on the first day of a tree planting initiative in Angers. Storm clouds gave way to blue skies as enthusiastic city staff, residents and children prepared to play their part in the fight against climate change by planting the first of 150,000 new trees in and around the city.
Increasingly valued for their ability to absorb and store the carbon dioxide emissions that are driving global warming, trees have huge potential as a climate change solution. And it's not surprising that Angers is on the case. It has, after all, been ranked top of the list of green cities in France by the National Union of Landscape Enterprises after assessment across six categories from green heritage to biodiversity preservation.
“We have a long tradition with the green industry”
“We have a long tradition with the green industry, with many researchers working in this field and many people working in agriculture,” says Frederic Moreau, head of the city's project management and contracting department for parks, gardens and landscapes, who is responsible for the tree planting project. “Because of the city's green identity, citizens were very pleased to be involved and to come and help plant the trees.”
Rapid deforestation requires a response
At a time when these potential climate change saviours are fast disappearing around the world, actions like Angers' are becoming critical. According to the United Nations' Food and Agriculture Organisation, 7.3 million hectares of trees are lost every year.
One recent study led by ETH Zurich university claims that a worldwide tree planting programme could remove two thirds of all the emissions from human activities that remain in the atmosphere today.
“It is available now, it is the cheapest solution possible”
Professor Tom Crowther, who led the research, brings home the accessibility of tree planting, writing that it is, 'a climate change solution that doesn't require President Trump to immediately start believing in climate change or scientists to come up with technological solutions. It is available now, it is the cheapest solution possible and every one of us can get involved.'
Urban areas, responsible for around 75% of global CO2 emissions, have even more reasons than most to get involved.
Trees planted by busy roads actively clean the air of harmful pollutants emitted by traffic, capturing ultrafine particles on the surface of their leaves and taking them out of circulation. Trees can limit the effects of urban heat islands, reducing the need for air conditioning and making city life more comfortable. They can also control surface water, lessening flood damage.
Then there are the personal wellbeing benefits urban trees can bring to citizens. These have long been recognised by the premium prices of properties on tree-lined streets and close to leafy parks. And they are increasingly being taken into account in urban policies and plans with ambitions to lower stress levels and encourage active transport and exercise.
It's very easy to see why trees are trending in urban actions. By helping to mitigate some of the negative effects of urbanisation, they have a clear role to play in making cities more resilient.
But there are words of warning from experts that planting trees to unlock this multitude of advantages is not a matter of simply putting any type of tree wherever you can.
When projects turn into disasters
Peter Wohlleben, a German forester and author of 'The Hidden Life of Trees', stresses that such projects, 'can turn to disaster if they aren't executed the right way'. He says there's a need for 'trees which support each other as they grow, sharing nutrients with those that are sick and struggling and creating an ecosystem that mitigates the extremes of heat and cold.'
This caution to consider the type and mix of trees to be planted reflects the great variation in their capabilities. Some high-performing species can, for instance, remove up to 20 times more toxic particles from the air than others.
As a city with arboriculture in its DNA, Angers is perfectly placed to make these decisions. It is home not only to universities specialising in plants but also to the Végépolys international competitive cluster for the plant sector and to one of the few European agencies dealing with plants, the Community Plant Variety Office (CPVO).
“There are 25 years of research behind our initiative”
“There are 25 years of research behind our initiative focused on improving the kind of trees we have in our city,” says Moreau. “There are many technical issues involved in planting trees in different, and sometimes difficult, urban soils. So the trees we are planting are varied depending on their location and the space they require on the ground and also in the air.”
Enabling the ecological transition
Angers' level of local knowledge - plus the city's commitment - has enabled the development of an ambitious and innovative approach to tackling climate change that includes 25 actions which aim to integrate plants within urban areas.
“We are taking a step forward from sustainable development projects to those supporting ecological transition,” explains Moreau. “This involves the development of trees to capture carbon emissions, to lower temperatures and to enhance biodiversity.”
A key element of the city's approach is carefully selecting sites for the new trees to, for example, limit urban sprawl and create new landscapes for the future.
There will be city centre plantings as well as trees planted to create urban woods between the five municipalities of the wider urban area, as a way of establishing boundaries and continuity. Many of the trees will be planted on the Grésillé plateau where they will form the foundations of an urban forest which will encompass layers of vegetation to encourage the development of rich biodiversity.
Educational awareness activities for children in schools near the Grésillé plateau is ensuring the younger generation learns about the importance of trees and the future of their environment. The city also organised pre-planting consultations with citizens - and actively promoted their participation in planting days.
So much more than a solution!
More and more cities are starting to realise the truth of the Chinese proverb: 'The best time to plant a tree was 20 years ago. The next best time is now!' And there is a growing range of tree planting initiatives they can be inspired by and take action with.
The most recently launched of these, the UN Trees in Cities Challenge, calls on mayors to make tree-planting pledges and report on progress. Three European cities - Bonn, Helsingborg and Malaga - have already signed up.
An important point to make though, according to Angers' International Relations Officer Bruno Bourdon, is that planting trees is just one part of the solution.
“a major smart city initiative”
“Our tree planting initiative happens to be one of the most visible plans in our overall strategy dedicated to climate change. We are also responding to the climate challenge in digital as well as ecological ways and are about to launch a major smart city initiative that will deliver technological solutions to help manage climate change.”
The thing about trees, though, is that they are more than smart solutions. They are natural wonders that lift our spirits and give us joy. So, whatever other positive functions they might perform, the more there are in our lives, the better!
The trees challenge in cities
Tree planting gets underway
One tree can store up to 150kg of CO2 per year
Volunteers listen to the planting plans
Read all stories here.