According to a study published in the journal Science we could remove around 25 percent of existing carbon dioxide from the atmosphere by planting 500 billion trees. The researchers emphasised that tree planting is not a replacement for reducing greenhouse gas emissions or phasing out the use of fossil fuels but argue that the study shows that forest restoration is the cheapest and best solution to the climate crisis facing us today.
It’s estimated that the forest restoration envisaged would take between 50 and 100 years to have its full effect and 500 billion trees is not an insignificant number, but several countries around the world have already started to implement extensive tree planting strategies. Ethiopia planted 352 million trees in one day earlier this year and the country had planted 3 billion trees by the end of July. The planting in Ethiopia is part of a national “green legacy” initiative to plant 4 billion trees in 2019. The strategy is for every citizen to plant at least 40 seedlings and the government closed public offices for civil servants to take part. Similar initiatives have been rolled out in India which in June planted 66 million trees in 12 hours.
The Irish government has also announced plans to plant 440 million trees by 2040 and plans to plant more than half a million native trees on former boglands over the next three years. Many have criticised the long timeframe and the Irish government will need to persuade farmers to plant more trees on their land if their initiative is to succeed, something which the government has acknowledged will not be popular.
Ireland also urgently needs a plan for its urban centres. Cities account for 60% of the world’s population but 80% of its emissions and while a single tree can cut air particles by up to 24%, Irish cities compare poorly with its European cousins when it comes to tree canopies. According to a study done by the Geographical Society of Ireland, Belfast has a tree canopy of just 3.5%, Waterford 6%, Dublin 7%, Cork 9%, Limerick 11% and Derry 16%. This contrasts with Stockholm which has a tree canopy of 57%, Helsinki 49%, Warsaw 36% and Copenhagen 28%.
Social and health benefits
Trees and green infrastructure (which includes natural areas, urban woodland and parks; green streets, squares and public realm; sustainable drainage systems and healthy waterways, cycleways and pedestrian routes; and smaller scale green roofs, walls and facades) make our cities more liveable. They achieve this by reducing carbon dioxide emissions that pollute our air, by removing air pollutants that can trigger respiratory illnesses and by boosting wellbeing, safety and prosperity.
Researchers from the University of Exeter, using data from 5,000 households over 17 years, found that people reported lower levels of mental distress and higher degrees of life satisfaction when they were living in greener areas.
A recent study carried out by the University of Aarhus in Denmark found that childhood exposure to green spaces, including urban nature, reduces the risk for developing an array of psychiatric disorders during adolescence and adulthood. Other studies have documented stress reduction, reduced mortality, and improved cognitive development in children.
Japanese studies have shown that being in nature for a couple of hours—so-called forest bathing—enhanced our bodies’ ability to combat cancer.
Numerous other studies have shown that green spaces contribute to better mental health, by alleviating stress, promoting social ties in the community, decreasing fears of violent crime and serving as a sign of investment in the neighbourhood, leading to people feeling less stigmatised or abandoned by society. According to a new study conducted in Philadelphia, turning derelict vacant lots into pocket parks resulted in reduced feelings of depression and worthlessness among people living nearby.
Green space also inspires people to walk or cycle more frequently. Research has shown that the more trees along a footpath, the more likely residents are to walk 60 minutes a week. City trees can also enhance traffic calming measures, making our cities safer and nicer places to be. Tall trees give the perception that a street is narrower than it really is, which results in drivers slowing down. Closely spaced trees give a similar effect by creating the illusion of speed. On the other hand, wide, treeless streets give the perception of being free of hazard and encourage faster and more dangerous driving.
Slideshow below: Irish cities are currently dominated by cars and grey infrastructure, but there is an alternative.
Green infrastructure can also increase social cohesion and reduce crime. A study of 98 vegetated spaces in Chicago showed that they cut crime rates in half by inspiring pride for the area and mitigating psychological precursors like stress and anxiety. In 2001, researchers at the University of Illinois found that people living in a group of 28 tower blocks who had contact with nature had significantly better relations with and stronger ties to their neighbours — meaning that those residents who lived with trees nearby socialised with their neighbours more, felt safer and suffered 52% fewer crimes. They also felt emotionally and physically healthier than those in treeless blocks.
As the Irish economy grows Irish towns and cities will increasingly find themselves competing with towns and cities across Europe for investment. The presence of good parks, squares, gardens and other public spaces will become a vital business and marketing tool as companies are attracted to locations that offer well-designed, well-managed public places and these in turn attract customers, employees and services. In town centres, a pleasant and well-maintained environment increases the number of people visiting retail areas, providing a much-needed boost to city centre retail currently struggling to compete with the growth of out-of-town shopping centres and on-line shopping.
Trees also protect people and buildings from wind and act as natural insulators and in a similar way installing green walls or green spaces on the roofs of buildings can provide insulation, resulting in significant energy savings for residents and businesses. The installation of a green wall at Edgware Road underground station in London has been shown to supply warming benefits to the building. The wall also acts as a physical filter for pollution when the fine particles (known as PM10s) are trapped on the surface of leaves. When carried into the lungs PM10s make chronic diseases such as asthma and bronchitis worse. Therefore, interventions such as these are effective in creating healthier urban conditions.
Research on the health and economic benefits provided by the urban forests of ten U.S. cities has shown that trees save lives, reduce hospital visits and reduce the number of days taken off work (this applies to both physical and mental health as people who can see green space from their office buildings take almost a quarter less time off work than those who cannot).
Green space has also been shown to increase land values. Between 1988 and 1996, the city of Chattanooga, Tennessee, managed to increase property value by 127.5% and tax revenue by 99% following a $500m investment in greenways and tree planting.
Meanwhile New York has shown through a cost benefit analysis of public amenities that trees provide an excellent return on investment. The analysis showed that the city’s more than 600,000 trees provided an annual benefit of $122m for the city and its businesses – more than five times the cost of planting and maintaining them.
Habitat destruction is one of the major threats facing biodiversity today. As cities expand, it’s important to remember that trees and other green infrastructure can provide shelter and food for birds and other wildlife. Biodiversity is vital to a healthy urban environment, but it can also provide a boost for the economies and resources of a city, providing tourist attractions and sources of revenue, as well as making the city feel more alive and fulfilling for citizens.
As the climate crisis worsens urban areas will have to cope with increased rainfall. Directing more rain into surface water drainage systems will often overload them, causing floods. The sustainable solution is to use natural systems to slow down, hold and buffer storm and rainwater and allow it to infiltrate naturally back into water courses. This means a better balance of floodable vegetation and more permeable surfaces in urban areas. Street trees, for example, can absorb up to 60% of rainfall, something that could be particularly helpful in Irish cities.
What is the rest of the world doing about it?
All around the world cities are making efforts to increase tree canopies and add green infrastructure to streets and neighbourhoods. Seoul recently planted more than 2,000 groves and gardens across the city. Milan plans to plant 3 million trees by 2030 to reduce air pollution. Melbourne aims to almost double its tree canopy to 40% by 2040. While in New York, city planners planted one million trees after research found that trees made city dwellers happier and smarter.
In fact, in New York property owners can request to have a tree planted on their street for free. Each location requested is surveyed by a city representative to make sure there are no conflicts with the surrounding infrastructure and that the site is a suitable one for a tree to grow and thrive. If the site is found to be appropriate, it’s added to a list of sites to be planted during the next available planting season.
In Paris, some of the city’s most treasured landmarks are set to host the city’s new “urban forests.” Under a plan announced in June this year, thickets of trees will soon appear in what today are pockets of concrete next to landmark locations, including city hall and the main opera house, the Gare de Lyon train station and along the Seine quayside. The new plantings are part of a plan to create “islands of freshness” throughout the city. By 2030, Paris city hall wants to have 50% of the city covered by fully porous, planted areas, a category that can include anything from new parkland to green roofs, meaning that when it comes to planting, pretty much any urban space will be up for grabs.
Vancouver launched its Urban Forest Strategy in 2010, which aimed to plant 150,000 trees by 2020 (at the time of writing the strategy has resulted in 125,854 trees being planted). To achieve its target, Vancouver introduced and changed a number of bylaws and policies governing trees across different departments and introduced initiatives to encourage tree planting such as twice annual tree sales where residents can buy trees and learn how to plant and maintain trees on their properties.
Basel also introduced several initiatives aimed at increasing the provision of green roofs in the city. Initially driven by energy-saving programmes, green roofs were funded by the city for a two-year period, during which time convincing evidence emerged that green roofs can protect endangered invertebrate species. Basel now has the highest area of green roofs per capita in the world.
In Milan, more than 900 cherry, olive and oak trees and other plants have been planted up the exterior of the two 110m and 76m Bosco Verticale buildings. Different tree varieties were tested in wind tunnels to discover how growing them at height would affect the buildings’ structures. Once the trees were planted, some 1,200 ladybirds were released to help improve the site’s ecosystem. Today, as residents go about their daily lives inside, the flourishing trees help improve air quality, provide shade and reduce noise pollution.
In London, The Living Wall at the Rubens Hotel is designed to provide waves of blossoming plants throughout the year, providing much needed habitat to wildlife, reducing street noise and helping keep the hotel cooler in summer and warmer in winter.
Green cities are not just beautiful, they mitigate the impacts of climate change and deliver a wide range of environmental, social and economic benefits. They safeguard the health and wellbeing of the people who live and work there and attract inward investment and tourism.
As climate change begins to impact everyday life it’s now more important than ever that central government and local authorities in Ireland start developing and implementing urban forest and green infrastructure strategies that can make our towns and cities safer, healthier and more attractive locations for people to work, live and visit.
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