The best way to keep cool in heatwaves? Plant 170,000 trees, according to Paris

Paris describes itself as one of Europe’s “most wooded capitals”. But recent heatwaves have exposed how a lack of trees and vegetation can make some parts of the French city much hotter than others.

Environmental campaigners in Paris this month recorded a temperature of 56°C bouncing from the surface of one of the treeless streets around the Palais Garnier opera house. This was double the 28°C found in the shade of the nearby tree-lined Boulevard des Italiens, Reuters reports.

Such temperature rises are known as the urban heat island effect – when a lack of tree cover and greenery makes urban areas much hotter than more rural areas.

Trees have a cooling effect in built-up areas, providing shade and moisture and deflecting the sun’s rays. This helps to offset the effect of urban structures and materials like roads, buildings, tarmac and concrete, which store and then release heat back into the environment.

Trees also cool the environment by absorbing carbon dioxide, which warms the atmosphere and contributes to global warming. Over the course of its life, a single tree can store up to 22 tonnes of CO2, experts say.

Paris says trees are the city’s “best allies” in fighting climate change – and plans to plant 170,000 new trees by 2026.

As well as absorbing CO2 and cooling the air, trees help improve air quality and rainwater management, the city says. They are also vital for biodiversity – helping to support a variety of plants and wildlife in the urban environment. And by providing a natural barrier against visual and noise pollution, trees contribute to “improving the health of residents and reducing stress”, Paris says.

Other cities working on urban greening initiatives include Singapore, Seoul in South Korea and Curitiba in Brazil, according to BBC Earth.

Singapore has pledged to become greener and more sustainable by the end of this decade, and has set out a series of actions in its Singapore Green Plan 2030. This includes planting a million more trees and developing more than 130 hectares of new parks – about the same area as 130 sports fields.

Seoul, a “megacity” of almost 26 million residents, is creating “wind path forests” along rivers and roads to funnel cool air from its mountains into the city centre. It hopes to reduce midsummer temperatures in the capital’s downtown area by 3-7°C.

Curitiba is often described as one of Brazil’s greenest cities, with more than 1,000 green spaces, including 14 forests and 16 parks. The city has been developing sustainability initiatives since the 1970s, BBC Earth says, and between 2013 and 2016 alone planted almost 140,000 trees in public areas.

In the United Kingdom, London is also working on an urban greening initiative to increase green cover in the built environment. Plans include ensuring that more than half of London will be green by 2050 and increasing tree canopy cover in the city by a tenth.

Forests are critical to the health of the planet, but their degradation and loss is destabilizing natural systems on a “scale unseen in human history”, the World Economic Forum says.

To help restore biodiversity and fight climate change, the Forum launched the 1t.org initiative to grow, restore and conserve 1 trillion trees around the world at Davos 2020.

Conserving and restoring forests is also important for jobs, livelihoods and human health – including new drug discoveries to treat current and future diseases.

In the United States, 1t.org has mobilized pledges to conserve, restore and grow more than 955 million trees by 2030. In Africa, 1t.org supports the Great Green Wall Initiative, which aims to regreen 100 million hectares of degraded land.

Other key regions for 1t.org include the Amazon rainforest, which is home to 10% of the world’s species and 30 million people. Work there is focused on creating a sustainable bioeconomy – for example, helping farmers grow food products that restore and conserve ecosystems, as well as creating income and jobs.