The Trees in Cities Challenge

A global campaign launched by UNECE Executive Secretary Olga Algayerova to promote climate action in cities


The UN Secretary-General António Guterres has said that climate change is “the battle of my life.” He is not the only one.

Climate change is a battle we are all fighting. More than ever, cities are where the battle takes place.

Rising sea levels, extreme temperatures, floods, droughts and storms are threatening the very basis of urban life; ravaging people’s homes, destroying infrastructure and jeopardizing vital access to basic services such as clean water and sewage.

But cities are not just at the receiving end of devastating consequences of climate change; they very much contribute to it. Some estimates suggest that cities are responsible for 75 per cent of global C02 emissions, with transport and buildings counting among the largest contributors.

This is why it is important to localize climate action and ensure that mayors and local authorities are taking adequate measures to tackle its most damning effects – not least because mayors are often best placed to take decisive action with immediate results.

One simple yet powerful way of building more sustainable and resilient cities is planting trees.

Strategically planted trees can cool the air by between 2 °C and 8 °C, thereby reducing air conditioning needs by 30 per cent. A single tree can absorb up to 150 kg of C02 per year and help mitigate climate change.

Trees also help control land erosion, reduce landslides and control surface water, and help mitigate flood damage.

Planting more trees in cities is a simple, inexpensive and yet deeply impactful way in which mayors can lead the efforts in tackling climate change.

The Trees in Cities Challenge is a global campaign launched by UNECE Executive Secretary Ms. Olga Algayerova to localize action taken to combat climate change and foster urban sustainability and resilience. It is a voluntary initiative aimed at mayors and corresponding urban authorities in cities across the world