Trees in Cities Challenge

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

Join the campaign today! Make a tree planting pledge!

What is the Trees in Cities Challenge?

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

Climate action now. Start with cities. Make a tree-planting pledge!

8.56 Million Trees Pledged!

as of 1 January 2020

each tree icon represents 1000 trees

How It Works



A mayor makes a formal written pledge to UNECE, committing to plant a pre-determined number of trees by 2020.


Keep track of the progress

The city keeps UNECE informed of its tree-planting progress.



UNECE will reflect the city’s progress on this website. This will include a “tree-meter” showing the number of trees planted and indicating measurable economic, social and environmental benefits for the city.


Report and share experience

Upon successful completion of the challenge, UNECE will provide the city with a progress report and invite the mayor to share their experience at a relevant international UNECE forum. The campaign was launched at the UN Climate Action Summit in September 2019 and will initially run until the end of 2020.

How do Communities Benefit?

Mitigate climate change and build urban resilience

By absorbing C02 and providing a natural way of air-cooling, trees help mitigate climate change and save energy by reducing the need for air conditioning.

Cleaner air and the environment

Trees exchange gases with the atmosphere and capture particulates and urban pollutants

Healthier cities

Presence of trees in urban areas is known to have a positive effect on human health by reducing levels of stress, preventing obesity, and accelerating the recovery from illnesses.

Improved public spaces for greater biodiversity

Trees provide shelter, food and home to animals and plants, contributing to urban biodiversity.

Stronger communities

Increased presence of urban green areas has been shown to have a positive impact on social cohesion and help to form stronger communities.

Increased property values

Healthy trees can increase surrounding property values by 2-10%.

Get Involved!


Take the challenge! Send a message letting us know how you'd like to contribute and we'll explain how you can make a pledge


Spread the word! Encourage your local government and city leadership to take tangible climate action by making a pledge through the Trees in Cities challenge

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The Sustainable Development Goals

UNECE supports countries in the implementation of the 2030 Agenda and the Sustainable Development Goals (SDGs). The following SDGs are particularly relevant to Trees in Cities. Visit UNECE and the SDGs homepage to learn more.

SDG 3: Good Health and Well-Being

SDG11: Sustainable Cities and Communities

SDG13: Climate Action

SDG15: Life on Land

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