Co-Carbon Tree Measurement

This citizen-science project aims to obtain the most realistic estimation possible of CO2 captured by urban trees, in order to understand their capture capacity across the entire urban environment.

Promoted by the Viladecans City Council and the Technical University of Catalonia -Barcelona Tech (UPC), the project encourages primary and secondary students to participate actively in measuring trees. This helps to reinforce social commitment and values of sustainability, joint responsibility, and the common good.

The resulting data is essential for measuring progress towards achieving the EU's climate neutrality goals by 2050. It also provides valuable information for the development of urban strategies aimed at combating climate change and reducing CO2 emissions. 

This project supports Viladecans 2030 City Strategy and its mission to become an emission-neutral city by 2030. 

Activities involve measuring the trunk diameter and height of a significant sample of urban trees in order to estimate their CO2 capture capacity from year to year. The data obtained can then be extrapolated to the entire city

The project is carried out in collaboration with the educational community, members of the general public, and municipal park and garden workers. A high point is 14 March, or Pi Day, which Viladecans has defined as the day to measure levels of CO2 fixed by trees across the city.

The first edition, on 14 March 2024, involved 662 students from primary and secondary schools in the city.  By getting citizens involved, this activity promotes awareness of carbon neutrality – and the importance of urban trees.

The methodology to obtain data on the CO2 encapsulated in a tree involves measuring the perimeter of the trunk at 1.37m height and the total height of the tree. By using scientific equations the total amount of carbon captured by a tree can then be estimated.

The campaign will be repeated yearly on the same trees to obtain annual data. The data will also shed light on trees’ reactions to different weather conditions. Findings will be shared with municipal staff and teachers, to inform new educational projects.  

Co-Carbon Tree Measurement offers a holistic approach to urban development that addresses environmental, social and economic dimensions simultaneously:

• Environmental: The objective of the practice is to obtain the data necessary to estimate the CO2 capture capacity of urban trees. Obtaining the most realistic estimate possible of the CO2 capture capacity of trees allows the city to assess progress towards the climate neutrality planned by the EU – a commitment reinforced by Viladecans City Council Mission. This also enables the planning of urban strategies to fight against climate change and reduce CO2 emissions.
• Social: This is a citizen-science and open-science project that places great importance on public involvement and awareness. Without citizen participation, it would be impossible to achieve a sufficiently significant number of tree measurements to ensure the accuracy of the scientific results. The project reinforces the values of sustainability and the fight against the climate emergency among citizens.
• Economic: Urban trees are not only decorative elements but also key players in capturing and cleaning CO2 from the atmosphere. This service is invaluable, as the alternative – CO2 capture machines – is less energy efficient than trees.  

In short, the energy and economic benefits of urban trees are enormous in terms of city cooling, carbon sequestration, wellbeing and more.

The project employs a participatory model, engaging various stakeholders from Viladecans and the Technical University of Catalonia as key contributors in obtaining essential data to estimate the CO2 capture capacity of urban trees. This data informs progress towards achieving climate neutrality objectives.

In the first edition, on 14 March 2024, 662 primary and secondary school students and teachers collaborated with municipal parks and gardens workers to measure the diameter and height of approximately 1 300 trees. Over a two-month period, a student trainee was hired by the City Council to support data compilation, CO2 calculation, school coordination and other tasks.

The Technical University of Catalonia - BarcelonaTech and Viladecans City Council jointly promoted this project. Dr Jordi Mazón (ORCID), Deputy Mayor and Councillor for the Promotion of Science and Scientific Dissemination at Viladecans City Council, also spearheads the city's Climate Mission and coordinates the project between the council and the university. The educational community of Viladecans, including primary and secondary schools and their students, actively participated alongside parks and gardens workers from the city council. 

Main results from the first edition of the Co-Carbon Tree Measurement project in Viladecans include:

• Participation of 662 students ranging from 6th grade to 2nd year from primary and secondary schools in the pilot project on 14 March 2024.
• Measurement of nearly 1 300 urban trees, with potential extrapolation to the entire city's tree population. 

The practice encourages citizen participation and social commitment to address the climate emergency we are experiencing, particularly in achieving climate neutrality goals. Citizens play a crucial and active role in collecting the data necessary for conclusive scientific results. This is also an educational project at the city level. 

One of the main added values of this practice is its ability to quantify the amount of CO2 captured by urban trees. Comparing data each year will help assess progress in combating climate change and identify areas for improvement. The data will also enhance understanding of tree responses and their potential for CO2 sequestration, while providing insights into annual weather conditions. This information will be accessible to municipal technicians and teachers from participating schools and high schools, enabling them to develop related educational projects. 

The practice contributes significantly to raising public awareness about urban trees as critical elements that provide numerous benefits, including city cooling, CO2 capture, and overall wellbeing. 

Co-Carbon Tree Measurement is relevant for any European city that is working towards carbon neutrality and recognises the importance of citizen involvement, awareness, and active participation to achieve this ambitious goal. It promotes better air quality, climate adaptation, and sustainable use of land through nature-based solutions – all EU Urban Agenda priority themes for cities.

The practice aligns with the European Green Deal and the European Climate Law, which aim to make Europe a climate-neutral continent by 2050.  It also supports the objective of "a greener, low-carbon transition towards a net zero carbon economy and resilient Europe" outlined in the EU Cohesion Policy 2021-2027. 

As for the Sustainable Development Goals, the activity is particularly aligned with: 3 Good Health and Wellbeing, 4 Quality Education, 11 Sustainable Cities and Communities, 13 Climate Action, 15  Life on Land, and 17 Partnerships for the Goals. 

The practice is flexible and can be adapted to any urban context, taking into account local characteristics such as type of trees, climatic conditions and citizen groups. It is not linked to a specific national governance or legislative context. 

For cities adopting this practice, the crucial requirement is the willingness of a significant number of citizens to measure the trees. The educational community is a very interesting target here. Ideally, to help coordinate the pilot, cities would work with scientific personnel specialised in citizen-science and open-science. However, if necessary, the citizen campaign could also be carried out without this support: collected measurements could be analysed by a third party or municipal staff.  

This model is easy to replicate, relatively inexpensive, and simple to run. People of all ages can take part without requiring any training. The initiative can have a great impact: both as a tool for measurement, and for raising awareness, engaging citizens, and promoting a change of mindset.