Cities in Need of Trees: Data Highlights the Global Metropolises Requirements

With human activities releasing more carbon dioxide (CO2) into the atmosphere than natural processes can remove, new analysis has shed light on the number of extra trees that cities around the world would need to neutralise their carbon footprint. 

Picterra, a leading cloud-native geospatial AI platform, has used its technology to visualise tree coverage in over 25 of the world’s most iconic cities, before analysing external data to estimate their CO2 emissions and the number of trees and the amount of space that it estimates would be required to offset the equivalent carbon.

Omitting an estimated 320,241,244 tonnes of CO2 every year, Tokyo would have to plant over 2 billion (2,001,507,775) trees, which would require a total of 3,091,141 acres of land, accounting for tree planting density guidelines.

On the opposite end of the scale, Rotterdam demanded the fewest trees to neutralise its approximate 7,930,313 tonnes of emissions, with 49,564,459 trees and 76,548 acres required.

Known for being home to one of the most visited city parks worldwide, New York came fifth in the rankings, needing the equivalent of 1,304 Central Parks to counteract its emissions. Meanwhile, London, landing in seventeenth place, would have to make room for another 1,330 Hyde Parks. 

Renowned for its skyscrapers and modern architecture, Dubai came in tenth place overall, yet fared the worst for the number of trees required per person to offset its CO2 levels, at an estimated 130.5 trees for each resident. 

Using its geospatial AI software, Picterra looked at the current state of forestry in each city, giving a realistic picture of how each city fares. 

Picterra enables its users to detect any objects, in this case, trees, faster than ever before by managing the entire geospatial machine learning pipeline with its cloud-native platform.

Commenting on the findings, Frank de Morsier, chief operating officer at Picterra, said:

“We aim to make a positive and meaningful impact on our planet and environment. That’s why we have used our geospatial AI tool to visualise the number of trees there currently are in each city’s centre, giving a realistic view of the state of forestation in the cityscapes we know so well, with stark differences evident.

‘While the analysis of existing data alongside these visualisations is simply an estimate of how many trees and acres are needed to neutralise carbon emissions, it serves to illuminate how deep of an issue current CO2 levels are.

“Planting trees remains one of the most effective ways to temper carbon emissions - though, as this analysis shows, this would need to be on an extreme scale to make progress towards neutrality.”

To view the full analysis, including the 26 cities ranked and Picterra visualisations go to https://picterra.ch/blog/mapping-the-urban-jungle-which-global-cities-need-trees-the-most/

Methodology

Using the 2022 total CO2 emissions for the world's largest countries, Picterra calculated the estimated total CO2 emissions produced per person, using population figures for the same year. With this, Picterra was then able to calculate the estimated CO2 emissions for 26 major cities around the globe, by accounting for each city’s population count.

According to recent data sources, 6 trees are required to offset 1 tonne of CO2, meaning 1 tree can be estimated to be equivalent to 0.16 tonnes of CO2, which the team used to work out the number of trees that would be required to neutralise each city’s yearly CO2 emissions, alongside how many trees would be required per person. 

The team then calculated the number of acres that would be required per location by using tree planting density guidelines by the Woodland Trust which shows a tree can be planted every 2.5 metres per hectare. We used this data to estimate how many iconic locations, like Central Park, Hyde Park, etc, of trees would be required to offset emissions by dividing the total acreage of forestation required by the acreage of each location.  

Picterra then used their geospatial AI detection platform to map the number of trees currently present in the 26 global cities they had data for, to provide a supporting visualisation of which cities are most in need of trees.

Limitations of our analysis

While our exploration into urban tree planting and carbon offsetting aims to be informative, it's crucial to acknowledge the inherent limitations of our approach. The calculation of CO2 emissions per person relies on generalised figures for major cities, and the use of a universal conversion factor of six trees per tonne simplifies the intricate processes involved. 

The estimation of required acres is based on standard tree planting density guidelines, overlooking the complexities of varying environmental conditions and urban constraints. Our comparison to well-known locations like Central Park serves as a visual aid but clearly falls short of capturing the intricacies of land use, soil conditions, and ecosystem dynamics. 

While interesting, we wanted to be clear that this study is more of a conceptual exploration than a precise scientific assessment, aimed at fostering awareness and dialogue on the potential impact of urban tree planting.