Urban green spaces such as gardens, parks and woodlands provide many benefits to people and vital habitats for wildlife. These include helping to mitigate climate change, reducing the likelihood of flooding and improving air quality.
During the summers of 2017 and 2018, over 1400 trees were surveyed by volunteer staff and students on the University of Leeds campus. By combining measurements of the trees with software called i-Tree Eco, the team were able to estimate the benefits being provided by the trees.
Over their lifetimes, the campus trees are estimated to have taken in, and are now storing, over 540 tonnes of carbon (which is almost 2000 tonnes of CO2), the equivalent to the annual carbon footprint for around 180 people living in the UK. It was estimated that each year the campus trees are removing a further 18 tonnes of carbon (66 tonnes of CO2) from the air – see pages 13-16 of the report.
Trees are able to capture particulate pollution from the air because it sticks to their leaves, needles or bark. Gases in the air, such as nitrogen dioxide and ozone, are taken in through holes on the leaf surface. Due to their big leafy canopies, the trees on campus remove an estimated 350 kg of air pollution per year – for nitrogen oxides in particular, this is equivalent to around 1 million cars driving past the University campus – see pages 17-19 of the report for more details.
The results demonstrate that the biggest trees on campus are having huge benefits: the largest 100 trees, which make up only 7% of the total number, provide over one third of the total environmental benefits in terms of carbon sequestration, pollution removal and flood risk reduction.