How Cotoneaster franchetii can absorb up to 20% more CO2 pollution compared to other shrubs in traffic hotspots.

It is no secret that CO₂ emissions are not only detrimental to human health, but they are also responsible for climate change & global warming.

The global transportation sector is a major CO₂ polluter & in 2020 produced approximately 7.3 billion metric tons of carbon dioxide (CO2) emissions. Passenger cars were the biggest source of emissions that year, accounting for 41 percent of global transportation emissions. (1)

Despite the decline in movement during the first two years of the Covid19 pandemic, cars remain the largest CO₂ emitters on the roads, with the average internal combustion engine passenger car emitting about 4.6 metric tons of carbon dioxide per year (numbers can vary based on a vehicle’s fuel, fuel economy, & the number of miles driven per year) (2)

In the UK in 2019 (pre Covid19 lockdowns) domestic transport was responsible for emitting 122 MtCO2e & 35% of Nitrogen Oxides (NOX) emissions (12% of NOX emissions came from cars alone) & 13% of Particulate Matter (PM2.5) (3)

Despite the introduction of ULEZ (Ultra Low Emission Zones) in major cities around the world, some international cities already being car free & the ramp up in electrification; emissions in built up urban areas where cars are still permitted, continue to produce CO₂, NOx & particulate matter at toxic levels, harmful to human health, biodiversity & contributory to global warming.

Even with the introduction of a myriad of technologies to reduce & recapture carbon emissions; one area of science which is still often overlooked but remarkably efficient at tackling emissions is Botany.

However, even though the worlds Governments have promised to plant billions of trees to offset the damage caused by human evolution; the science does not support the claims that this would ultimately assist with CO₂ offsetting.

“Plants absorb CO₂ from the atmosphere, transforming it into leaves, wood & roots. This everyday miracle has spurred hopes that plants – particularly fast growing tropical trees – can act as a natural brake on climate change, capturing much of the CO₂ emitted by fossil fuel burning.” (4)

The fact is that there aren’t enough trees to offset society’s carbon emissions – & there never will be. I recently conducted a review of the available scientific literature to assess how much carbon forests could feasibly absorb. If we absolutely maximised the amount of vegetation all land on Earth could hold, we’d sequester enough carbon to offset about ten years of greenhouse gas emissions at current rates. After that, there could be no further increase in carbon capture.” (4) Bonnie Waring, Senior Lecturer, Grantham Institute – Climate Change and Environment, Imperial College London

However, in a world where natural resources are being ravaged by the human population, access to habitable areas suitable for human development are at risk & megacities are set to become the norm.

In 2018, 1.7 billion people (23% of the world’s population) lived in a city with at least 1 million inhabitants. In 2030, a projected 28% of people worldwide will be concentrated in cities with at least 1 million inhabitants. Globally, the number of megacities is projected to rise from 33 in 2018 to 43 in 2030. (5)

Despite the bleak facts from Bonnie Waring of ICL, humans need to try everything at their disposal to try & offset CO₂ emissions & in doing so are turning to natural approaches wherever possible, not only for health, but also to help balance biodiversity.

A Science Paper by RHS (Royal Horticultural Society) published in 2020 identified a super plant which could transform carbon sequestering in urban areas.

Scientists believe that that the bushy, hairy-leafed Cotoneaster franchetii is the latest ‘super plant’ to help boost the environment & improve human health because of its special ability to fight pollution by trapping harmful airborne particles. (6)

The RHS science paper released in 2020 looks at the effectiveness of hedges as air pollution barriers.  The Cotoneaster franchetii (Franchet’s cotoneaster) is at least 20% more effective at soaking up pollution compared to other shrubs in traffic hotspots. (6)

Dr Tijana Blanusa, research lead for the paper & RHS Principal Horticultural Scientist, said: “On major city roads with heavy traffic we’ve found that the species with more complex denser canopies, rough & hairy-leaves such as cotoneaster were the most effective. (6)

“We know that in just seven days a one metre length of well-managed dense hedge will mop up the same amount of pollution that a car emits over a 500 mile drive.” (6)

With the push to remove as many ICE cars from our inner cities continuing, the introduction of Cotoneaster franchetii into roadside hedging, alongside other dense canopied species of plants & shrubs; could, as Professor Alistair Griffiths, RHS Director of Science & Collections, says:

“RHS science has shown that underlying traits of certain plant species & cultivars, such as leaf shape & root features, help alleviate numerous environmental issues. (6)

“We are continually identifying new ‘super plants’ with unique qualities which when combined with other vegetation provide enhanced benefits while providing much needed habitats for wildlife.” (6)

The battle to reduce transportation emissions is ongoing & scientist across a broad spectrum of specialisms are developing ways to combat the impact of human made emissions, to halt climate change, protect our biodiversity & improve human health.

Written & cited by Katy-Jane Mason for & on behalf of Dolphin N2.

1. https://www.statista.com/statistics/1185535/transport-carbon-dioxide-emissions-breakdown/
2. https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-typical-passenger-vehicle
3. https://www.gov.uk/government/statistics/transport-and-environment-statistics-autumn-2021/transport-and-environment-statistics-autumn-2021
4. https://theconversation.com/there-arent-enough-trees-in-the-world-to-offset-societys-carbon-emissions-and-there-never-will-be-158181
5. https://www.gov.uk/government/publications/trend-deck-2021-urbanisation/trend-deck-2021-urbanisation#:~:text=In%202018%2C%201.7%20billion%20people,at%20least%201%20million%20inhabitants.
6. https://www.rhs.org.uk/science/articles/super-cotoneaster