Trees: the good, the bad & the ugly


8 August 2018 13:41
Dr Kirsti Ashworth

Dr Kirsti Ashworth is interested in the air that we breathe, the woodlands we enjoy and the food that we grow, and how vegetation, in particular trees, can affect it for both good and bad.

“Trees absorb carbon dioxide and other pollutants, and so are generally viewed as an ally in the fight to reduce climate change and air pollution, and as beneficial to human health and well-being,” says Kirsti.

“Less well known and understood is that vegetation, especially trees, also emit to the atmosphere a large quantity of hydrocarbons, equivalent to the combined weight of every man, woman and child on the planet each year”.

“These compounds react rapidly and in regions with high levels of nitrogen oxides, released during the combustion process in transportation and industry, their oxidation leads to the formation of ozone and aerosol particles (particulates). These not only affect the climate but are also key air pollutants with strict limits set by the World Health Organisation.”

Kirsti is a Dorothy Hodgkin Research Fellow: this prestigious Royal Society scheme funds ‘outstanding scientists at an early stage of their research career.’ The £307,000 five year fellowship enables Kirsti to focus on her research, only taking on teaching responsibilities gradually. 

She is now building a research team around her, and has recently won two more competitive grants, available only to Royal Society fellows, to fund PhD projects researching vegetation-atmosphere interactions near major cities.

“This will enable us as a society to better understand how air pollution interacts with vegetation in and around urban areas.,” Kirsti says.

“This offers us a potential way to improve air quality, not only improving human health in both urban and rural regions but safeguarding food supply in the future.

One of Kirsti’s new PhD students, funded by a £90,000 Research Fellows Enhancement Award, will focus on crop production, initially carrying out a meta-analysis of how nitrogen dioxide and particulates affect yield. This analysis will then be integrated into a global crop model to assess how crop production around three mega cities - Beijing, Delhi and Lagos - would be affected by different scenarios of future climate and pollution. The student will be co-supervised by Kirsti’s Lancaster Environment Centre colleagues Professors Oliver Wild and Steve Long FRS.

A second PhD project, funded by a £150,000 Research Grants for Research Fellows award, aims to help establish how climate change might affect the exchange of reactive gases between forests and the atmosphere.

“At the moment we rely on forests as carbon sinks to remove atmospheric carbon dioxide, this project is looking at how future changes might affect the capacity of forests to take in as well as emit air pollutants,” said Kirsti.

The research student, co-supervised by Professors Ian Dodd at Lancaster Environment Centre and Rob McKenzie of the Birmingham Institute of Forest Research (BIFOR), will measure gases emitted from the soil and trees in two forests, one near Birmingham and one just outside Rome.

Both forests are dominated by oak and experience similar levels of air pollution. In the Birmingham Forest, BIFOR has set up areas where carbon dioxide levels can be increased to mimic the conditions that might exist in 50 years’ time. In Rome, the hotter climate will provide a proxy for projections of future drought. 

She is also currently hosting two visiting researchers with interests in the links between vegetation, reactive gases and urban air quality. Kerneels Jaars, a Newton International Fellow, is making leaf level measurements of the reactive gases emitted by vegetation in Delhi. These will be incorporated into models to study how these emissions contribute to air pollution in a megacity.

Dr Gabriel Habiyaremye won a Commonwealth Rutherford Fellowship to research the interactions between indoor and outdoor air quality in urban and rural areas of Rwanda. He is currently undertaking field work to measure air pollution inside and outside dwellings in Kigali.

Kirsti praises the support offered by the Royal Society Dorothy Hodgkin Fellowship Scheme.

“It’s made a huge difference to me. The opportunity to focus on research and on building a research group while gradually working up towards taking on a full teaching load is fantastic.” 

Find out more about the Dorothy Hodgkin fellowship here.

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