A breath of fresh air

17 April 2012

PhD Candidate Bingqin Xu with Dr Neil Mitchell, of the School of Environment.

A sound carbon accounting programme at the University is now a step closer thanks to research funded by Property Services’ “living laboratory” scholarships – funding which engages senior students with an academic staff member to help find a solution to an operational challenge.

Of interest in this instance was the uptake and storage of carbon by trees on the University’s grounds and reserves and whether it could form part of the University’s response to climate change. At present, the focus is on reducing carbon emissions by reducing energy consumption in buildings.

“Carbon off-setting is a relatively new area of scientific research and it has been difficult to find reliable information on the off-setting capabilities of our trees,” says Dr Lesley Stone, Manager of the University’s Sustainability and Environment programme. “This is because carbon uptake and storage depends on particular tree species’ growth patterns and the effects that local climatic conditions have on them.”

Dr Neil Mitchell, of the School of Environment, had previously done innovative research in this area with his colleague Dr Luitgard Schwendenmann. And so, together with PhD candidate Bingqin Xu, Neil teamed up with Property Services to find out how much carbon was being absorbed and stored by trees on the City Campus, in what is known as the “Conservation Area”.

At 41,500 square metres, the Conservation Area makes up the majority of what is referred to as Sector 100 – an area of the City Campus bordered by Waterloo Quadrant and Princes, Alfred and Symonds Streets. It has more than 400 trees, most of which are considered “mature” and greater than 10 metres in height – two of the more important variables in the world of carbon off-setting, as Neil explains.

“Carbon sequestration is the ability to capture carbon dioxide from the atmosphere and it is largely dependent on a tree’s maximum potential age and where in its growth stage it is. For most trees, the ideal carbon capturing time comes during its fast growth stage which lasts for about half the tree’s life span.”

Working with data previously collected by the University’s grounds and precincts manager Stanley Jones, the researchers quantified carbon storage within the Conservation Area, using growth rate formulae and educated assumptions based on previous research.

The best performer is the Norfolk Island Pine which stands tall at the eastern end of the lawns of Old Government House. It stores approximately five per cent of the total carbon content estimated for the entire Conservation Area.

Given the expert assumption that most of the trees in the area are in their fast growth stage, the future looks particularly bright provided the trees stay healthy. The researchers estimate that over 220,000 kilogrammes of carbon will be captured in the Conservation Area alone in the next 20 years.

With such positive outcomes coming from a small area of the University, work has already begun on seeing where else in the University may prove equally beneficial. Grounds staff have already measured trees at the Epsom Campus and are working their way through the remaining campuses and the University’s reserves. Once this work is completed, the University will have a clearer picture of the role that sequestration can play in its carbon off-setting programme.