Felled trees under scrutiny to help climate-change battle

Dr Neil Mitchell studies a sample of trees at Newmarket Park to find out how much carbon the trees have processed. Photo / Greg Bowker

Twenty trees felled in the revamp of Newmarket Park will have a second life as research subjects in the fight against climate change.

Researchers will cut up and weigh the trees, roots and all, to figure out exactly how much carbon has been tucked away in 25 years of growing.

Auckland University ecologist Dr Neil Mitchell said it was unusual to study trees when the exact age was known and the roots were intact.

"It's rarely been done anywhere in the world."

He hopes the study will improve calculations of how much carbon is stored in trees to help people wanting to offset their greenhouse gas emissions or gain carbon credits to sell to polluters.

Buying carbon credits to offset activities such as driving or flying has become more popular in recent years and there are plenty of calculations of trees' carbon-sucking potential.

But Dr Mitchell said his project would give more accurate data because every part of the tree would be weighed.

He said the haul included popular species including karaka, kanuka, lemonwood and pittosporum, making it handy for measuring New Zealand "carbon farming" projects.

The trees were cut down as part of work by the Auckland City Council to re-contour and stabilise the park, which sits on an old landfill.

Dr Mitchell said once the trees were chopped into manageable chunks and weighed, samples of the wood would be analysed to work out how much carbon was stored.

Trees measured so far weighed in at about 150kg each, he said.

Dr Mitchell plans to publish his findings and provide them to local councils. He said they could help work out the value of planting in local and regional parks.

"It's suddenly giving a value to all the plantings they (the councils) have done."