Tree pairing may aid zero carbon goal

Fast and slow-growing exotic and native trees could be grown together to help New Zealand capture carbon dioxide and protect biodiversity, a parliamentary select committee has been told.

At the third day of the environment committee’s Christchurch hearings into the Climate Change Amendment (Zero Carbon) Bill, Canterbury University forestry professor Euan Mason said the case for using exotic trees, such as pines and eucalypts, to capture carbon dioxide was compelling.

Unfortunately, indigenous vegetation grew too slowly and could not sequester carbon dioxide fast enough to allow the country to meet its emissions targets.

‘‘I would love to say: let’s go plant to¯ tara; but you couldn’t get there,’’ Mason said.

However, there was no reason why native trees could not be grown below the exotic plantings, eventually taking over as the country’s carbon dioxide reservoirs.

Radiata pine was a good species for capturing carbon dioxide and some dryland eucalypts might be even better in some cases, he said.

According to Mason’s submission, between 2008 and 2012 radiata pine planted after 1990 sequestered carbon dioxide at an average rate of 34 tonnes per hectare per year.

He recommended radiata pine and other exotics be established as permanent carbon forests with the proviso that, for every 10ha of exotics, 1ha of local native stands ‘‘are either identified or established to act as seed sources for the gradual succession to native forest as carbon reservoirs’’.

In his submission, Dairy Farms NZ chief executive Craig McBeth told the select committee the company supported a cleaner dairy industry, and smaller domestic and international environmental footprints.

The industry here already produced some of the world’s most efficient ‘‘carbon-emission equivalent’’ nutrition.

‘‘It has become fashionable for dairy farming in New Zealand to be seen as a focal point for all environmental concerns.

‘‘There is a great risk that this bill will drive dairy farm system change in New Zealand that reduces our nutritional efficiency and in so doing ‘exports’ the agricultural sector carbon-dioxide equivalent to less efficient producers of both animal and plant-based nutrition.’’

The company supported the bill’s plans to distinguish between methane as a short-lived gas and carbon dioxide and nitrous oxide.

Care was needed to make sure targeted methane emissions were achievable.