A limit to trees saving the planet and farms - report

That's the key message from the Parliamentary Commissioner for the Environment Simon Upton in his just released report 'How much forestry would be needed to offset warming from agricultural methane'.

Upton says he's always expressed strong reservations about using forests to offset fossil carbon dioxide emissions. However, he believes that using forestry to help offset agricultural emissions might be more justifiable because the warming from methane and the compensating cooling effect of planting a forest are both largely temporary.

"Methane is a much stronger gas than carbon dioxide, so we needed to know how much forest you need to plant to say that you were making a useful contribution to heading off dangerous climate change," he told Rural News. "To test the feasibility, I commissioned Professor David Frame and Dr Nathaniel Melia to calculate what area of forestry would be required to offset livestock emissions using a warming-based approach."

Upton says there are no recommendations in the report as such, rather the objective is to foster a better and more informed debate on what might be possible.

In a summary document, which is effectively a précis of the detailed and highly technical full report, Upton notes that there is genuine confusion about how much warming is being caused by NZ livestock. The document also notes that while methane emissions from dairy cattle have increased, emissions from beef, sheep and deer have decreased and that total livestock methane emissions have basically remained constant since 2000.

One key fact highlighted in the report - and set out in graphic form - is the amount of new plantation forestry that would be needed to offset methane emissions of individual animals. In the case of a dairy cow, 0.6ha would be required, 0.4ha for a beef cattle, 0.2ha for a deer and 0.08ha for a sheep. The report says that planting 770,000ha of plantation pine forest - between now and 2050 - would have the effect of reducing by 10% methane emissions from the livestock sector.

However, Upton points out that if the planting of trees was to go on unconstrained, the country would run out of land. He also highlights the adverse economic, social, cultural and environmental impacts of this in the report - as well as the negative effect on infrastructure, such as roads.

"What I am saying is that some trees will have a cooling effect and what I have given is the exchange rate and the limit to what trees can do," Upton explains. "But I don't think you should completely discount them."

The report looks at options on farm and suggests that other farm vegetation - such as riparian plantings and scattered bush fragments, woodlots and shelter belts - would likely have minimal impact at a national level.

Upton adds that the goal is to reduce agricultural emissions and a lot of options, such as breeding animals that produce low emissions, vaccines and other tools, are being devised. He stresses how research into these areas is a high priority and says recent government initiatives will help in this regard.

Uneven Playing Field

One issue that Upton continues to express concern about it is the fact that fuel emitters have access to forestry to offset their emissions, while the agricultural sector doesn't.

He says this makes for a playing field that is tipped against agriculture.

"It has never made sense to me that you allow offsetting for fossil fuel emissions but don't allow them for agriculture," Upton explains.

The complex report, which probably needs to be read and reread - offers another perspective on how NZ could deal with agricultural emissions. For many, planting trees has been seen as an option, but this has drawn fire from those who see productive pasture being wasted by tree planting.

What is clear is that confusion and uncertainty still reign and this document is Upton's offering to the debate.

"All I can say is we really need to move on this stuff - that is a real reduction in emissions," he says. "Trees might be able to add something to it, but we can't rely solely on trees because there isn't enough land."