New Zealand’s high carbon emissions contribute to its potential to mitigate climate change by planting forests to sequester large amounts of carbon. There is debate over whether to continue establishing radiata pine plantations or focus on native trees. However, a transitional forest model could achieve the best of both worlds by transitioning radiata pine forests into native forests over time through targeted management.
The New Zealand Emissions Trading Scheme (ETS) provides income from growing trees to store carbon, which is crucial for meeting domestic and international climate change targets, including the 2050 target set by the Climate Change Response Act 2002. A newly planted native forest will absorb approximately 40 tonnes of atmospheric CO₂ per hectare over ten years, while an exotic radiata pine forest will achieve five to ten times this amount over the same period.
Extravagant carbon farming has an enormous advantage over natives, as it takes five to ten times more farmland using natives to absorb a given quantity of carbon during the early stages of reforestation. While some object to pine planting on aesthetic grounds, the urgency to mitigate climate change requires turning as much unprofitable pasture into forest as possible.
Radiata forests are criticized for being monocultures lacking biodiversity, but the pasture they replace also contains less biodiversity. Planting trees on pasture reduces gross emissions by reducing animal stock and methane emissions. Aotearoa New Zealand has 78.8 million tonnes CO₂ equivalent per year, which would require planting 20 million hectares of pasture in native trees and waiting ten years for them to grow. To offset this, another treeless country would need two to four million hectares.
To offset 11 tonnes of CO₂ emissions, one person would need to plant over a quarter of a hectare of native trees and wait ten years for them to grow. Aotearoa will need to purchase 100 million tonnes of offshore carbon credits to meet its international commitments, costing between NZ$3.3 billion to $23b between now and 2030. Reducing emissions is the priority, but from a climate perspective, planting too many trees is not feasible. Exotic carbon forests are criticized for their short lifespan, but pine plantations in New Zealand can accumulate carbon for at least a century if not harvested.
Carbon storage is permanent when exotic forests transition into self-sustaining native forests. This process occurs naturally but can be accelerated through targeted management. Radisa pine, which requires light to grow, will naturally decline over time and gradually replace native forests. To provide structural and species diversity, native trees need to be planted and pine trees thinned. Fruiting natives attracts birds and enhances seed dispersal. Income from carbon credits through the ETS can be used for further plantings and intensive animal pest control. This strategy provides both permanent carbon storage and carbon capture that continue beyond a century, and within decades, large areas of highly biodiverse native forests will return.
