Natives hungry for carbon

A new study shows New Zealand’s native forests are absorbing more carbon dioxide than previously thought, particularly in the South Island.

Study leader, NIWA atmospheric scientist Dr Beata Bukosa, says the findings could impact NZ’s greenhouse gas reporting, carbon credit costs, and climate and land-use policies.

She says previous studies may have underestimated the amount of carbon taken up by NZ’s mature native forests, which were thought to be roughly carbon neutral.

Using advanced modelling and NIWA’s supercomputer, researchers examined a decade of atmospheric data, from 2011 to 2020, to better estimate the amount of carbon dioxide absorbed by NZ's land ecosystems.

NIWA worked on the study with GNS Science and Landcare Research as well as other NZ and overseas universities and institutes.

“It was thought that some areas and land use types were in a near-balance state with the absorption and release of carbon dioxide. Earlier estimates of how much carbon was removed by NZ land ecosystems ranged from a net 24 to 118 million tonnes a year,” Bukosa says, “Our research found that New Zealand’s natural environment absorbed approximately 171 million tonnes of CO₂ annually.”

She says the largest differences between earlier estimates and the new findings came in the South Island.

“This was especially in areas dominated by mature native forests and certain grazing lands. We also found seasonal variation, as during autumn and winter, less carbon is released into the atmosphere than earlier estimates suggested.”

Bukosa says the results, due to be published shortly, have important implications for NZ’s tracking of carbon emissions and climate policies.

“We need to better understand why our native forests are absorbing more CO₂ than expected, and what this could mean for our efforts to reduce greenhouse gas emissions and achieve our domestic and international targets.”