New Zealand: Native forests absorbing more carbon dioxide
This project included data from NIWA’s clean air station at Baring Head, near Wellington, its atmospheric research station at Lauder in Central Otago, and measurements taken from a ship that collects observations on a line between Nelson and Osaka, Japan.
“The inverse approach integrates information about carbon dioxide sources and sinks from atmospheric data, ocean data and models,” Dr Steinkamp says.
“The story the atmosphere is telling us is that there’s a big carbon sink somewhere in the South Island, and the areas that seem to be responsible are those largely dominated by indigenous forests. However, we cannot rule out an important role for carbon uptake in the hill country or from pasture from our current data. ” Indigenous forests cover about 6.2 million hectares in New Zealand.
Dr Mikaloff-Fletcher says that was a very surprising result mainly because strong carbon sinks are expected when there is a lot of forest regrowth.
“Carbon uptake this strong is usually associated with peak growth of recently planted forests and tends to slow as forests mature. This amount of uptake from relatively undisturbed forest land is remarkable and may be caused by processes unique to New Zealand or part of a wider global story. “
The National Inventory method reported by Ministry for the Environment reports annually on New Zealand’s carbon uptake. This internationally standardised methodology puts the amount of carbon being absorbed by all New Zealand forests at 82 teragrams (Tg) CO2 (A teragram is one millon metric tons) total over 2011-2013, the period studied by Dr. Mikaloff-Fletcher’s team.
Once accounting rule differences are corrected for, the new NIWA measurement approach finds that actual carbon uptake could be up to 60% higher.
The inventory-based method estimates carbon uptake using measurements of tree growth taken from about 100 sampling areas, and extrapolates this to the entire country using statistical techniques and modelling. There is still considerable work to be done in comparing the two independent approaches
“We need to find out definitively what processes are controlling this unexpectedly large carbon uptake, in order to understand the implications for land management and climate treaties. We need additional measurments to tell us if this is unique to the southern half of the South Island or holds across a wider range of New Zealand.”
Dr Mikaloff-Fletcher says the ability of forests to absorb carbon is a powerful tool to help address the challenge of climate change.
Next steps include incorporating data from NIWA’s newest atmospheric CO2 observing site, Maunga Kākaramea/Rainbow Mountain in the central North Island, deploying two new atmospheric CO2 observing sites and a major improvement to model resolution. This will start to shed light on what’s happening in the North Island and the Canterbury plains.
This article appeared on the Scoop website at http://www.scoop.co.nz/stories/SC1702/S00050/native-forests-absorbing-more-carbon-dioxide.htm