Greenhouse Gas 'Guru' Does Sums On NZ Emissions

Media Release - 25 March 2004

Greenhouse gas 'guru' does sums on New Zealand emissions

A leading international greenhouse gas scientist is in New Zealand to examine our system for estimating nitrous oxide emissions.

Despite our clean, green image, New Zealand has a unique greenhouse gas problem. Our many millions of sheep and cattle produce considerable quantities of methane and nitrous oxide. Although much greenhouse gas publicity focuses on carbon dioxide, methane is 21 times more effective than carbon dioxide at trapping the heat of the sun, and nitrous oxide an astonishing 310 times more effective. Nitrous oxide makes up about a sixth of New Zealand's greenhouse gas output. It is generated mainly from surplus nitrogen in soils, which originates from dung and urine of sheep and cattle.

Landcare Research is hosting Professor Changsheng Li from the University of New Hampshire in the United States. Professor Li originally developed the definitive model for estimating nitrous oxide emissions on agricultural or horticultural land. Many countries, including China, Japan, the UK, Germany, Italy and Australia now use this model to produce their nitrous oxide emission inventories under the United Nations Framework Convention on Climate Change (UNFCCC).

Landcare Research scientist Dr Surinder Saggar says he and his colleagues have adapted Professor Li's model for New Zealand conditions, and Professor Li is confirming the correctness of their changes.

"We adjusted the model to account for differences in climate, soils, and year-round livestock grazing systems * the three main variables controlling emissions here. We will be able to simulate emissions on both regional and national scales from New Zealand's pastures, under a wide range of conditions.

"Professor Li is helping us to fine-tune our equations and apply the model over larger land areas."

Dr Saggar says the model has already helped provide much useful information for New Zealand. "Our preliminary estimates indicate that our direct nitrous oxide emissions total about 18,000 tonnes a year, depending on rainfall and the amount of time stock spend on pastures. Also, we now know that poorly drained soils make the emissions problem much worse. Our early estimate is that the 9% of our dairy pastures that are on poorly drained soils are responsible for about 20% of our nitrous oxide emissions.

"Armed with this information, the agricultural sector may decide to invest money in soil drainage, or introduce restricted grazing during winter, when soils are wet and emissions are highest."

As well as his work with Landcare Research, Professor Li has been presenting seminars and workshops to other Crown research institutes, MAF, MfE, the New Zealand Climate Change Office, and MFAT staff.

He departs tomorrow to work with scientists and government agencies in Australia.

ENDS

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