13 Apr 2023

NZ's gross greenhouse gas emissions drop for second year in a row

1:24 pm on 13 April 2023
Industrial air pollution smoke chimney.

Energy emissions, which include transport, grew slightly - 0.3 percent - but remained below pre-pandemic levels. Photo: 123RF

The Ministry for the Environment says the country's gross greenhouse gas emissions decreased for the second successive year in 2021.

In figures released this morning, it said gross emissions that year were equivalent to 76.8 million tonnes of carbon dioxide - 0.7 percent less than the year prior.

The ministry said the main driver was reduced agricultural emissions. The sector's emissions fell 1.5 percent, largely due to fewer dairy cattle and sheep, and less use of synthetic nitrogen fertiliser.

Energy emissions, which includes transport, grew slightly - 0.3 percent - but remained below pre-pandemic levels.

The waste sector cut its emissions 1.6 percent in 2021, compared to 2020.

The 2020 drop of 3 percent was partly down to Covid-19, which saw New Zealand locked down in the first half of the year to eliminate the initial outbreak, and other regions - notably Auckland - repeat the exercise at later dates.

The ministry said the virus "continued to have some impact on emissions in 2021 but was not the biggest driver of reductions".

Net emissions rose 3 percent, due to "historically high harvest rates in our plantation forests".

"Because of this, we have a higher proportion of younger forests which grow more slowly and sequester less carbon than older ones. In addition, in 2021, harvesting returned to pre-pandemic levels," the ministry said.

Since 1990, New Zealand's gross emissions have increased 19 percent and net emissions, 25 percent.

The only sector to have reduced its output in that time was waste. Most of the rise has been in energy (up 30.7 percent) and industrial processes (28.8 percent). Agriculture emissions have gone up 13.4 percent in the last three decades.

The biggest rise in contributions to gross emissions between 1990 and 2021 was 'enteric fermentation from dairy cattle' - cow methane - up 122.6 percent.

Gross methane emissions fell 1.2 percent between 2021 and 2020, and nitrous oxide was down 2.5 percent. Carbon dioxide emissions rose 0.2 percent.

According to the Intergovernmental Panel on Climate Change's Fifth Assessment Report, one tonne of methane is considered to have the warming potential of a couple of dozen tonnes of carbon dioxide, and nitrous oxide more than a couple of hundred. The 2023 figures use these calculations to work out the equivalent carbon dioxide emissions, as per the Paris Agreement.

New Zealand's gross and net emissions peaked in the mid-2000s. Gross emissions in 2006 were the equivalent of 82.8 million tonnes of carbon dioxide, and net 59.5 million tonnes.

The full data can be found on the Ministry for the Environment's website.

Globally, gross emissions have risen 40 percent since 1990. The figure - currently at about 54 billion tonnes - has shown signs of stabilising over the past decade.

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