Sunday, March 28, 2021

Submission on the New Zealand Climate Change Commission’s proposals, 2021

Profile: Euan Mason is a Professor at the New Zealand School of Forestry, University of Canterbury, where he teaches silviculture, statistics, modelling, and research methodology.  His research interests include forest growth and yield modelling, tree physiology, and silviculture.  He has published numerous peer-reviewed articles and a chapter in a text book relating to climate change and forestry, and has been employed by government ministries and political parties to advise them on climate change issues from time to time.  He is a New Zealand citizen, born in Invercargill.  He was educated at universities in New Zealand and the United States of America.


The Climate Change Commission should be commended for making a very helpful, comprehensive report on such a difficult topic. The Commission is right to state that our long term focus must be on reducing greenhouse gas emissions. However, the targets New Zealand has set for 2035 and 2050 have been watered down, and will perpetuate the very transactional, ineffectual approach that has seen New Zealand do virtually nothing to mitigate climate change up until now.

With respect to forestry issues there appear to be a number of unsubstantiated assumptions, and also the case for native forest establishment appears to be based on an appeal to public sentiment rather than on any benefit for New Zealand’s efforts to get to greenhouse gas neutrality.

Historical perspective

While academics had discussed the likelihood that emissions of CO2 from fossil fuels would likely result in climate change for almost 100 years, the issue did not gain political attention until the 1990s, when New Zealand joined other countries in signing the Kyoto Protocol. Probably the most important consequence of the protocol was that most countries officially recongnised that we had a problem. The protocol also set out international trading in carbon credits that was deeply flawed, mostly because credits were grandfathered for “allowed emissions” of greenhouse gases (GHGs). Despite almost all countries nominally meeting their Kyoto commitments the rate of accumulation of atmospheric GHGs continues to accelerate (Figure 1).

New Zealand joined the Kyoto Protocol with a commitment to reduce our annual net greenhouse gas emissions between 2008 and 2012 to the level of our gross emissions in 1990. This habit of comparing present day net emissions to gross emissions in the past is one way in which countries can pretend to do something about climate change while continuing business as usual. In fact, New Zealand came close to not meeting our commitments and having to buy carbon credits on the international market, but we were saved from this prospect by the fact that investors had planted new plantation forests during the 1990s (Figure 2). New forest acts as a sink for CO2, increasing the storage of carbon in the landscape. More than 500,000 new hectares of mainly radiata pine had been established during the 1990s, and they were calculated to have absorbed about 34 tonnes of CO2 per hectare per year during the commitment period, which almost exactly offset the difference between our annual net emissions of GHGs between 2008 and 2012, and our gross emissions during 1990.

Figure 1 – Atmospheric CO2 measured at Mauna Loa, Hawaii


Figure 2 – Annual rates of afforestation and deforestation in New Zealand since 1920.

New Zealand’s GHG emissions resemble those of a third world country (Figure 3), and are currently approximately 80 million tonnes of CO2-e per year.


Figure 3 – New Zealand’s GHG emissions in 2012, compared with those of other nations

New Zealand set up an emissions trading scheme (ETS) that mirrored the Kyoto scheme, complete with grandfathering of credits, but also with a piecemeal approach to different sectors. Most notably the agricultural sector was not required to join the scheme with respect to methane and nitrous oxide, two especially potent GHGs. Methane, for instance is about 84 times worse than carbon dioxide as a greenhouse gas on a 20-year timeframe, but it has a much shorter life in the atmosphere. Currently the international community prefers to handle this by adopting a 100-year timeframe and reducing the calculated relative effects of methane accordingly. Unless we can convince the international community to change its approach to methane pollution we should retain the current international accounting scheme for it. The case that methane really doesn’t matter because it is a short-lived atmospheric gas, made by those trying to protect agriculture, does not make sense. All GHGs have half-lives, and would eventually reach a new equilibrium level in the atmosphere in the face of increased emissions. None of them have yet done so. Our recent increase in anthropogenic methane emissions is extremely dangerous.

The government has engaged in a practice labelled “grandfathering” in our ETS, where polluters are given credits for “allowed emissions” up to a portion of their actual emissions and then they have to surrender credits for some of their emissions.  The extent of grandfathering has reduced recently, but “trade-exposed” industries still receive credits for up to 90% of their emissions.  Grandfathered credits represent no cleaning of the atmosphere and flood the credit market with credits that are as bogus as “hot air” credits from Eastern Europe (Mason, 2013).  They also impose awkward administrative difficulties, requiring people to assess “additionality” of climate change responses, and such judgements can at times appear rather arbitrary and costly (Valatin, 2012).

Why grandfathering makes emission trading irrational

In a well-functioning emissions trading scheme, polluters would have to submit credits in order to be allowed to pollute, and they would purchase credits from those who cleaned up their pollution.  So if the cost of cleaning was higher than the cost of reducing pollution in the first place then they'd choose to reduce emissions. Either way the atmosphere would not receive any more GHGs and purchasers of carbon credits could rightly call themselves "greenhouse gas neutral".

However, that's not what's happening.  If a polluter reduces their pollution below the cap then they can sell grandfathered credits. They also assert that purchasers of their credits can claim to be "greenhouse gas neutral". They are wrong.

There are many ways to explain why they are wrong.  You could use stories, mathematics, graphs or even children's blocks. Let's use the latter.

Blocks below represent levels of greenhouse gas in the atmosphere and levels planned to be emitted by two polluters.

Figure 4

Then polluter 2 opts to no longer pollute and has grandfathered carbon credits for sale. Polluter 1 purchases those credits and is allowed to pollute. The result is more greenhouse gas in the atmosphere, as shown below.  Polluter 1 clearly cannot claim to be "greenhouse gas neutral".

Figure 5

So, what kinds of credits can confer greenhouse gas neutrality on a purchaser? Let's reach for the blocks again.  In this case, we have the atmosphere, a potential polluter and someone who will take greenhouse gas from the atmosphere (maybe using new trees, a scrubber, or perhaps by seeding the ocean with iron to promote plankton); a sequesterer.

Figure 6

The sequesterer receives carbon credits for removing greenhouse gasses from the atmosphere. They are purchased by the polluter, who then goes ahead and pollutes, but the amount of pollution is exactly equal to the amount of sequestration and so the result is shown below:

Figure 7

Clearly, the atmosphere gains no new greenhouse gas and the polluter can now claim to be greenhouse gas neutral.

It is generally much cheaper to do nothing than to extract greenhouse gasses from the atmosphere. If we allow people to sell carbon credits for simply reducing outputs of greenhouse gas, we effectively pay them for nothing (they get the benefit of having to submit fewer credits, and being able to sell grandfathered ones represents a double payment), and it takes much longer for emissions trading schemes to work because few will engage in activities that extract greenhouse gasses from the atmosphere.

A further problem with forestry in cap and trade schemes

Cap and trade schemes are meant to work by limiting the availability of credits to a known volume, but each credit earned by forestry potentially adds to the level of the cap. One could argue that the cap applies to “net” rather than “gross” GHG emissions, and so forest-based credits could be considered to be “net cap-neutral”, but this begs the question of how to deal with the fundamental difference between forest-based credits and credits manufactured from thin air by government, as outlined above.  Our current scheme is essentially irrational with respect to forest-based credits.

Similarly, the government’s scheme to auction credits simply waters down our approach to climate change mitigation. These auctioned credits are about as credible as those purchased from eastern Europe for as little as 10 cents each (see below).

The failure of New Zealand’s emissions trading scheme

New Zealand has clearly failed to address climate change. Our emissions have continued at approximately 80 million tonnes of CO2-e (Figure 8), despite emissions trading since 2008.

Figure 8 – New Zealand’s net and gross greenhouse gas emissions (source: NZ Ministry for the Environment)

The scheme failed partly because it was irrational (see above), but also because we adopted an excessively transactional approach to the issue. This meant that between 2011 and 2015 we were quite content to allow emitters to purchase carbon credits anywhere in the world, and many of those purchased were fraudulent as they did not actually represent any action taken to either stop emitting or clean up the atmosphere. The result was that New Zealand unit (NZU) (domestic carbon credit) prices fluctuated wildly. Moreover, imported credits were often purchased at far lower prices than those of NZUs, and people grandfathered NZUs stored them while meeting surrender requirements with international credits worth as little as 10 cents each. This means that we still have a large mountain of NZUs in our NZU registry that were grandfathered in previous years but were not surrendered by GHG polluters.

Figure 9 – Spot prices of New Zealand Units

Our current position

We are among the worst GHG polluters per capita in the world, and we have done virtually nothing to stop polluting. Our ETS has been fragmented, irrational and applied differently to different sectors of the economy. We seem not to have really cared about emissions, instead wishing to seem to have done something about climate change when in fact we have achieved almost nothing.

A small shaft of light

In 2016 the New Zealand government and opposition parties jointly commissioned the “Globe” report (Vivid_Economics, 2017), which outlined pathways for New Zealand achieving GHG net neutrality during the second half of this century. In essence, the authors identified that true net-neutrality by 2050 was not possible without a contribution from forest sinks. Neutrality without a contribution from forestry might be achievable by 2090, leaving a triangle of required sequestration (Figure 10). 

This report was thorough, compared net with net and gross with gross emissions in setting targets, and covered all GHGs.

Only newly established forests are likely to be C sinks; forests in aggregate eventually become reservoirs of C despite local fluctuations in C storage. It is therefore appropriate to use new forests on a limited scale to fill a gap in our GHG accounts as we work to reduce emissions to zero.


Figure 10 – How New Zealand might reach greenhouse gas neutrality by 2050 (Vivid_Economics, 2017)

Watered down targets

As mentioned previously, New Zealand consistently engages in transactional thinking, and cooks the books to give the impression that we have achieved more to mitigate climate change than we have actually achieved. This is true for our 2035 target, which not only pledges to get net emissions down to an earlier gross level, but also has shifted the “earlier” level from 1990 to 2005, a year when our emissions had greatly increased compared to those in 1990 (Figure 8). This means that in effect, we have pledged to increase our net emissions, not decrease them.

Similarly, as 2050 approaches, we have shifted the goalposts on net neutrality, now claiming that the target applies to CO2 but not methane or nitrous oxide. The latter two gases represent almost 50% of our GHG emissions. As explained above, this distinction is irrational.

Recommendation: Rewrite your report on the assumption that our target is to be truly GHG neutral by 2050

Forestry issues in the Climate Change Commission’s proposals

The “impermanence” of forests as a carbon reservoir

Forest C storage is said to be “impermanent”. What matters is the total area of New Zealand in forest, not whether or not any particular forest stand blows down, burns or is harvested. If we commit to increasing the total national area of forest and to ensuring that the very small areas that blow or burn down, or those areas that may be harvested, will be re-established, we can enlarge a very stable, permanent C store in forests.

2. Forest is said to be risky because climate change will increase the risk of fires. New Zealand’s forests have long been far more likely to blow down than burn down, and the frequency of forest fires has not yet been shown to have increased in New Zealand (Figure 11). Australia, at similar latitudes to the Sahara and with continental climate patterns, has always been subjected to greater forest fires than us, and our opinions on this matter appear to have been strongly influenced by anecdotes from across the Tasman Sea. This is poor evidence on which to base policy.

Figure 11 – Percentage of forest area burned each year in New Zealand

3. There appears to be an implicit assumption that native forests are more permanent than exotic forests, and to the extent that exotics tend to be pioneer species from an ecological point of view, this is true for unharvested forests, but the conclusions that we must plant native forests and that these forests will greatly help us reach our 2050 target are flawed. Native forests sequester C very slowly compared to our most productive exotics, and areas of native forest required to have the necessary impact on our C accounts by 2050 are simply too large and expensive for us to contemplate. There is abundant evidence that we could take advantage of rapid sequestration rates of exotics to fill gaps in our C accounts (these gaps result from a necessarily slow pace of change in greenhouse gas emissions and are acknowledged by the Commission) while gradually transitioning these pioneer exotic carbon forests to later seral stage native forest over many decades (see below). This latter approach would have substantial advantages. It a) is much cheaper, in dollars and in land area required, than directly planting native C forest; b) ensures that forests actually fill the gaps in our C accounts; and c) ultimately provides extra native forest which many of us would like to see, but in a more natural way.

Areas of forest establishment proposed

The climate change commission sets out a proposed planting programme to help fill a gap in our GHG accounts. Their proposals are modest because the targets have been greatly watered down. I prefer to compare them to the true gap identified by Vivid Economics. I have modelled the likely impact on our accounts of this planting programme with a range of assumptions (Figure 12). The overall assumption is that marginal, particularly erosion-prone land is the target.

Figure 12 – Sequestration rates from forest establishment proposed by the Climate Change Commission. The red line shows the gap to be filled (according to the Vivid Economics study). The purple line shows sequestration by pine if all the new forest is unharvested and left to become native forest eventually (see below). Light blue: Sequestration or emission from pruned and harvested pine. Dark blue: Credits earned by pine forest owners under “averaging”. Green and brown: sequestration by native forest assuming government “lookup” table and my personal estimates respectively.

A number of things are apparent from this simulation:

1.       None of the proposed plantings will get us to GHG neutrality by 2050;

2.       “Averaged” credit entitlements do not properly represent the medium-term impacts on the atmosphere; and

3.       Establishing 300,000 ha of extremely expensive native forest will do very little towards meeting our targets.

Simulations suggest than annual plantings beginning at 12,000 ha and rising annually to 45,000 ha per year by 2050 (1.75 M ha in total) would fill the gap if 75% of the plantings were pruned, harvested then replanted while 25% was left to eventually transition to native forest. An alternative would be a total of a bit less than 1 M ha planted on a similar schedule and all of it left to transition to native forest.

The case for exotic tree species transitioned to native forest

Many imported species grow and sequester CO2 much more rapidly than native species within the time frames required to meet our target. Radiata pine has been chosen as an example for the following reasons (although other species such as dryland eucalypts might do the job equally well or even better in some cases):

1)     It grows rapidly and sequesters C at a much higher rate than native species. Between 2008 and 2012, our national carbon accounts indicate that radiata pine planted after 1990 sequestered at an average rate of 34 tonnes of CO2-e/ha/year, and rates might be even higher with silvicultural regimes aimed at maximising value from sequestered carbon credits. By contrast, estimated rates of sequestration for native species are often below 10 tonnes of CO2-e/ha/year during the years following forest establishment (Scott et al., 2000; Trotter et al., 2005), and the slower development of young native stands would mean that they would take longer to begin any effective sequestration. In older indigenous stands higher rates have been reported on some sites, but not near the rates typical of radiata pine. To be fair, studies of native forest sequestration are uncommon, but we can also get an idea of relative sequestration rates by comparing the more numerous reports of growth rates of stems of various species (Pardy, Bergin, & Kimberley, 1992; Silvester & McGowan, 1999), and native species typically take 3-4 times longer to reach equivalent volumes of radiata pine plantations at harvest.

2)     We are experts at producing seedlings for exotic species and they are cheap.

3)     Radiata pine will grow on a wide range of sites and we understand how to establish it on diverse sites, despite its sensitivity to shade and frost.

4)     Radiata pine is not a high country wilding risk (Ledgard, 2008).  It is very intolerant of both shade and frost, and would only seed naturally on moist lowland areas where adjacent land was not intensively grazed (which is a rare condition in New Zealand). Our wilding species are commonly other, more hardy imports, such a P. contorta, P. ponderosa, P. nigra and Douglas fir. These wilding risk species should be avoided in carbon forests.

5)     On warm, moist sites (either medium or high productivity categories), it would act as a nurse crop for native forest, and the C reservoirs we establish would ultimately change to become native forest so long as seed sources were available in the local vicinity (Figure 13). Understoreys of native vegetation are common in plantations on such sites (Brockerhoff, Ecroyd, Leckie, & Kimberley, 2003; Ogden, Braggins, Stretton, & Anderson, 1997). This issue has been much studied by a PhD graduate from the School of Forestry named Adam Forbes (Forbes, Norton, & Carswell, 2015a, 2015b, 2016). In order for native forest to regenerate under pines local native seed sources are essential.

6)     Studies suggest that radiata pine will continue to sequester carbon for up to 100 years on some sites (Woollons & Manley, 2012), but we have assumed 60 in this analysis.  This means that the forests would remain as sinks for some considerable time.

7)     Exotic tree species are much cheaper to plant than native forests. Conservatively we estimate that native forest establishment will cost at least four times as much as exotic forest planting. The alternative is natural regeneration of native forest, but this would delay appreciable GHG sequestration by several decades.


Figure 13 - Forest biomass dynamics after introducing the exotic pine species Pinus radiata to the native species pool. Dynamics are modeled for a site near Christchurch, New Zealand. Species aboveground biomass is cumulative. "Kunzea and Leptospermum" include the early colonizing species K. ericoides and L. scoparium. "Others" include the species Griselinia lit- toralis, Pittosporum eugenioides, Aristotelia serrata, Elaeocarpus hookerianus, Fuchsia ex- corticata, Nothofagus fusca, and N. solandri var. solandri Figure from Hall (2001).


Recommendation: New Zealand policy should encourage the establishment of radiata pine and other selected exotic species as permanent carbon forests, with the proviso that for every 10 ha of exotic species, 1 ha of local native stands are either identified or established to act as seed sources for the gradual succession to native forest as carbon reservoirs. 

Recommendation: The area proposed should be extended to fill the gap so that New Zealand becomes truly GHG neutral.

Recommendation: Carbon forests require on-going protection and management, and this requirement should be built into any grant schemes or ETS rewards for tree planting.

Euan G Mason


University of Canterbury


Brockerhoff, E. G., Ecroyd, C. E., Leckie, A. C., & Kimberley, M. O. (2003). Diversity and succession of adventive and indigenous vascular understorey plants in Pinus radiata plantation forests in New Zealand. Forest Ecology and Management, 185(3), 307-326.

Forbes, A. S., Norton, D. A., & Carswell, S. E. (2015a). Accelerating Regeneration in New Zealand’s Non-harvest Exotic Conifer Plantations. Paper presented at the Sixth World Conference on Ecological Restoration, Manchester, United Kingdom.

Forbes, A. S., Norton, D. A., & Carswell, S. E. (2015b). Artificial canopy gaps accelerate restoration within an exotic Pinus radiata plantation. Restoration Ecology. doi: 10.1111/rec.12313

Forbes, A. S., Norton, D. A., & Carswell, S. E. (2016). Tree fern competition reduces indigenous forest tree seedling growth within exotic Pinus radiata plantations. Forest Ecology and Management(359), 1-10.

Hall, G. M. J. (2001). Mitigating an organisation's future net carbon emissions by native forest restoration. Ecological Applications, 11(6), 1622-1633.

Ledgard, N. J. (2008). Assessing risk of the natural regeneration of introduced conifers, or wilding spread. New Zealand Plant Protection, 61, 91-97.

Mason, E. G. (2013). The New Zealand Emissions Trading Scheme: What has gone wrong and what might we achieve? New Zealand Journal of Forestry, 58(2).

Ogden, J., Braggins, J., Stretton, K., & Anderson, S. (1997). Plant species richness under Pinus radiata stands on the Central North Island volcanic plateau, New Zealand. New Zealand Journal of Ecology, 21(1), 17-29.

Pardy, G. F., Bergin, D. O., & Kimberley, M. O. (1992). Survey of native tree plantations 

Scott, N. A., White, J. D., Townsend, J. A., Whitehead, D., Leathwick, J. R., Hall, G. M. J., . . . Whaley, P. T. (2000). Carbon and nitrogen distribution and accumulation in a New Zealand Scrubland Ecosystem. Canadian Journal of Forest Research, 30, 1246-1522.

Silvester, W., & McGowan, R. (1999). Proceedings of a Conference entitled "Native Treees for the Future" 

Trotter, C., Tate, K., Scott, N., Townsend, J., Wilde, H., Lambie, S., . . . Pinkney, T. (2005). Afforestation/reforestation of New Zealand marginal pasture lands by indigenous shrublands: the potential for kyoto forest sinks. Annals of Forest Science, 62, 865-871.

Valatin, G. (2012). Additionality and climate change mitigation by the UK forest sector. Forestry, 85(4), 445-462.

Vivid_Economics. (2017). Net Zero in New Zealand: Scenarios to achieve domesticemissions neutrality in thesecond half of the century 

Woollons, R. C., & Manley, B. R. (2012). Examining growth dynamics of Pinus radiata plantations at old ages in New Zealand Forestry, 85(1), 79-86.