Ongoing concern about climate change has fuelled debate about the part carbon sequestration might play in reducing New Zealand’s net carbon emissions. Land use change is happening at pace in New Zealand. Companies plant forests and then earn income by selling carbon credits through the Emissions Trading Scheme (ETS).
Recently, some companies are claiming they will transition radiata forests to natives. They have already planted tens of thousands of hectares of land. Despite many people in these companies and some academics passionately believing that radiata can transition to native forests, in my opinion, this looks very like greenwashing.
When examining images of real 15-year-old radiata forests and digitally-constructed 100-year sequence forests in the company advertising material, the difference is stark. One is sparse, the other is lush. It is enough to make us question whether ‘transition forest’ claims are valid.
Even with the current depressed price for carbon, forest owners can make huge returns by selling carbon credits to industries that pollute. Under the current rules, owners of radiata forest that will be harvested can only claim the first 16 years of sequestration as this is the average carbon held by their forest over several harvest cycles.
Radiata forest owners with a short-term outlook can make much more money by becoming a ‘permanent forest’ under the ETS; they pledge never to harvest their trees. Under ETS rules they can then continue to earn carbon credits for as long as the forest is growing faster than trees are dying. For 70-90 years they can earn a lot, but after that the income ceases the land can never be used for another purpose as the trees (and the carbon they contain) must be maintained in perpetuity. ‘Permanent’ radiata forests have a high fire risk, as can be seen in the cover photo, they have a lot of dead wood due to not being thinned or pruned.
The other problem with permanent radiata forests is that they have a bad public image. The public would far rather see hills covered with green pasture or diverse native forests. Unfortunately, native forests are expensive to establish and grow slowly earning far fewer carbon credits than radiata in the short term. These are the social and economic forces that have led companies to spend tens of thousands of dollars promoting transition forests, that is, using radiata as a nurse crop for native trees.
These companies use a management regime that will maximise revenue from carbon credits. They avoid any dip in earnings by only thinning a few trees. The early research behind the idea of radiata transitioning to natives was done under pine forests at Kaingaroa. These forests were grown for timber at 300 trees per hectare; which allows some light to support ground cover. The bare carpet of needles seen in the picture are under a forest with over double this number of trees.
The whole idea is dependent on nearby remnant bush providing a source of seed. Even for seeds dispersed by birds, 80-90 per cent of seed is dropped within 100m of the source. When there are no nearby seed sources, the owners propose making light-wells and planting species that can withstand some browsing. This is because most new forests (unlike those at Kaingaroa) are surrounded by farmland. They have very high populations of goats and deer which go out to feed on the surrounding pasture and return to the shelter of the forest.
The model below shows the amount of carbon dioxide (CO2) the real forest is likely to store under the management proposed for transition to natives. Due to the effects of deer, goats, and invasive weed species, it looks nothing like the computer-generated marketing images. Worse still, if we follow the modelling out beyond 100 years, we see a false peak followed by a long period in which dying radiata emit carbon before the natives grow large enough to re-absorb it.
Note: Currently MPI only have look-up tables for natives for their first 50 years of growth. This graph is based on numbers produced by NZ Forest Research Institute. A technical reviewer of this model stressed that these sequestration numbers are very optimistic.
It is my belief that Greenwashing is being used to persuade us to give social license to forests that will still look like dark, gloomy radiata forests for the next 100 years or so. These ‘permanent forests’ will leave a huge carbon liability for future generations. It would be easy for these companies to walk away at the false peak of storage with all their profits. Their legacy will be a further 100 years of carbon emissions that would need to be covered by carbon credits purchased by the taxpayer at huge expense.
