Monday, July 8, 2019

Radiata pine and climate change

Open letter to Radio New Zealand:

As a response to your article quoting Jim Salinger, please consider the following points.

1) Radiata pine and native forest can store roughly equivalent amounts of total carbon if they are left unharvested.

2) Radiata pine sequesters carbon at a vastly higher rate than native forest. We would need at least four times the area of native forest compared to radiata pine forest to get equivalent annual rates of sequestration (and I'm being generous to native forest here).

3) We can't realistically establish enough land to get to our net zero by 2050 target with native forest, but we can easily do it with pine forest.

4) Any type of forest, if periodically harvested (and this is legal for native forest plantations), will obviously have a lower average storage than unharvested forest, but the number is usually around 60% of final carbon storage at harvest age, not zero.

5) Radiata pine can act as a nurse crop for native forest if there is a sufficiently close seed source and the environment is not extreme.

6) Native forest is much more expensive to establish than pine forest. One recent project was running at $14/tree for native forest. This is 5-10 times the cost of establishing radiata pine.

7) Given how often we plant radiata pine it is very rarely a wilding. The reason is that for a wilding to prosper you need a species that can germinate and survive in a downwind environment from a takeoff site, where there is very little grazing downwind. It turns out that radiata pine cannot germinate and survive in most environments where grazing is either low intensity or absent. Frost kills the young germinants because unlike many other species radiata pine has almost no response to changing daylength and is still growing when out of season frosts hit. That’s why most wilding problems are from species we rarely plant, such as Douglas fir, Pinus contorta, Pinus ponderosa, Pinus mugo and Pinus nigra. There are three exceptions that I know of, where we have radiata pine wildings in warm, wet environments where grazing is of low intensity or absent; parts of the Sounds, West Dome in Southland, and Mt Tarawera. Moreover, some relatively shade tolerant species such as Douglas fir threaten our native forests but shade intolerant radiata pine does not. The general public thinks that our wilding problems with other species are caused by radiata pine, but they are mistaken.

So in radiata pine we have a species that is cheap to establish, sequesters C very rapidly, is unlikely to be a wilding, and will act as a nurse crop for native forest if we are smart about how we set policy. Policy should be to either identify or establish local native seed sources and never harvest the pine. 

With a relatively small area we could meet our 2050 target and our grandchildren could enjoy native forests where we established the pine. According to the Globe study we cannot meet our 2050 target without using new forests as sinks. The earliest the authors projected GHG neutrality without using forests in NZ was 2080 and even that was unlikely.

By promoting native forest planting from the regional development fund we are ensuring that we will not meet our 2050 target.

Kind regards,
Euan Mason

School of Forestry
University of Canterbury
Christchurch, New Zealand