How will climate change affect plantation forestry?

As our planet faces greater threat from climate change, a new paper projects that New Zealand-grown Pinus radiata will grow at a faster rate but also grow taller and slimmer in the future. While sequestering more carbon, the trees will be face higher risks from extreme winds and wildfire.

Researchers from Crown research institutes Scion and Manaaki Whenua have studied climate change and future biosecurity threats’ impacts on New Zealand’s plantation forests.

Considering the effects of growing levels of carbon dioxide on photosynthesis, the productivity of radiata pine could increase on average by 10 per cent by 2040, and double that by 2090.

Lead author, Scion’s Dr Michael Watt says: “Increasing concentrations of carbon dioxide in our atmosphere will increase the rate at which trees grow. An increased growth rate will result in trees becoming taller and more slender.”

However, the greatest threat to New Zealand’s plantation forests is likely to come from increased wind damage as increasingly slender and taller trees will be more vulnerable to future wind storms. The risks of breaking or uprooting can be reduced somewhat by changing certain forestry practices such as timely thinning and earlier harvesting, according to co-author Dr John Moore.

It is also predicted that very high and extreme fire risk days will increase, where the length of the average fire season will increase by about 70 per cent by 2040 and 80 per cent by 2090. Fire scientist Grant Pearce predicted that the most fire prone regions (Gisborne, Marlborough, and Canterbury) will stay the most at risk, but the relative increase in risk is highest in Wellington and coastal Otago, where it may double and triple to 30 days and 20 days per season, respectively.

New Zealand is currently free of any significant damaging insects, but population growth and damage may be higher in the future as warmer temperatures result in an environment suitable for foreign species’ growth and accelerate insect development. Weeds are also likely to spread their range under climate change and become more competitive with plantations.

“A decade’s worth of research into multiple climate change effects on New Zealand’s plantation forests has been summarised here,” said Michael Watt. “Determining the magnitude of climate change effects is crucial for informing national economic strategies, forest management and offsetting increasing carbon emissions as the country progresses toward a net carbon zero economy.”