Tuesday, October 24, 2017

Climate change: A lot of trees

Labour and New Zealand First signed their coalition agreement today, and one item caught my eye: "Planting 100 million trees per year in a Billion Trees Planting Programme." That is a lot of trees. Its also potentially a huge step towards meeting our climate change targets.

At the moment New Zealand plants about 40,000 hectares of trees a year, mostly as replanting of existing plantations. 100 million trees is about 100,000 hectares (assuming a stocking rate of 1,000 trees per hectare; actual numbers vary from 600 to 1,400). As that graph shows, its going to mean a huge increase in the propagation industry, to a level even higher than the mid-90's peak. Its in theory doable, but difficult, and may take a number of years to ramp up.

As for the payoff, once established, a hectare of pine aborbs 25 tons of CO2 a year, every year, for 40 or 50 years. A years planting will soak up 2.5 million tons of CO2 every year. And the government plans to do that for a decade. Which is going to make a huge difference to our emissions profile in the long term.

And we're going to need it. Because all those trees planted in the mid-90's are starting to be cut down. Which means we're going to face a huge peak in our emissions over the next decade. A mass tree-planting programme will smooth that peak, and help stabilise things, buying us a bit of time. But fundamentally, if we are to solve this, we need to cut emissions (including the sacred cow of agricultural emissions), rather than just planting trees.