In 2016 I wrote this. People have been warning about the disastrous effects of poor land management for decades. My dad grew up in rural Whanganui, and as a young man he farmed on Banks Peninsula, and he always said that to stop the erosion, NZ’s steeply folded major catchments would need to be reforested in native bush.
The destruction of Aotearoa-NZ's dense, multi-story, water retaining native forest in order to plant pasture, led to a massive loss of top soil as rains eroded the bare tops of steep land. (1) This sort of erosion resulted in the silt laden flooding that has occurred before in exceptional rains in places like the Esk Valley.
What we now know, or should, is that these once exceptional rains are now happening frequently.
Pinus radiata grows faster in NZ than anywhere else on the globe. Historically, mass planting of it and other exotics was done by the state to stabilise areas of land exposed to erosion by earlier native forest clearance, and on so-called marginalland as job creation schemes during the Great Depression.
The planting to stabilise eroding catchment areas staved off the erosion problem for a time until, as happens with all mass commercial planting, the trees reach harvesting stage, and are clear felled.
What was not known then, and is seldom commented upon even now, is the fact that pine trees give off large amounts of gases containing alkaloids which have the useful by-product of making the area around the trees hostile to other plant species.
When these gases react with the sort of airborne artificial chemicals produced by human activity, they create toxic biogenic particles which "are chemically transformed by free radicals after they are first formed in the atmosphere."
The greater the numbers of pine trees there are combining with airborne artificial chemicals from human activity, the worse this aerosol pollution will be, and it can travel for hundreds of kilometres on the wind, and is not just harmful to human beings. (2)
To allow access for the giant trucks and other huge machines on which commercial forestry depends, roads are carved out which, on steep land, become water courses and add to erosion.
Clear felling is carried out even though not all trees will be ready or suitable for harvest. Clear felling is purely for industry convenience. The only logs that are wanted are those of a certain range of diameter, straightness, and length. All others and the tops of the trees, roots, side branches, bark etc are left as waste.
Screenshot of part of the Esk River catchment from Google Maps
Areas are cleared in the forest for the processing and stacking of logs, and the slash is rowed up, or pushed into heaps. When water rushes down off the bare hillsides in heavy rains, it takes with it vast amounts of this debris – combining with loose rock and top soil into a literal lahar.
The destructive force of a heavily silt laden river is bad enough, add rock and wood and it becomes the sort of monster we have recently seen devastate parts of Hawkes Bay.
The forest floor in a commercial pine plantation is a desert because dense pine forest is inimical to most other plants species, and to native birds. One plant that can co-exist with pine if there is enough light, is gorse – one of the most invasive noxious weeds in NZ. Gorse also grows here faster than anywhere else and it can seed up to three times a year. When the pines are felled, before any new planting can be done, plants like gorse take off.
Far more of the alkaloids pine releases when it burns are produced in cooler, smouldering fires such as you might see in a controlled burn or in the burning of slash, which brings me to the question of how the industry ought to dispose of its monumental amounts of waste.
I’ve read some stupid, politically motivated posts on social media from people claiming that the burning of slash was stopped in the 1980s because of pressure from environmentalists. Given these people cannot envisage the possibility of forestry corporations being expected to invest in other ways of disposing of their waste, they conclude that the destruction we saw last week was caused by "greenies and lefties". (3)
The issue of carbon emissions from huge fires aside, those who think burning forestry slash is a problem-free solution should address themselves to the other potential adverse effects of the practice.
You either leave the slash to dry out, which creates a flood and fire risk while it’s drying, or you burn it green, which means it smoulders possibly for weeks, and as stated above, green pine burning at lower temperatures produces larger amounts of toxic alkaloids. So, if it's burned when still green, there will be an increase air pollution.
If it's left to dry, even if rains like the ones we saw last week don't occur, there's an increased fire risk given these huge piles of slash can smoulder for weeks and possibly months, and be reignited in dry and/or windy conditions. (4)
The fire risk is exacerbated by the fact that even if it’s quickly replanted, other plants which tolerate the wasteland created by densely planted pines will have started growing. The most prolific of these is gorse, which is both highly invasive, difficult to eradicate, and highly flammable even when young and green.
Recently, as part of the emissions trading scheme, the planting of massive pine forests has become doubly attractive to corporations, both as a longer term cash crop and to create carbon credits. Moves by the NZ Labour government to remove such forests from the ETS were blocked by the forestry lobby. Māori especially objected, claiming it could cost the Māori economy billions of dollars given Māori are major forest owners (they will own 40% once Treaty settlements are completed), and make up around 40% of the forestry workforce.
Environmental activists who are calling for an end to dirty dairying must also face the realities of filthy forestry, especially when mass planting of pines under the ETS moves from forestry on marginal land to planting on productive farmland, and if bad forestry management practices result in more disasters such as the one we have just seen in Hawkes Bay.
Notes:
1. NZ always has and continues to lose top soil at one of the highest rates in the world. For an economy that depends on agriculture and viticulture, that’s several stops past Stupid and Unsustainable.
2. Aerosol pollution is unquestionably deadly; in the United States alone it kills more than 50,000 people each year.
3. This is on a par with right wing radio hosts using the cyclone as a political weapon with which to beat the government, and appealing to those people who are already convinced the country’s “going down the woke toilet”, we have lost resilience, etc etc. Arguably the least “resilient” people in the country riding their political high horse was a sight some of us will never forget or forgive.
4. A man who had a huge macrocarpa tree on the boundary with a property with extensive native plantings, created a stockaded area under the tree from old dry wood from conifers in his shelter belt. Unbeknown to his neighbours, he build a campfire under the tree, with a tripod for his billy and he’d go down there and make himself a cup of tea. The region had a few days of gale force nor’westers, which, unusually and fortunately for the neighbours, had dumped a lot of rain. In a break in the gales, even though more were predicted, the man decided to light his campfire and boil his billy. Having doused the fire, he went back indoors. The wind picked up again and his neighbours looked out a while later to see smoke on their boundary, then saw the flames race up through the huge tree. The fire the man thought he had totally doused had enough life in it for a damp nor’wester to reignite it, and blow burning embers into the dry wood of his stockade which burst into flames and set fire to the tree. The fire burned fiercely enough to kill the huge old tree, melt fence wires and burn deep into fence posts. Fortunately, the volunteer fire brigade put it out before it could travel downwind into neighbouring properties.
