By Mark Bloomberg*
The severe impacts of Cyclone Gabrielle on the North Island, and the five severe weather events experienced by the Thames–Coromandel region in just the first two months of 2023, are merely the latest examples of more frequent erosion-triggering rainfall events over the past decade.
Inevitably with the heavy rain, soil, rocks and woody material (also known as “slash”) from landslides have flowed down onto valleys and flood plains, damaging the environment and risking human safety.
Clear-fell harvesting of pine forests on steep erosion-prone land has been identified as a key source of this phenomenon.
So we need to ask why we harvest pine forests on such fragile land, and what needs to change to prevent erosion debris and slash being washed from harvested land.
Pine was a solution
Ironically, most of these pine forests were planted as a solution to soil erosion that had resulted from the clearing of native forests to create hill country pastoral farms.
The clearing of native forests happened in the 19th and early 20th centuries, but the consequences – erosion, flooding and floodplains covered in silt and rocks – only became apparent decades later.
Research has shown that pastoral farming on our most erosion-susceptible soils is not sustainable. The productivity of the land is being degraded by loss of soil and large areas have been buried with sediment eroded from hill country farms upstream.
So the need to reforest large areas of erosion-prone farmland is scientifically well accepted.
Why pine?
But why did we choose radiata pine for our reforestation efforts instead of other tree species?
Even today, it is hard to find affordable and feasible alternatives to radiata pine. Affordable is the key word here. We are not a rich country and our liking for “Number 8 wire” solutions makes a virtue out of necessity – we don’t have the money to pay for anything fancier.
Radiata pine is a cheap and easy tree to establish and it grows fast and reliably. Planting native or other exotic trees, such as redwoods, is possible, but it costs more and needs more skill and care to grow a good crop.
'Has to be done': Forestry industry under fire as McAnulty calls for slash to be investigated https://t.co/7lx5G2t07W
— Newshub Politics (@NewshubPolitics) February 14, 2023
The problem with radiata pine is that if grown as a commercial crop, it is clear-fell harvested after about 28 years.
The clear-felled land is just as erosion-prone as it was before trees were planted – with the added threat of large amounts of logging slash now mixed in with the erosion debris.
It can take six years or more after harvesting before the replanted pine trees cover the ground and once again provide protection to the soil.
Benefits of pine come with a cost
If we take a long-term perspective, research shows that even a radiata pine forest that is clear-felled once every 28 years will still significantly reduce erosion, compared with a pastoral farm on erosion-prone hill country.
This is because the erosion from the clear-felled forest is outweighed by the reduced erosion once the replanted trees cover the land.
However, this is not much comfort to communities in the path of the flood-borne soil and logs from that clear-felled forest. It’s difficult to take a long-term perspective when your backyards and beaches are covered with tonnes of wood and soil.
Slash a byproduct of efficiency
Whatever benefits radiata pine forests bring, we need to transition forest management away from “business as usual” clear-felling on erosion-prone hill country.
This transition is possible, but one important problem is not often discussed. The pine forests are privately owned by a range of people including iwi, partnerships made up of mum-and-dad investors and large international forestry companies.
All these people have created or acquired these forests as an investment.
A typical pine forest investment makes a good financial return, but this assumes normal efficient forestry, including clear-felling large areas with highly-productive mechanised logging gangs.
It has become clear that we need to manage forests differently from this large-scale “efficient” model to reduce the risk of erosion and slash from erosion-prone forests. Changing how we manage these forests will inevitably reduce the economic return, and forest investors will absorb this reduction.
When a cyclone bears down on the East Coast, it’s not just wind and rain residents brace for. https://t.co/h9TJr3Q2dv
— Stuff Business (@NZStuffBusiness) February 15, 2023
Time for a permanent fix
If we go back to when the pine forests being harvested today were planted, the forests had a social value – not just in reducing erosion but in providing employment in rural areas where few jobs were available.
This social value was recognised by government funding, initially through tree planting by a government department, the NZ Forest Service. With the rise of free market economics in the 1980s, such direct government investment was considered inefficient and wasteful.
The Forest Service was disbanded in 1987 and its forests were sold to forestry companies. However, the government continued to promote tree planting on erosion-prone land with subsidies to private investors.
As these forests grew, they came to be considered purely as business investments and were bought and sold on that basis. When the time came to harvest the trees, the expectation was that these could be clear-fell harvested in the same conventional way as commercial forests growing on land with no erosion risk.
As erosion started occurring on the harvested sites, it became clear why these trees were originally planted as a social investment to protect the land and communities from soil erosion.
Aotearoa New Zealand has achieved control of erosion with a Number 8 wire solution- encouraging private investors to grow commercial pine forests on erosion-prone land. The problem with Number 8 wire solutions is that after a while the wire fails, and you have to find a permanent fix.
Conventional commercial pine forestry was a good temporary solution, but now we need to find a more sustainable way to grow forests on our most erosion-prone lands – and it won’t be as cheap.
*Mark Bloomberg, Adjunct Senior Fellow Te Kura Ngahere – New Zealand School of Forestry, University of Canterbury. This article is republished from The Conversation under a Creative Commons license. Read the original article.
56 Comments
Nope, just another one created, and one unresolved.
This is a good article. Diversification, selective-felling and continuous rotation, plus permanent forest (mostly but not necessarily all, native) are up for discussion. I made the mistake of mono-cropping when planting, 28 years ago. Not pine, but still.... Nowadays, I'd mix it up. Sure, less money because of the harvest not being efficient, but money is worth what, exactly? compared to topsoil retention, slower run-off, wellbeing....
Pyrolyse the slash, use the biochar as a biocatalyst for local industry or for permanently improving the soil, use the excess heat for whatever local use, or heating the next load of wood.
A biochar making, electricity producing PowerPallet would be valuable in Tairāwhiti right now.
Better than burning, which only leaves ash and pollution.
Then replant in a perennial polyculture - native or cropping plants, take your pick.
Then read The Carbon Farming Solution to see what else you can do
The current ETS favours Pinus so whilst Natives and other species provide a greater diversity without incentives clear felled pines may simply not be replaced and greater issues created. Govt needs to talk with Forestry owners/investors and the Harvesting industry to come up with practical solutions.
"it is hard to find affordable and feasible alternatives to radiata pine. Affordable is the key word here. We are not a rich country and our liking for “Number 8 wire” solutions makes a virtue out of necessity – we don’t have the money to pay for anything fancier."
Yet oddly there's always money for pollies favourite pork barrel. What it should say is "in spite of destroying old growth forest for a brief period of privatised farming profits, we couldn't be bothered prioritising the retention of our one off top soil endowment"
Pinus radiata the cheap option? Well quite obviously not.
I really don't understand the need for government to underwrite business returns that we seem to have a penchant for. Trees were planted, forest bought and sold, situations change, that's a risk. A forest may have been worth $millions on 1/1/2023 today it maybe a liability.
Perhaps native regeneration will be slower but in the long run I'd see it as far superior let alone the longterm carbon credit income.
Redcows - check out the carbon look up tables on MBIE website to see the difference between Pinus and all other species and not the regenerating bush is the slowest sequestrator and has little to no value commercially. Th ere answers but that requires lawmakers to listen to those who understand the problem and what practical solutions are possible - I live in hope not expectation.
My Letter to the mayor of Gisborne in January. Too late to be of any use in this situation but they need to be stopped now and made to clean up their mess and only allowed to resume if and when they can demonstrate safe environmentally sound processes.
Dear Mayor Stoltz
As most of the country is saying, the forestry slash and topsoil being washed down our rivers and onto our beaches from forestry operations is well beyond totally unacceptable and has now directly resulted in the death of a child. More will follow unless something very significant is done. I believe that the time is now well past when these operations must be stopped and the burden of responsibility shifted to operators to show that they can operate without any of these consequences.
I believe that the council is fully empowered to issue an abatement notice under section 322 of the Resource Management Act (appended). This gives the provision that an abatement order can be issued by your enforcement officers if in their opinion the activity is likely to be noxious, dangerous, offensive, or objectionable to such an extent that it has or is likely to have an adverse effect on the environment. If what we see happening does not meet these criteria, then I don't know what does, so you have an imperative responsibility to act accordingly.
Yours sincerely
That is for them to sort out. In the meantime they are out of business.
It is amazing what a bit of motivation can achieve.
If they cannot sort it then they are out of business permanently. Maybe somebody with a solution will come along and take the forest off their hands.
yes...all the unemployed could roam the hills and gather up sticks. Each day they could drop their sticks off at a large furnace where a steam engine is producing electricity for the mill.
The children take the sticks and split them with their adzes.
Inside the ladies are working with the flax that is delivered daily by the prison gangs.
Great idea, but at the moment isn't cost effective. Remembering that most forests are far away from any electrical loads.
Best solution would be use as biomass, but again at the moment there is no financial incentive to do so. When demand for biomass picks up (and it will) this should become more feasible.
Pulp logs only get $ 30 per tonne , but they still collect them , and take to mill. processing and transport costs need to be worker out .
Areas with large pine forests and no large hydro power nearby , i can think of Gisborne , Coromandel and Northland . All could have done with local generation lately. Schools and hospitals with boiler systems on a smaller scale.
Since commissioning the Ngawha geothermal generation expansion, the Far North of Northland has a surplus of electricity to its current needs. The problem here is downed lines in the distribution system. That is not uncommon, and is one of the factors why we have off-grid solar. When we moved here15 years ago electricity was less reliable than the third world countries that we had been working in during the previous 10 years, that and retail electricity cost being amongst the highest in the country.
https://www.stuff.co.nz/business/farming/131170132/fonterra-and-genesis…
Maybe difficult but maybe we will see.
There's a fairly powerful partial solution already in place... carbon credits.
If forest owners sell their credits then they are committed to either walking away from the forest, or harvesting and replanting.
On these more marginal lands it might just be easier on all involved to leave the trees standing and to make coin from the credits.
How about a managed forestry approach, but with emphasis on quality above volume and over a long term.
Propose for 200 ha of forest every year 1 ha of forest can be clear felled and replanted. Rotate through the whole thing over the 2 centuries till they get back to the start. This way native forests become commercially viable and the amount of clear fell is reduced sevenfold.
Way too long term. There's a struggle with 28 year rotation being to long.
But yes that is the answer, selective logging of native, expensive but longterm the only logical answer bar locking it up completely. West coast millers might be a tad angry at such a move.
Natives will never replace exotics as a reliable timber source. Quite simply they grow to slow. The reason pines became the prime timber source is their productivity.
NZ basically ran out of timber in the early 1900's hence the planting of exotics.
Pines are fine as a nurse crop for native in the right locations. Carbon capture will help pay for the retirement of erodible hill country.
Many hill farmers are approaching retirement and carbon is a good way to ease them out of unsustainable areas. Eventually the land could be donated to the state or local Iwi.
The only reason we can use pinus radiata to build is because we treat it with poison. The only reason we can export logs is because we treat them with poison.
The only reason we ran out of native is because we went all out sort term and exported all the good, actually, great stuff.
Coppiced woodland species and hybrid natives seem under investigated - worth thinking about. We've got to get around to getting out of pinus radiata. Probably needs regulation to specify what tree where when re-planting as well as no-fell zones for existing forest lots.
The problem in Gisborne is the massive long faces where if they are in grass have a enormous catchment area of runoff…trees slowdown runoff.
other issue in East-coast Gisborne is the distance from CNI pulp mills makes clearing broken - heads from felling uneconomic… the region needs a solution to either chip or make use of pulp-grade logs
If we want to use these fragile lands for commercial use, farming or forestry, we need a far more refined look at the land. Steep, skeletal soils staring straight into waterways should not have production pasture or production radiata. It's a challenge to work out what to do here, the same faced after Bola and essentially then radiata was the only option as the land bled like a seriously wounded soldier in triage, you had to do something fast. There's a lot of change happening but it will take a long time to bear results.
Much land, forest and farm, needs to be retired to protection forest, native and non radiata exotic (or carefully transitioned radiata). Permanent carbon is the only thing that offers a chance for many landowners to survive - effectively all of NZ pays by a carbon fuel levy - and stop the slash and soil erosion carnage.
Until farming and forestry accept this nothing will change. Going on the hatred trotted out re permanent forest on all sides I do despair at times for these landscapes and their communities.
How many more times are they washed away before they all go broke and all jobs and income with it in these areas.
Why does it have to be forestry. If government subsidy is the only way to make sustainable forestry viable on this country then why not subsidize sustainanable pastoral farming on this land .
Sustainable pastoral farming on this land might include planting natives in places like gullies and back faces. Subdivision and water reticulation on the better country (intensification) and low density poplar planting on the medium country.
It cannot just be locked up in carbon stores because one day it WILL burn. And the next flood after the great fire will make this look like a picnic.
Research why this was planted in the first place in pines. We are trying to sort out the damage from the native forest being removed here and elsewhere over the last 100 plus years.
Even then reports by geologists etc warned the hills would fall into the sea and rivers but we ignored science and reality.
There is no sustainable production landuse on much of this land and until we recognise this the same will happen.
Yes. I recall all the discussion post-Bola. Seems to me the immediate action to be taken regards this hill country erosion as a means to prevent further silting of freshwater sources while we work out what next for the land - would be to aerial spray all barren/exposed slopes with a fixing agent. Something that won't pollute the waterways below when run-off occurs during rainfall events, and which can be planted in (i.e., broken through easily) in future.
None really.
I don't know of any councils that have serious existing rules regarding waste (i.e., slash or site) management post-harvest.
If there are no regulatory rules, there is no liability under the RMA - and I doubt many consent conditions would be of help either.
section 322 of the Resource Management Act re abatement notices seems pretty all encompassing if the local bodies choose to invoke them. That is the problem isn't it, they will never invoke them against powerful overseas interests. If they did, what would the government do?
Do you think that an abatement notice could be used to require a landholder to remove slash from flooded areas/waterways that originated on their land? I think such a matter might be out of scope unless there are rules in plans that have been breached;
I suspect if that would require all the costs of slash clean up and bridge/fence repair to be borne by the forest-owner(s), then local authorities would have used that legal mechanism in the past.
Yes, it could. Not sure whether RMA s322 is the best/most appropriate legal mechanism, but I think both forest owners and the general public (incl. local and central government) realises that new rules/regulation regarding harvest are needed.
Central government can achieve a lot of these initiatives (i.e., temporary halts on harvest, building/re-building, etc.) using powers under the emergency management legislation.
I do think it makes good sense/regulatory practice to pause a lot of activities previously undertaken and/or presently underway until we have a handle on the current problems/situation.
For example, there is a lot of talk about whether this already consented housing development should be put on pause/hold;
As if there are "powerful overseas interests" that could control NZ Govt, that's a myth.
Quite simply forest has been harvested in an accepted way for years. Now erosion prone land is doing what it has always done and eroded.
Obviously forestry practices have to change in these areas. And change is happening. Second rotation forests will be planted differently with large set backs from water ways etc.
Same problems occurred late 1800's and early 1900's after massive areas of native vegetation was cleared for farms. every flood created huge amounts of debri in waterways and beaches filled with logs.
In my time the re
clearing of native vegetation in the late 70's and eary 80's for farm land created exactly the same senario of erosion and woody debri. Much of this land is now part of the million or so hectares that need to be retired.
The reality is much of this country should never have been cleared of native. Progressively we need to transition back to only native, permanent cover of steep erodible land. Continue to crop what is easily sustainably harvestable – but progressively, not clear fell complete hillsides. Do not burn – the last thing needed is more release of carbon. The slash left behind is very important organic matter for what comes next. Is there a cost – yes, one which land and forest owners must own. Thirty years ago I planted trees that with hindsight cannot be sustainably harvested – which I am now progressively poisoning. Stop right now carbon credits for pine forest (I have surrendered all my pine carbon credits – these are completely unsustainable). The answers are simple – stop whinging, no handouts, take responsibility, all land owners with steep erodible land need to get on with it
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