During Cyclones Hale and Gabrielle the poor management of exotic plantations in Aotearoa New Zealand — primarily pine — has again led to extensive damage in Tairāwhiti.

Critical public infrastructure destroyed; highly productive agricultural and horticultural land washed away or buried; houses, fences and sheds knocked over; people’s lives and dreams upended; people dead.

The impacts on natural ecosystems are still unknown, but there will have been extensive damage in terrestrial, freshwater and marine environments. Similar damage occurred during storms in June 2018 and July 2020.

• READ MORE: Cyclone Gabrielle triggers more destructive forestry ‘slash’ — NZ must change how it grows trees
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While heavy rainfall and flooded rivers are a major factor, it is sediment and slash from plantation harvesting that has been the cause of most of the damage.

Slash is the woody material (including large logs) left after clear-fell harvesting of commercial forests.

Landslides in harvested sites pick up the material and carry it downstream, causing significant damage. All the evidence from Cyclone Gabrielle shows that much of the damage was caused by radiata pine slash.

The legacy of poor land management
Sediment and slash from exotic tree harvesting sites were established as major factors in the damage that occurred during the June 2018 Tolaga Bay storm in recent court cases taken by Gisborne District Council.

Five plantation companies were found guilty and fined for breaching resource consent conditions relating to their management practices.

Multiple groups have called for an inquiry into the way plantation harvest sites are being managed in Tairāwhiti and elsewhere.

But given the severity and ongoing nature of these impacts, is it not time we move beyond focusing on management practices and address the broader underlying issues that have triggered this situation?

These ultimate causes are complex but primarily revolve around historic poor land management decision-making and human-induced climate change.

‘East Coast disaster’: Environmental group calls for inquiry into forestry practices https://t.co/pjTVIiy0Cf pic.twitter.com/MQYkVZCMAY

— nzherald (@nzherald) January 13, 2023

Among the key drivers of the current problems in Tairāwhiti are the large areas of exotic tree plantations that were established with government support after the devastation of Cyclone Bola.

But this devastation also reflects earlier poor land management decisions to clear native forest off steep, erodible hill country in the late 19th and early 20th centuries, which was also encouraged by the government of the day.

Looming climate change
The other underlying driver of the disaster is human-induced climate change. Atmospheric CO2 levels are now 150 percent above pre-industrial levels and climates are changing rapidly with new and unprecedented events becoming the norm.

While increasing global temperatures are the most obvious feature of human-induced climate change, it is the increasing frequency and intensity of extreme weather events that are having the biggest impacts on people and the environment.

It is essential that we hold the forestry sector accountable in Tairāwhiti and elsewhere. But we also need to urgently address the underlying causes because no matter how strict harvesting rules are, storm events are going to occur with increasing frequency and intensity.

Time for urgent action
With more than 40 years experience researching forest ecology and sustainable land management in Aotearoa, I believe there are four key areas where we need to urgently act to address these issues.

1. As a country we need to rapidly reduce greenhouse gas emissions and rapidly increase the draw-down of CO2 out of the atmosphere. These are national issues and not confined to Tairāwhiti but as a nation we seem to be sleepwalking in our response to the climate emergency.
2. We need a comprehensive catchment-by-catchment assessment across all of Tairāwhiti (and likely other areas of Aotearoa) to identify those plantations that are located in the wrong place in terms of potential harvesting impacts. There should be no further harvesting in Tairāwhiti plantations until this exercise has been completed. We also need to identify those areas that currently lack plantations but should never be planted in exotic tree crops (for any purpose).
3. The government then needs to buy out the current owners of these plantations and embark on a programme of careful conversion to native forest. This will come at a cost, but it needs to be done. We already have models for this in Tairāwhiti where the Gisborne District Council has started converting pine forests in its water supply catchment to native forests.
4. Finally, we need to establish substantially more native forests throughout all Tairāwhiti, and Aotearoa more generally, to help build resilience in our landscapes.

The consequences of short-term thinking
For too long we have been fixated in Aotearoa with maximising short-term returns from exotic tree crops without thinking about long-term consequences. The legacies of this fixation are now really starting to impact us as the climate emergency exposes the risks that poorly sited and managed exotic tree crops pose.

And we are now making the same mistakes with exotic carbon tree crops, again leaving unacceptable legacies for future generations to deal with because of a focus on short-term financial gains.

Exotic tree plantations have dominated forest policy in Aotearoa and we urgently need to shift this to a focus on diverse native forests.

Our native rainforests provide so many benefits that exotic tree crops can never provide.

They are critical for the conservation of our native biodiversity, providing habitat for a myriad of plant, animal, fungal and microbial species. They also regulate local climates, enhance water quality and reduce erosion. This helps sustain healthy freshwater and marine environments.

Native replanting initiatives championed by charities like Pure Advantage need to be the primary focus of forest policy in Aotearoa now and in the future.

Dr David Norton, emeritus professor, University of Canterbury.  This article is republished from The Conversation under a Creative Commons licence. Read the original article.

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.

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• Other Cyclone Gabrielle reports

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 licence. Read the original article.