In February 2023, Cyclone Gabrielle tore through New Zealand's North Island, killing 11 people and causing an estimated $13.5 billion in damage. The storm exposed a deadly consequence of the country's forestry practices: massive quantities of logging debris, known as slash, that transformed hillsides into weapons.

Woody debris from harvested pine plantations swept down hills, blocked rivers, destroyed homes, and killed people. The images were apocalyptic: entire valleys choked with timber, houses crushed by walls of wood and mud, communities cut off by debris-blocked roads.

The government promised reform. New research published in The Conversation shows little has actually changed.

What Is Forestry Slash?

Forestry slash is the branches, bark, and offcuts left behind after trees are harvested. In New Zealand's pine plantations, which cover over 1.7 million hectares, the standard practice has been to leave slash on hillsides where trees were cut. The industry argues this helps prevent erosion and returns nutrients to the soil.

But during extreme weather events, that debris becomes deadly. Cyclone Gabrielle demonstrated what happens when heavy rainfall mobilizes thousands of tons of wood sitting on steep, unstable slopes. The slash doesn't just wash away; it accumulates mass and destructive power as it moves downhill, picking up soil, rocks, and more debris.

In Tairāwhiti (the Gisborne region) and Hawke's Bay, two areas hit hardest by the cyclone, the damage from forestry slash was catastrophic. Entire river systems were transformed. Infrastructure was destroyed. People died.

Mate, Cyclone Gabrielle was New Zealand's most expensive natural disaster. The forestry industry turned it into something worse.

The Promise of Reform

In the cyclone's aftermath, the government established inquiries and promised stricter regulations on forestry practices. The industry pledged better management of slash. Regional councils talked about new rules for harvesting on steep slopes.

Two years later, researchers have found limited evidence of meaningful change. The same practices that contributed to Cyclone Gabrielle's destruction continue across much of the country's plantation forestry sector.

The research points to several factors: weak enforcement of existing regulations, industry resistance to costly changes in harvest practices, and the simple reality that much of New Zealand's plantation forestry is on steep, erosion-prone land where managing slash is difficult and expensive.

Climate Change Amplifies Risk

This isn't a problem that's going away. Climate projections for New Zealand predict more frequent and intense rainfall events, exactly the conditions that mobilize forestry slash. The country is effectively locked into a cycle: extreme weather events expose the risks of current forestry practices, the government promises reform, limited changes are implemented, and the next storm arrives before fundamental problems are addressed.

New Zealand has about 500,000 hectares of plantation forestry on highly erodible land. Much of this is due for harvest in the coming decades. Without significant changes to how slash is managed, future storms will likely produce similar disasters.

The economics complicate reform. Removing or burning slash adds substantial costs to forestry operations. In a sector where margins are often tight and operators are competing with international timber prices, those costs can make operations unviable. Many forestry companies have argued they can't afford the changes being proposed.

Who Pays for the Damage?

This raises a fundamental question: who should bear the cost of preventing forestry-related disaster damage? Should it be the industry, which profits from the timber? Should it be the government, which zones land for forestry and issues harvest permits? Or should it be communities and taxpayers, who currently foot the bill for cleanup and rebuilding after disasters?

Cyclone Gabrielle's damage bill was $13.5 billion. Much of that cost fell on the government, insurance companies, and uninsured property owners. The forestry companies whose slash contributed to the damage faced limited liability.

Some have argued for regulatory changes that would make forestry operators strictly liable for slash-related damage, similar to how polluters can be held liable for environmental contamination. Others propose restrictions on harvesting in high-risk areas or mandatory slash removal requirements.

But two years after the worst disaster in New Zealand's modern history, these remain proposals, not policies.

The Next Storm

The research is a warning. New Zealand knows forestry slash poses severe risks during extreme weather. The country knows climate change is making extreme weather more frequent. It knows where the vulnerable areas are and which practices need to change.

What it hasn't shown is the political will to force those changes before the next Cyclone Gabrielle arrives.

Mate, climate disasters are getting worse. The country hasn't learned from the last one.