Driving through the countryside, I have often wondered about the scorched earth look of the hillsides where pine forests have been harvested.

As mentioned by Dame Anne Salmond yesterday, poorly managed forestry is one of the industries that is impacting our waterways.

When this clear cutting of the Californian-native Pinus Radiata occurs, aside from making the landscape look like a desolate war zone, there can be many other problems that come from this industry that claims to be "saving the world one tree at a time" through their signage.

If you have done much diving around our shores, then you will be aware that after rain, it is usually impossible because the visibility is too bad. This is because sediment is washing down our waterways each time it rains and humans cause nearly all of it.


It is particularly obvious when you compare the turbidity (or clarity) of water that has come down from a native bush block to that of a forestry block. Heavy rain can pass through primary forest and you can still see underwater, but if you are in front of a slope that has been clear cut you may as well forget about going underwater.

Increased sedimentation from erosion is considered to be the leading global cause of water pollution. This can be a disaster for coastal and freshwater ecosystems. In the Firth of Thames, The Landcare Trust estimates that over 150,000 tonnes of sediment per year is threatening an internationally-recognised wetland system from the Waihou River alone (for those of you who have driven across the Kopu Bridge to get to Coromandel - it is the dark brown coloured river underneath).

Now don't get me wrong - planted forests can be a good thing generally for the environment if they are managed well and they are certainly not the only cause of sedimentation we have, but minimising the environmental damage of forestry requires robust rule-setting and enforcement when it comes to the high-impact stages of forestry, namely the road making and harvesting.

And before some readers dismiss this issue as "just another environmental problem that should be subservient to economic growth" please understand that erosion can (and frequently does) have a big impact on our pocket. When forests are clear cut the all-important layer of topsoil (one inch of which can take 500 years to form) gets washed down with the leftover wood. This means that water is able to pass straight through the damaged earth afterwards rather than being filtered and regulated by the topsoil and makes the land much more prone to flooding.

In fact in 2004 and 2005 serious flooding in Manawatu-Wanganui and the Bay of Plenty that was caused by erosion resulted in $198 million of taxpayer funds being provided to fix roads, bridges and for relief payments.

When I did an educational roadshow along the East Cape in the 2011 winter I saw it for myself. Hundreds of tonnes of "slash" had come down from the clear-cut forestry lands to litter the beaches (to the point that school children could hardly access them to remove the plastic with us) and destroyed the bridge in Ruatoria, costing the council a bomb. This issue is widespread in areas from the East Cape all the way down to the Hawkes Bay as the photo above shows.

The other lesser-known fact about our biggest introduced tree is that pines are extremely thirsty. The Ministry for the Environment confirms this in their current proposal to create a national environmental standard for plantation forestry. Only time will tell whether the effect of the Erosion Classification in this proposal will actually be to reduce the consenting fetters placed on forestry companies, several of which are wholly owned by overseas interests that couldn't care less about whether our waterways are impacted by sediment (or whether the odd worker dies during the extremely dangerous work), or actually afford the environment increased protection.

Before this proposal becomes law, perhaps the ministry and industry should have a think about our reputation overseas and look at complying with PEFC Certification the only entirely not-for-profit global certification system. This would ensure that we have rules in place that will "avoid the introduction of soil into watercourses" and no doubt do wonders for our export market to an increasingly connected and discerning customer.

Even better would be to look at Switzerland, who realise that the value of forests for watershed and erosion protection far outweighs their value to the community as sources of lumber. Understanding that the pastoral settlements and tourism activities below the forestry depend on clean water (just like in New Zealand) they maintain a continuous forest cover through single stem harvesting - where one tree is taken at a time and the growth of the neighbouring trees will close the gap.

Riparian planting can also help and perhaps such measures could be forced upon those companies that want to clear cut our countryside through this new proposal. This creates buffer zones that will trap and filter out a significant amount of sediment and hold together crucial areas to protect against erosion. The Canadian Journal of Forest Research has also shown that riparian buffers will also reduce the temperature in streams after harvesting which is also a very important ecological impact that needs to be minimised.

So what can we do about it?

Wood can still be considered a much more environmentally-friendly alternative to steel or masonry, which use far more energy to produce. The best choice is to look for demolition materials that have already been used - therefore reducing the overall footprint altogether. Failing that, check for timbers that have been certified and do a little research about what the certification actually proves. As purchasers and voters, we have the power to change the practices of producers and demand robust regulations. If we all were to exercise these rights together it will have a big impact for the better.