In the Chronicle on June 16, an article says that Shane Jones and Horizons are planning to plant millions of exotic pine trees on "erosion-prone" land. I believe this would be an ecological disaster and beg them to consider my findings.

I am retired on my Whanganui lifestyle block. The surrounding hills were planted about 70 years ago with exotic pine trees. I managed to get many of these unstable and dangerous trees felled and cleared before I developed the property.

But still many pine trees that remained have hampered my efforts to restore the block to an ecologically stable and natural landscape.

Some of the problems that I have seen and experienced are that pinus radiata, (the most common of the exotic pine species) sheds massive quantities of toxic debris (pine needles, cones, pollen etc.) that smothers all other fauna except their own seedlings.

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Their pollen (which is unattractive to bees) travels for great distance and causes major problems to water systems. Radiata seedlings quickly outgrow other species (even gorse) and in 6 months can be 1m high on inaccessible hill faces.

This species can suck up all available moisture and store it in its own canopy to prevent other species growing.

Pine timber when harvested, rots very quickly unless treated with toxic anti-fungal/insecticide solution immediately. It must then be treated with even more dangerous chemicals if it is being used for fencing or building material. Large areas contaminated by arsenic are thought to be caused by these timber treatment processes.

Now 45m high, exotic pine trees screen many hilltops causing loss of vision and life-giving winter sun. Fire is a natural cycle for these trees in their native habitat, and they can actually create fire hazards to remove their opposition.

Many older trees carry unstable, high, heavy branches, making them dangerous and expensive to fell. Their roots can travel large distances and form "jacking pads" that can destroy concrete foundations weighing several tons.

Old dying pine trees on fragile land leave 100mm diameter roots that have penetrated down 10m into the sub soil. These quickly rot to channel storm water into the subsoil which can cause major slips taking out whole hillsides. This happened on my block several years ago, taking out a 0.8ha native forest and depositing the topsoil in the Whanganui River.

These are some of the dark sides I have experienced with these northern imports.

Hundreds of millions of years of natural evolution designed native coniferous trees specifically for our unique island continent. These include rimu, totara, kahikatea, miro and others.

These podocarps have many advantages over exotic pines, like their ability to bear fruit that feed our native fauna. These, plus of course kauri and other native plants and trees, have evolved erosion prevention abilities for our soils in our climate. In my 18 years of bush farming experience, native landscapes are not a fire hazard like pine trees are.

Our early governments decided to replace our native trees with exotic pine trees, against nature and documented scientific advice. And 250 years later we have increasing damage to our environment, flora and fauna.

Let us now try trusting science and nature and control the planting of these dangerous species.