Planting native trees capital idea for Kiwis

David Scoullar

For years I've stuck up for planting native trees over introduced species and now a reason I hadn't thought of to bolster my advocacy has come to light - they stand up to our climate so much better.

Outgoing Director-general of the Department of Conservation Al Morrison gets the credit for helping my case. Following the violent southerly storm which battered Wellington in June he wrote an interesting article in which he said this natural disaster had provided a "first-hand lesson in the value of native natural capital".

Thousands of trees were blown down - and those which caused the most damage were exotics - species such as pines, macrocarpa, eucalyptus and poplars - trees that were brought here.

Morrison concedes that common natives, such as pohutukawa and ngaio, also suffered but compared with their imported counterparts they largely stood their ground. He offers a simple reason for this: macrocarpa, pine and poplars are not evolved for our climate or our landscapes. Our natives are made in New Zealand. They have developed over hundreds of thousands of years to withstand our storms.

In coastal environments, native trees don't tend to grow straight and tall, they are adapted for our soils and, more often than not, their root systems cling on, he notes. They tend to provide protection as opposed to threatening damage.

"Start adding up the bill from exotic plantings and it doesn't take long to see there is ... value in retaining our natives," Morrison concludes. "Economists have a term for this value, they call it 'natural capital'. It's the value that a healthy, natural environment delivers.

"Look after your native natural surroundings and you build your environmental resilience and increase your stocks of natural capital. Alter that natural environment and you will inevitably have to pay the cost."

Scientists tell us that New Zealand's plant forms and lifestyles spring from protracted lonely ocean voyages and, more recently, a land regularly reshaped by earthquakes and volcanoes.

Our plants have evolved within a temperate but very windy climate that can also, at times, be very cool, on land masses assailed in spring by northwesterly gales from across the Tasman Sea and in winter by freezing polar blasts from the Antarctic.

Long geological isolation means that most flora is unique. Our native trees and forests look, smell and feel like no other forests.

A wide variety of native trees are adapted to all the various micro-climates with the native bush (forest) ranging from the subtropical kauri forests of the northern North Island, temperate rainforests of the West Coast, the alpine forests of the Southern Alps and Fiordland to the coastal forests of the Abel Tasman National Park.

The New Zealand Plant Conservation Network has published a list of indigenous vascular plants, including all 574 native trees and shrubs. This list also identifies which trees are endemic and which are threatened with extinction.

So if you're on the point of planting a tree on your property, think about a native and preferably one with flowers or berries that will attract birds.

As a footnote to this rant, I visited the stopbank near the Imlay works recently. When this was built, I lamented that extensive native plantings in the area would be lost but a Horizons spokesman responded that these would be replaced. They were, but what a sad lot they are.

Many of the natives have died and some survivors are struggling.

Not a good look. It appears some new plants have now been put in, but a huge effort is needed to really beautify this area.

David Scoullar is a keen tramper and conservationist and member of the Te Araroa Whanganui Trust