Fire an opportunity for natives
AFTER a fire tore through more than 300 hectares of South Island vegetation last week, scientists say there is a brief window to take action before an inevitable reinvasion of exotic pines.
The fire last week near Flock Hill, not far from Arthur’s Pass, burned for days while the Department of Conservation and firefighters tried to get it under control.
Much of the vegetation that was burnt through was covered with wilding pine – a catch-all name for pine species escaped from plantations.
Landcare Research plant ecologist Peter Bellingham said that without intervention, those pines would re-establish following the fire.
Before humans arrived in New Zealand, fire was a rare occurrence. The main ignition source would have been lightning, which Bellingham said was mostly ‘‘wet’’ (it came with rain) and concentrated off the west coast of the South Island, where it wouldn’t ignite dry vegetation.
That means few of our plant species have adapted to the presence of fire, in stark contrast with exotic species like pine, which are equipped to deal with, and even thrive in, frequent fire.
Bellingham said the South Island high country landscape that we’re familiar with now was not what would have been found when humans arrived about 800 years ago.
‘‘Fundamentally we know from pollen cores not far away from [Flock Hill] at Cass, mountain beech was the predominant tree.’’
Right up to the tree-line, the alpine valleys of inland Canterbury would have been dominated by mountain beech for at least 7000 years.
Native beech could take on almost any type of disturbance you could throw at it, Bellingham said, including earthquakes and landslides. But not fire. That went for most of the New Zealand flora. It hadn’t had to adapt to fire, so most hadn’t.
So within 100 years of human settlement, the dry parts of the routes Maori were taking between Canterbury and the West Coast were burnt.
‘‘In short, that area was naturally forested,’’ Bellingham said, although people are rather sentimental about the alpine tussock landscape that now predominates. Fellow Landcare Research ecologist Larry Burrows said there was a history of plant introductions around Flock Hill. ‘‘It’s not only pines, there are eucalypts there as well.’’
That equated to a ‘‘huge amount of extra fuel’’ for when a fire did ignite.
Landcare Research plant ecologist Dr Duane Peltzer said the locally-common lodgepole pine, Pinus contorta, would thrive after the fire.
It had serotinous cones which remained ‘‘glued’’ together until extreme heat melted the resin and released the seeds.
The Flock Hill fire would provide a boon of lodgepole pine seeds and Peltzer said that meant one thing – lots more lodgepole pine in years to come.
What’s clear about the Flock Hill fire is that it isn’t a clean slate. There might be a brief window to make a decision about whether we should intervene and try to push the ecosystem back to something more natural – but it’s not clear what that would be.
It may be that the land is topdressed and put back into grazing, which would suppress the regrowth of wilding pines.
Trying to coax it back into native forest would be a long game and it’s unclear whether it would be feasible.
Or we do nothing, and in a few years time wilding pines will crop up and start the cycle all over.
Given residents at Castle Hill had an evacuation plan ready to go, there’s something to be said for controlling vegetation as part of overall fire management plans.