Pine trees pervasive and major eco threat – study
A new study has found radiata pine trees are pervasively invading New Zealand’s natural ecosystems and more work is needed to stop them spreading.
The study suggested a levy on new non-native conifer plantations would help pay for the costs of managing invasions.
The researchers, led by Dr Peter Bellingham of Manaaki Whenua Landcare Research, also suggested stricter regulation is needed to protect vulnerable ecosystems.
The study was done to test the commonly held theory that radiata pine is a minor invasive species in New Zealand, as debate rages about whether the trees are a viable part of the Emissions Trading Scheme or should be cut down and replaced with natives.
The modelling showed up to 76% of New Zealand land is climatically capable of supporting pine trees, and data from the National Vegetation Survey showed the trees are growing far more widely than previously appreciated.
Radiata pine has mainly invaded grasslands and shrublands but also some forests and at least three naturally uncommon ecosystems – geothermal, gumlands and inland cliffs – which are home to more rare species.
Because of their rapid growth and flammability, the trees are likely to alter naturally uncommon ecosystems and to drastically alter forest regeneration, the paper said.
Professor Euan Mason, from the New Zealand School of Forestry at the University of Canterbury, said the researchers did a good job identifying where radiata pine would grow and when it is a wilding problem.
‘‘Ability to grow and ability to reproduce are not the same thing, however,’’ he said.
Natural regeneration of radiata pine was restricted by frost – much more severely than other problematic species such as lodgepole pine, Corsican pine, Douglas fir and Scots pine – and high grazing often kept it in check on unforested, lower elevation, warm, wet sites, Mason said.
He agreed that people who planted trees that reproduced as wildings on neighbouring properties should be held responsible for the control of those wildings but he thought a levy on the whole non-native conifer industry would be unfair.
Meanwhile, the National Wilding Conifer Control Programme is helping remove wilding pines in areas like the Far North – where pines mature at five years old and cost 30% more to control each year they are left to grow.
The study – The right tree in the right place? A major economic tree species poses major ecological threats – was published in the journal Biological Invasions earlier in August.