Radiata pine a ‘pervasive and ongoing threat to NZ’

PROTECTING THE ECOSYSTEM: The modelling showed up to 76 percent of New Zealand land is climatically capable of supporting pine trees, only the very coldest and wettest areas are unsuitable. NZ Herald file picture

New research has found that invasive radiata pine is spread more widely across Aotearoa than was previously thought, with modelling showing that up to 76 percent of the country's land is climatically capable of supporting populations of the trees.

The researchers, led by Dr Peter Bellingham of Manaaki Whenua — Landcare Research, said their findings demonstrate “pervasive and ongoing invasion of radiata pine outside plantations”, with more work needed to manage current invasions and prevent future ones.

They recommend a levy on new non-native conifer plantations to offset costs of managing invasions, and stricter regulations to protect vulnerable ecosystems.

University of Canterbury lecturer in forest ecology Dr Sarah Wyse said the research paper was valuable, timely, and a much-needed review of the ecological threats posed by pinus radiata to many native New Zealand ecosystems.

“The authors phrase nicely that there is a view that (pinus radiata) is relatively unimportant as a biological invader.

“This view is likely to have arisen perhaps from an assumption that wilding conifers are an issue of the high country, where there are large tracts of vulnerable land,” Dr Wyse said.

“In such habitats other conifer species are indeed worse than radiata, being more suited to the climate and having been planted in abundance in those areas.”

She said radiata, in contrast, was often planted surrounded by landscapes that were less vulnerable to invasions, such as highly managed landscapes, farmland with high stocking densities, or native forest.

Based on what the authors illustrate, Dr Wyse said radiata certainly had the ability to pose a threat to vulnerable habitats such as sand dunes, gumlands, geothermal communities and systems in the early stages of forest successions (eg following a fire or other disturbance) if they were nearby.

“As the authors highlight, radiata is structurally and functionally very different from the native plants of the ecosystems or successional stages that it invades, and it is therefore likely to have considerable effects on the ecosystems and future forest successions.

“The work is likely a conservative estimate of the current and potential future situation.”

Dr Wyse said due to the nature of the modelling, which uses occurrence records of where the species has been recorded, they cannot overestimate suitable habitat, but are likely to underestimate it if locations where the species is present simply haven't been documented.

“Likewise, there may be other ecosystems impacted by radiata that have not yet been documented.

“I hope this work will encourage recognition that radiata is an invasive species in New Zealand, and that care and consideration needs to be given to the landscapes where it is planted.

“If we are to expand our radiata plantations, particularly for carbon sequestration, we need to be very mindful of the threats posed by the species to vulnerable ecosystems,” Dr Wyse said. “This work therefore provides much-needed evidence to help guide policy and management.”