New national forest biosecurity surveillance system

Biosecurity officials report an average of three new pests and diseases establish in New Zealand every year. Understanding how exotic species make their way here is the best chance we have to detect and eradicate them before they can become permanently established. New Zealand’s new national Forest Biosecurity Surveillance (FBS) system has been designed by identifying high biosecurity risk areas for the introduction of overseas tree pests and pathogens.

Work to overhaul the existing forest health surveillance system and develop the new national forest biosecurity surveillance system began in 2015.

Using a new model, a team from Bayesian Intelligence and Scion has addressed the risk of biosecurity incursion across seven import pathways (sea vessels, used vehicles, used machinery, sea containers, wood packaging, wooden furniture, live plants), and the movement of people.

The new model estimates the relative probability of introduction of a selection of potential invaders at main entry points such as sea and airports, and all other locations in New Zealand. These ‘introduction risk’ probability maps are in turn used in an optimisation model, co-developed by AgResearch and Scion scientists, which works out the best allocation of surveillance effort. For any defined budget, the optimisation process defines which types of survey should be performed within each area, and what resources should be allocated to maximise detection efficiency.

Insect species transported as eggs or pupae, which can remain undetected and survive during long distance transportation, represent significant biosecurity threats. For example, the gypsy moth family has members of high-concern to forestry. They are not yet established in New Zealand, but the moth egg masses are regularly intercepted at our borders.

The model estimated the risk of introducing this pest via each of these pathways (cars, containers, sea vessels), taking into account the volumes and spatial redistribution of items transported, as well as their estimated rates of infestations. Overall, it estimated that the probability of egg hatching, and the escape of caterpillars, is principally at ports, followed by critical locations in the container pathway (such as container cleaning sites) and the imported cars pathway (car registration sites and car yards).

This new pathways-based approach to biosecurity risk evaluation and surveillance is a departure from the traditional view that tree health surveillance should be conducted in the forest. The new model recommends that 90 per cent of surveillance efforts should be focused on urban and peri-urban areas, however the data that went into the model did not cover all pathways and some surveillance effort will also go into monitoring the forest estate. Following these recommendations, the team has carried out a feasibility trial and completed a five year plan for rolling out surveys on a fully operational nationwide scale.

David Cormack, Chair of the Forest Owners Association Forest Biosecurity Committee, says, “The forest industry has been surveying its estate under the Forest Health Surveillance system since the 1950s to detect new pests and pathogens, monitor forest health and provide trade assurances. The Forest Biosecurity Surveillance system is specifically designed to detect harmful pests and pathogens early enough so that eradication is still an option, rather than long-term management.

“We have confidence in the science and look forward to rolling out the FBS over the next few years.”

Collaborators: CEBRA, Bayesian Intelligence, AgResearch, Ministry for Primary Industries, Forest Owners Association
Investment: Ministry for Primary Industries, Forest Growers Levy Trust, Strategic Science Investment Funding, Better Border Biosecurity