Before planting, or replanting a commercial forest, you must assess the risk of conifer species spreading to land outside the forest site. Use the Wilding Tree Risk Calculator to assess the risk for your site.
On 25 June 2026, the updated Wilding Tree Risk Calculator came into effect. The updated calculator must be used from now on. We have removed the previous version from this page.
The paper worksheet and Excel spreadsheet step-by-step guides have been updated. They now include options for working out the windiness of a planting area if the Global Wind Atlas doesn't return a result.
The Wilding Tree Risk Calculator helps you assess the risk of planted conifer species spreading beyond a commercial forestry site.
Using the Wilding Tree Risk Calculator is a legal requirement under the National Environmental Standards for Commercial Forestry (NES-CF).
Find out more about the NES-CF
You must use the Wilding Tree Risk Calculator to assess the risk of wilding conifers spreading if you are:
You must get the assessment risk score no more than 8 months before you give notice to your local council for:
If your score is less than 12, planting or replanting is permitted. If it is 12 or higher, you need resource consent.
If you are replanting:
You’ll need to give the score and worksheets to the council to meet the NES-CF permitted activity conditions for afforestation and replanting on your site. There are other conditions you’ll need to meet for these activities.
Read more about this in the guidance:
National Environmental Standards for Plantation Forestry guidance
If you’re using the calculator to comply with the NES-CF, a suitably competent person must do the assessment. This means a person with:
The calculator and guidelines on how to use it are available below.
Wilding Tree Risk Calculator and guidelines [PDF, 1.5 MB]
Wilding Tree Risk Calculator worksheet only [PDF, 226 KB]
The guide below helps you do a wilding tree risk assessment using the calculator. It explains how to use the different tools needed for each step.
Wilding Tree Risk Calculator: Paper worksheet step-by-step guide [PDF, 3.3 MB]
The document below contains references to the published research used to support the calculator.
To help you use the Wilding Tree Risk Calculator, these tools are available.
You can use the Excel spreadsheet below to calculate the risk score.
Automated DSS1 Calculating Wilding Spread Risk From New Plantings [XLSX, 47 KB]
This guide helps you do a wilding tree risk assessment using the Excel spreadsheet.
Wilding Tree Risk Calculator: Excel step-by-step guide [PDF, 2.7 MB]
You’ll need to know how much of the land surrounding your planting site and the downwind land is covered by each land cover and land management type.
For the wilding tree risk assessment, the surrounding and downwind land is called the ‘receiving environment’. Downwind land refers to land in the direction the wind blows with the most force.
Find out how to get this information in the step-by-step guide.
You can use R script to identify the receiving environment for your site. There is guidance on how to do this in the step-by-step guide.
To use the R code, you’ll need RStudio. RStudio is a free, open-source Integrated Development Environment (IDE) designed for the R programming language.
Download RStudio here:
Download the R script:
R script for receiving environment [DOCX, 93 KB]
An updated Wilding Tree Risk Calculator came into effect on 25 June 2026. The main changes to the calculator are:
The previous version of the Wilding Tree Risk Calculator is no longer in effect and should not be used. You can download the previous version on the NES-CF website page, in the ‘Changes to the NES-CF’ section:
Development, reviews, and changes to the NES-CF
If you have questions about the NES-CF, contact Te Uru Rākau – New Zealand Forest Service:
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