Waihi North Project: Assessment of Terrestrial Ecological Values & Effects 62138 WNP AEE 11 3.2.2 Revisions to the conservation status of formerly ‘Not Threatened’ Plants In 2018, several plant species in New Zealand and which have representatives in the SNA area underwent significant conservation status changes, from ‘Not Threatened’ to ‘Threatened- Nationally Vulnerable’ and ‘At Risk- declining' (de Lange et al. 2018). The rationale for these changes was driven by the recent emergence and spread of two serious, infectious diseases that affect Myrtaceae (Myrtle) plants (Myrtle Rust) and kauri trees (Kauri Dieback). There is currently no known effective treatment for infected plants. Different Myrtle species are considered to have different susceptibility to Myrtle Rust disease and patterns of infection and decline overseas suggest that the full impact of this disease has not yet been realised in New Zealand. Therefore, a precautionary approach was taken in the threat classification assessments to include all Myrtle species in New Zealand (de Lange et al 2018) where the other usual criteria for inclusion are not meet. Myrtle Rust has been found throughout most of the North Island now, and across the top and on the west coast of the South Island. It is recognised that there is resistance in NZ Myrtaceae. In May 2018 the New Zealand biosecurity response was closed. Given the widespread distribution of the disease, targeted surveillance and control activities have ceased and there is no current evidence of largescale dieback in the Myrtaceae (MPI 2018). The implications of this conservation status change are that widespread and common species, such as kānuka and mānuka (typically dominant components of regenerating ecosystems and planting mixes), are attributed a very high value (e.g. EIANZ 2018) and their occurrence causes a technical “significant” classification under most district or regional plans according to the Resource Management Act 1991 (RMA) (e.g. criterion 3, Section 11A, Waikato RPS). This is not consistent with valuations of common, robust species. Species identified from SNA 166 that are affected by these status changes are mānuka (Leptospermum scoparium), kānuka (Kunzea robusta), all rata (Metrosideros spp), pōhutukawa (Metrosideros excelsa) . All of these species were assessed as ‘Not Threatened’ prior to 2018 (de Lange 2013) because they were, and still are, widespread within their natural ranges (e.g. Waikato Regional Council considers > 30% of mānuka / kānuka scrub to remain in the region and > 20% of this habitat type lies in protected sites). Kānuka, mānuka and kauri, in particular, form components of selected planting mixtures throughout the Waikato Region and within the WNP area. Contrarily, kauri systems are clearly threatened by kauri dieback disease. Kauri dieback is caused by a fungus-like organism, called Phytophthora agathidicida (PA), that lives in the soil and infects kauri tree roots, causing infected trees to starve to death. There is currently no known cure for the disease. Unlike kānuka and mānuka, kauri are neither “common and robust” nor early successional. 3.2.2.1 Approach to valuation and assessment of effects Myrtle species are identified in this assessment where they occur and their value is acknowledged according to their abundance, potential function and condition in the sites they are found. However, the approach taken with respect to valuations and corresponding effects assessments, whereby single specimens (including kauri) that are not components of naturally occurring populations (as determined by presence of other individuals or seedlings in the surrounding area, or where they are components of planting mixtures) or where the species is particularly widespread and abundant throughout their natural range (kānuka, mānuka, pōhutukawa), are noted on the basis of their status (de Lange et al. 2018) but will not, in this assessment, trigger the rare (threatened) RPS criterion, or the higher values threshold in the values assessment of the EIANZ (2018). This approach is consistent
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