Heenan et al. (2024) on the basis of molecular data, used in isolation of other lines of evidence elected to treat all Aotearoa / New Zealand Kunzea as one widespread species K. ericoides. Their work did not consider the morphological and cytological disparity, nor the sympatry / syntopy between the species recognised by de Lange (2014), and the analyses used to derive their conclusions have been disputed by others as the authors did not pay attention to the cautions on the modelling and statistical analyses pointed out when using multi-coalescent theory (Sukumaran and  Knowles 2017).

The species is accepted by the New Zealand Plant Conservation Network (www.nzpcn.org.nz) and New Zealand Indigenous Vascular Plant Threat Listing Panel.

As defined here, Kunzea linearis is a tree with hairy (hairs copious, antrorse, appressed) dark green linear or filiform leaves, spicate racemes, linear or filiform pherophylls, narrowly lanceolate-acute, long persistent erecto-patent sepals, erecto-patent petals, and brown bark which peels into small, tessellated, semi-lunate flakes (de Lange 2014, 2023). The species is sympatric / syntopic with K. amathicola, K. robusta and K. sinclairii.

Kunzea linearis is a shrub or small tree, endemic to Aotearoa / New Zealand where it occurs on Te Ika a Maui / North Island, as well as a a few trees on offshore islands off of North Island. The total population size is estimated to be more than 100,000 mature individuals in situ. However over large parts of this species' range it is threatened by land conversion to farmland / plantation forestry, residential development, and trees are still felled for firewood. Recruitment is often lacking due to the suppressing effects of weeds, or because stands are under browsed by livestock. At this stage no Kunzea have been reported to be infected by the rust Austropuccinia psidii in the wild, but it is inevitable that occurrences will happen. Once this rust is recorded to infect this species in situ the impact and long-term survival of Kunzea linearis and other allied species must be regarded as uncertain as there currently is no known cure. Therefore, extreme decline of the species is anticipated in the near future from the rust Austropuccinia psidii. Based on an ongoing suspected decline of up to 30 % over three generations this the species is assessed as Near Threatened.

This species is endemic to Aotearoa / New Zealand where it occurs on Te Ika a Maui / North Island (Te Paki south to the northern Waikato – with an outlier in the Taipo of the Eastern Wairarapa), as well as a a few trees on offshore islands of North Island, including on the Hen & Chickens and the Poor Knights, and one tree on Aotea / Great Barrier Island. Distribution map is generalised.

No accurate counts of individuals have been made. However, the species is still widespread over large parts of Te Paki (where it is the dominant Kunzea species present), the sand country of Te Aupouri, and parts of western Northland (especially the Pouto Peninsula). Its locally present in the eastern portion of Northland (as a result of land development and forest clearance) persisting in remnant stands across the Waipu Plain and along the coast line to the Waitemata Harbour. The species went extinct in the northern Waikato sometime in the mid 2000’s as the few stands left were cleared for road works and housing. Scattered trees are still present on Aotea / Great Barrier Island and the eastern side of the Coromandel Peninsula. Despite these losses there is likely to be ≥100,000 mature individuals based on the species dominance and the areas occupied. However over large parts of this species range it has declined from land conversion to farmland / plantation forestry, residential development, and trees are still felled for firewood. Recruitment is often lacking due to the suppressing effects of weeds, or because stands are under browsed by livestock. The species was assessed as ‘Threatened / Nationally Vulnerable’ qualified ‘DP’ [Data Poor] pathway E1 by de Lange et al. (2018) mainly because of the threat posed by Austropuccinia psidii (see under Threats) but without data to confirm this assessment. Decline rates historically would have been considerable and are still severe over large parts of its range as it occurs on private land now being converted for housing or avocado (Persea americana) orchards, so a decline rate of 10–15% of the species over this parts of its range (Te Aupouri especially) in the next 10 years is probable. Declines are also ongoing in sites of plantation forestry, though pine felling temporarily provides opportunities for regeneration, provided remnant trees are not felled for firewood.

This species is likely to live for over 50 years. There is no information available on when the species begins to reproduce. Consequently a generation length of 20–30 years is given to measure continuing decline. This also reflects that this is a small species of tree. The population decline has been measured over a moving window considering two generations in the past and one generation into the future as decline is continuing (1960–2050). Across this time the population is suspected to experience a decline of up to 30%, particularly if Austropuccinia psidii affects Kunzea linearis in situ.

Kunzea linearis is primarily a species of coastal to lowland shrubland habitats overlying impoverished soils and peat bogs (de Lange 2014, 2023). It is only very rarely found at any distance inland. The sole exception appears to be Te Paki where it is virtually the only Kunzea species present and so seems to occupy a much greater range of habitats than it would usually. Elsewhere within its range, even in apparently suitable inland gumland scrub habitats overlying leached soils, and on the clay podzols of the Northland Peninsula, it is usually replaced by K. robusta. K. linearis seems to reach its greatest abundance on sand podzols overlying older usually Pleistocene-aged sand dunes, especially in places where these grade into peat (de Lange 2014). Because it is tolerant of seasonal flooding, waterlogged soils, and extreme drought K. linearis is usually the dominant species on the sand country of the Te Aupouri Peninsula, as well as the acidic leached clays and older sand soils of Te Paki (de Lange 2014). It is also the dominant woody shrub on the margins of the oligotrophic peat bogs and lakes of the Taumatatotara Flats (Te Paki), the Motutangi-Kaimaumau Peat Bog, Lake Ohia, Karikari Peninsula lakes and in parts of the Ahipara Gumlands (de Lange 2014). Outside these habitats K. linearis has been found growing within shell banks and low-lying clay banks subject to saline inundation within the mangrove (Avicennia marina subsp. australasica) swamps of the upper Whangaroa Harbour (de Lange 2014, 2023). In western Northland it may occasionally colonise mobile sand where it is then usually sympatric with and often out-competed by K. amathicola. In parts of Te Paki and also on the Poor Knights Islands, K. linearis can sometimes be found in abundance within mixed indigenous forests, though mostly then on skeletal soils developed on outcrops of hard volcanic rock or on deeply leached clay podzols (usually in association with kauri (Agathis australis). These situations are exceptional and, as a rule, K. linearis is not found in mature forests (de Lange 2014). South of the Pouto Peninsula and Te Arai, K. linearis has a patchy distribution. In these areas it is usually found on cliff faces growing amongst pohutukawa (Metrosideros excelsa). In places where the cliffs abut land that has been frequently fired, K. linearis may be a local component of the fire-induced gumland vegetation (de Lange 2014).

Key threats to the species are clearance for farmland / plantation forestry, residential development, felling for firewood, wild fires, invasive weeds and fallow deer (Dama dama). Recruitment is often lacking due to the suppressing effects of weeds, or because stands are under browsed by livestock. In regards to plantation forestry, though pine felling temporarily provides opportunities for regeneration, provided remnant trees are not felled for firewood. The species went extinct in the northern Waikato sometime in the mid 2000’s as the few stands left were cleared for road works and housing. 

Another key threat is Austropuccinia psidii. This rust is now the most serious threat. It reached Aotearoa / New Zealand from Australia in 2017. The impact of this rust on Myrtaceae worldwide is serious, and it is known to kill inoculated Kunzea species in cultivation susceptibility trials, so it is regarded as a serious threat to members of the genus and indeed all of the indigenous Myrtaceae in Aotearoa / New Zealand (de Lange et al. 2018). It is solely for this reason that K. linearis now has such a high threat listing in Aotearoa / New Zealand. Currently there is no cure for this disease either. At this stage wild occurrences of infected Kunzea have yet to be reported but it is inevitable that they will happen. Once they are recorded the impact and long-term survival of K. linearis and other allied species must be regarded as uncertain.

This species is felled for firewood.

The key threat to Kunzea linearis will inevitably be Austropuccinia psidii. All other known threats can be effectively managed but the rust, so far, has not been. The impact on wild Kunzea is as yet unknown but it is believed that it will be severe, infections of inoculated cultivated plants result in the death of seedlings and saplings within less than a year from the first infection. As the rust continues to spread, and infections increase, there will be more spores spread, so the severity in infections of host plants is anticipated to increase. Currently there is no known cure for Austropuccinia, all that can be hoped for is that some lineages of host plants have or develop resistance. To date there has been no evidence for this.

As the rust is wind dispersed quarantine measures are also ineffective. The seed of Kunzea has short-term viability and viability is affected by desiccation and freezing, so conventional seed banking is of limited value. Current measures to secure the species should consider holding tissue-cultures. Consideration should be given to cultivating the species outside the global distribution of Austropuccinia, to see if at those sites the species can be secured in Botanic Gardens and other threatened plant collections.

Research into finding a cure for Austropuccinia is a global issue and many organisations are working in this area. Like all research however, those investigations are subject to funding issues and political whim. Austropuccinia is a global problem, a global response is needed – only time will tell if humanity understands the consequences of the loss of the Myrtaceae on world ecosystems and takes the right steps to find solutions to help manage this rust.

The other key threat to the species is Fallow Deer (Dama dama) which are spreading into Northland. Fallow Deer numbers are not being effectively controlled and in places they are now causing canopy collapse. Deer could be controlled, if the public understood the problem better, education is needed. Similarly trees are routinely felled for firewood, a practice that is not sustainable and will over time eliminate the species from areas that can ill-afford deforestation.