Olearia crebra is a small tree endemic to Aotearoa / New Zealand, where it occurs on Waima Forest, south of Hokianga Harbour, Te Tai Tokerau / Northland, Te Ika a Maui / North Island. It was assessed as ‘Threatened / Nationally Endangered’ in 2017, using the New Zealand Threat Classification System (de Lange et al. 2018), and this assessment was affirmed in 2023 (de Lange et al. 2024). The largest site with this species is estimated to have c. 800–1,000 subadults and adults scattered covering an area of c.1 ha, and then with sporadic trees / and stands of 5–20 trees in four widely scattered sites elsewhere within the Waima Forest. The main threat to the species is browsing by possum and goats, and browsing animal control is necessary for the species survival. It is suspected that without sustained possum and goat control this species will decline more than 20 % over the next two generations. It is assessed as Endangered.

This species is endemic to Waima Forest, south of Hokianga Harbour, Te Tai Tokerau / Northland, Te Ika a Maui / North Island, Aotearoa / New Zealand. Distribution map is generalised.

The largest site is estimated to have c. 800–1,000 subadults and adults scattered covering an area of c.1 ha, and then with sporadic trees / and stands of 5–20 trees in four widely scattered sites elsewhere within the Waima Forest (Heenan and Cameron 2002, de Lange et al. 2010, de Lange 2024). Thus far it is known only from this forested area, which covers an unnamed mountain range on the southern side of the Hokianga Harbour. It is suspected that without sustained possum and goat control this species will decline more than 20 % over the next two generations.

This species is confined to cloud forest above 500 m asl and regenerating partially cleared land and reverting farmland (Heenan and Cameron 2002, de Lange et al. 2010, de Lange 2024). The most important site is found in regenerating forest on the top and sides of a cliff face and associated slip scar. Other sites are found at gulley and stream heads, on slip scars and on track sides. Olearia crebra is naturally confined to sites prone to frequent disturbance in a region known for the highest rainfall in Northland. Seedlings often germinate on the trunks of Alsophila smithii and Sphaeropteris medullaris. Common associates include Ackama rosifolia, Veronica flavida, Alsophila smithii, Sphaeropteris medullaris, Metrosideros robusta and Olearia rani.

This species is threatened by possum (Trichosurus vulpecula) and goat (Capra hircus) browsing. Possums and goats were introduced to Aotearoa / New Zealand from 1771 and 1837 onwards, and are a major threat to the indigenous flora of that country. Goats kill seedlings, juveniles and adults, and possums target young growth and especially immature inflorescences. Feral goats however, are the main threat, and though goat numbers in the Waima Forest are now much reduced they are common on adjacent private land from where they reinvade the Waima Forest. 

Olearia crebra is fickle in cultivation, plants are prone to sudden collapse and will not tolerate drying out. Despite attempts to cultivate trees in 1987–1990, and again in 2002–2003 the species remains scarce in cultivation.

As this species is difficult to maintain in cultivation it is not known to be commercially available (de Lange 2024).

The Waima Forest is subjected to periodic wild animal control, which may at times include aerial drops of Sodium fluoroacetate (1080) which is extremely effective at controlling possums, goats, rats, and other browsing animals to the levels needed to induce recovery not the indigenous vegetation and species such as Olearia crebra. However, 1080 drops are considered controversial and are not favoured by many people and some iwi (Maori people) who exercise mana whenua (traditional ownership of the lands) thus its long term use at Waima Forest is not certain. Other practical solutions to wild animal control in that forest are not considered viable due to its topography and isolation. Without sustained possum and goat control Olearia crebra is unable to recruit, and over time heavily browsed specimens are killed.

Until a more publicly acceptable possum control approach is developed, Olearia crebra requires 1080 drops to manage wild browsing animal populations roughly every five years to maintain the species and ensure recruitment. Maintaining the fences between private land and Waima Forest is also a priority.

New Zealand Threat Classification System assessed this species as ‘Threatened / Nationally Endangered’ Qualified ‘CD’ [Conservation Dependent], ‘OL’ [One Location], ‘RF’ [Recruitment Failure] (de Lange et al. 2018) and affirmed this assessment though qualifying it differently (‘DPS’ [Data Poor Size], ‘DPT’ [Data Poor Trend], ‘RR’ [Range Restricted]) in 2023 (de Lange et al. 2024).