Gowland, K, 2021
In 2021 WA sandalwood was placed on the International Union for Conservation of Nature and Natural Resources (IUCN) international threatened species list, the 'Red List', a listing that followed a review by five scientists including two former senior DBCA scientists.
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Red List Category & Criteria: Vulnerable A2acd+3cd+4acd ver 3.1
Date Assessed: July 21, 2021
Santalum spicatum, Australian Sandalwood, is a small tree or large shrub endemic to Australia’s arid and semi-arid environments in the southern two-thirds of Western Australia and in South Australia. It has a broad extent of occurrence (EOO) but is locally patchy (Loneragan 1990). The area of occupancy (AOO) of this species is less than 2,000 km² (AVH 2021). It is now listed as endangered in South Australia.
Australian Sandalwood is one of the most highly prized species of sandalwood in the world, second only to Indian Sandalwood, S. album, a species of tropical environments. Santalum spicatum is sought after for its fragrant heartwood and oil and has been exported from Western Australia to Asia for nearly two hundred years (since 1845). Harvesting of this species is entirely destructive, the whole tree and roots being removed (Loneragan 1990). It was once the state’s biggest export item and continues to contribute to the state’s economy.
However, this species has naturally very low regeneration, is hemiparasitic (that is, it needs to parasitise another shrub/tree species), and has a very slow growth rate. To date, all commercial harvest of this species has been from wild individuals that are typically between 90–115+ years of age, the time it takes to reach a marketable size (Loneragan 1990). Regeneration has been significantly reduced due to grazing of seedlings by introduced, and native, herbivores; consequently, there has been very little natural regeneration outside of conservation reserves since at least the 1930s (Kealley 1991).
Legislative protections, plantations (which are soon to come of marketable size), active regeneration operations, and measures to control introduced herbivores have been introduced; however, legal and illegal harvest of this species is occurring at more than six times the recommended level by the Department of Biodiversity, Conservation and Attractions (DEC 2012).
Publicly raised concerns regarding the sustainability of the wild harvest of this species have been circulating for more than 100 years, yet wild harvest has continued throughout most of this period. Current population estimates are difficult—the last population estimate was set at 23 million (Kealley 1991), and many thousands of tonnes of mature plants have been removed since then with little wild regeneration.
Efforts to facilitate regeneration in the wild are continuing; however, germination and establishment of this species is complex and dependent on suitable host species and 2–3 years of repeated high rainfall. So, there is likely to be a generational gap of 100–200 years before the effects of past and current threats are ameliorated (Standing Committee on Environment and Public Affairs 2014). Furthermore, herbivore consumption, land use change, increasing drought and aridity, and increased fire frequencies remain a threat to this species.
Historic agricultural land-use change has not been included in this assessment because of a lack of definitive information on the impact on the species. Consequently, this species is assessed as Vulnerable A2 due to its past population having reduced by more than 30% in the last three generations (300 years). Given the lack of plants in the lower size classes, the observed lack of regeneration in the wild (Kealley 1991, DEC 2012), and the slow maturation times, its population decline is likely to continue over the next 100–200 years (DEC 2012), with a 30–49% decline expected over a 300-year period (three generations), including the past and the future (1821–2121). It is, therefore, assessed under A4 and A3.