Guaiacum coulteri 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Zygophyllales Zygophyllaceae

Scientific Name: Guaiacum coulteri Gray
Common Name(s):
Spanish Guayacan

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2c ver 3.1
Year Published: 2017
Date Assessed: 2016-08-25
Assessor(s): Rivers, M.C.
Reviewer(s): Oldfield, S. & Leaman, D.J.
Contributor(s): López-Toledo, L. & Burslem, D.
Guiacum coulteri is a large tree found in Mexico. Its timber is highly valued and the species has been logged and traded for a long period. The species can now be found on CITES appendix II. It is assessed here as Vulnerable. Population decline is considered to fall in the range of 41.4 and 50% over the last three generations. These estimates are based on the decline of the species native habitat in studies conducted in 2011 and a 2005 respectively. Although, the population size of the species is over 10,000 mature individuals, there is still a need for better in situ protection and more effective conservation action for this species.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Guaiacum coulteri is endemic to the west coast of Mexico (Gordon et al. 2005, López‐Toledo et al. 2011).
Countries occurrence:
Mexico (Baja California Sur, Colima, Guerrero, Jalisco, Michoacán, Nayarit, Oaxaca, Sinaloa, Sonora)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population size is estimated to more than 10,000 mature individuals (López‐Toledo et al. 2011) and the population is scattered and patchy within its local range (Gorson et al. 2005). The species has an approximate generation length of 100 years. The species was previously more widespread but due to the expansion of agriculture (livestock and crop) and the development of human settlement the population size and habitat range of G. coulteri has reduced. Population decline is estimated to 41.4% (López‐Toledo et al. 2011), calculated as a loss in area of occupancy (AOO) from 1976 to 2011 which is within three generations (300 years) for this species. Another estimate (Gordon et al. 2005) infers that the species has undergone a >50% reduction in population of mature individuals over the last three generations based on the 50% loss of the species native dry forest in Mexico. As the species is not evenly distributed through these forests and there is likely to be some natural regeneration here it is not expected that population has declined by the whole 50% over the last three generations. Therefore it is concluded that the species population has declined by between 41.4 and 50% over the last 300 years using habitat loss as a proxy for population decline.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes

Habitat and Ecology [top]

Habitat and Ecology:Guaiacum coulteri is an evergreen tree. It can reach up to 15 m all, although these trees are now rare due to logging, and often found now as a understory shrub (Gordon et al. 2005). It is a dry forest species and can be found on dunes in rocky outcrops along the sand. It is thought to be slow growing. There has been a continuing decline in the species habitat this is due to an increasing anthropogenic use of the forest. López‐Toledo et al. 2011 calculated habitat loss across the species range based on decline of forest cover within each state of the species range from 1976 to 2000 by overlaying land use maps. It was concluded that overall rate of habitat loss for G. coulteri was 0.69%/per year from 1976–2000 (López‐Toledo et al. 2011). Gordon et al. 2005 estimated a 50% loss of dry forest cover.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):100

Use and Trade [top]

Use and Trade: Guaiacum coulteri is a long-lived timber tree logged intensively over a long period in all parts of its natural distribution. Logging of large trees of G. coulteri took place during the last century to supply commercially valuable timber. The species is now exploited for local use as firewood and as a specialty wood for handicrafts. Flowers and resin from G. coulteri have been used in the past as colouring agents (Oldfield 2005). The species also have medicinal properties, and has been used as an expectorant, blood purifier, mild laxative and to treat rheumatoid arthritis. The berries of G. coulteri have been traditionally used as medicine (Conway 2001).

Threats [top]

Major Threat(s): The remaining stands of G. coulteri are threatened with habitat loss and over exploitation. Logging of large trees of G. coulteri took place during the last century to supply commercially valuable timber, to the extent that a recovering population now remains largely composed of small individuals (Gordon et al. 2005). The species is now exploited for local use as firewood and as a speciality wood for handicrafts. Mexican dry forests have suffered high rates of conversion to a variety of extensive and intensive agricultural uses.

Conservation Actions [top]

Conservation Actions: In Mexico, the dry and semi dry forests, which represent the main habitats, are not well protected. Thus, only 1.3% of the entire range of Guaiacum coulteri are found in protected areas (López‐Toledo et al. 2011). Fourteen ex situ collections are known from botanic gardens and arboreta worldwide (BGCI 2016). It is necessary to increase the area under protection in the federal. At some areas, the species was over logged illegally and now the species is low-abundant and therefore restoration actions would be desirable. Sustainable forest management may contribute to conserve populations. The species is also listed under CITES Appendix II.

Citation: Rivers, M.C. 2017. Guaiacum coulteri. The IUCN Red List of Threatened Species 2017: e.T30847A68085761. . Downloaded on 20 January 2018.
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