Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Cycadopsida Cycadales Cycadaceae

Scientific Name: Cycas tansachana
Species Authority: K.D.Hill & S.L.Yang

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2cd; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) ver 3.1
Year Published: 2010
Date Assessed: 2009-10-31
Assessor(s): Hill, K.D.
Reviewer(s): Donaldson, J.S. & Bösenberg, J.D.
This species has an extremely small area of occupancy and extent of occurrence (less than 10 km²), is known only from a single location and has declined dramatically due to mining of limestone for the making of cement. At one stage it was thought to be Extinct in the Wild after limestone outcrops were destroyed, but was subsequently found on adjacent outcrops.
Previously published Red List assessments:
2003 Critically Endangered (CR)

Geographic Range [top]

Range Description: This species is endemic to south central Thailand, occurring to the north east of Khong Khi Sua in Sariburi Province. Occurs at an elevation of 400 m.
Countries occurrence:
Number of Locations: 1
Upper elevation limit (metres): 400
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Plants are locally abundant (2,500 to 10,000 mature individuals) but very restricted in their distribution.
Current Population Trend: Decreasing
Additional data:
Number of mature individuals: 2500-10000
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: This species grows on limestone outcrops growing in full sun or partial shade in crevices on bare rock. The limestone outcrops are covered with sparse, seasonally deciduous forest.
Systems: Terrestrial
Generation Length (years): 40

Threats [top]

Major Threat(s): This species is apparently quite restricted in occurrence and under severe pressure from plant collectors and limestone mining operations.

Conservation Actions [top]

Conservation Actions: This species is listed on Appendix II of the CITES Appendices.

Classifications [top]

1. Forest -> 1.5. Forest - Subtropical/Tropical Dry
suitability: Suitable  
0. Root -> 6. Rocky areas (eg. inland cliffs, mountain peaks)
suitability: Suitable  
1. Land/water protection -> 1.1. Site/area protection
4. Education & awareness -> 4.3. Awareness & communications

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
In-Place Species Management
In-Place Education
  Included in international legislation:Yes
  Subject to any international management/trade controls:Yes
3. Energy production & mining -> 3.2. Mining & quarrying
♦ timing: Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.2. Gathering terrestrial plants -> 5.2.1. Intentional use (species is the target)
♦ timing: Ongoing    
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

♦  Pets/display animals, horticulture
 National : ✓  International : ✓ 

Bibliography [top]

Hill, K.D. and Stevenson, D.W. 1998 - 2006. The Cycad Pages. Available at:

Hill, K.D. and Yang, S.-L. 1999. The genus Cycas (Cycadaceae) in Thailand. Brittonia 51(1): 48-73.

IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.3). Available at: (Accessed: 2 September 2010).

Jones, D.L. 2002. Cycads of the World. Smithsonian Institution Press, Washington, DC.

Whitelock, L.M. 2002. The Cycads. Timber Press, Portland, Oregon.

Citation: Hill, K.D. 2010. Cycas tansachana. The IUCN Red List of Threatened Species 2010: e.T42042A10636225. . Downloaded on 13 October 2015.
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