HANOI, VIETNAM – 13 May 2013: ICEM researchers have identified that the effects of climate change in the vulnerable Mekong wetlands will add to the threats on the critically endangered Siamese Crocodile.

Temperature changes during their breeding and hatching season are projected to become a critical climate change concern for the species. Climate change in the Mekong region is expected to cause temperature variability – which will affect the sex ratio of hatching reptiles.

Crocodile hatchlings – usually emerging in June or July – may become a completely female or male brood, depending on temperatures during incubation. Temperature is the critical component which defines the embryo sex of crocodiles. If the incubation temperature is higher than about 32oC, the brood will be female. In addition, warmer temperatures are also known to increase appetite in crocodiles, which combined with decreasing habitat may place further stress on the Siamese Crocodiles in the lower Mekong Basin.

The vulnerability of the Siamese Crocodile (Crocodylus siamensis) was identified during a case study was conducted in 2011 – 2012 in the Xe Champhone Wetlands by ICEM’s local partners in IUCN Lao. The study was part of a basin wide assessment of climate change threats, vulnerability and adaptation options for the wetlands in the Lower Mekong Basin and adaptation commissioned by the Mekong River Commission and carried out by ICEM and its partners, the International Union for the Conservation of Nature, WorldFish Centre & Southeast Asia Regional START Centre. The Xe Champhone Wetlands covers approximately 450 km2 of central Lao PDR – part of the Xe Bang Hieng River basin. The Siamese Crocodile is the species of highest conservation concern in the region, which holds the largest population of this species in Lao PDR with approximately 75 animals living in scattered lakes and marshes. Experts believe there could be as few as 300 Siamese Crocodiles remaining in the wild in South East Asia. The principal threat to the crocodiles continued existence in the wild is the loss of wetland habitat.

The Siamese Crocodile breeding and hatching season will be critically affected. This endangered species is just one of many which will become increasingly more vulnerable as a result of climate change. To understand how we can best protect the Siamese Crocodile and other species in these important wetland areas we first need to understand the localized impact of climate change for animals and plants. ICEM’s local data research, hydrological modeling and analysis will become critical tools as we address the challenges of protecting these endangered species.
Peter-John Meynell, ICEM Team Leader
The ICEM team studied the species’ sensitivity to changes in temperature. Climate change is expected to cause a 2 °C increase in the monthly mean daily maximum temperature by 2050 in the lower Mekong Basin, including the Xe Champhone Wetlands. There is likely to be a rise of between 2.1 – 2.7 °C during the crocodile breeding season (April-May) and hatching season (May – July). Days in which the temperatures exceeds 33 o C is predicted to increase from 47 to 76 days in a typical year as a result of climate change. Please see graph below (Figure 1) showing the period of time each breeding season which will exceed a given temperature.

The Siamese Crocodile is considered to be highly vulnerable to these increasing temperatures during hatching season and ICEM researchers warn that climate change will add additional pressures which may push the species beyond the extinction threshold. Adaptation measures include maintaining and protecting the wetland habitats and most specifically ensuring that there is adequate shelter (natural or artificial) in the nesting sites to protect against direct heating.
Figure 1: exceedence 2