Tropical species may be particularly vulnerable to climate change because they experience minimal fluctuations in annual temperature and are already near their maximum thermal tolerance (Tewksbury et al. 2008; Corlett 2011). Species unable to adapt or move will face local or global extinction and this is more likely to happen to species with narrow climatic and habitat requirements and limited dispersal abilities, such as amphibians and reptiles. In forested areas, birds may be less affected by range-shift gaps than some plants, insects, reptiles and amphibians that are poor dispersers.
There is still much to learn before we can assess accurately the impacts of climate change on biodiversity in Myanmar. Few field studies on the potential impacts of climate change to biodiversity have been conducted in the Indo-Myanmar Hotspot and there are currently no studies on biodiversity and climate change in Myanmar. A global Hotspot analysis estimated that, depending on different modeling scenarios, between 1.9 and 40.5 percent of endemic plant and vertebrate species in the Indo-Myanmar Hotspot may become extinct due to climate change over the next century (Malcolm et al. 2006). Approximately 20 to 30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C over 1980-1999 levels.
The interactions and consequences of climate change on biodiversity are complex and multidimensional in nature. However, it is possible to represent some of the likely impacts on the three broad realms, terrestrial, freshwater and marine ecosystems.
Lowland Forest Ecosystems
First, many are impaired already by other pressures with which climate interacts. These include eutrophication, organic pollution, sediment release, acidification, impoundment, urbanization, hydropower development, flood-risk and invasion by exotic species (Ormerod & Durance 2009).
Second, climate will affect river conditions and processes indirectly by changing the human use of river catchments, riparian zones and floodplains. Climate change is anticipated to alter seasonal flow regimes and the timing, extent and duration of flooding, but predictions are confounded by modeling limitations and natural hydrological variability (Kingston et al. 2010).
Hotter and drier conditions, especially toward the end of the dry season, could result in the drying out of small floodplain water bodies and the contraction of shallow-water zones in lakes such as Inle Lake in Myanmar. These habitats support some of the most threatened fauna in the hotspot. For seasonally flooded grasslands such as those in the Hukaung Valley Wildlife Sanctuary, a critically endangered habitat, hotter dry seasons and rising CO2 concentrations could facilitate fire and the invasion of woody plants. Altered seasonal flow levels could impact habitat quality for freshwater populations of Irrawaddy Dolphin Orcaella brevirostris and their prey in the Ayeyawady River.
Climate change impacts in Myanmar’s wetlands are of particular concern given the critical ecosystem services they provide for human populations and biodiversity. Further, climate change impacts in the Greater and Eastern Himalayas can be expected to have repercussions for the flow of the Ayeyawady River and its tributaries that support important rice-growing regions of Myanmar.
In the nearer term, sea-level rise and increased water temperatures are projected to accelerate beach and coastal erosion and cause degradation of mangroves and coral reefs. These would in turn negatively influence human communities through impacts on water supply and fisheries productivity. Myanmar hosts 8.8% of the total mangrove forests area of South East Asia with, 46% of the total area of mangroves located in Ayeyawady Region, 37% in the Taninthayi Region and 17% in the Rakhine State (Giesen et al. 2006). They are all considered already under threat from human activities such as pollution, harvesting and coastal development. Problems will be exacerbated for mangrove stands where landward migration is restricted by topography or human developments.
In addition to impacts on mangroves, sea-level rise is expected to impact globally threatened species of migratory shorebirds through the loss of intertidal mud flats (Tordoff et al. 2002; Buckton & Safford 2004; Tordoff et al. 2005). Breeding colonies of seabirds and turtles may be particularly vulnerable to sea-level rise (Duffy 2011).
Global climate change through ocean acidification poses a substantial risk to the biodiversity, ecosystem functioning and productivity of coral reefs in Myanmar and thus threatens their socioeconomic value to dependent human communities. Increasing ocean acidification leads to a reduction in coral calcification and affects coral reefs, which provide habitat for about a quarter of all marine species and are the most diverse among marine ecosystems (Roberts et al. 2002). Coral reefs are extensive on the south west coast of Myanmar and around the islands, extending further south into Thailand, covering 1,870 km², with the majority of coral reefs found in the Myeik Archipelago of the Taninthayi Region. Coral reefs in Myanmar need to be more fully surveyed, better protected and monitored for climate change impacts since they provide many functions, services and goods in terms of coastal protection and sediment retention, nurseries and habitats for aquatic organisms and feeding grounds for economically important species of fish.