Micronesia [FSM] - Climate

The climate is tropical with heavy year-round rainfall, especially in the eastern islands. The FSM is located on southern edge of the typhoon belt and occasionally experiences severe storm damage.

The islands of FSM were severely impacted by drought during El Niño conditions of 1997-1998. Insufficient rainfall caused water and food shortages including staples such as taro, coconut, breadfruit, banana, yam, sweet potato, citrus, sugar cane, and others. Communities among the atolls survived because bottled water, food supplies, and reverse osmosis pumps were imported.

In 2007 and again in 2008, FSM communities were flooded by a combination of large swell and spring high tides that eroded beaches, undercut and damaged roads, intruded aquifers and wetlands, and inundated communities.20 Once again food and drinking water were in short supply.

Over the last two decades, this area has experienced at least two highly destructive typhoons (i.e., 1990 in Pohnpei and 2004 in Chuuk and Yap), as well as some bleaching, with limited mortality (e.g., 1998 20% bleaching in Yap and 2004 minor bleaching in Kosrae and Pohnpei).

Reefs in the FSM are generally in good shape, but there are water quality concerns in areas where there is ongoing coastal development and agriculture. Some degradation of reef ecosystems has already occurred in the more populated areas. Several large development projects, such as construction of an airport and a deep draft harbor, have had significant impacts on mangrove forests and local reefs. Reefs located near population centers, within harbors, and close to shipping lanes have had the largest impacts from fishing and ship groundings. Over-fishing and other harmful fishing practices are also causes of concern.

Atoll aquifers consist of a layer of freshwater floating on saltwater. Recharge from rainfall typically forms a thin lens of freshwater that is buoyantly supported by denser, underlying saltwater, and mixing forms a zone of transitional salinity. The thickness of this mixing zone is determined by the rate of recharge, tidal dynamics, and hydraulic properties of the aquifer.

Low islands, coral reefs, nearshore and coastal areas on high islands, and highelevation ecosystems are most vulnerable to climatic changes. Freshwater supplies will be more limited on many Pacific Islands, especially low islands, as the quantity and quality of water in aquifers and surface catchments change in response to warmer, drier conditions coupled with increased occurrences of saltwater intrusion.

Extreme spring tides, known in Micronesia as “king tides,” are the forefront of this change. King tides cause marine inundation that damages groundwater resources, taro beds, soil, and agro-forestry resources in coastal settings, especially on low atoll islets. On high islands, communities located at the intersection of intensifying storm runoff and rising ocean waters may endure increased flooding and drainage problems.

Rising sea levels will increase the likelihood of coastal flooding and erosion, damaging coastal infrastructure and agriculture, negatively impacting tourism, reducing habitat for endangered species, and threatening shallow reef systems. Extreme water levels will occur when sea-level rise related to longerterm climate change combines with seasonal high tides, interannual and interdecadal sea-level variations (e.g., ENSO, Pacific Decadal Oscillation, mesoscale eddy events), and surge and/or high runup associated with storms.

Higher sea-surface temperatures will increase coral bleaching, leading to a change in coral species composition, coral disease, coral death, and habitat loss. Coastal erosion is widespread. On atolls, coastal erosion threatens groundwater supplies and agroforestry production. Mangrove and coastal strand forests have been lost, exposing the shoreline to environmental damage including erosion and coastal sedimentation. Dredging and use of coastal sand and gravel for construction has caused coastal erosion, beach loss, and led to shoreline hardening.

Rising ocean acidification and changing carbonate chemistry will have negative consequences for the insular and pelagic marine ecosystems; although potentially dramatic, the exact nature of the consequences is not yet clear.

Distribution patterns of coastal and ocean fisheries will be altered, with potential for increased catches in some areas and decreased catches in other areas, but open-ocean fisheries being affected negatively overall in the long term.

Increasing temperatures, and in some areas reduced rainfall, will stress native Pacific Island plant and animal populations and species, especially in high-elevation ecosystems, with increased exposure to non-native biological invasions and fire, and with extinctions a likely result.

Threats to traditional lifestyles of indigenous communities in the region (including destruction of coastal artifacts and structures, reduced availability of traditional food sources and subsistence fisheries, and the loss of the land base that supports Pacific Island cultures) will make it increasingly difficult for Pacific Island cultures to sustain their connection with a defined place and their unique set of customs, beliefs, and languages.

Mounting threats to food and water security, infrastructure, and public health and safety will lead increasingly to human migration from low islands to high islands and continental sites.