Thursday, December 22, 2016

Rising Seas Are Killing Southern Forests

Saltwater intrusions into low-lying fresh water ecosystems are killing stands of hardwood trees like red cedar, live oak and wax myrtles turning once vibrant, diverse fresh water ecosystems into salt-water "ghost forests".  A visit into the Withlacoochee Gulf Preserve in the Big Bend region of Florida's Gulf Coast by journalist Roger Drouhin is reported at He viewed hummock islands that once were populated by hardwood trees, that are now infested with salt-water tolerant plants and dead or dying trees.  The US Geological Survey is studying dying Cypress trees in the swampland along the Savannah River. Besides killing trees, species that depend on hardwood stands such as woodpeckers are also affected. The same phenomenon is occurring throughout the coastal floodplains in the south and as far north as New Jersey and Delaware, as sea levels rise due to global warming.

NOAA estimates that since 1992 sea levels are rising 1.2 inches per decade, caused by the waters' thermal expansion, and the loss of land-based ice to the oceans.  The oceans are absorbing more than 90% of increased atmospheric heat due to emissions from human activity.

Albemarle Sound, North Carolina
Low levels of salt penetrating the soil slows down hardwood growth and fewer seeds are produced.  Salt also breaks down peat, partially decomposed vegetation which builds up over time to create a viable growing medium at a rate of about a tenth of an inch per year.  Loss of peat causes land to subside which allows salt water to penetrate further inland. Once forest habitat transitions to salt marsh and eventually to open salt water.  Ecologists see these changes taking place now, providing an early warning of what will be in the future [photo credit: M. Ardon] The death of native species allow salt tolerant invasive species to take their place such as the salt marsh reed, Phragmites.  Scientists say the toll on freshwater marshes and bottom land hardwood forests will be severe.  An important function of coastal wetlands is the buffering of storm surges which will be lost if these lowlands eventually become open water.  When one considers that 40% of the US population lives near a coast, this is a drastic impact for the worse; see the charts below for just two southern populated regions that will be affected the most.