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Life on a Barrier Island - August 13, 2017

              Barrier islands are dynamic ecosystems always in motion. With the ocean on one side and a coastal bay, sound, or lagoon on the other, a barrier island is hounded day and night by the wind and waves coming off the surrounding bodies of water. Despite these harsh conditions, life still thrives on these narrow strips of sand and mud. Plant and animal species adapt to survive the difficult conditions they constantly face on these exposed islands.

                Beginning in the ocean and walking towards the shore, one would first encounter the beach and dune habitat that eventually gives way to the maritime forest habitat. As one continues into the forest, it gives way to marshes that eventually lead into the coastal body of water. Due to the dynamic nature of these habitats, animals and plants that colonize these areas have adapted morphologically and behaviorally to take better advantage of their surroundings.

                A perfect example of animals adapting to these environments are the world-famous Assateague ponies. The ponies are regular horses that were placed on the island roughly 250-300 years ago by local colonists seeking to evade taxes on livestock. Throughout the years, the ponies have changed to look like the infamous animals that we are now familiar with today on Assateague Island.

                The Assateague ponies have adapted to life on a barrier islands quite well. They are now shorter than their mainland cousins and look much more bloated. These physical changes are primarily due to their food source. The Assateague ponies eat plants covered with salt from ocean spray, as well as many salt marsh grasses that contain large quantities of salt. In order to stay hydrated, the ponies must drink three to four times more fresh water than a regular horse thus giving them a bloated appearance.

                The ponies have also adapted behaviorally to life on the island. During hot, summer days, the ponies will generally stay on the beaches and dunes o escape the swarms of mosquitos and biting flies that inhabit the inland portions of the island. During storms and foul weather days, the ponies will move inland toward he maritime forests and use the trees and shrubs as buffers against the harsh wind and rain that occurs on the island.

                Ponies are not the only organisms that have adapted to life on the island; trees such as the black and loblolly pines have also adapted to life on this unforgiving stretch of sand. The trees on Assateague will never reach full height; they are shortened due to a lack of vital nutrients and salt spray from the ocean. These pine trees also do not grow to their full height to avoid toppling over in strong winds; during the winter winds can reach 25-30 miles per hour in the winter and even higher in storms such as Hurricane Sandy.

                The endangered sea beach amaranth is also perfectly adapted to life on a barrier island. These small plants live mostly in over-wash areas on the island; areas where large waves from storm action have pushed sand further inland away from the beach. These plants have hard, thick leaves which collect and store water.

                These plants and animals are only a few examples of the amazing adaptation strategies that have evolved to deal with the harsh and ever-changing conditions of Assateague Island and barrier islands like it. Throughout countless generations, these species of flora and fauna have become altered from their mainland cousins in order to have a better chance of survival and reproduce in these difficult and dynamic islands.

Jackson is the former Education Coordinator for Maryland Coastal Bays Program. 



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