Fox Hill Marsh EarthCache

The approach to this Earthcache is via an easy walk along a beautiful nature trail. The path will lead to an observation deck from where you can observe and learn everything necessary to complete this Earthcache.

A salt marsh is an environment in the upper coastal intertidal zone between land and salty or brackish water. The plant life you'll see here therefore is dominated by plants which are very tolerant of the salt content of the water. The grasses, shrubs, and other plant life here provides support for the marsh by trapping sediments that wash in. Salt marshes are essential to both the aquatic food chain and to land animals and migrating birds.

Salt marshes in New England are subject to strong tidal influences and show distinct patterns of zonation. In low marsh areas with high tidal flooding, a monoculture of the smooth cordgrass, Spartina alterniflora dominate, then heading landwards, zones of the salt hay, Spartina patens, black rush, Juncus gerardii and the shrub Iva frutescens are seen respectively. These species all have different tolerances that make the different zones along the marsh best suited for each individual.

Plant species diversity in the salt marsh is relatively low, since the flora must be tolerant of salt, complete or partial submersion, and anoxic mud substrate. However, you can probably pick out different levels of marsh by observing the plants that grow at different places. The most common salt marsh plants are glassworts and the cordgrass. They are often the first plants to take hold in a mudflat and begin its ecological succession into a salt marsh. Their shoots lift the main flow of the tide above the mud surface while their roots spread into the substrate and stabilize the sticky mud and carry oxygen into it so that other plants can establish themselves as well. Plants such as sea lavenders, plantains, and varied sedges and rushes grow once the mud has been vegetated by the pioneer species.

Humans are having a dramatic impact on salt marshes. The coastal region is an attractive natural feature to humans through its beauty, resources, and accessibility. As of 2002, over half of the world’s population was estimated to being living within 60km of the coastal shoreline, making our coastlines highly vulnerable to human impacts from daily activities that put pressure on these surrounding natural environments. In the past, salt marshes were perceived as coastal ‘wastelands,’ causing considerable loss and change of these ecosystems through land reclamation for agriculture, urban development, salt production and recreation.

Reclamation of land for agriculture by converting marshland to upland was historically a common practice. Dikes were often built to allow for this shift in land change and to provide flood protection further inland. For centuries, livestock such as sheep and cattle grazed on the highly fertile salt marsh land. Land reclamation for agriculture has resulted in many changes such as shifts in vegetation structure, sedimentation, salinity, water flow, biodiversity loss and high nutrient inputs. There have been many attempts made to eradicate these problems for example, in New Zealand, the cordgrass Spartina anglica was introduced from England into the Manawatu River mouth in 1913 to try and reclaim the estuary land for farming. A shift in structure from bare tidal flat to pastureland resulted from increased sedimentation and the cordgrass extended out into other estuaries around New Zealand. Native plants and animals struggled to survive as non-natives out competed them. Efforts are now being made to remove these cordgrass species, as the damages are slowly being recognized.

The indirect effects of human activities such as nitrogen loading also play a major role in the salt marsh area. Nitrogen loading through human use indirectly affects salt marshes causing shifts in vegetation structure and the invasion of non-native species. Human impacts such as sewage, urban run-off, agricultural and industrial wastes are running into the marshes from nearby sources. Salt marshes are nitrogen limited and with an increasing level of nutrients entering the system from anthropogenic effects, the plant species associated with salt marshes are being restructured through change in competition. The New England salt marsh is experiencing a shift in vegetation structure where S. alterniflora is spreading from the lower marsh where it predominately resides up into the upper marsh zone. The loss in biodiversity is not only seen in flora assemblages but also in many animals such as insects and birds as their habitat and food resources are altered.