More than 90% of the world’s salt marshes may soon succumb to sea level rise

More than 90% of the world’s salt marshes may soon succumb to sea level rise

Subject :Environment

Context: Salt marshes have been playing an outsized role in stabilising the environment. But more than 90 per cent of these biologically productive ecosystems may soon succumb to sea level rise by the turn of the century, according to a new research.

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• Scientists from the Marine Biological Laboratory (MBL) have been tracking vegetative cover in Great Sippewissett Marsh in Falmouth, Massachusetts, for the last 50 years to analyse the implications of higher nitrogen levels on marsh grass species.
• Increased nitrogen favoured higher levels of vegetation and accretion of the marsh surface. However, these ecosystems won’t be able to outpace submergence from global sea level rise, noted the study.
• The only choice for salt marshes then would be to migrate landward. But even this choice can be impacted by anthropogenic activities and other factors.
• Marshes all over the globe experience ‘coastal squeeze,’ where their movement is obstructed by sea level rise, anthropogenic activities and geographical factors. For instance, a seawall that protects a home from inundation will prevent a wetland from naturally migrating to higher ground.
• These barriers, whether they be geographic like a hill or a cliff, or people building along the edges of the ecosystem, constrain the potential for landward marsh migration.

Salt marshes

• Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides. They are marshy because the soil may be composed of deep mud and peat.
• Because salt marshes are frequently submerged by the tides and contain a lot of decomposing plant material, oxygen levels in the peat can be extremely low—a condition called hypoxia. Hypoxia is caused by the growth of bacteria which produce the sulfurous rotten-egg smell that is often associated with marshes and mud flats.
• Salt marshes occur worldwide, particularly in middle to high latitudes. Thriving along protected shorelines, they are a common habitat in estuaries.
• These intertidal habitats are essential for healthy fisheries, coastlines, and communities—and they are an integral part of our economy and culture.
• Ecological Function of Salt Marshes
  • Habitat: Salt marshes provide important habitat for a variety of fish and wildlife species. They serve as nurseries for commercially important fish and shellfish species, as well as a variety of birds, reptiles, and mammals.
  • Nutrient cycling: Salt marshes are highly productive ecosystems that play an important role in nutrient cycling. They absorb excess nutrients from the water, such as nitrogen and phosphorus, and convert them into organic matter, which can be used by other organisms.
  • Water quality: Salt marshes are natural filters that help improve water quality. They absorb pollutants and excess nutrients from the water, which can help reduce the risk of harmful algal blooms and other water quality problems.
  • Carbon storage: Salt marshes are important carbon sinks that store large amounts of carbon in their soils and plant biomass. This can help mitigate climate change by reducing the amount of carbon dioxide in the atmosphere.
  • Coastal protection: Salt marshes serve as natural buffers against storms and floods. They help reduce the impact of waves and storm surge, which can help prevent erosion and protect coastal communities.
• Threats: Salt marshes are under threat from a variety of human activities, including coastal development, dredging, and pollution. Climate change is also a major threat to salt marshes, as rising sea levels and increased storm activity can lead to erosion and inundation of the marsh.