mangrove-coverage-is-declining

Context: A study was conducted to explore changes in mangrove forest diversity under a broad range of sea-level rise rates and sediment supply conditions, both in the absence and presence of a tidal barrier like a dike / seawall that obstructs inland migration.

More about the study published in Environmental Research Letters 

  • Methodology: The researchers conducted simulations for a period of 330 years. 
    • The first 30 years were used as an adaptation period during which mangroves could settle, allowing the analysis of mangrove assemblage dynamics over the remaining 300 years.
    • The model tracked key forest characteristics, including tree density, type of species, stem diameter, tree height and associated biomass. 
    • Focus was on changes in total forest coverage and species distribution.
  • Significance: The study helps to understand mangrove species zonation linked to a dynamic coastal profile, differences in lateral accommodation space (coastal progradation and landward migration) and mangrove properties like root density.

Key Findings of the study

  • Alarming rate: Mangroves forests are being threatened at an increasing pace: 
    • River dams negatively impact the supply of mud that raises mangrove soils. 
    • The space required for mangroves survival is increasingly getting occupied by buildings and seawalls. 
    • Tidal barriers have proven to be disastrous for mangrove coverage and can result in species loss. 
  • Sign of hope: But mangrove coverage can increase despite sea-level rise if sediment supply is sufficient and land accommodation space available.
    • Mangroves depend on a steady supply of sediment flowing down from rivers. 
    • But the delivery of sediment from most rivers reduced over the past three decades.

 

Mangroves

  • Mangroves are various large extensive types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics - mainly between latitudes 25 N and 25 S.
  • Mangroves are salt tolerant trees (halophytes) adapted to live in harsh coastal conditions. 
  • They contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action. 
  • They are adapted to the low oxygen (anoxic) conditions of waterlogged mud.

Image Source: DTE