The narrow region where land and ocean meet is among the most dynamic and complex collection of physical and biological systems on Earth. These can include salt marshes, mangroves, wetlands, estuaries, reefs, and bays often linked in an intricate network of physical, chemical, and biological interchanges above and below the water. They are often highly productive, highly valued, and highly accessible, making them a natural intersection between the human and natural worlds.
In addition to their role in the wider marine and terrestrial systems they link to, oastal ecosystems provide a broad range of benefits to humans. They can act as storm barriers and water filters, they are nurseries and habitat for commercially important plants and animals, and they are among the most popular tourist destinations.
Coastal systems are also very sensitive to environmental conditions. Small changes in such things as temperature, salinity, nutrient availability, or sediment load, whether natural or human-induced, can have wide-ranging impacts.