Characterizing Different Types of Wetlands

There are many different types of wetlands, they are varied and diverse, and many types are specific to their areas. In Hawaii we have our own types of wetlands many of which are not found elsewhere. Because of this diversity it is even difficult for the experts to agree on a single classification system. So in many cases a local definitions and characterizations are used. Hawaiian wetlands are also areas that have been historically utilized and highly valued by Hawaiian society because they contain the most precious and abundant resources such as food and water. The RAMSAR definitions have a broad application because it refers to their geology and place within the watershed. The “Ramsar Convention” has adopted a Ramsar Classification of Wetland Type which includes 42 types, grouped into three categories: Marine and Coastal Wetlands, Inland Wetlands, and Human-made Wetlands.

The RAMSAR definitions have 5 groupings of the major wetland types:

  1. Marine (coastal wetlands, coastal lagoons, rocky shores, seagrass beds, coral reefs)
  2. Estuarine (deltas, tidal marshes, mudflats, mangrove swamps)
  3. Lacustrine (wetlands near lakes)
  4. Riverine (wetlands near rivers/streams)
  5. Palustrine (marshes, swamps, bogs)

Wetlands can be natural or manmade: Man-made wetlands can be intentional or unintentional. Intentional wetlands include artificial wetlands or wetland mitigation. Mitigation wetlands (like the ones at Azeka/Pi’ikea in Kihei) are where the original wetlands are relocated. It is widely understood that natural wetlands are far superior to artificial wetlands in many ways. Wetlands are far more than “water features”, they are also repositories of biological diversity, and habitat to macro and micro flora and fauna. For every species of plant you can see there are millions of bacteria dependent on those plants that you cannot see. A balanced wetland ecosystem will have millions of species of microorganism that depend on the life cycles of various plant and animal species. So a long-established natural wetlands will have a far greater biological diversity that is not easily replicated by man.

ANTHROPOGENIC FACTORS: The word “Anthropogenic”, refers to “human impacts”. When human activities such as construction alter the natural hydrology of an area, the location and disposition of wetlands change and new wetlands can be created. Examples of human-influenced wetlands can include, dams, lakes, watercourses, retention ponds, and water features on golf courses. Also retention basins, leech fields, French drains, culverts, irrigation ditches, fish ponds, wetland agriculture, fish-farms, marinas, breakwaters, land reclamation, dikes and levies, sewerage ponds, stormwater retention basins, and wetland mitigation.

DEWATERING: When humans want more land they often repurpose natural waterscapes such as wetlands by “dewatering” them. Many wetlands are deliberately dewatered so that the land can be used for “useful” purposes, such as agriculture or land for development. Drainage ditches are a major factor in wetland health and distribution. Drainage ditches and canals crisscross the landscape, to “dewater” naturally wet areas. On Maui, dewatering wetlands has occurred on a massive scale. And if ever the dewatering infrastructure was to fail, these areas would quickly “re-water” themselves and revert back to their natural wetland hydrology.

WETLAND DISPLACEMENT: When one wetland is displaced another is often created. Areas of man-made surface runoff are regularly diverted onto open ground. Culverts and bridges along roadways have the tendency to concentrate water flows into new areas. Stormwater management infrastructure redistributes the hydrology supporting wetlands and can cause them to migrate, or reappear in totally new areas. Irrigating farmland causes new sources for water, and an altered hydrology. Transporting water from sources like rivers to other areas creates a new pathway for water and new hydrology for wetlands.

RECLAIMED WETLANDS: Much of coastal lands used for development are built on “reclaimed wetlands” Often a system of drainage ditches are used to reduce the water levels. However if this drainage system is not maintained or ever fails the original hydrology is likely to return, and then the original wetlands will reclaim these areas.

UNDERLYING HYDROLOGY: It is very difficult to totally remove the underlying hydrologic geography that creates these wetlands. Wetlands can be temporarily disrupted my man’s activities but the underlying architecture usually remains, waiting for the water to return.

CLIMATE CHANGE: Climate change, increasing rainfall, and rising water tables will hasten the return of wetlands. Wetlands have the ability to revert back to naturally functioning wetlands fairly quickly, and many wetland species are always ready to inhabit any new territory, or re-inhabit an old one.