Tidal Marshes: A Global Perspective

January 1, 2006 by Gregory Gough

Tidal marshes line temperate coastlines around the world. Their combined area is roughly 45,000 square kilometers, about the size of Denmark.

Distribution of Tidal Marshes

ContinentCoastlineArea (km2Vegetation
North AmericaAtlantic, Pacific, Gulf16,440Spartina, Phragmites, Salicornia
South AmericaAtlantic2,300Spartina, Juncus
EuropeAll1,400Salicornia, Spartina, grasses
AsiaPacific25,000Chenopods, Phragmites
Australia, New Zealand, TasmaniaSouthern (temperate)772Sarcocornia, other chenopod shrubs
South AfricaSouthern70Sarcocornia, Spartina, grasses

Although the tidal marsh habitat is saline and floods regularly, it is quite productive. However, much of that productivity occurs below the ground and in the water. Therefore, tidal marshes have few terrestrial animals that regularly inhabit them.

Ipswich Marshes, (painting),  Name: Heade, Martin Johnson,  Date: 1860s

Ipswich Marshes, (painting), Name: Heade, Martin Johnson, Date: 1860s

The vegetation typically consists of grass-like or salt-tolerant plants near the water, and taller grass-like plants and shrubs nearer the land.

Approximately 25 species (or subspecies) of birds, reptiles, and mammals live only in tidal marshes—and 24 of them are confined to North America. It is unknown why there are so many endemics in North America as opposed to the rest of the world but it may be because refuges existed during recent Ice Ages.

Tidal marshes are fragile habitats and face threats from: coastal development, sea-level rise, invasive species, and toxins and pollutants.

This article summarizes the information in this scientific paper:

Greenberg, Russell S., Maldonado, Jesus E., Droege, S. and McDonald, M. Victoria 2006. Tidal Marshes: A Global Perspective on the Evolution and Conservation of Their Terrestrial Vertebrates. Bioscience, 56(8): 675-685.

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