Where streams & rivers meet the sea

Estuaries are the depositional surfaces where freshwater streams and rivers meet the sea. This category and its first 2 sub-categories consider the intertidal portions of these habitats. The 3rd sub-category addresses the adjoining supratidal meadows, shrub thickets, and young spruce forests that are especially common in the north where glacial rebound is occurring.

Typical array of elevational zones in northern Southeast, where land is rising relative to sea level.

Typical array of elevational zones in northern Southeast, where land is rising relative to sea level.

 

Mapping estuaries over a large region like Southeast Alaska is a classic exercise in landscape ecology. This requires dependence on huge spatial databases that may or may not be founded on ecological realities. In our work with freshwater wetlands, we’ve found the National Wetlands Inventory (NWI) to be of limited utility. But salt marshes, mudflats and algal beds are more easily distinguished and mapped than the subtleties of peatlands and forested wetlands. Here is how NWI plays out in the search for Southeast’s largest estuaries:

The National Wetlands Inventory maps about 350,000 acres of tidal estuaries on the Tongass, about 2% of its land area. Only 42,000 acres of this are covered with “emergent” vegetation, or salt marsh. But whether marshy or muddy, each estuary is the ecological nexus of its watershed, important far out of proportion to the area covered.

The National Wetlands Inventory maps about 350,000 acres of tidal estuaries on the Tongass, about 2% of its land area. Only 42,000 acres of this are covered with “emergent” vegetation, or salt marsh. But whether marshy or muddy, each estuary is the ecological nexus of its watershed, important far out of proportion to the area covered.

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