New Zealand drained 90 percent of its wetlands in about 150 years
For centuries swamps were written off as worthless ground, good only for hunting and trapping, so people drained them. Nine tenths of New Zealand's wetland vanished within roughly a century and a half, and Europe has probably lost close to half of its own. Only recently has it become clear how much work those soggy forests were doing.
A swamp is a wetland dominated by trees and shrubs, which sets it apart from a marsh, where soft-stemmed grasses and herbs rule. Its soils are waterlogged and its water moves slowly, arriving from rain, groundwater, tides or river floods. The water may be fresh, brackish or salty: freshwater swamps line big rivers and lakes and depend on seasonal flooding, while saltwater swamps fringe tropical and subtropical coasts. Some contain hammocks, low islands of drier ground. In Canada's boreal north, people loosely call bogs, fens and muskeg swamps.
These wetlands clean water as it seeps through, with plants absorbing phosphorus and nitrogen and leftover pollutants settling into buried sediment. They soak up floodwater that would otherwise spill into surrounding land, and their dense roots hold soil against erosion. Floodplain swamps also sustain fisheries: two thirds of the fish and shellfish harvested commercially worldwide depend on wetlands. Ecologists add carbon storage and wildlife habitat to the list.
The losses came from farming, logging, building and efforts to cut down on insect-borne disease. Drainage ditches and canals dried swamps out and, near coasts, let seawater intrude, turning forest into marsh or open water; Louisiana is a textbook case. The United States began enforcing tougher protections in the 1970s, and restoration is spreading in Europe and North America, often starting simply by plugging ditches and removing levees.
Swamps exist on every continent except Antarctica. The Amazon floodplain is the largest in the world, remarkable for its variety of fish and trees, and the Bangweulu Floodplains form Africa's biggest. Western Siberia's Vasyugan Swamp covers more ground than Switzerland. Indonesia holds about 210,000 of the world's roughly 440,000 square kilometres of tropical peat swamp. In the United States, the Atchafalaya at the foot of the Mississippi is largest, while Reelfoot Lake in Tennessee was created by the New Madrid earthquakes of 1811 and 1812.
Source: Swamp
