The Effects of Global Warming on Wetlands

The Effects of Global Warming on Wetlands

Introduction

Wetlands are highly productive ecosystems. Wetlands include marshes, estuaries, bogs, fens, swamps, deltas, shallow seas, and floodplains. Wetland habitats support a vast range of plant and animal life, and serve a variety of important functions, which include water regime regulation, flood control, erosion control, nursery areas for fishes, fish production, recreation, plant production, aesthetic enjoyment, and wildlife habitat. Wetlands account for about 6% of the global land area and are among the most valuable environmental resources.

The Problem

The potential impacts of climate change on wetlands are of great concern. Increasing atmospheric concentrations of carbon dioxide and other greenhouse gases released by human activities are generally expected to warm the Earth a few degrees (C) in the next century by a mechanism known as the "greenhouse effect." Such warming could raise sea level by expanding ocean water, melting mountain glaciers, and eventually causing polar ice sheets to side into the oceans. Among the coastal areas of greatest risk in the United States are those low-lying coastal habitats that are easily eroded and which occur along the northern Gulf of Mexico and southern Atlantic coasts of the U.S. These coastal wetlands are especially vulnerable to direct, large-scale impacts of climate change, primarily because of their sensitivity to sea-level rise.

Observational records indicate that sea level has already risen between 10 and 25 cm globally over the past 100 years. In addition, the Intergovernmental Panel on Climate Change (IPCC) has projected a sea-level rise of 15-95 cm as a consequence of global warming. Sea-level rise will also increase the depth of coastal waters and increase inland and upstream salinity intrusion, both of which affect fresh and brackish water wetlands. Sea-level rise has the potential for increasing the severity of storm surges, particularly in areas where coastal habitats and barrier shorelines are rapidly deteriorating. These direct consequences of global- and regional-scale changes will increase the vulnerability of coastal wetlands which are already heavily impacted by human activities.

Analysis of sites in five coastal states indicate that many marshes and mangrove ecosystems receive adequate mineral sediments to produce enough organic sediment and root material to remain above sea level at the present rate of sea-level rise (1-2 mm per year globally). However, three of the twelve wetlands studied were not keeping pace with the current rate of sea-level rise. If sea-level rise accelerates, some additional sites would also begin to slowly deteriorate and submerge.