Land loss is the term typically used to refer to the conversion of coastal land to open water by natural processes and human activities. The term land loss includes coastal erosion. It is a much broader term than coastal erosion because land loss also includes land converted to open water around the edges of estuaries and interior bays and lakes and by subsidence of coastal plain wetlands. The most important causes of land loss in coastal plains are erosion, inadequate sediment supply to beaches and wetlands, subsidence, and global sea level rise. The mixture of processes responsible for most of the land loss will vary according to the specific part of a coastal plain being examined. [1] [2] The definition of land loss does not include the loss of coastal lands to agricultural use, urbanization, or other development. [3]
Although seemingly related, wetland loss, is defined differently than land loss. Commonly, wetland loss is defined as the conversion of vegetated wetlands into either uplands or drained areas, unvegetated wetlands (e.g., mudflats), or (submerged habitats (open water). According to this, and similar definitions, wetland loss includes both land loss and land consumption as components of it. In historic times, both wetland and land loss typically are the result of a varying, often controversial mixture of natural and anthropogenic factors. [4] [5] There are other definitions of wetland loss commonly used. For example, some researchers defined wetland loss as "the substantial removal of wetland from its ecologic role under natural conditions." [6]
The main causes of land loss are coastal erosion, inadequate sediment supply, subsidence, and sea level rise. Coastal erosion occurs when the rate of sediment deposition is slower than the rate of sediment removal by coastal currents. [7] The most important cause of decreased rates of sediment deposition is the construction of dams and reservoirs although sediment control and conservation programs can also play a role. [8] Once a dam is constructed, sediment that previously traveled freely in the river is trapped in the reservoir. Decreased sediment loads downstream of the dam prevent sediment from replenishing the delta. [9] Subsidence is the compaction of soil resulting in a lower elevation. Subsidence can occur when oil, gas, or groundwater are extracted. These substances hold the land up until they are removed. Compaction due to heavy urban infrastructure also occurs. [10] Sea level rise due to climate change is another threat to coastal land. [11]
Because of a highly variable combination of sea level rise, sediment starvation, coastal erosion, wetland deterioration, subsidence, and various human activities, land loss within delta plains is a significant global problem. [1] The large delta plains of the world, including the Danube, Ganges, Brahmaputra, Indus, Mahanadi, Mangoky, McKenzie, Mississippi, Niger, Nile, Shatt el Arab, Volga, Yellow, Yukon, and Zambezi deltas, have all suffered significant land loss as the result of either coastal erosion, internal conversion of wetlands to open water, or a combination of both. For the 15 deltas studied by Coleman and others, [12] these deltas experienced a total irreversible land loss of 5,104 km2 (1,971 sq mi) of wetlands between the early 1980s and 2002. During this period, the total average land loss for all of these deltas was about 41 km2 (16 sq mi) per year. In case of the Mississippi River Delta, they found that in a 12-year period, some 253 km2 (98 sq mi) of wetlands had been converted to new open water at a rate of 21 km2 (8.1 sq mi) per year. [12] The factors contributing to land loss in the deltas below are not including direct conversion of delta wetlands into agricultural or urban land, although this is happening concurrently in many of them.
Land loss is the term typically used to refer to the conversion of coastal land to open water by natural processes and human activities. The term land loss includes coastal erosion. It is a much broader term than coastal erosion because land loss also includes land converted to open water around the edges of estuaries and interior bays and lakes and by subsidence of coastal plain wetlands. The most important causes of land loss in coastal plains are erosion, inadequate sediment supply to beaches and wetlands, subsidence, and global sea level rise. The mixture of processes responsible for most of the land loss will vary according to the specific part of a coastal plain being examined. [1] [2] The definition of land loss does not include the loss of coastal lands to agricultural use, urbanization, or other development. [3]
Although seemingly related, wetland loss, is defined differently than land loss. Commonly, wetland loss is defined as the conversion of vegetated wetlands into either uplands or drained areas, unvegetated wetlands (e.g., mudflats), or (submerged habitats (open water). According to this, and similar definitions, wetland loss includes both land loss and land consumption as components of it. In historic times, both wetland and land loss typically are the result of a varying, often controversial mixture of natural and anthropogenic factors. [4] [5] There are other definitions of wetland loss commonly used. For example, some researchers defined wetland loss as "the substantial removal of wetland from its ecologic role under natural conditions." [6]
The main causes of land loss are coastal erosion, inadequate sediment supply, subsidence, and sea level rise. Coastal erosion occurs when the rate of sediment deposition is slower than the rate of sediment removal by coastal currents. [7] The most important cause of decreased rates of sediment deposition is the construction of dams and reservoirs although sediment control and conservation programs can also play a role. [8] Once a dam is constructed, sediment that previously traveled freely in the river is trapped in the reservoir. Decreased sediment loads downstream of the dam prevent sediment from replenishing the delta. [9] Subsidence is the compaction of soil resulting in a lower elevation. Subsidence can occur when oil, gas, or groundwater are extracted. These substances hold the land up until they are removed. Compaction due to heavy urban infrastructure also occurs. [10] Sea level rise due to climate change is another threat to coastal land. [11]
Because of a highly variable combination of sea level rise, sediment starvation, coastal erosion, wetland deterioration, subsidence, and various human activities, land loss within delta plains is a significant global problem. [1] The large delta plains of the world, including the Danube, Ganges, Brahmaputra, Indus, Mahanadi, Mangoky, McKenzie, Mississippi, Niger, Nile, Shatt el Arab, Volga, Yellow, Yukon, and Zambezi deltas, have all suffered significant land loss as the result of either coastal erosion, internal conversion of wetlands to open water, or a combination of both. For the 15 deltas studied by Coleman and others, [12] these deltas experienced a total irreversible land loss of 5,104 km2 (1,971 sq mi) of wetlands between the early 1980s and 2002. During this period, the total average land loss for all of these deltas was about 41 km2 (16 sq mi) per year. In case of the Mississippi River Delta, they found that in a 12-year period, some 253 km2 (98 sq mi) of wetlands had been converted to new open water at a rate of 21 km2 (8.1 sq mi) per year. [12] The factors contributing to land loss in the deltas below are not including direct conversion of delta wetlands into agricultural or urban land, although this is happening concurrently in many of them.