the Mississippi River Delta environment. Given the ubiquity of this compaction-prone sediment in southern Louisiana, coastal restoration project managers (see: Louisiana Coastal Protection and Restoration Authority) must consider the underlying geology of their regions prior to development as to not exacerbate rates of compaction. An extensive levee system aided by locks and dams has been developed in the waterways of the lower Mississippi River. The levees (designed to prevent flooding along the waterways) prevent needed sediment from being distributed into the marshes downriver. With no new accretion and with steady subsidence, the wetlands slowly are replaced by encroaching saltwater from the Gulf. As a result of this apparent engineering dilemma, large areas of marsh are being lost to the ocean. Since 1930 water has consumed more than 1,900 square miles (4,900 km2) of the state's land. This loss equates to the disappearance of 25 square miles (65 km2) of wetlands each year, or a football field sized area every 30 minutes. This loss can be reversed (at least in some areas) but, only with large scale restoration, including the removal of levees to allow the Mississippi River to carry sediment into these areas. Another factor that damaged wetlands was large scale logging, particularly the extensive logging of cypress forests in the early 1900s. One early logger described it this way: "We just use the old method of going in and cutting down the swamp and tearing it up and bringing the cypress out. When a man's in here with all the heavy equipment, he might as well cut everything he can make a board foot out of; we're not ever coming back in here again". This logging often required construction of canals, which, once the logging was finished, allowed salt water to enter the wetlands and prevent regeneration of the cypress. As if these problems were not enough, the introduction of nutria from South America in the 1930s provided an entirely new species of grazing mammal. Although only a few escaped, there are now millions. Natural grazing by muskrat was now accelerated by grazing from nutria. By removing plants, nutria both cause loss of vegetation, and, perhaps more seriously, a loss of dead organic matter which would otherwise accumulate as peat and raise the level of the marsh One of the most important natural controls on nutria is large alligators, which may provide a useful tool for biological control of