The Lake Pontchartrain Basin in southeast Louisiana is a 9645 mi2 (24,980 km2) area composed of low-lying coastal forests hydrologically coupled with deltaic estuaries associated with the Mississippi River and the Gulf of Mexico. The two largest cities in Louisiana, New Orleans and Baton Rouge, are within the basin. Since European settlement in 1718, population increase, landscape modifications, accidental events, and exploitation of natural resources have had a profound impact on the natural landscape.
A database of several hundred environmental impacts from 1718 to 2002 was developed. Examples of impacts are introduction of invasive species, extirpation of species, deforestation, dredging of wetlands, land clearing, Mississippi River modifications, oil and gas activities, the development of superfund (contamination) sites, and water pollution. The chronology was evaluated four ways to identify the most significant ecologic impacts. Based on the analyses of the chronology, five periods of anthropogenic activity are proposed to have resulted in the most significant negative impacts to the Lake Pontchartrain Basin since European settlement in 1718. These five periods are:
Land clearing and settlement of natural levees and ridges from 1718 to 1844
Construction of artificial levees along the Mississippi River from 1844 to 1900
Deforestation of virgin forests by commercial logging from 1890 to 1938
Dredging and armoring of estuaries from1930 to 1974
Increases in water pollution from 1950 to 2002
These selected activities affected approximately 76% of the area of the basin and may have reduced habitat quality by 50% initially, which later recovered to nearly 60% functionality. Generally, these impacts still result in latent impairment or increasing damage. Three of the periods contribute significantly to the wetland land-loss crisis in southeast Louisiana.
The near 300-year legacy represents unsustainable land or natural resource utilization. Many of the impacts predate modern physical and biological techniques, and, therefore, a true baseline of conditions without alteration by European settlers is poorly known for the Lake Pontchartrain Basin.