What factors have led to changes in the environment of the Mississippi delta?

Question

What will be an ideal response?

Answer 1

Answer: The Mississippi delta is a vast area of over 50,000 km2, largely consisting of wetlands near sea level. These wetlands have been created and modified through millions of years of sediment accumulation and support a highly diverse ecological community. The nutrients from inland delivered to the Gulf help support a similarly rich and diverse marine community in the gulf of Mexico. Huge accumulations of oil and gas in both the delta and offshore areas have been formed from nutrients and organic matter delivered by the river. In the last century, two factors related to land use and river management have transformed these environments.

First, millions of large and small dams have been built throughout the watershed, both on the main stem and its many tributaries. These dams, combined with navigation structures on the main stem, have shut off the supply of sediment to the vast wetlands of the delta. These wetlands are naturally sinking, and the lack of addition of sediment from inland is leading to a loss of about 50 km2 of wetlands per year.

Second, the use of vast amounts of fertilizer on farms has caused very large amounts of nitrogen to be delivered to the waters of the Gulf. This nitrogen stimulates growth of floating plants, which sink to bottom waters when they die. Decay of this plant matter depletes oxygen, creating a "dead zone" in which aquatic life is significantly limited.