Saving the Deltas
Saving the Deltas
Coastal deltas occupy only 1% of Earth’s land surface, yet they are home to 500 million people; this translates to a population density that is 10 times the world average. More amazing, these people all live within only 5 m of sea level! The importance of deltas for global agriculture cannot be overstated, as they are the “rice bowls” of the world, providing one of the major food staples for human populations. Unfortunately, many of these systems are threatened by sea-level rise and flooding in the future. In fact, most coastal plains around the world less than 1 m above sea level are under the threat of being drowned within the next century, something that has not happened at this rate over the past 7,000 years. This means that major cities like Shanghai, Dhaka, and Bangkok are currently threatened and, in most cases, have no viable plan to deal with this threat. A concrete scientific plan is needed to manage and sustain these dynamic systems, or many will be lost. Although the effects of climate change on coastal regions and issues of management response have been topics of concern for at least the last 20 years, other human drivers of environmental change that are specific to certain regions, primarily linked with population expansion, have made it difficult to develop comprehensive plans for coastlines. The northern portion of the Nile River Delta, whose fertile soil allowed Egypt to become one of the cradles of civilization, is tilting and sinking toward the Mediterranean Sea at an alarming rate. In the northeastern part of the delta, near the Suez Canal, the land is sinking by as much as 0.5 cm/yr. Recent studies show that the weight of river sediments accumulated over the centuries has resulted in enhanced subsidence of deltaic sediments. Subsidence is an inherent problem in all delta systems because of the high accumulation of sediments, which over time continue to settle, resulting in compaction and dewatering of these thick mud layers.
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