What’s one indirect consequence of building seawalls? A. It rises the sea level, which infiltrates groundwater aquifers. B. It causes an excess amount of fertilizer to become stuck in the sand. C. It increases the frequency of algal blooms. D. The shoreline habitat is destroyed through loss of sand.
The correct answer and explanation is:
Correct Answer: D. The shoreline habitat is destroyed through loss of sand.
Explanation (300 words):
Seawalls are structures built parallel to the coastline with the primary purpose of protecting human infrastructure—such as buildings, roads, and ports—from erosion and the force of ocean waves. While they offer direct protection, seawalls can lead to several indirect environmental consequences, particularly regarding the natural dynamics of coastal systems.
One major indirect consequence of building seawalls is the destruction of shoreline habitat through the loss of sand. Seawalls interfere with the natural processes of sediment movement and wave action. Normally, beaches are dynamic systems where sand is constantly being deposited and eroded. However, when a seawall is installed, the energy of incoming waves is reflected back to the ocean rather than being absorbed by the beach. This reflection leads to increased erosion at the base of the seawall, which gradually removes sand from the beach.
Over time, this erosion can result in the narrowing or complete loss of the sandy beach in front of the seawall. This process is known as “coastal squeeze.” Natural habitats—such as dunes, intertidal zones, and nesting areas for wildlife like sea turtles and shorebirds—may be lost when the beach cannot migrate landward due to the hard barrier of the seawall.
Moreover, these changes reduce the ecological value of the coast. The loss of sand limits the beach’s ability to support plant life and marine species that rely on soft sediments for nesting or burrowing. Thus, although seawalls may provide a short-term solution for human development, they often do so at the cost of long-term environmental degradation.
In conclusion, the loss of shoreline habitat due to sand erosion caused by seawalls is a significant indirect impact, making option D the most accurate answer among the choices provided.