Harmful Effects of Sand Plug Removal

The Ecological Importance of Estuary Wetlands and Coastal Wetlands in Hawaii


Estuary wetlands and coastal wetlands play a crucial role in maintaining the delicate balance between land and sea ecosystems. In Hawaii, these unique habitats provide essential services such as sediment trapping, nutrient cycling, and habitat provision for diverse flora and fauna. However, the removal of sand plugs from these wetlands can have detrimental effects on both the marine environment and terrestrial ecosystems. This article explores the harmful consequences of sand plug removal, emphasizing the need for conservation efforts and sustainable management practices.

1. Introduction

Estuary wetlands and coastal wetlands are dynamic ecosystems that bridge the gap between land and sea. They serve as critical buffers, mitigating the impact of land-based activities on coastal zones. In Hawaii, these wetlands face increasing threats due to urban development, agriculture, and aquaculture. One common practice that exacerbates these threats is the removal of sand plugs. Here, we delve into the ecological implications of sand plug removal and its effects on both oceanic and terrestrial environments.

2. Sand Plugs: A Vital Component

Sand plugs, also known as sediment barriers, naturally accumulate in estuaries and coastal wetlands. These deposits consist of fine sediments, organic matter, and plant debris. Their presence is essential for several reasons:

  1. Sediment Retention: Sand plugs trap sediments carried by freshwater runoff from the mountains. By doing so, they prevent excessive sedimentation in downstream areas, including coral reefs and seagrass beds.
  2. Nutrient Cycling: These wetlands act as nutrient filters. Sand plugs retain excess nutrients (such as nitrogen and phosphorus) from agricultural runoff, preventing their entry into coastal waters. This nutrient retention supports healthy marine ecosystems.
  3. Habitat Creation: Sand plugs create diverse microhabitats for aquatic organisms. They provide shelter, breeding grounds, and feeding areas for fish, birds, and invertebrates.

3. Harmful Effects of Sand Plug Removal

Despite their ecological significance, sand plugs are often removed for various reasons, including flood control, navigation, and land development. Unfortunately, this practice has severe consequences:

  1. Increased Sediment Transport: Without sand plugs, sediments flow freely into coastal waters. Excessive sedimentation harms coral reefs, seagrass beds, and other sensitive marine habitats.
  2. Nutrient Overload: Sand plug removal disrupts nutrient cycling. Nutrients that were once retained now enter the ocean, leading to algal blooms, oxygen depletion, and eutrophication.
  3. Loss of Biodiversity: Sand plugs support a rich array of species. Their removal reduces habitat complexity, affecting fish, birds, and other wildlife.

4. Case Study: Hawaii’s Coastal Wetlands

In Hawaii, the removal of sand plugs has been observed in several coastal wetlands. For instance, contractors dredged over a million cubic yards of sand from Delaware Bay to restore eroded beaches and barrier dunes1. While this intervention aimed to protect human infrastructure, it disrupted natural processes and impacted local ecosystems.

5. Conservation Strategies

To safeguard estuary and coastal wetlands, we propose the following measures:

  1. Prioritize Conservation: Identify critical wetland areas and prioritize their protection. Implement best management practices to reduce sediment and nutrient losses from terrestrial watersheds.
  2. Educate Stakeholders: Raise awareness among policymakers, developers, and the public about the ecological value of sand plugs. Encourage sustainable land-use practices.
  3. Restoration Efforts: Invest in wetland restoration projects, focusing on creating and maintaining sand plugs. Restore degraded wetlands to enhance their resilience.


Estuary wetlands and coastal wetlands are irreplaceable components of Hawaii’s natural heritage. By recognizing the importance of sand plugs and advocating for their conservation, we can ensure the long-term health of both land and sea ecosystems.


  1. Bruland, G. L. (2018). Coastal wetlands: function and role in reducing impact of land-based managementNatural Resources and Environmental Management Department, University of Hawaii Ma ̄noa 2.
  2. Coastal Recovery: Bringing a Damaged Wetland Back to LifeYale Environment 360 1.
  3. Wetlands and EstuariesU.S. Geological Survey 3.
  4. Basic Information about Wetland Restoration and ProtectionU.S. Environmental Protection Agency 4.

2: Read more 1: Read more 3: [Read more](https://www.usgs.gov/science/science-explorer/coasts/wetlands-and-estu