Construction projects in coastal cities and communities may be built on land reclaimed from the sea. In many areas, wide shallow reef flats have been reclaimed and converted to airports, industrial, or urban lands. Dredging activities (e.g., deep-water channels, harbors, marinas) and dumping of waste materials in the coastal and marine environment can also damage and destroy adjacent coral reefs.
Land clearing and construction projects may change the natural drainage patterns, resulting in freshwater, nutrient, and sediment runoff onto adjacent reefs. Sedimentation can directly smother a reef or increase turbidity in the coastal waters, which reduces light available to corals and their symbiotic zooxanthellae. Corals depend on their zooxanthellae to generate food photosynthetically, therefore light deprivation can cause corals to starve. While some coral reefs thrive in turbid water, the reefs are typically less diverse and are more restricted in depth ranges than those in clear water.ref The combination of suspended, re-suspended, and deposited sediment can limit coral growth, feeding patterns, photosynthesis, recruitment, and survivorship.
Impacts from Coastal Development
These include the following:
- Construction projects (piers, channels, airstrips, dikes, land reclamation, etc.) — can kill corals directly
- Degradation of coral reefs — can result in lost tourism revenue in countries that depend on reef-based tourism and reduce fish populations
- Coastal construction — can cause chronic sedimentation, sewage effluent, industrial discharge, and changes in water flow and runoff, which can adversely affect coral growth rates and metabolic activities as well as directly kill corals
- Removal of reefs — can result in beach erosion, land retreat, and sedimentation
- Sedimentation — can smother reefs or increase turbidity in coastal waters, thus reducing light needed for coral growth and survival
- Pollutants — can lead to increases in coral disease and mortality, cause changes in coral community structure, and impede coral growth, reproduction, and larval settlement (e.g., nutrient runoff can lead to algal blooms that stifle coral growth)
- Mining of coral for construction materials — can lead to long-term economic losses in terms of lost benefits for fisheries, coastal protection, tourism, food security, and biodiversity
As coastal populations increase and natural coastal protection is degraded or lost, sea-level rise and changes in storm patterns are likely to increase the effects of harmful coastal development activities. Local impacts of land-based sources of stress will occur in combination with global and regional stressors, such as climate change, land-use practices, and freshwater inputs, further threatening the survival of coral reef ecosystems. For example, increases in storm impacts linked to climate change could exacerbate run-off of sediments and other pollutants.
Reducing the effects of coastal development is critically important; it threatens nearly 25% of the world’s coral reefs, particularly in Southeast Asia, and the Indian and the Atlantic oceans.ref The impacts of coastal development can be drastically reduced through effective planning and land use regulations. For example, planning and management approaches can include land-use zoning plans and regulations, protection of coastal habitats (such as mangroves), coastal setbacks that restrict development within a fixed distance from shoreline, watershed management, improved collection and treatment of wastewater and solid wastes, and management of tourism within sustainable levels.