When ecologically unsustainable, fishing can lead to the depletion of key functional groups of reef species in many locations, with cascading impacts on coral reef habitats and associated species and ecosystems. Common factors contributing to unsustainable fishing practices include rapid human population growth, demand for fishery resources, use of more efficient fishery technologies, and inadequate management and enforcement which can all lead to the depletion of key reef species and habitat damage which has already occurred in many locations. Specific impacts of fishing on reefs generally include one or more of the following: 1) overexploitation of fish, invertebrates, and algae for food and aquarium trade; 2) removal of a species or group of species impacting multiple trophic levels; 3) by-catch and mortality of non-target species; and 4) physical damages to reef environments associated with fishing techniques, fishing gear, and anchoring of fishing vessels. Coupled with other coral reef stressors such as climate change and land-based sources of pollution, these threats are compounded.
Pollution is a broad term to include land-based pollution, newly introduced pathogens, as well as the introduction of an invasive species. Land based sources of pollution can be attributed to agriculture, deforestation, storm water, impervious surfaces,coastal development, road construction, and oil and chemical spills resulting in negative effects such as increased sedimentation, nutrients , toxins, and pathogen introduction. This pollution often leads to disease and mortality in sensitive species, disrupts critical ecological functions, causes trophic structure and dynamics changes, and impedes growth, reproduction, and larval settlement.
Climate change impacts have been identified as one of the greatest global threats to coral reef ecosystems. As temperature rise, mass bleaching, and infectious disease outbreaks are likely to become more frequent. Additionally, carbon dioxide (CO2) absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering sea water chemistry through decreases in pH (ocean acidification). In 2007, the Intergovernmental Panel on Climate Change noted that the evidence is now “unequivocal” that the earth’s atmosphere and oceans are warming. They concluded that these changes are primarily due to anthropogenic greenhouse gases, especially the accelerating increase in emissions of CO2.
Coral reef ecosystems are some of the most valuable ecosystems on Earth. They provide billions of dollars in economic and environmental services—food, protection for coasts, and tourism. As home to the richest marine biodiversity, coral reef ecosystems are beautiful and awe-inspiring. Coral reefs face serious threats, especially from the impacts of climate change (including ocean acidification), fishing, and land-based pollution. A 2008 Global Coral Reef Monitoring Network report says “The world has effectively lost 19 percent of the original area of coral reefs.” Disappearing coral reefs means loss of underwater buffers that reduce wave strength during storms, loss of nature’s nurseries for fish species that generate 200 million jobs and food for a billion people, and loss of the home for plants and animals used to treat cancer and HIV and other viruses.
Content borrowed from http://coralreef.noaa.gov/