Habitat alteration, simply put, is a change, or alteration, to a particular environment. What is unclear from its designation, however, is the adverse affect changes - big or small - have on the broader environment and related plant and animal life. According to the Nature Conservancy, habitat alteration, along with invasive species, are the two main causes of fish extinction. Furthermore, in the United States 40 percent of fish and amphibians, 50 percent of crayfish, and 70 percent of mussels are endangered due largely to habitat alterations resulting from such practices as bottom trawling, anchoring, coastal developments, and cyanide and blast fishing. These activities create change with devastating effects on marine ecosystems.

Once restricted to sandy, flat bottom areas, technical innovations such as rollers and rockhopper devices have allowed for bottom trawling at depths as great as 6,000 feet. This practice entails the dragging of massive bag-shaped nets along the ocean floor to collect targeted fish. But they damage sensitive and complex deep-sea ecosystems along the way. With some rockhoppers weighing as much as 300 pounds, coral forests, rock pinnacles, and boulder-covered areas (great places for fish to hide, feed, and lay eggs) face serious long-term damage. A quick pass of a trawl and one sweep can kill non-targeted marine life such as bottom-dwelling invertebrates that can take three, five or more years to recover. Additionally, fishing nets can become lodged on rock outcroppings, which in turn can wear away the polyps and upper tissue layers of the coral reef reducing useable habitat for fish, mammals and birds. According to the Pew Oceans Commission, fisheries in Northern California and New England are typically trawled more than once a year. (Pews Oceans Commission, 2003)

Cyanide fishing also has a profound effect on habitats. While largely illegal around the world, it continues to thrive in countries such as the Philippines, Indonesia, Cambodia, the Maldives, Thailand, and Vietnam. Fishermen dive and squirt concentrated cyanide into the crevices of the coral reef, which stuns the fish, making them easier to catch. This practice also "bleaches" the coral reef, killing its polyps. Without these polyps, the reef will die. In an effort to escape the cyanide, the fish burrow deeper into the coral only to face a fisherman's hammer that breaks apart the reef to reach the fish, which are targeted for transport and sale to home aquarium enthusiasts.

Blast fishing, the use of dynamite or other homemade explosives to kill or stun reef fish, is also common practice dating back to the advent of explosives . Extremely cost effective, the results are devastating. According to the Encyclopedia of Earth, (www.eoearth.org) a single bomb costs about $1 to $2 to build and may result in $15 to $40 worth of fish. The dead fish float to the water's surface, while divers force any remaining fish from their hideouts in the reef. Blast fishing can bring about tremendous loss of coral cover, diminished ability for coral re-growth, and localized extinction of coral-dependent fish species.

One should not single out fishermen as the cause for damage. Cruise ships running aground and the indiscriminate dropping of anchors and chains that can weigh up to 5 tons have wrecked havoc and cause irreparable devastation to coral reefs and sea grass beds. The damage from one drop in a calm, windless sea can take a reef nearly 50 years to repair (www.see-the-sea.org). Drop that same anchor in a storm and it's likely dragged across coral reefs, dislodging coral, grinding it into rubble, or destroying its underlying limestone structure. In high usage areas, like the Florida Keys, the installation of mooring buoys has lessened the pressure on the reefs. However, these moorings are expensive to install and maintain. For large vessels very few moorings have been built.

According to See-the-Sea.org, coastal development is an increasing threat. Currently, 60 percent of the world's population lives within 60 miles of a coast (www.see-the-sea.org). This close proximity of human development is affecting coastal marshes and estuaries. Florida, for example, has experienced a population growth from 2 million in 1940 to over 14 million today, which has caused more than 50 percent of the original Everglades - a complex system of interdependent ecosystems - to be turned into agriculture or urban areas.

As disturbing as these facts are, individuals can effect change now with simple steps like remaining mindful of eating responsibly - selecting sustainably caught fish and incorporating varieties and alternatives to fish into one's diet. Many fish are caught for aquarium use rather than consumption - it's important to remain mindful of their means of capture, avoid the purchase of illegally caught fish, and consider discontinuing one's aquarium hobby. If you embark on a cruise, inquire into their anchoring practices. If you live near the coast, monitor your activities for the least amount of impact possible.