Global tourism has been growing ever since its expansion in the middle ages and is still increasing rapidly (IUCN, 1996). The tourism and recreation industry on coral reefs is worth $3,008 ha-1yr-1 (Costanza et al., 1997). The effects of tourism can be from infrastructure such as jetties, harbours etc or from activities for example boating, swimming, fishing, diving/snorkelling (Hardiman and Burgin, 2010). Tourism in areas around reefs can increase the amount of nutrients added to the water column (Hardiman and Burgin, 2010) (see the page on eutrophication for the effects). Removing mangroves and saltmarshes for development (i.e. resorts) can lead to a decrease in reef fish populations (Hardiman and Burgin, 2010), because some reef fish use mangroves and saltmarshes as nursery grounds (Jones et al., 2010). The building of infrastructure can increase the abundance of sessile organisms for example mussels, which in turn affects the whole species composition (People, 2006).
SCUBA diving (Figure 4) is one of the most destructive activities to a reef; reefs that are dived often show signs of higher breakage, especially in branching corals (Hawkins and Roberts, 1992a). Most of the damage done to corals is caused by fins or hands, either purposely or accidentally and may be because of poor buoyancy control (Harriott et al., 1997). There is thought to be a carry capacity for dive sites, which depends on the amount of damage and the ability of the ecosystem to recover. Estimates of carrying capacity range from 5,000 (Dixon et al., 1993) to 50,000 (Hawkins and Roberts, 1992b) divers per site per year. The quantity of damage can be limited by improving dive briefs to contain information about the importance of buoyancy control, how fragile the environment is, and remaining 1m above the substrate, also making it compulsory for refresher courses, having no touch regulations, or limiting the number of divers (Harriott et al, 1997).
Boats damage coral reefs when anchoring above (Figure 2). This is enhanced in large cruise ships whose anchors can be extremely large. Smith (1988) measured the damage to a reef off Grand Cayman Island from the cruise ship, MV Starward, whose anchor weighed 4540kg . All corals were crushed in a 3m radius of the anchor, and up 1-2m either side of the chain. Corals were scraped and had some damage up to 10m from the chain as the ship swung back and forth. After the ship left 2,248m2 of coral were completely destroyed and 1,004m2 were damaged. He also witnessed damage from live aboard dive ships, although smaller than cruise ships the damage from the anchors was still as serious especially when they visit the same spots multiple times and try to anchor directly over the dive site.