The activities of researchers, students, and members of the public also sometimes contribute to biological decline. When people take nature walks, they inevitably widen the trails, compact the soil, trample the plants, and so on. Sometimes, even such small amounts of damage threaten the survival of certain species.
Some alpine tundra habitats are especially vulnerable because large numbers of walking humans are lured by majestic mountain views and spectacular wildflower displays, and stray off of designated paths. Concern has been expressed about the tourist impact on tundra around Trail Ridge Road in Rocky Mountain National Park in Colorado (United States).
Trampling has been shown to have a rather dramatic effect on the diversity of the tiny animals in grassland litter and decaying leaves. Not only on land but in water, too, where humans can sometimes break off pieces of coral or disturb sand, changing the behavior of certain animal and plant species. Reefs are often damaged by the anchors of pleasure boats in some areas. About one fifth of the staghorn coral at Fort Jefferson national Monument off Florida has reportedly been damaged in that way.
Sadly, animals can often be hurt by human ignorance. The Manatee, or sea cow, feeds on aquatic weeds and is the gentlest of mammals. They will not attack even if their young are threatened. They have long been hunted for their meat, their ivorylike bone, oil, and leathery skin. They are also an important control organism for the exotic weeds that choke waterways throughout the warmer parts of the world. The propellors from boats often scar a significant proportion of the 800 to 1,000 sea cows in Florida. Curious divers often harass the animals, and sometimes people have killed them deliberately. Others often drown in flood-control structures or because they become entangled in fishing gear. Others are crushed by barges.
Off-road vehicles (ORVs) are almost ideal devices for smashing plant life and destroying soil. A dirt bike will degrade an acre of land in a twenty-mile drive, even if drive with extreme care. A four-wheel-drive vehicle will have the same impact in just six miles. They help strip away vegetation, and begin an erosion process that continues the destruction. In California's coastal mountains, ORV trails that have been in use for only six years are eight-foot-deep gullies. These vehicles also exterminate animals by exterminating the plants they depend upon, and also run them over and crush their shallow burrows.
Indirect Causes - Transportation
