The word 'hiking' is understood in all English-speaking countries, but there are differences in usage. In some places, off-trail hiking is called 'cross-country hiking', 'bushwhacking', or 'bushbashing'. In the United Kingdom, hiking is a slightly old-fashioned word, with a flavor more of heartiness and exercise than of enjoying the outdoors; the activity described here would be called hillwalking or simply 'walking'. Australians use the term 'bushwalking' for both on- and off-trail hiking. New Zealanders use 'tramping' (particularly for overnight and longer trips), 'walking' or 'bushwalking'. Hiking in the mountainous regions of India and Nepal and in the highlands of East Africa is sometimes called 'trekking'. Overnight hiking is called 'backpacking' in some parts of the world. Hiking a long-distance trail from end to end is referred to as 'thru-hiking' in some places.
Hikers often seek beautiful natural environments in which to hike. Ironically, these environments are often fragile: hikers may accidentally destroy the environment that they enjoy. The action of an individual may not strongly affect the environment. However, the mass effect of a large number of hikers can degrade the environment. For example, gathering wood in an alpine area to start a fire may be harmless once (except for wildfire risk). Years of gathering wood, however, can strip an alpine area of valuable nutrients.
Generally, protected areas such as parks have regulations in place to protect the environment. If hikers follow such regulations, their impact can be minimized. Such regulations include forbidding wood fires, restricting camping to established camp sites, disposing or packing out faecal matter, imposing a quota on the number of hikers per day.
Many hikers espouse the philosophy of Leave No Trace: hiking in a way such that future hikers cannot detect the presence of previous hikers. Practitioners of this philosophy obey its strictures, even in the absence of area regulations. Followers of this practice follow strict practices on dealing with food waste, food packaging, and alterations to the surrounding environment.
Human waste is often a major source of environmental impact from hiking. These wastes can contaminate the watershed and make other hikers ill. Bacterial contamination can be avoided by digging 'catholes' 10 to 25 cm (4 to 10 inches) deep, depending on local soil composition and covering after use. If these catholes are dug at least 60 m (200 feet) away from water sources and trails, the risk of contamination is minimized. Many hikers warn other hikers about the location of their catholes by marking them with sticks stuck into the ground.
Sometimes, hikers enjoy viewing rare or endangered species. However, some species (such as martens or bighorn sheep) are very sensitive to the presence of humans, especially around mating season. Hikers should learn the habits and habitats of the endangered species, in order to avoid adverse impact.
There is one situation where an individual hiker can make a large impact on an ecosystem: inadvertently starting a wildfire. For example, in 2005, a Czech backpacker burned 7% of Torres del Paine National Park in Chile by knocking over an illegal gas portable stove. Obeying area regulations and setting up cooking devices on bare ground will reduce the risk of wildfire.
Hiking may produce threats to personal safety. These threats can be dangerous circumstances while hiking and/or specific accidents or ailments. Diarrhea has been found to be the most common illness afflicting long-distance hikers in the United States. (See wilderness diarrhea.)
Dangerous hiking circumstances include losing the way, inclement weather, hazardous terrain, or exacerbation of pre-existing medical conditions. Specific accidents include metabolic imbalances (such as dehydration or hypothermia), topical injuries (such as frostbite or sunburn), attacks by animals, or internal injuries (such as ankle sprain).
Hikers often propose a set of behavioral prescriptions to minimize these threats. A well-known example of such a set of prescription is the Ten Essentials.