erosion, breaking rock features, chalk accumulation, litter, abandoned bolts and ropes, human excrement, introduction of foreign plants through seeds on shoes and clothing, as well as damage to native plant species (especially those growing in cracks and on ledges as these are often intentionally removed during new route development through a process commonly referred to as cleaning). Clean climbing is a style of rock climbing which seeks to minimize some of the aesthetically damaging side effects of some techniques used in trad climbing and more often, aid climbing by avoiding using equipment such as pitons, which damage rock. Climbing can also interfere with raptor nesting since the two activities often take place on the same precipitous cliffs. Many climbing area land managers institute nesting season closures of cliffs known to be used by protected birds of prey like eagles, falcons and osprey. Many non-climbers also object to the appearance of climbing chalk marks, anchors, bolts and slings on visible cliffs. Since these features are small, visual impacts can be mitigated through the selection of neutral, rock-matching colors for bolt hangers, webbing and chalk. The use of certain types of climbing gear is banned altogether at some crags due to the risk of damage to the rock face. In such cases, climbers use knotted slings and ropes for climbing protection. Blowtorching is another climbing-induced impact that affects the rocks themselves. Blowtorching is when a climber uses a blowtorch to dry holds on a wet route. This mainly happens in areas that tend to have wet climbing conditions. Blowtorching is not only detrimental to the rock itself and can have permanent damage but it also leaves a very large burn mark that most non-climbers would object to the appearance of. Vandalism The most significant form of vandalism directly attributable to rock climbers is the alteration of the climbing surface to render it more climber-friendly. With the advent of hard, bolted sport climbing in the 1980s, many routes were "chipped" and "glued" to provide additional features, allowing them to be climbed at the standard of the day. This attitude quickly changed as the safer sport climbing technique allowed climbers to push hard without much risk, causing the formerly more-or-less fixed grades to steadily rise. Altering routes began to be seen as limiting and pointless. Unlike traditional climbing which generally uses protection only as a backup in case of falls, some forms of climbing—like