20 years. Environmental impacts Picnic tables are a principal amenity affecting the quality of park users' recreational experience and their interest in using a particular park. This can have both positive and negative effects. There are often severe trampling effects on the ground immediately around a picnic table, but often these impacts are highly localized. However, in rainy areas the damage caused by trampling may in turn give rise to sheet erosion of the picnic site. During picnic season, picnic tables are often a center of attention from non-human animals seeking access to either humans or their food. Nymphs of the Western black-legged tick, Ixodes pacificus, have been found on picnic tables at roughly the same frequency as in leaf litter. Hornets and other wasps may similarly nest under picnic table platforms or benches, which provide a sheltered location convenient to a food source. As a source of food subsidy from humans, picnic tables have been found to affect corvid activity as these birds seek out areas near picnic tables and may refrain from scavenging deeper in the forest. Males of the Steller's Jay in particular seek out territory near picnic tables because of the superior feeding opportunities. Other approaches Picnic tables are not the only specialized tables used for outdoor dining. For example, in Korea, where it is traditional to sit on the floor to dine, outdoor meals are often held on low wooden platforms known as pyeongsang, and diners sit directly on the platform rather than next to it. Sometimes referred to as "portable wooden decks", pyeongsang have a picnic-table-like ability to foster communal interaction when used as street furniture. In addition, in both Korea and Japan, picnic mats or sheets are sometimes used to create a comfortable, portable dining space. See also Patagonia picnic table effect Works cited References Tables (furniture) Parks Outdoor recreation Table