There is some criticism of trail riding when excess or improper use of trails may lead to erosion, the spread of invasive plants, conflict with hikers, or harassment of wildlife. Off-road or trail activity is usually not permitted, as such activity may also raise the risk of soil erosion, spread weeds, and cause other damage. However, many responsible equestrians, mountain bikers, and off-road motorcyclists, especially those who get involved in these sports by joining an organized club, perform hours of trail maintenance every year. Many organizations also sponsor educational events to teach newcomers about safety, responsible land stewardship and how to improve riding techniques.