Data collection and research may have a bias: areas near roads get seen by specialists who may hesitate to venture too far off the beaten track due to cost, time available, physical difficulty and dangers. Some areas are also easier for people to get access to, and thus the first, and perhaps the only areas, to show stress. Problem situations may also be identified because officials and researchers see them only at certain times when they appear degraded in a misleading way which is not typical of the longer term or wider scale.