The spread of pest plants is a trans-boundary problem that causes losses to biodiversity and disrupts ecosystems. Much social research into, and policy development for, weeds has conceptualised their control as a problem facing individual landowners, rather than as a collective action problem. In the case of serrated tussock (Nassella trichotoma), a highly invasive, noxious weed that is widespread in southeastern Australia, landowners and government staff are acutely aware that this weed is a communal problem.

Impervious surface is a key indicator for monitoring urban land cover changes and human-environment interaction. Although the normalized difference impervious surface index (NDISI) has shown the potential to extract impervious surface areas (ISA) from multi-spectral imagery, it may lack robustness due to the spectral heterogeneity within urban impervious materials and confusion between other land covers. In this letter, a multi-source composition index is proposed to overcome the limitations of the original method.

Area estimation is a common application of remote sensing especially in relation to studies of land cover change. The use of an imperfect, nongold-standard, reference is shown to be a source of substantial error in estimates of change area. The relationships between the accuracy of land cover classifications, both real and perceived, together with area of change are explored over the full range of change abundance. The magnitude of mis-estimation varies with the abundance of change and the quality of the data sets used but may be large.