Figure 2
Figure 2: Research on the processes underlying biotic invasions (systems knowledge) increasingly considers human agency as an important explanatory factor. The picture shows a subalpine grassland at the slope of Mauna Kea in Hawaii covered in alien grasses and herbs. The past land use of this area as a cattle ranch, that involved the deliberate sowing of grazing-adapted alien species and the accidental introduction of further alien species as contaminants of the seed, helps to explain the invasion of alien species such as Holcus lanatus, Plantago lanceolata, Senecio madagascariensis or Verbascum thapsus in these areas (Photo by Eva Schumacher).