This is a tough one. GDM or Generalized Dissimilarity Modelling is probably the most complex tool within the Spatial Portal. It is normally used over a large number of species (a group such as Eucalyptus or lifeforms such as amphibians) and over regions to continental areas to identify how well all the species align with environmental factors.

GDM accepts any species list and a suite of environmental layers and then warps the environmental layers to best align with the species distributions. For example, if you use Western Australia as an area, Eucalyptus as the species list and say rainfall, temperature and solar radiation layers, you will produce new rainfall, temperature and solar radiation layers that best align with the distribution of Eucalypts in Western Australia. These new layers could be used in further analysis such as area classification.

More information can be found at Tools | GDM.