Ecosystem diversity measures based on the species composition of flora, or fauna, or other ecosystem properties, are all equally justifiable: but measures based on different criteria tend to give different results. It is also important to note that diversity measures used for ecological units, such as ecosystems, assume that these units are basically the same in form throughout a wide area and in different places. In reality,however, this is rarely true. These diversity measures cannot, therefore, be effectively used for purposes of generalisation.