You have been requested to provide preliminary information on the data requirements for a GIS that is to be used to hold an inventory of continental scale vegetation maps for coarse scale land surface and climate modelling purposes. The GIS should be able to represent the broad vegetation types of a single continent in its entirety. The information you are requested to provide: 

What is the primary source of data for the application? Do alternatives exist? 
What is the most appropriate scale for the digital map data sets that are to be produced? 
What are the key considerations in the choice of Datum of the digital map data sets? 
What map projection and co-ordinate system would you chose for this application? 
For each of the points above, you should provide a short paragraph justifying your choices (why have you decided on your particular choice over possible alternatives) and consider any possible limitations, drawbacks or problems that may arise from these.