I'm surprised about this not being straightforward - where can I download a table or anything parseable from which I can get numeric taxonomic IDs from Uniprot's five-character identifiers? For example 9606 for "HUMAN", 8030 for "SALSA", etc.
You can download taxanomic identifier from this link given on uniprot website.
http://www.uniprot.org/taxonomy/
Also you can add taxanomic identifier ID and taxanomic lineage in search option also. Simply add the column of taxanomic lineage and idetifier in your search criteria.