Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_22897 ( "land formation" text, "area, km\u00b2" real, "of which currently forests, km\u00b2" real, "% forests" text, "habitat type" text )

### Question ###
When middle prut valley is the land formation what is the highest of which currently forests, km ?

### Accurate SQL ###

SELECT MAX("of which currently forests, km\u00b2") FROM table_22897 WHERE "land formation" = 'Middle Prut Valley'