Replace 'have' with 'has'.
Here, the subject 'land' is an uncountable noun i.e. used in singular sense, so the verb should also be singular.
| Half of, One third of, Two thirds of, Three-fourths of|
Some, Some of, All, All of, Enough, Most, Most of, Lots of, A lot of, Plenty of
- If noun is uncountable, it is used in 'singular' sense, then verb is also 'singular'.
- If noun is countable, it is used in 'plural' sense, then verb is also 'plural'.