Agriculture is a technical subject. Basically if you study Agriculture and Forestry, it would be tantamount to studying more than 2 subjects of 100 marks each (agriculture was already under-rewarding at 100 marks in the previous syllabus) for only 100 marks in total.
Environmental Sciences is a much better choice I think.
EDX also has a very engaging course available for basics of environmental science.
PS: There is no immediately spot-able overlap in either of the 2 subjects with Geography. So I don't see why it should impact your decision.