I try to distinct between 你还是不同意吗 and 你还不同意吗.
你还不同意吗 implies (given something aforementioned), you still disagree?
你还是不同意吗 implies (given something aforementioned), your attitude/stance is still no/disagree?
OP already listed their different definitions. They don't seem to be interchangeable at all.
The meaning of 'still' may be the only one where either word-choices can be used in the same sentence, but there's still some subtle differences between them:
Fact 1 + 还 + Fact 2 describes the facts without emphasizing any.
Fact 1 + 还是 + Fact 2 emphasizes the ...
草原 should mean animal agriculture(畜牧業) and any other nature resources related to grassland.
海洋 have similar concept of 草原.
You could use 農林漁牧業 to indicate agriculture,forestry,fishing and animal agriculture industries.