Ons besluit of klimaatbeheer nodig is al dan nie.

Here of means whether, not or.

So Ons besluit of klimaatbeheer nodig is al dan nie means We decide whether climate control is necessary or not.

This is a very common use of of in Afrikaans:

• Ek weet nie of hy kom nie. = I don’t know whether he is coming.
• Hulle vra of dit waar is. = They ask whether it is true.

Because this part of the sentence is a subordinate clause introduced by of.

In main clauses, Afrikaans usually keeps the finite verb in second position:

• Klimaatbeheer is nodig. = Climate control is necessary.

But after a word like of, the verb usually moves toward the end:

• ... of klimaatbeheer nodig is = ... whether climate control is necessary

So:

• main clause: Dit is nodig
• subordinate clause: ... dat/of dit nodig is

This is one of the most important word-order patterns in Afrikaans.

Al dan nie means or not.

In this sentence, it reinforces the idea of uncertainty or choice:

• of klimaatbeheer nodig is al dan nie = whether climate control is necessary or not

It is a fixed expression, so learners should try to remember it as a chunk:

• of ... al dan nie = whether ... or not

You can often leave it out.

These two are both possible:

• Ons besluit of klimaatbeheer nodig is.
• Ons besluit of klimaatbeheer nodig is al dan nie.

The version with al dan nie is a bit more explicit, because it clearly means whether it is necessary or not. Without it, the meaning is often still understood from context.

Afrikaans very often writes compound nouns as one word, much like Dutch and German.

So:

• klimaat = climate
• beheer = control/management
• klimaatbeheer = climate control

This is completely normal in Afrikaans. English often uses two words where Afrikaans prefers one compound word.

Nodig is an adjective meaning necessary or sometimes needed, depending on context.

In this sentence:

• klimaatbeheer is nodig = climate control is necessary

Afrikaans often uses adjectives after is in this way:

• Dit is belangrik. = It is important.
• Water is nodig. = Water is necessary / needed.

Besluit here is present tense:

• Ons besluit = We decide

Afrikaans verbs do not change much for person:

• Ek besluit
• Jy besluit
• Ons besluit
• Hulle besluit

So unlike English, you do not get forms like decide/decides. The verb usually stays the same.

Not really in a direct, word-for-word way.

In many contexts, dan can mean then, but in al dan nie it is part of a fixed idiomatic expression. So it is better not to translate each word separately here.

Treat al dan nie as one unit meaning:

• or not
• whether ... or not

That will help you sound more natural and avoid overanalyzing the phrase.

Yes. That would change the tense to the future:

• Ons besluit of klimaatbeheer nodig is al dan nie. = We decide whether climate control is necessary or not.
• Ons besluit of klimaatbeheer nodig sal wees al dan nie. = We decide whether climate control will be necessary or not.

So the original sentence is about what is necessary, while the second version refers to what will be necessary.

Yes, it is grammatical and natural.

A speaker might also say:

• Ons besluit of klimaatbeheer nodig is.
• Ons besluit of klimaatbeheer nodig is of nie. in some contexts, though al dan nie is the more standard fixed expression for whether ... or not.

The sentence is a good example of:

1. of meaning whether
2. subordinate clause word order
3. the fixed phrase al dan nie