Learn Dutch: Indien we de bomen verwijderen, moeten we dit ergens compenseren. - If we remove the trees, we must compensate for this somewhere.

Indien means "if" or "in case," just like als. However, indien is more formal and is mostly used in written Dutch, official documents, or professional discussions (which fits the context of urban planning and removing trees). In everyday speech, you would almost always hear als.

Why does the second part of the sentence start with the verb moeten?

This is due to the V2 (verb-second) rule. The entire "if" clause (Indien we de bomen verwijderen) acts as the first block of information. Therefore, the conjugated verb of the main clause (moeten) must immediately follow the comma to take the second position, pushing the subject (we) to the third position.

The English translation says "compensate for this", but there is no Dutch word for "for". Why?

In English we say "compensate for [something]", but the Dutch verb compenseren takes a direct object. You don't need a preposition here. You simply compensate the action itself, which gives us dit compenseren.

What exactly does dit refer to in this sentence?

Dit refers back to the entire preceding action: the removal of the trees. When pointing back to a whole situation, action, or clause rather than a specific "de" or "het" noun, Dutch uses the neuter pronouns dit (this) or dat (that).