Answer: It is not necessary the subjunctive mood.
Step-by-step explanation:
The subjunctive mood is used to talk about things that are subjective and/or possible, but not certain. This includes things like doubts, wishes, recommendations and opinions.
The main clause is "Es obvio" que the subjunctive mood will be necessary.
"It is obvious" that the subjunctive mood will be necessary.
If something is obvious it means that it is considered true, so the subjunctive mood is not necessary.
Spymore