Answer: ominous
Explanation:
In this paragraph, the word forbiding means the same as ominous. Ominous simply means that something that's threatening or bad.
From the passage, we are informed that a "dark and forbidding wood of giant arborescent ferns rose". This gives us the impression that there's something threatening there and that's an ominous sign.
Some problems that might occur is that you might forget some schedules, cause there is going to be several schedules, or you might forget something, etc.
