For the purpose of the wild empathy ability, a nature warden's class level stacks with levels in all classes with the wild empathy ability. When in her favored terrain, a nature warden adds her favored terrain bonus to wild empathy checks. She may also choose to use wild empathy to demoralize an animal or magical beast rather than improving its attitude, as if using Intimidate rather than Diplomacy.
At 4th level, a nature warden no longer suffers a penalty when using wild empathy to influence or demoralize magical beasts. At 7th level, she may use wild empathy to affect vermin (whether mindless or with Intelligence 1 or 2). At 10th level, she may use it to affect plant creatures (whether mindless or with Intelligence 1 or 2).