Hi there, welcome to the board!
I'm in love with my two young EM's (8 month male Knox, 13 week female Roux), as well as the adult male EM (Gunner) that belongs to the family I work for (I'm a full-time nanny). They are fiercely loyal, loving, and accepting of their family pack. With strangers, they tend to be more aloof and weary - Gunner has been known to bite unwelcome strangers that enter their property. While it's true that EM's are very aware of their surroundings and like to know where their humans are at all times, I can't promise that an EM will be as protective (particularly against wildlife) as you're looking for. Naturally, a lot of that will depend on the temperament and training of the dog, but I'm fairly certain that Knox and Gunner would be just as afraid of a bear as I would be. Now, if it came to protecting me from a strange person, I'd feel more confident in Knox's natural protectiveness kicking in, but again... I can't say for sure.
Are you looking for something to alert you to a bear's presence? Or looking for something that will physically fend off a bear? If you're looking for an intimidating alarm system, an EM fits the bill. But if you're looking for something that will physically take on and scare off a bear, you might want to do more research. I would, if possible, speak to reputable breeders about your specific desires in a dog - and be honest - as they will surely have the most thorough knowledge.
And also, as mentioned before, EM's (or any giant breed, for that matter) require special accommodations when it comes to nutrition, exercising, vet care, and hygiene. Not to scare you, just a caution to consider ALL the elements of owning a giant breed, not just it's natural protectiveness.
Hope you find the answers you're looking for!