Guardians of Hyjal

The Guardians of Hyjal are a new faction that appeared in World of Warcraft: Cataclysm, whose job is to protect Mount Hyjal and Nordrassil. They are worshippers of the Ancients, such as Aessina and Tortolla, and wish to repopulate the region with animal life. Much like the Cenarion Circle, they are Neutral and made up mainly of druids.

Background
The immense Mount Hyjal has been under increased protection since it was the site of a great battle between Archimonde (a commander of the demonic Burning Legion) and the defenders of Azeroth. It's no longer the charge of any one particular race to protect the mountain; instead, that duty has fallen to an alliance between the Cenarion Circle and green dragonflight known as the Guardians of Hyjal.

The guardians have brought their veneration of the land and ancient demigods like the forest lord Cenarius to Hyjal in times of peace, but it's only now that their presence has become truly crucial. Ragnaros the Firelord and his army of minions have set the mountain aflame with their presence, and they will not rest until Hyjal is reduced to ash around them.

Those heroes who would join with the guardians to heal the land and drive off the invading elementals and their cultist allies can count Archdruids Malfurion Stormrage, Hamuul Runetotem and the green Dragon Aspect, Ysera, among their supporters, and they can add equipment born of the mountain and the World Tree Nordrassil to their arsenal.

Yet another united offensive has formed, much less concerned with the defensive maneuvers of the Guardians of Hyjal. This group, the Avengers of Hyjal, has instead focused on ending the threat of the Firelord once and for all by invading his own realm - the deadly, smoldering Firelands. While this effort might seem suicidal, the Avengers insist that if they don't act against Ragnaros while they have the opportunity, they may not have a world left to defend.

Reputation
Players start at neutral with this faction. Completing all the available Mount Hyjal quests is enough to attain revered status.

Further reputation may be gained in Cataclysm Dungeons (by equipping Tabard of the Guardians of Hyjal), or by doing the Firelands Invasion quests, added in Patch 4.2.

Faction description
Faced with the impending devastation of Mount Hyjal, the most powerful members of the Cenarion Circle have joined forces with their Emerald Dragonflight allies to fend off Ragnaros' elemental hordes and the Twilight's Hammer.

Speculation
Several members of the Guardians of Hyjal wear the Cenarion Expedition Tabard, possibly implying that they draw their military strength from the Cenarion Expedition members.