The flora and fauna of this region are unnaturally fertile. Hal’laman is a center for all forms of animal husbandry, and also holds the largest spawning pools of the Dominion. When Lamannia is coterminous, growth rates spike dramatically; it’s always a struggle to keep the city safe during these times, with aggressive beasts swept into frenzies and vegetation becoming shambling mounds.
Source: Exploring Eberron