ecoregion 
noun
An area defined in terms of its natural features and environment.In 65 chapters and hundreds of local Groups spanning 21 ecoregions and two Nations, Sierra Club members are hard at Work protecting our natural heritage....
- There are over 200 ecoregions in Canada and even more ecodistricts, so this site will only deal with ecozones.
- Conservation efforts in the Chihuahuan Desert are complicated by the fact that the ecoregion extends across an international border and numerous state boundaries, both in Mexico and the United States.