I would like to see the Orcs living in a dangerous zone, a zone where life is difficult and only the strongest can survive, not only a "Dead zone" where everything is just dead, a zone where NATURAL SELECTION is very hard and cruel, a volcanic jungle or volcanic mountain.
They reproduce rapidly and in large numbers, which means that NATURAL SELECTION works very well on them. Those that CAN'T SURVIVE the hard conditions die young and don't pass on their GENES.
I like the idea, but instead of TESO-style volcanic geography, a prairie/savannah with one or two volcanoes close by would be better.
Maybe something like: The orcs are a very numerous people because where they live the mortality is very high because of the predators in the region.