By MathKnight – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=19698684

They rumble in herds across the grassland plains
Devouring once fertile fields and leaving them stripped
Felling trees, trampling grass and crops and weeds
Indiscriminately they track their way across the countryside
Leaving behind their droppings of concrete and asphalt
Attempting to fulfill their unending hunger and thirst
As they transform the fecund earth into urban sprawl
And their consumption goes unchecked in their environment
For they are all herbivores consuming all that is green in their path
No natural predator, no carnivorous beasts stalk their herds
Nothing tracks and preys upon these monstrous beasts
Nothing culls the herd or limits their destruction
So fields become neighborhoods and concrete jungles of suburbia
As the urban landscape is drawn outward by the mechanical herds
In their quest for new  lands to be consumed by their hungry mouths