Another way to describe it is as a conflict of values. The humans value their livestock as a source of livelihood and security. Lobo values his pack and his role as their leader, which means finding food for them. This difference in values causes the main strife in the story.
One more way to describe the main conflict is as a power struggle. Lobo is the powerful king of Currumpaw, ruling over his pack. The humans, with their guns and traps, are also a powerful force. The story is about who will ultimately have the power in Currumpaw - Lobo to continue his natural way of life or the humans to impose their will and protect their economic assets.
The main conflict can also be seen as a territorial one. Lobo considers Currumpaw his territory where he hunts for his pack. The humans have encroached on this territory with their ranches and livestock. When Lobo hunts the livestock, it's seen as an attack on the humans' economic interests within what they also consider their territory. So, it's a battle over the use of the land and the resources on it.