I'd think the growing Cazador population would be enough, but then in Lonesome Road, we're told that the Tunnelers are also slowly moving in. So between these two creatures beginning to take over, it seems to me that the Mojave is pretty screwed.

I guess if Mr. House used his Securitron army to defend the area, it could work, given that they have good precision and firepower. Caesar's Legion could also work against the Tunnelers, they'd fight well with their melee weapons. And I suppose the 1st Recon and Rangers could easily supplement the NCR, and if the Brotherhood is spared, their power armor and laser weaponry would also be effective. But that's just conjecture, as the true size of the Tunneler/Cazador population hasn't been truly gauged.

Just a thought I had the other day when I was wandering through the northwest of the Mojave, carefully wading through the Cazadors.

Tunnelera are no more of a threat then death claws.
If you look at the death claw that you see the tunneler kill, and shoot it before it gets a chance to kill it.

The death claw dies in like two shots.

Put a normal death claw vs a tunneler? The death claw will destroy it

I don't think the Brotherhood would get involved unless it started to get to them directly .

I think the Tunnellers could be a match for Deathclaws though. One on one a deathclaw might destroy a tunneller but I get the impression that Tunnellers work in packs and use tactics to bring down others.

Well that's just a technicality. They can't have Tunnelers being powerful enough to one or two-hit-kill a Deathclaw, because then that means when they attack you, you're dead just the same. It's more of a balance issue.

I'm speaking less from a gameplay standpoint and more from a hypothetical standpoint, because whenever gameplay is involved, the PC is always overpowered. All the military games on the market have you singlehandedly killing off whole armies, but other than the protagonist, everyone is normal.

So rather, since Tunnelers are deadly enough in packs to kill a Deathclaw, can multiply quickly, and also tunnel underground, they add up to be a major problem.

I doubt Cazadors will cause the Mojave to be screwed. If they become a serious problem people will deal with it and destroy their nests. People can wipe them out in a couple generations or at least make them manageable. You could draw parallels with Killer Bees. They are a problem in some areas and can be deadly and when they started moving into the states people freaked out. Yet we haven't seen mass exodus of the states in which they have moved into.

Tunnelers are another matter. But they are afraid of light and noise. All we have to go on that they are a threat is Ulysses. A man who we must remember was very fatalistic and genocidal to the point where we has going to nuke a lot of people. Of course he would be the type to see Tunnelers and believe that they would take everything over and kill everyone.

Once they get beyond The Divide I am sure they will slow their advance if they even indeed advance into the Mojave. People will figure out they don't like sound and light. The strip is nothing but sound and light, so I am sure they will stay away from that.

Let's not forget about Elijah and his plans to unleash the Cloud on the Mojave - suppose it depends on whether there could be anyone else like the Courier with the skill to penetrate the Vault and then to make the decision to work with Elijah, not to kill him. He's tried a number of people in the short time that he's been there, after all. He is getting old but chances are someone will come along like the Courier.