You need to clear all 15 acres? All at once or can you do it slowly? Can you leave the stumps?

How many trees are we talking about? How big are they? Doghair versus 12-18 inchers?

A small tractor with backhoe and skid steer will not do the job on the roots you hope it will. Those trees, especially if slow-grown wild ones, are amazingly tough for their size with massive root systems. It takes larger than farm-size equipment to clear right of ways of 12-inchers.

If you have tall, relatively straight trees, a local craftsman or wood dealer might be willing to remove some or all of them in exchange for the wood. It's superb furniture and flooring material and it's not cheap.

Or, call a firewood dealer and make a trade: they cut and haul the wood for sale. It's fabulous firewood and BBQ material. $80-90 a pickup load here.

1. You need a 4WD tractor! Big 'un! Even with 4WD, and "counterweights"on the tractor, you run the risk of burying your rear wheels, and getting stuck? Tractor size means everything here. Mesquites have roots that go to China, and beyond (into the next galaxy?). Do not know the size of the trees, size of the tractor/backhoe, and the type of soil that they are anchored within. 15 acres?

have you tried calling one of the tree farms, you could
possibly make arrangements for them to bring their equipment
and get them like they do in construction sites. Could be
a win win situation, you get your land cleared and they
get the trees.