If installed correctly, a hardwood floor should not buckle. In fact, if any buckling does occur, it will actually be the sub-floor that is installed below the hardwood and not the actual hardwood floor. However, it does look like it is the flooring itself due to the placement of the individual boards. Thankfully, it is somewhat easy to fix wood flooring after the sub-floor has buckled.
In older homes, it often looks like buckling has occurred. However, when looking underneath the flooring, it becomes apparent that it is the base or piling that has sunk. This can either be repaired by pulling up the wood flooring and filling in the areas underneath, or by putting new piling underneath and pushing the entire structure upwards. Both of these will eventually result in a newly flat surface for the individual pieces of wood to lay upon.
Once there is a new flat surface, the individual pieces of wood can be pulled back up and examined for damage. This will usually reveal that the pieces are largely intact. Pieces that have been damaged will need to be repaired or replaced. This can take a little bit of time, but it is worth it in the end.
Once all of the pieces have been looked over or replaced, it is time to refinish them and make sure that they are ready to be re-laid. sending out any rough spots, sealing the individual pieces, and making sure that they lay together correctly is all that is needed at this stage.
Finally, you can lay all of the pieces together, sealing them once the entire floor has been put together. Properly maintained, this new floor can last a very long time without the need for refinishing. When buckling does seem to be happening, checking the sub-flooring will usually allow you to stop it before it damages the wood again.