I mainly workoutout in thegym and I use different machines to help me strenghten my back. I would reommend that you workout your whole body and than back fat should start shredding.
Cardio and back extension as well as superman, reverse fly, planks and push ups
Cable rowing and back hyper extensions. They both are great if done correctly, and you can do a ton of reps of both to really burn calories and increase blood flow to the lower back.