Hi,
The 4 listed are behaviour changes (impacts) on the map. the fact you can't come up with the goal means that impact mapping as a technique is succeeding, in a sense that it's forcing you to think and talk to the stakeholders why on earth you'd be doing the whole thing in the first place. customer satisfaction might be a goal (that's what your stakeholders I guess care about), but there might be some other things in play. it could be that this is about reducing reputation risk, meeting some externally-mandated service level agreements or political promises, or even protecting the environment. But there's no way to know until you actually talk to the people sponsoring this.
Perhaps organise a meeting with the stakeholders and check how they would know the project hasn't failed to deliver -- I often find that failure criteria is easier to agree on than success. Ask people what they would measure or look for as indicators of failure, and you will probably start to uncover the goal.