The punctuation of the sentence is correct because when a word like <em>however, as a result, consequently </em>starts a sentence, it should be followed by a comma. These words are called transitional phrases or conjunctive adverbs.
Transitional phrases are placed at the beginning of the sentence and are used as a linking device with the ideas in the previous sentence. In this way, the transition between the two sentences is much more smoother and the result is a cohesive piece of writing.
