Complex sentence: The International Council for Bird Protection placed this reserve on the list of Important Bird Area, and did so for good reasons: this reserve is the largest of its kind in this part of Europe, in terms of both size and diversity.
Split into simpler sentences: The International Council for Bird Protection placed this reserve on the list of Important Bird Areas, and did so for good reason. This reserve is the largest of its kind in this region of Europe, in terms of both size and diversity.