Complex sentence: The life span of horses on Cumberland Island is approximately half that of their ancestors, due to infestations of parasites, disease, and digestive issues linked to the ingestion of sand, which causes intestinal blockages and abdominal distension.
Split into simpler sentences: The life span of horses on Cumberland Island is approximately half that of their ancestors, due to infestations of parasites and disease. They also suffer from digestive issues linked to the ingestion of a great amount of sand, which causes intestinal blockages and abdominal distension.