Complex sentence: The eradication began in 2013 with 3,500 Reindeer killed, nearly all the rest were killed in early 2014, with the last (about 50) cleared in the 2014/15 southern summer.
Split into simpler sentences: The eradication began in 2013 with 3,500 Reindeer killed. Narly all the rest were killed in early 2014, with the last (about 50) cleared in the 2014/15 southern summer.