Complex sentence: The swamp would have been covered in "Phragmites" marsh grasses and today there is a small area of this remaining in Khao Sam Roi Yot National Park, a relic of the original landscape.
Split into simpler sentences: The swamp would have been covered in "Phragmites" marsh grasses. Today there is a small area of this remaining in Khao Sam Roi Yot National Park, a relic of the original landscape.