Complex sentence: The number of visitors to the Park declined from 75,000 in 2000 to 55,000 in 2005, but since 2005 visitor use has been slowly increasing.
Split into simpler sentences: The number of visitors to the Park declined in the 21 st century, from 75,000 in 2000 to 55,000 in 2005. Since 2005, visitor use has been slowly increasing.