Complex sentence: The forests have largely regrown with the hemlock and white pine trees being replaced with thriving populations of various hardwood trees, thanks in large part to the efforts of the young men of the Civilian Conservation Corps during the Great Depression.
Split into simpler sentences: The forests have largely regrown with the hemlock and white pine trees being replaced with thriving populations of various hardwood trees. Thanks in large part to the effortso of the young men of the Civilian Conservation Corps during the Great Depression.