( This ( ( ( is ( largely ( due ( to ( the fact ) ) ) ) ) ( that ( it ( is ( difficult ( to ( monitor ( ocean ( living species ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (ADJP (RB largely) (JJ due) (PP (TO to) (NP (DT the) (NN fact)))) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ is) (ADJP (JJ difficult) (S (VP (TO to) (VP (VB monitor) (NP (NN ocean) (NN living) (NNS species)))))))))) (. .)))
This is largely due to the fact that it is difficult to monitor ocean living species.
(ROOT (S (NP (NP (DT The) (NN majority)) (PP (IN of) (NP (NNS species)))) (VP (VBP live) (PP (IN in) (NP (DT the) (NN ocean)))) (. .)))