( ( Human overpopulation ) ( , ( ( which ( is ( ( crowding out ) ( other species ) ) ) ) . ) ) )
(ROOT (FRAG (NP (JJ Human) (NN overpopulation)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (VP (VBG crowding) (PRT (RP out)) (NP (JJ other) (NNS species)))))) (. .)))
Human overpopulation, which is crowding out other species.
(ROOT (S (NP (NNP Human) (NNP overpopulation)) (VP (VBZ is) (VP (VP (VBG crowding) (PRT (RP out)) (NP (JJ other) (NNS species))) (CC and) (VP (VBG making) (S (NP (NP (PDT all) (DT the) (JJ other) (NNS causes)) (PP (IN of) (NP (NN extinction)))) (ADJP (RBR worse)))))) (. .)))