( ( As ( populations ( increase ( above ( ( the ( carrying capacity ) ) ( of ( the environment ) ) ) ) ) ) ) ( , ( ( certain ( density ( dependent mechanisms ) ) ) ( ( ( kick in ) ( to ( reduce ( population size ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (NNS populations)) (VP (VBP increase) (PP (IN above) (NP (NP (DT the) (VBG carrying) (NN capacity)) (PP (IN of) (NP (DT the) (NN environment)))))))) (, ,) (NP (JJ certain) (NN density) (JJ dependent) (NNS mechanisms)) (VP (VBP kick) (PRT (RP in)) (S (VP (TO to) (VP (VB reduce) (NP (NN population) (NN size)))))) (. .)))
As populations increase above the carrying capacity of the environment, certain density dependent mechanisms kick in to reduce population size.
(ROOT (S (NP (NNS Humans)) (VP (VBP are) (ADJP (JJ unique) (PP (IN in) (NP (PRP$ their) (NN ability) (S (VP (TO to) (VP (VB alter) (NP (PRP$ their) (NN environment)) (PP (IN with) (NP (NP (DT the) (JJ conscious) (NN purpose)) (PP (IN of) (NP (NP (JJ increasing) (VBG carrying) (NN capacity)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ acts) (PP (IN as) (NP (NP (DT a) (JJ limiting) (NN factor)) (PP (IN on) (NP (NP (NNS populations)) (PP (IN in) (NP (NN general))))))))))))))))))))) (. .)))