( ( As ( forests ( ( ( ( are cleared ) and ) not ) replaced ) ) ) ( , ( ( ( the amount ) ( of ( ( carbon dioxide ) ( in ( the atmosphere ) ) ) ) ) ( ( rises ( to ( ( much greater ) levels ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (NNS forests)) (VP (VP (VBP are) (VP (VBN cleared))) (CC and) (RB not) (VP (VBD replaced))))) (, ,) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))))) (VP (VBZ rises) (PP (TO to) (NP (ADJP (RB much) (JJR greater)) (NNS levels)))) (. .)))
As forests are cleared and not replaced, the amount of carbon dioxide in the atmosphere rises to much greater levels.
(ROOT (S (PP (IN During) (NP (DT the) (JJ early) (NN paleozoic))) (, ,) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))))) (VP (VBD was) (ADJP (RB much) (JJR greater)) (PP (VBN compared) (PP (TO to) (NP (NN today))))) (. .)))