( ( ( The ( incidental introduction ) ) ( of ( ( aquatic ( nuisance species ) ) ( including ( biological ( and ( terrestrial exotics ) ) ) ) ) ) ) ( ( is ( ( ( considered ( by ( some ( as ( ( the ( ( most serious ) threat ) ) ( of ( environmental pollution ) ) ) ) ) ) ) ( to ( our country ) ) ) today ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ incidental) (NN introduction)) (PP (IN of) (NP (NP (JJ aquatic) (JJ nuisance) (NNS species)) (PP (VBG including) (NP (JJ biological) (CC and) (JJ terrestrial) (NNS exotics)))))) (VP (VBZ is) (VP (VBN considered) (PP (IN by) (NP (NP (DT some)) (PP (IN as) (NP (NP (DT the) (ADJP (RBS most) (JJ serious)) (NN threat)) (PP (IN of) (NP (JJ environmental) (NN pollution))))))) (PP (TO to) (NP (PRP$ our) (NN country))) (NP (NN today)))) (. .)))
The incidental introduction of aquatic nuisance species including biological and terrestrial exotics is considered by some as the most serious threat of environmental pollution to our country today.
(ROOT (S (NP (NNP Overharvesting)) (VP (VBZ is) (NP (DT a) (JJ serious) (NN threat)) (ADVP (RB particularly)) (PP (TO to) (NP (JJ aquatic) (NNS species)))) (. .)))