( ( ( ( New ( production systems ) ) or ) ( environmental changes ) ) ( ( ( increase access ) ( to ( certain foods ) ) ) . ) )
(ROOT (S (NP (NP (NNP New) (NN production) (NNS systems)) (CC or) (NP (JJ environmental) (NNS changes))) (VP (VBP increase) (NP (NN access)) (PP (TO to) (NP (JJ certain) (NNS foods)))) (. .)))
New production systems or environmental changes increase access to certain foods.
(ROOT (S (NP (NP (DT A) (NN change)) (PP (IN of) (NP (NP (NN season)) (CC and) (NP (JJR less) (NN food))))) (ADVP (RB usually)) (VP (VB cause) (S (NP (JJ certain) (NNS animals)) (VP (TO to) (VP (VB migrate))))) (. .)))
A change of season and less food usually cause certain animals to migrate.