(S (S (NP (BASENP (NNS Areas)) (PP (IN in) (BASENP (NNP Nigeria)))) (VP (VBP have) (VP (VBN been) (ADJP (JJ subject) (PP (TO to) (NP (BASENP (NNS damages)) (VP (VBN caused) (PP (IN by) (S (VP (VP (VBG increasing) (BASENP (NN erosion))) (PP (IN for) (BASENP (QP (RB over) (NN 50)) (NNS years))))))))))))) (PERIOD .))