1.   But they described a dense population, a vibrant economy and open grassland.

2.   ...areas of open grassland.

3.   Grazers and herders began arriving in the open grasslands of the West with cattle from Texas and Mexico after native populations had been driven from the area.

4.   In the West, though, he said, more trees may mean only that suppression of natural fires has allowed trees to encroach on naturally open grasslands.

5.   Instead, we floated at a gentle, leisurely pace, alternating between open grassland and canopied rainforest.

6.   The research indicated that the australopithecines, which walked upright but also climbed trees, already were venturing out of their usual forest habitat to forage in open grasslands.