Forests open up
As the world dries and cools, closed canopy gives way to woodland and scattered grass.
- When
- —
- Duration
- 6 million years
- Known to
- ± 3 million years
- Era
- Eocene, Cenozoic
The late Eocene cooling reduces rainfall in continental interiors, and the dense closed forests of the early Eocene begin breaking into more open woodland and shrubland, with grasses present but not yet forming true grassland. The mammals respond: limbs lengthen for running in open ground, and teeth start the long trend toward higher crowns to cope with tougher, grittier plant matter. The full grassland world is still 20 million years away, but the direction is set here.