3. The Devonian is a geologic period of
the Paleozoic Era spanning from the end of
the Silurian Period, about 419.2 mya to the
beginning of the Carboniferous Period, about
358.9 mya.
“Greening of land” Is the main event that took
place.
Forests evolved.
4. Ancient earth had climate and environment
that was pure and stabilized compared to what
it is now.
When CO2 levels became too low for plants to
grow properly, forests kept the climate in check
by slowing down the removal of carbon dioxide
from the atmosphere.
5. Because there were no fossil fuels being burnt
up
Less biodiversity, thus less organisms produced
or emitted CO2 .
No urbanization
7. Over the last 24 million years, the geologic
conditions were such that atmospheric
CO2 could have fallen to very low levels – but it
did not drop below a minimum concentration
of about 180 to 200 parts per million. Why?
Scientists recreated past environmental
conditions by growing trees at low, present-day
and high levels of CO2 in controlled-
environment growth chambers
8. When the level of carbon dioxide drops from
1500 ppm to 200 ppm
1500 ppm
200 ppm
9. Less weathering thus plants and fungi can’t
grow properly in low levels of carbon dioxide
12. Some studies have suggested that the ability of
oceans and plants to absorb carbon dioxide
recently may have begun to decline and that
the airborne fraction of anthropogenic carbon
dioxide emissions is therefore beginning to
increase.