Quote:
Originally Posted by cbacba
Finding out why the sahara's forests died out originally might be good and it might indicate they stressed out due to a lack of co2 concentration.
|
The collapse of the Sahara forests occurred at a time when atmospheric CO2 was at the high point in its natural cycle, not a low point.
Until the recent increase due to the combustion of fossil fuels, Atmospheric CO2 concentrations have cycled between essentially the same levels for at least a million years, being about from 180ppm to 280ppm.
Analysis of plant pollens and bones have shown that the collapse of the Sahara to desert only occurred about 5000-6000 years ago. The ice age had ended, and the warmest part of the ice age cycle had arrived already. CO2 concentrations were over 250ppm, significantly above the 200ppm that existed 10,000 years before that.
Forests don't tent to die from lack of CO2, especially rainforests, which house a large proportion of the world's biodiversity. Quite the opposite.
This paper published in October last year shows that overall during warm "greenhouse" periods, biodiversity is lower, while extinction rates and species origination rates are higher than in cool periods.