Back when CO2 levels were ideal, and there were 1 billion less cars than today, monsoons always happened in the same place, the rain was the same year after year, and there were no local extinctions of animals.
If we could only return to renewable slave power:
[ScienceDaily] The researchers identified five episodes over the past 6,000 years when dramatic changes occurred in Egypt’s mammalian community, three of which coincided with extreme environmental changes as the climate shifted to more arid conditions. These drying periods also coincided with upheaval in human societies, such as the collapse of the Old Kingdom around 4,000 years ago and the fall of the New Kingdom about 3,000 years ago.
“There were three large pulses of aridification as Egypt went from a wetter to a drier climate, starting with the end of the African Humid Period 5,500 years ago when the monsoons shifted to the south,” Yeakel said. “At the same time, human population densities were increasing, and competition for space along the Nile Valley would have had a large impact on animal populations.”
No climate models were harmed in the production of this paper.
(It’s not like they have anything to say about major climate shifts during times of CO2-sameness.)
6,000 years ago there were a lot of different mammals in Egypt:
Around six millennia ago, there were 37 species of large-bodied mammals in Egypt, but only eight species remain today. Among the species recorded in artwork from the late Predynastic Period (before 3100 BC) but no longer found in Egypt are lions, wild dogs, elephants, oryx, hartebeest, and giraffe.
What is an environmentalist to do? Evidently people without cars, factory assembly lines, oil rigs, and x-boxes can cause local extinction and shifts in climate patterns. (Who can deny that humans were “in upheaval” at the same time that the climate changed?)
University of Santa Cruz Press release had a different emphasis.
Justin D. Yeakel, et al (2014). Collapse of an ecological network in Ancient Egypt. PNAS, September 8,. DOI: 10.1073/pnas.1408471111