Damn that Al Gore and his "carbon credit" idiocy.
Look what he's done. It's - 40 out when it should be only -11. He and his tree planting enviro geeks have brought on an ice age...
As for these so called "Scientists", it's a JOKE to consider that all the "reforested land" was somehow "aboriginal farmland". How about reforestation after recession of the great ice age? Carbon in lakes and sub souls? How about thousands of years of forest fires burning out of control year after year?
Or did Aboriginals have giant flying pelicans that they used for water bombers?
Actually, the change coming after 1500, makes sense. The Spaniards introduced European diseases like measles and smallpox which may have eliminated as much as 4/5ths of the Aztec, Maya, and Inca populations, as well as others that they had contact with. It is estimated that in North America the indigenous population was at least 20 million before northern Europeans brought in their diseases.
Of course, they returned the favor by giving syphilis to the returning Spaniards. Also the potato. ;-)
Indians used to set forest fires frequently. Deer and other wildlife live at the interface between forest and meadow, so the ideal hunting environment is forest pockmarked by many fire-caused meadows.