I don't understand how your friend did not address the rate of change or specie extinction by asking this question
> why haven’t the sheep herders returned to Greenland?
Tell your friend sheep herders never left Greenland. Sheep slaughtering has never stopped since they were introduced in Greenland.
>280 tons of meat sold to slaughter in 2016
>largest average production in the history of the sector, with an increase of 22% in comparison to the 1990s. (thanks to climate change the industry is kicking ass)