Agricultural net primary production in relation to that liberated by the extinction of Pleistocene mega-herbivores: an estimate of agricultural carrying capacity?

Mega-fauna (defined as animals > 44 kg) experienced a global extinction with 97 of 150 genera going extinct by ∼ 10 000 years ago. We estimate the net primary production (NPP) that was liberated following the global extinction of these mega-herbivores. We then explore how humans, through agriculture, gradually appropriated this liberated NPP, with specific calculations for 800, 1850, and 2000 AD. By 1850, most of the liberated NPP had been appropriated by people, but NPP was still available in the Western US, South America and Australia. NPP liberated following the extinction of the mega-herbivores was ∼ 2.5% (∼1.4 (between 1.2 and 1.6) Pg yr ^{− 1} of 56 Pg C yr ^{− 1}; Pg: petagrams) of global terrestrial NPP. Liberated NPP peaked during the onset of agriculture and was sufficient for sustaining human agriculture until ∼ 320 (250–500) years ago. Humans currently use ∼ 6 times more NPP than was utilized by the extinct Pleistocene mega-herbivores.