Are there now more herbivores than in the 1800-1900’s?

I have always wondered about this. Especially since our livestock have come under scrutiny regarding their carbon footprint. If there were about the same with more or less the same total weight, then it implies that the carbon footprint must have been the same as both groups would have eaten similar feeds (primarily veld), and therefore similar methane output. And if it is so, then it supports our notion that the problem of methane emissions in the atmosphere is largely due to fossil fuel and other sources rather than livestock. I decided to consult the literature which led me to the article cited below.

The authors calculated the methane production of wild herbivores from the Late Pleistocene period (LP) of about 10 000 years ago which was just before humans began to farm with livestock, through the 1800’s until the present. The comparison between the LP (no livestock, just wild herbivores) and today’s livestock plus wild herbivores showed methane productions of respectively 138.5 and 147.5 Tg methane per year, which do not differ much. Between 1800 and 1900 livestock numbers started to increase substantially and wild herbivore numbers declined drastically because of heavy hunting in Africa (mainly here), and also because of the almost decimation of bison in North America and Rinder Pest at about 1900, the latter also affecting livestock. As a matter of interest the total numbers of livestock which consist of cattle, buffalo (mainly in India), pigs, sheep and goats were 1.13 billion in 1800, 1.30 billion in 1850, 1.52 billion in 1890 and 4.51 billion in 2006. The respective methane productions calculated were 30.9, 37.4, 45.7 and 128.3 Tg per year. The collective numbers for wild and domestic herbivores were about 74 Tg methane per year in 1800, 89 Tg per year in 1850 and 88 Tg per year in 1890; the relative small increase been explained by the drastic decline in wild herbivore numbers because of the reasons described above.

Thus, given the fact that there is little difference between methane production today and at the LP, the comparatively low methane productions of wild and domestic herbivores in the 1800’s is actually a coincidence, because of the decimation. Often today’s methane productions are compared with those in the 1800’s to support the argument that the large livestock pool in the world is a significant contributor to the carbon footprint and therefore should be drastically reduced.

Reference:

Smith F.A., Hammond, J.A., Balk, M.A., Elliot, S.M. et al., 2016. Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget. PNAS 113, 874-879.