I think you are underestimating the scale of our cattle. The majority of deforestation is due to cattle [1]. The world is basically dominated by us and our cattle [2] leading to massive losses in biodiversity [3].

If everyone in the world would eat the recommended USDA diet (mostly backed by industry and totally not healthy for you) we'd need another Canada to sustain us all [4]. By the way, most of the grasslands are man-made and we should try and reforest those areas to combat losses in biodiversity and climate collapse. Furthermore about a third of all fresh drinking water (not rainwater) is used for cattle [5].

[1]: https://rainforests.mongabay.com/0812.htm / https://scholar.google.nl/scholar?hl=en&as_sdt=0%2C5&q=defor...

[2]: http://peakoilbarrel.com/carrying-capacity-overshoot-and-spe...

[3]: https://www.ipbes.net/news/Media-Release-Global-Assessment

[4]: https://journals.plos.org/plosone/article?id=10.1371/journal...

[5]: http://www.takepart.com/article/2016/02/18/4-billion-people-...