Chickens weigh more than all elephants, bison, zebras, and all other wild land mammals combined.
When talking of our planet, imagine the scenes of David Attenborough, from roaming elephants to grazing bison. But all these animals are only a tiny fraction of the biomass of mammals.

We used to have a lot more wild mammals, but even 100.000 years ago, all wild land mammals only weighed as much as today's pigs!

One of the biggest ways in which humans have changed the surface of the Earth is through farm animals, and most of all through cows
A field with cows might not look like a big impact but each of those cows requires 60 kg of food per day.
And that requires a lot of space, about 1-3 football fields of grass per year, per cow
But space is limited on our planet, and so forest is cut down to make space for grassland. 1/2