I remember in the late 1950s my JrHi teacher told us that a squirrel could go from New York to the Mississippi river without ever touching the ground.
From the Mississippi to the Rockies it was prairie.
Lightning strikes in NY and IA, then, could cause wild fires that would burn the entire eastern half of the US. And nothing to stop it.
Never mind the steppes in Russia. Not sure about Africa.
I’m guessing all that biomass being converted to CO2 beats our cattle flatulance and auto exhaust all to hell.
My Dad’s approach to environmentalism works for me. “Clean up your own messes and make sure the other guy does the same.” “Never shoot a song bird and only kill animals for their meat.”
The Indians set more fires than lightning, I suspect, to improve hunting. They extended bison to the east coast.