Why did they try to reduce the population of cows worldwide?

The Republic of Ireland plans to kill off around 200,000 cows to reduce methane emissions. The Irish government intends to slaughter 65,000 cattle per year for three years in order to mitigate agriculture emission. Now the move is in lockstep with European Union regulations aiming to slash one quarter of current emission levels by 2030. Elon Musk reacted to the framework on Twitter claiming killing cows will do nothing for the environment.

What is the real aim of The Global Methane Hub? Will it help to save the planet?