If it would slow climate change and help the environment in general, would you be willing to accept minimal packaging of everything you purchase? For an entire year?It would, and I think that most people would agree to it.
Would you agree to doing it for eleven years? What if there's something that would accomplish as much in one year as minimal packaging would in eleven?
Well, there is. Following a vegan diet for one year reduces greenhouse gases by as much as it takes eleven years to accomplish through minimal packaging.
To be honest, there is nothing in halacha—Jewish religious law—that specifically requires or even encourages veganism. There is a general ethical principal called bal tashchit—בל תשחית, "do not destroy"—and it doesn't take a lot of imagination to understand that it prohibits destroying the earth.
The principal stems from an injunction in Deuteronomy not to cut down fruit trees during a war. Early rabbinic law extends it all unnecessary destruction.
But Judaism still does not require veganism, and I'm not endorsing it across the board. What I'm recommending is that we return to the lifestyle of many of our ancestors, who reserved meat for Shabbat and Yom Tov, not because they wanted to, but because they had to. If you could only afford meat about once a week, why not reserve it to honor Shabbat?
That changed with prosperity. It especially changed in North America, where meat, since at least the nineteenth century, has been extraordinarily plentiful. But just because we can eat meat every day, if we want to, doesn't mean that we should.
Think about it: eleven times as much benefit as something you probably wouldn't mind doing. Or, if you have meat about one day a week, 9.4 times as much benefit.