I've read somewhere that one major factor is agriculture. Almonds and pistachios require over a gallon of water per nut, or over 1 trillion gallons/year for the former [0] and it seems like that's where at least 10% of california's water supply is going[1]. Along with actively killing bees[3] I struggle to wonder if growing those nuts are even worth it.

[0] https://www.gainesville.com/story/opinion/2021/08/24/douglas...

[1] https://web.archive.org/web/20201203025513/https://fruitgrow...

[2] https://www.theguardian.com/environment/2020/jan/07/honeybee...