They can be, in NZ there are is a huge amount of land that has been converted to dairy through massive irrigation schemes which has caused massive problems for the rivers that flow naturally through these places... I imagine there are other places in the world used for dairy that wouldn't be suitable if not for irrigation?

The almond example is frequently brought up, but this is still half of what dairy milk requires, without taking into account the difference in land use too

In New Zealand HUGE amounts of fertiliser are used to boost the amount of grass grown and thus cows per unit area. Some ends in groundwater and a lot can end up in streams and rivers too.

The light rail tunnel to Albany seems mad to me, I thought the northern busway was designed to accommodate light rail so I can't understand why one would build tunnels to Albany instead of putting light rail along the current busway corridor.