Can you tell me whats the difference between "consume less"and "consume differently"?

As we all konw the mainstream approach methods focuse on "consume differently", while alternative focuse on "consume less". But in my opinion this two definitions are related.
For example, when government put an levy on the plastic bags, people will change to use other material bags. This can be identified as "consume differently". However, this change also means the consuming of plastic bags becomes less.
So how can I identified the government levy? Is it a mainstream one or alternative one?

The limitation of mainstream SC

I just read the Chapter 2 of "The New Economics of Sustainable Consumption" and this chapter mentioned some failure of the mainstream. They are as followed.

1.princing failures
The ecological modernisation approach to SC is based on a free market system which means the each people aims to satisfaction. However, our real market  is different.

2.information failures
The mainstream is based on neo-classical economics which assumes that all the consumers are fully informed, rational, selfish,and weigh up all their options before choosing to make a purchase. In real society, no one can do that.

3.self-regulation failure
In the case of both green and ethical consumption, most companies will not self-restrict, which is on the opposite to the assumption.

to be continued...

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