De-linking the economy and ecology: what does that mean?

For economists it is clear what has to be done: "de-linking". But what does that mean?
It refers to the notion that we need energy and materials in our economy. So more growth of the economy means more materials, energy and pollution. This is the "link" between wealth and environmental degradation.
There is a way out, however. It is a better efficiency in physical as well as economic sense. Efficiency is here energy as well materials efficiency. Efficiency is also about efficient prevention measures for environmental pollution.
The Brundtland Report calls out for "an new era of economic growth", meaning an economy with a better environmental efficiency.

It is good to realise that there are basically two means to save the environment:
a. less wealth (less consumption), to be forced upon people
b. more environmental efficiency in production
The problem with less wealth is that this will bring social unrest (even wars) in our world. So less wealth seems no option, however, less growth of wealth of the western world seems to be a must.
The challenge of environmental efficiency is to convince people that is has to be done and that it is doable. The challenge is to make people aware that they must do something for the next generation.

The issue of de-linking can be explained by Fig.1.5 (note that GDP is a economic measure for wealth):
- when we do nothing, we will follow the black line,
..example: the US (and many other countries)
- when we stimulate economic growth at the cost of the environment, we follow the red line,
..example: China
- when we de-link the economy and ecology, we spent part of our effort and money on Best Practices
..and system innovations, and follow the blue line,
..example: EU

The issue of de-linking has triggered the question of how much the efficiency must improve. This is the issue of the "factor 4" (or 10, or even 20?)