Prof Benton added that evolutionary change added an additional pressure to population management schemes, namely that it was much more difficult to reverse than ecological change.

BBC: Environmental change 'triggers rapid evolution'

If you really want to reduce energy consumption, extreme social pressure is the way to do it, says Prof Anderson.

BBC: Technology

But in the public sector, workers are trying to create political pressure on the government, making public opinion crucial, Prof Gall says.

BBC: Strikes: How important is public support?