It is not known who invented the term. The British politician David Miliband used it when he was appointed Secretary of State for the Environment in May 2006, both in his blog and in an article on the BBC News website. He initiated the launch of a wiki to form an environmental contract. However, the site was edited heavily by Government officials, rendering pointless the exercise to interact with the public.
The term can be seen as an invitation to invite parallels with the idea of a social contract between workers, employers and the state which underpinned the foundation of the welfare state. Some have argued that, just as the social contract was a way of addressing social dislocation, so the environmental contract can be a way of addressing the environmental impacts which pose a threat to people and the planet in the 21st century.
Because of its emphasis on rights and responsibilities, there are clear links between the environmental contract and notions of environmental citizenship (EC).
Sustainability justifiable in its own right
The idea can seem to boil down to a sort of 'I will if You will' type of idea. But action for sustainability, such as having regard for the needs of future generations (including addressing environmental impacts) is arguably justifiable in its own right. Similarly, if there is the view that action on climate change, for example, is urgent and imperative, then an 'I will, irrespective of what you do' approach might be argued as more responsible.
Some of the criticism of the idea of social contract would also seem to apply here.