The idea to set up a World Environment Organisation was a popular, sexy one – but it would have been a big step back

The front page of O Globo, one of Brazil's main newspapers, displays a photograph of the heads of state and government who are assembled here in Rio on the first of the three-day summit. There are so many of them – almost 200 – that it's a bit like a school photo.

Judging by the looks on their faces, the assembled world leaders don't much seem in the mood for fun. O Globo's huge banner headline says "ONGs REJEITAM DOCUMENTO DA RIO+20". You don't have to be much of a linguist to work out that even here in Rio, where one might expect this giant conference to receive a favourable press, the jury is still out.

I think the NGOs, including Greenpeace and WWF, may be too harsh in their first judgments.

From my point of view, as someone who has attended every single one of these giant jamborees since the original United Nations Conference on the Human Environment held in Stockholm in June 1972, one of the triumphs of the 50-page document which the heads of state and government are going to endorse is not what it says, but what it manages not to say.

For more than a decade there has been talk of the need to create a World Environment Organisation (WEO). Former French president Jacques Chirac, one of the original proponents, was especially keen. In the run-up to Rio+20, the EU actually adopted this idea as one of its official negotiating goals, even though some of the main EU players, such as the UK, remained sceptical. The EU stuck to its guns until the 11th hour. Happily those guns have now been spiked.

If the Rio+20 conference had followed the EU route and created the WEO, the environment itself might have paid a heavy price. Yes, it would have made for some striking headlines this week – WORLD LEADERS AGREE ON NEW BODY TO SAVE PLANET, perhaps – and they would be smiling for the final photo-call.

But in practice the decision would have been a giant step backwards. It would take years to negotiate the constitution and mandate of the new body. The treaty would have to be ratified, and conceivably, some countries such as the United States would have been unable or unwilling to join. More importantly, existing international structures could be fatally undermined, or at best left in limbo.

The truth of the matter is that there is already a world environmental agency in all but name, and that is the United Nations Environment Programme, which was proposed at that 1972 conference in Stockholm, and offically endorsed by the United Nations general assembly later that year. It is called UNEP. Go back and read the general assembly resolution and you will see that its mandate is near perfect. In this day and age, with all the economic and financial problems, there is no chance at all that such a mandate would be agreed.

Amazingly, brilliantly, the world leaders here in Rio seem to have got the message. Hold on to nurse for fear of finding something worse! They have refused to agree on a WEO. More to the point, they have decided to endorse some practical and workable proposals for strengthening UNEP. It may not be as sexy as proposing a WEO, but it is certainly the right choice.

(By Stanley Johnson, Guardian.co.uk, 21/06/2012)