If you've ever seen large-scale deforestation, especially of the rainforest, and seen it close up when it's just happened, you feel you're in the aftermath of an armoured battle. The scale of the destruction stuns you: cleared ground which seems to be everywhere smoking, burning tree stumps flickering like huge candles. It feels as if some giant beast has torn off a great lump of the landscape and savagely consumed it, leaving bits of it bleeding behind.
Serious deforestation has been going on for more than 30 years across the tropical zones of the world, starting in Amazonia and gathering speed, spreading to Indonesia and then to West Africa.
The effect has been staggering: rainforests, which provide us with so much, from oxygen production to carbon storage, once covered 14 per cent of the Earth's surface; now they cover about 6 per cent, and the devastation is continuing.
This is something which the Green Movement, despite immense effort and a certain amount of progress, has not been able to stop. There have been many success stories in modern environmentalism, some of which featured in these pages yesterday.
But if we examine the 50 years of the Green Movement's existence and try to tot up its failures, the inability to halt deforestation would probably be near the top of the list.
We might bracket it with a similar calamity, this one taking place in the world's oceans: overfishing, and the parallel inability, despite great exertions, to bring it under control.
According to the UN's Food and Agricultural Organisation, some 77 per cent of the world's fisheries are either fully-exploited, over-exploited, depleted or recovering from depletion, and the problem continues.
Why have green activists had such success in limiting pollution, but not in curbing overfishing and deforestation? The answer is that pollution is in essence a tactical environmental issue, something that can be dealt with on its own, while the other two are strategic, meaning they are part of the very structure of things.
So pollution can be brought right down by operating your company differently, and the only reason companies did not do that in the first place was either laziness or miserliness: truly bad publicity will always make them change.
But deforestation and overfishing are something else entirely, part of the human exploitation of natural resources. The pressure for these processes to continue may in the first instance be driven by the greed of private companies and particular individuals, but it is ultimately driven by rising demand, which is in turn caused by the rise in human numbers – or to put it another way, by the ever-expanding scale of the human enterprise.
How to deal with that? There's no "end of pipe" solution to the effects and demands of a world population which doubled from three billion to six billion between 1960 and 2000, is now seven billion-plus, and likely to be nine billion before 2050.
Dramatic confrontations by eco-warriors in small boats might have ended the dumping of British nuclear waste in the sea, but such actions will do nothing to halt the soaring demand for more and more forests to be cut down and turned into agricultural land to feed the coming hunger of nine billion.
Serious environmental thinkers realise the problem now is strategic rather than tactical, and although public attitudes have clearly been changed by the Green Movement, some of them would say that the biggest failure of all during its first 50 years has been not to change those attitudes profoundly enough.
Andrew Simms of the New Economics Foundation says: "If your objective is to give the greatest priority to nature and society, you cannot win in an economy built on endless accumulation and the legal guarantee that the interests of capital come first."
The former director of Friends of the Earth, Tony Juniper, sees the problem as even deeper, about culture rather than economics.
"There are two really big failures of the Green Movement, underpinned by a third," he says.
"The first is that there are two parallel discourses going on: one is about planetary boundaries and nature, and the other is about is about economic growth, and they're going in polar opposite directions.
"The second is that we have failed to link an ecological narrative with popular culture. The fact that most people in the country regard a trip to the shopping mall on a Saturday as a better day out than a trip to a nature reserve says quite a lot." And he adds: "But the profoundest failure of all is our underlying disconnect from the Earth.
"We work to take on these environmental challenges without having any kind of profound connection with nature. We've lost it talking in a mechanistic, policy-oriented way.
"We've tried to make it all about numbers, parts per million, complicated policy instruments, and as a result, we've lost something that's essential. Most people couldn't tell you the names of country flowers by the side of the road, the birds that are singing. It's a disconnect in our world view – a failure in our philosophy."
Changing culture is much harder than changing what comes out of a pipe. It's a recognition that that the next 50 years of the environment movement may not offer the clear-cut, achievable victories of its first half century.
Additional research by Tim Greiving
Tomorrow: Part 5 - After the first half-century, we look at the green movement's next 50 years