The Soil Association's conference drew more than 600 people to Cardiff a couple of weeks ago. FW's deputy business editor Ian Ashbridge reflects on the message of peak-oil - and what society might look like in a powered-down world...
Do you switch off the light when you leave a room? Turn the TV off or leave it on standby? Do you wash clothes at 30 or 40? Buy local food? Compost your kitchen waste? Grow your own veg?
Well, you'd better start - and even then it might not be enough.
It's called climate change. Or global warming. Or we-can't-overlook-this-thing-any-more. And if that wasn't enough, a growing number of people believe we are at or very near "peak-oil" - the year when oil extraction peaks and fossil fuel stocks start to decline rapidly.
Because the Soil Association isn't just about organic food and farming anymore. Director Patrick Holden believes the "second chapter" of its work lies in working to equip society for a post-fossil fuel age.
He suspects future generations will look back with incredulity at the twentieth century - the time when we squandered the accumulated energy resources of 150 million years of planetary evolution in a few decades.
Peak-oil is variously pegged to come anywhere between, well, now and 2030. But the frightening thought is that once the 'tipping point' is reached, each of us may have to face a fossil-fuel- ration, which declines by 3% a year. Assuming we're at or very near to peak oil, that means managing with just half the energy we now use by 2030.
I have never lived through an energy 'crisis', unless you count 2000, when prices jumped nastily and people wasted a perfectly good weekend queuing up at petrol stations. So I can only imagine the much more serious business in 1974 that brought us the three-day week and long periods by candlelight when the power was off.
Speakers at the Soil Association conference would probably say that is only the tip of the ice-berg, and one that can be partially mitigated by developing sustainable energy sources now, such as ground-source heat pumps and woodchip boilers.
Sitting (in fact, standing) in the packed conference room, I listened to Rob Hopkins describe a world suffering the withdrawal pangs of a fossil fuel obsession.
The last time we faced an energy crisis on this scale, he argued, was during the Second World War.
But we no longer have a pre-Beeching railway or canal network, or a plethora of small, local abattoirs or food processing infrastructure. And as farmers, we are all too aware that many urban dwellers have no idea where their food comes from or how to grow it for themselves.
Rob Hopkins is right when he says the most frightening aspect of an acute energy crisis relates to the production and distribution of food. Now, the populations of developed countries, most of whom live in major urban centres, are totally dependent on the 'just-in-time' distribution of food from a system based on oil- and gas-derived fuels.
If energy became much more scarce and this led to trade conflict or war, it's not hard to imagine cities running out of food. The potential consequences of this could be catastrophic.
I'm not sure I am ready to believe that things could become so acute, so quickly. But, after the conference, the words that keep coming into my mind are Patrick Holden's.
The oil crisis of the 1970s started a back-to-the-land trend, long before organic food made its way onto every supermarket's shelves. It was partly the uncomfortable realisation that food production and distribution was so dependant on finite fossil fuels that gave the organic movement some added momentum.
The drive towards self-sufficiency drew my father towards food and farming and a proper understanding of where food comes from and how to produce it - and that in turn rubbed off on me.
And it's the thought of my generation's legacy that haunts me. Patrick Holden's suspicion that our chapter in history might be as those who burned 150m years of planetary energy in a just a century and left future generations with none, is not a comforting one.
It's easy, in the conventional farming sector, to dismiss the organic movement as a minority group that produces a fraction of the country's food by carping about mainstream farming methods and using unsubstantiated health benefits to market itself.
You'll probably never reconcile those two camps on that issue. But in calling for a unified approach to tackling climate change and developing sustainable energy systems, the Soil Association deserves to be heard.
What the organic movement has failed to do is to engage its conventional cousins in a constructive dialogue. I bet there were few conventional farmers in that audience. It's one thing to have a growing band of followers, but preaching to the converted doesn't get you far.
So I'm left with more questions than answers. How will we know when we have reached peak oil? The world population is rising and we have to feed it - how? Can we feed the world organically?
I am not convinced that Nitrogen fertiliser in farming is bad. The carbon captured from the extra biomass the fertiliser creates, more than offsets the carbon released when it is manufactured. So I haven't fully converted to the organic church.
But it is incumbent on all of us to acknowledge that one day, perhaps tomorrow, perhaps in a century, our fossil fuels will run out. We need to develop sustainable energy systems, not necessarily the old favourites: wind farms, biofuels, etc. New technologies will come - necessity is, after all, the mother of invention.
But above all, we must recognise energy as the precious gift it is. So please turn off the lights.