I’ve never experienced such contrasting ones! During several humbling days of sea-sickness, my horizons shrank to perhaps the narrowest ever; the uniquely vile sensation of overwhelming nausea and the proximity of the nearest bucket. Out on the joyful far-side of sickness, our horizons are immense. 360 degrees of sea and sky. Day after day, out of sight of land and other vessels, swaying across under sail in the company of shearwaters and storm petrel, flying low and stiff winged over the waves. These are pelagic birds, living in motion out here for months on end, only visiting land to rear young. On the early watch, a colourless sun turns the shifting waves to a runway of dynamic molten silver. At dusk, as the light leaches away, the sea turns pewter, then gun-metal grey, the wave surfaces etched and chiselled and constantly in motion. At night, there’s an immensity of stars, silent above the black sea. It’s the biggest space I’ve ever been in. it’s extraordinarily, exhilaratingly, utterly wonderful. And I suspect, as I notice my distinctly mixed reactions to the news that we might reach land tomorrow, addictive.

The daily trawls for plastic and plankton continue, with one distinctly challenging version in substantial swell (though what happened in the sea-sawing galley qualified as far more extreme I’m told). We’re working away at this one tiny piece of the science jigsaw in the immense and complex potential catastrophe that is the human impact on global ocean ecosystems. All of life depends on ocean life and plankton are at the very base of it so the significance of our negative impacts on them would be hard to overstate. After the trawls have been raised and emptied we gather on deck for discussion; about plastic and how it got to be here in the big blue sea; about what we can do; about what it is that lies beneath our multiple environmental problems. What are the underpinning structures and systems and worldviews and mind-sets that have somehow seduced the (allegedly) most intelligent species on the planet into systematically undermining its own habitat? In snatched chunks of time between watches and trawls we grapple briefly with candidates for the unholy position of environmental crises Root Cause: the collision between an economic system that requires indefinite growth and a finite planet with ecological limits; its evil twin, consumerism; and the dominant stories embedded within industrialised societies about the human relationship with nature. You know the story; that humans are somehow outside nature, separate from and superior to all other living things and systems, understood in turn as essentially a set of resources for us. Macfarlane, coming back from an ocean voyage to the Arctic to witness some of the impacts of global warming first hand wrote there is ‘no more urgent intellectual task facing the human species….than thoroughly to rethink our relationship with nature.’ He recommends, as the far-sighted N.American conservationist Aldo Leopold did 60 years before him, that we change our perception of ourselves as managers – or exploiters – of nature to ‘plain members and citizens’ of the ecological community. What would this mean for, say, the way we design products, to have the interests of nature, of our ecological community, held in view as a priority from the very outset? What would it mean for all of us, in our ordinary life choices to live well as citizens of our ecological as well as social communities?

There’s a sudden shout. ‘A bird’! It’s a tiny bird, a house martin I think, dwarfed by the sky and sea, on its unlikely migration somewhere to the south. It clings for a moment to a ridge on the white mainsail, pulling us all back from the big picture and the conceptual to the immediate. I feel an uprush of fierce (and entirely impotent) compassion for this unfeasibly small creature on its long, long journey. I want to communicate, ‘stay, land, have some fresh water and a rest with us here.’ But of course, I can’t. And then it’s gone, swept back into the wind and currents. We are left hoping the brief unlikely rest might just help tip the precarious balance between survival and arrival, and a small exhausted tragedy in the waves.