The Lost Gardens of Eden

Tim Smit and John Willis famously re-discovered Heligan after 80 years of abandonment, dereliction, and overgrowth. This led me to wonder; what would they have found if, instead of pushing open that now famous door into the walled gardens of Heligan, they’d peered down into Bodelva pit?

So i'll play this idea out: what would Eden be like after 80 years of abandonment? Imagine the visitors stop coming, the gardeners lay down their tools, and the lights turn off. For the purposes of this thought experiment i'll assume Eden is allowed to rot and be reclaimed by nature because of some kind of population evacuation, apocalypse, or neglect. Nearly every civilisation deludes itself into thinking it is living in an age of cultural permanence, but the wheel of history starkly shows us this isn’t the case. I won’t linger on any potential causes of this abandonment, I’m sure your imagination can run riot here…

I regularly stand groups in front of Peter Randall Page’s Seed sculpture in the Core (probably the largest rock moved in the British Isles since the megaliths at Stonehenge) and ask, “Imagine you’re an archaeologist in the distant future and you find this…what would you think?” I won’t share the common responses, but perhaps ponder that question next time you visit.

When the electricity flickers and dies the ‘pit’ would slowly begin to fill with water. The bottom of Bodelva was raised about 25 metres to protect against flooding and make room for a new pumping system, which superseded the old fly pumps from the mining operations (you can still see the old pump-house on the hill behind the Link building). It’s because of this highly sophisticated, and mostly hidden, system that Eden is relatively dry today. The great flood of 2010, when the pumps were swamped in a huge cloud burst, gives us a clue as to the speed the pit may fill up… The flood also served as a warning to remain hyper-vigilant about the state of our drainage systems.

To keep dry we continuously pump water, up to 24 litres per second, away from the pit. This is collected off the biomes, some of which is recycled to water the plants and flush loos, and that flows in from one of the 50 or so streams that pour through the granite walls. It’s worth remembering that Eden was planted in the wettest winter on record when it rained for 120 days non-stop in 2000/1. Although this was water torture on an epic scale for the horticulturists it did reveal the numerous waterways that drained into the pit, so it’s probably helped us out long-term.

When the electricity goes, so too will the gas and with it Eden’s main source of external heat. Much of Eden is heated by gas – while we hunt for a more sustainable long-term solution, such as a deep geothermal power plant. The heat from this system is used to heat the biomes, particularly the Rainforest, through heat exchange in a network of ‘Air Handling Units’ to keep the extraordinary plant collection in prime condition. The Air Handling Units and the biome’s climate are controlled by a sophisticated Building Management System (BMS), which will also cease, leaving the environment at the mercy of the elements.

Even after the power is gone the formidable energy efficiency of the biomes will retain huge amounts of heat. Their south facing aspect, the huge thermal mass of the granite walls, the triple glazing, and even the biomass of the soils and plants, will store energy for a long time. Some of this will depend on what time of year the lights go out. During the first summer the biomes won’t cool down much, but during the first winter we’ll see numerous casualties. Much of Eden’s plant collection is sensitive to air and soil temperatures; for example, the Hevea rubber trees, natives of tropical Latin America, will begin to die after prolonged exposure below 18C.

Gradually the plant communities will change as both the average annual and minimum temperatures fall, but the real killer will be when the biome pillows fail (pictured left).

The plastic foil covering the biomes is ethylene tetraflouroethylene (ETFE for short) and is a close chemical relative of poly tetrafluroethylene (PTFE), which goes by the trade name ‘Teflon’ and is famed for its non-stick properties. Eden’s triple-glazed ETFE pillows will give the plants some respite from the cold if only one layer breaks, but the first hexagon to lose integrity in all three layers will spell the end for a host more plants and kick-start a rapid change in environmental conditions.

It’s hard to say how long it will take for this to happen. The pillows are all connected and gently inflated with air to maximise the volume of warm air trapped in them (this is an elegant example of a ‘greenhouse effect’ in action) and this air is stripped of water by a filtered compressor to prevent the build-up of algae inside the pillows. With no electricity the compressors that keep the pillows inflated will fail, so rather like a bicycle with a slow puncture the pillows will gradually begin to sag. But it won’t be quick. Kevin Applegath, an expert on Eden’s technical infrastructure, thinks it would be “many years” for the pillows to completely deflate.

But when they do, they will face a new and interesting challenge. If well-maintained and inflated the pillows have a theoretical life-span of 25 years. Many of the original pillows installed in 2001 are still intact, so presumably some are nearing the end of their operational life. But deflated and sagging their life span would be considerably reduced. I suppose the easiest way to think about them in a deflated state would be as huge aerial pond-liners merrily collecting rain water until eventually the seals can’t take any more weight and they terminally rupture. This would be quite a sight as thousands of gallons of water dumps unceremoniously on the plants below!

Eden employs two full-time people skilled in high ropes access, Luke Fox and Jamie Robson, who spend much of their time swinging from the biomes. They can spot faults emerging and pre-emptively fix them, but they also carry out repairs on any pillows that do fail. Interestingly, one of the main causes of pillow failure is seagulls scrabbling at the panels. This became such a problem a few years ago that we turned to electronic bird-scarers and even employed Harris's Hawks to scare away the winged threats. 16 years on from opening one rather lovely side-effect of the ecological regeneration of Eden is that the pit is now patrolled by a veritable fleet of raptors. Buzzards, kestrels, sparrow-hawks, and even the occasional red kite and peregrine are regularly seen overhead and do much to keep seagull numbers low.

By the time the pillows have failed, the pit would be filled with water to its maximum height. There’s a natural overflow just above the Core, which incidentally will be completely submerged, where a stream flows to the sea at Par a few miles away. Eden has a discharge licence into this stream, but when the lights go out this will be completely unregulated. Interestingly for local ecologists, this stream used to be seasonal and relatively lifeless, but due to Eden’s excess water an entire freshwater ecosystem is now dependent on it.

The Mediterranean Biome will be a rather sorry sight. It will be almost completely deluged, with only a smidge of structure poking above the waters. What a bizarre diving experience that would be! But the Rainforest with its greater elevation would be a different story. The water would come roughly half way up its terrestrial elevation and draw a line submerging, perhaps prophetically, the Oceanic Islands, much of SE Asia, Spice, the Bamboo House, and chopping the banana plantation in half. So here, 80 years after abandonment, we would encounter a strange scene: a warmish lagoon fringed with the remnants of the world’s largest indoor rainforest. But what would the plant communities look like?

Gradually, and over successive winters, most of the true tropical plants and trees would die off. But clinging on would be some sub-tropical plants and the pan global generalists, such as grasses, vines, hibiscus, and some of the bamboos.

The super-structure of the Biomes is made from zinc galvanised steel, a material chosen for its durability and anti-corrosion properties. This structural durability would result in a truly bizarre sight. In 80 years we can imagine, confidently, that the instantly recognisable twin-layered hex-tri-hex geodesic structure would be largely intact. There would be some rust and the odd bit of gnarled twisting, but probably not too much. It’s a slightly grotesque vision, but also strangely enticing. The extent of any twisting will largely depend on how much movement there is in the clays below. Since 2001 the ground under the biomes hasn’t moved much, in fact their shape was chosen specifically to cope well with subsidence, but then again the foundations have never been tested by being 30 metres under water…

As the tropical trees die, and light gaps appear on the forest floor, seeds would blow in from outside. Ecological pioneers like gorse, willow, and hazel would find niches and begin to compete with the remnants of the original planting. Ivy would join the climbing communities of Ipomoea (Morning Glory), Thunbergia (Black-eyed Susan), and Allamanda and clamber all over the buildings un-restrained by our horticulturists.

When I asked Eden’s Director of Life Sciences, Mike Maunder, which plants would take over the Rainforest his answer was short and sweet. “Buddleia,” he said. He’s probably right, buddleia thrive in scrub and in cracks on the warm walls of the biome. As the concrete, sprayed on to secure the original granite walls, erodes and cracks so buddleia would be among the first to occupy these new high altitude niches. And as the air vents and pillows increasingly fail in would march a steady influx of native wildlife. The Biomes have become permanent home for a collection of British birds; it’s easy to find blackbirds, wagtails, robins, wrens, and dunnocks scrabbling around among the introduced Sulawesi white-eyes and roul rouls. Over time, sadly, the tropical birds, lizards, and tree frogs would probably perish and the communities would shift to a predominantly native population.

The outdoor landscape, that which isn’t submerged, would be familiar but bizarre and over-grown. The Outdoor Gardens at Eden are full of plants that survive and thrive in the cool temperate climate of Cornwall. Occasionally, we've pushed the boundaries of what’s horticulturally possible; an outdoor Mediterranean exhibit for one, a collection of Chilean forest plants another. Without management; weeding, pruning, coppicing and or any landscape or drainage work, we can imagine that these communities would change, but in 80 years the overall structure and landscape design might still be recognisable to us just as the overall structure of Heligan was visible to Smit and Willis. The trees; particularly oaks, hazels, conifers would be approaching full height and a scramble of bramble and gorse would envelop any likely areas. Some of Eden’s most important collections, such as the tree ferns and the National Collection of Kniphofia, would be lost beneath the waters, but the communities on the fringes of the pit would appear truly ‘wild’. These fringes were mainly planted using a technique called ‘hydro-seeding’, which is a fancy way for saying a slurry of wild seeds and fertiliser was sprayed all over the landscape.

Other abandoned clay pits nearby (pictured is a beauty near St Dennis) have filled up with water and re-vegetated so we have a pretty good idea of what our dystopian Bodelva would be like. In recently abandoned pits un-washed clays suspended in water gives many of the pools a distinctive milky blue-green appearance and in some woodland remnants poke through the creamy waters. We would also find echoes of these ghost forests in Bodelva, particularly around the high tide mark. I asked mining expert and ex-Edenite Peter Whitbread-Abrutat what would happen to the water over time. He told me, “the strange water colour in China clay pits is caused mainly by suspended minerals washed in from un-vegetated slopes. The colours are most marked in newish pit lakes. Once vegetation becomes established on the surrounding terrain, the surface erosion of minerals, like mica, is substantially reduced. The particles suspended in the water column eventually settle and the lakes develop their own ecology in what can become crystal clear water.”

In 80 years' time then, the overall picture would be one of broken majesty. Twisted honeycomb-inspired steel; cloaked in ivy, floating gently above dark clear waters, by now teeming with fish and water birds. Dense woodland scrub would spill down the steep sides of the Eden pit making it hard to tell where Eden’s planting ended and the wild encroachment began.

I imagine it to be a serene scene, and I’m forced to wonder… Would Tim Smit and co take on this particular restoration challenge?

Thanks to all those who helped think about these problems with me, and special gratitude to Robin Owen from Eden’s Design Team for bringing this vision so dramatically to life.