Mark Paul’s house is built on a sandstone cliff. There was no soil for a garden. While the absence of growing medium might daunt many a would-be gardener, Paul’s expertise is in soil-free ecosystems, specifically green walls and green roofs. He founded the Greenwall company, the first of its kind in Australia, 25 years ago and and the first greenwall he built is still thriving. Consequently, the lack of soil at home was more of a challenge than a crisis. His solution combines engineering, horticulture and a fine appreciation of the movement and uses of water to create a garden of fascinating nooks and crannies, and plenty of exploratory and fun experiences for his two boys, including tadpoles, fish, a pool, vegetables, and a trampoline cleverly placed atop the chook run.
All the water that falls on the block is collected. Initially it runs from two roof slopes to a planted rooftop that supports some 240 plant species. This biodiverse terrain drains into rainwater tanks that are used for the very little irrigation required in the garden, as well as to flush the toilets and to fill the pond system. There are wetland ponds and rills and a deeper pond for waterlilies and carp. The plants remove excess nutrients from the water and are harvested a few times a year to feed the compost. And of course, there’s a greenwall, featuring 140 different species in a lush tapestry of texture and flower.
It looks like a garden but it’s also an ecosystem and a blueprint for Paul’s inspiring ambition to build greener urban spaces. His passion is for the natural development of ecosystems. He first noticed the interactions of plant communities and creatures working as a marine biologist for the fisheries department. That same attention to the interactions and relationships of the natural world now feed into his design practice, which seems to be led by two questions – what is going on? and where is the water coming from?
The latter consideration has led him to currently be completing a greenwall system for a barristers’ chambers in Sydney that will be irrigated by drips collected from the air-conditioning units. He suspects they’ll end up with too much water. The former question leads to even bigger thinking. He startled the burghers of Melbourne recently with his observations about seagulls on disused warehouses around the docks. He noticed that the birds were essentially creating greenroofs by building nests. Fertilised by guano and watered by Melbourne weather they were very successful. Paul dug further and found that 250 mating pairs of seagulls would collect 14,500 tons of putrifying waste a year. What if instead of paying people to collect rubbish, you utilised the birds to make greenroofs and and to collect the city’s dropped chips!
Paul’s only half-joking about this. Provide the right conditions and ecosystems build themselves. Imagine if all those new buildings going up at Barangaroo and Darling Harbour weren’t cliff faces of steel and glass, but of biodiversity. The model is right there, in his garden.