Chaos and Complexity – Pushing the Boundaries of Gabion Baskets
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The combination of man-made structures and materials with the natural world, not only delivers a great aesthetic, but provides the chaotic mix of structure vital for rich biodiversity. It’s the speed with which abandoned sites become so good for wildlife that really is so important. There is a post-industrial site to the east of London that has more biodiversity per m2 than any other site in the UK! That’s happened within 50 years of the site being abandoned. We can’t replicate ancient meadows or woodlands easily, but we can design new landscapes to mimic the best post-industrial sites. What an exciting prospect for our future landscapes.
The combination of organic and inorganic materials in this ‘living wall’ provide opportunities for biodiversity, particularly invertebrates. Photo: John Little
How do we package the chaotic structure of post-industrial sites in a way that looks good and appeals to the public? One way is to use gabion cages or baskets. These wire baskets, when installed, represent carefully and perfectly level ‘tidy’ materials that otherwise would be unacceptable within a new landscape. They hit all the marks for habitat creation and can be embedded in the planting design as an engineering solution, or even as stand-alone structures.
Incorporating Gabion Baskets Into Your Design
Gabion baskets are a great unit of ecology, so it is best to present you with the advantages/benefits of using them, namely:
The use of decomposing logs to introduce complexity and biodiversity richness into the land scape. Photo: John Little
Speed of construction
Habitat/shelter feature - for a wide range of wildlife, especially spiders - a habitat that is often lacking in rural locations
Permeability to water
Strength - not prone to vandalism
Can protect slopes from erosion
Creates basking areas (filled with rubble) – which results in greater heat exchange and thermoregulation, which is important to reptiles and various invertebrates
Durable and low maintenance - gabion walls are extremely long lasting, durable, sustainable and no maintenance is required compared to traditional brick walls.
Local materials may be used for filling them, such as wood, and even hardcore, building waste. So, the transport costs and the associated fuel consumption are reduced dramatically compared to a traditional brick wall.
Gabions are unfixed so there can easily be reused and moved to different locations rather than destroyed.
Cost efficient - can be filled with inorganic and organic materials - rubble and logs, which may be present on site, recycling waste, instead of it going to land fill.
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In recent years we have started to push the possibilities of what gabion baskets can offer. We have been attempting to add further habitat and complexity within the gabion basket itself. Some examples of this include the use of log piles (slow decay for saproxylic invertebrates); inserting of bumblebee nest boxes; hoverfly lagoons; vole nest boxes; and solitary bee tubes. The possibilities seem endless and it very much ‘early days’ in terms of gabion basket design. All these features will help to increase biodiversity richness, connectivity and structural complexity through an urban landscape.
Gabion Basket Case Study
Essex Wildlife Trust Car Park and new visitors centre Langdon Nature Discovery Centre, Essex, UK
Backfilling around gabion baskets to increase plant biodiversity. Photo: John Little
We were asked to look at the car park attached to the new £2,000,000 visitors centre in July 2020. Sadly, both the centre and the car park went through planning without insisting on any green infrastructure or habitat creation requirements. Bizarrely, no emphasis had been put on the wildlife potential of the development by either the architect or the Wildlife Trust until they asked us to give some thought to the possibilities within the car park. Let’s hope with the introduction of the Biodiversity Net Gain matrix (See Living Architecture Monitor – Biodiversity Issue, 2022) this sort of planning consent never happens again in the UK.
The main nature reserve attached to the centre was on heavy clay and although in places high in biodiversity, it offered little opportunity for Open Mosaic Habitat. Open Mosaic habitat is bare ground with, typically, very early pioneer communities, more established open grasslands, scrub and patches of other structural habitats.
It made sense to design a contrasting landscape that would drive biodiversity, rather than replicating existing habitats and simply increase their biomass.
A typical budget default for development meant we were only left with £40,000 to landscape and add habitat to the 150-space car park. Since the plans had already been passed, we were limited to a 1200 (48 inch) mm outer edge and a 900mm (36 inch) centre spine to work with. To form the main structure, we opted for Gabion baskets. These we hoped would mark out the parking bays, provide a retaining wall for the new substrates and most importantly act as a vessel to create nesting and hibernation for a wide mix of invertebrates and mammals. Mined gabion stone, often transported many miles to the site is the common default fill; but we opted for 75-150mm (3 to 6 inches) of crushed demolition waste
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The new gabion basket filled habitat transforms this dead parking lot in the U.K. Photo: John Little
made from local houses, sourced from within 2 miles of the site. Alongside this backbone of gabions, it was decided to take back 8 of the 150 parking bays, far too many in our opinion, and replace them with ‘garden bays’. These would be framed to the regulation 5.5m x 2.5m (18’ x 8’) with box steel and filled with a mix of construction waste and local sand. The new bays would reinforce the need to reduce our reliance on cars and 'big up’ the potential for everyday infrastructure to become important places for wildlife. The bays were planted and seeded with native plants and to finish, a bee post was added to give space for arial nesting solitary bees. The non-native climate adapted planting was also used in the central spine and importantly was paired with good interpretation.
Behind the gabions around the perimeter, we backfilled with local sands from the A13 road widening no more than 2 miles from the site. These sands provided the ideal weed free, low fertility substrate to take the native seed mix. The sand also had the advantage of providing breeding space for many of the local bees and wasps, especially as we added the topography to ensure plenty of warm south facing slopes.
Gabion basket wall filled with demolition waste and planted with native plants to generate biodiversity at a parking lot in the UK. Photo: John Little
So, we had taken a sterile piece of planning permission and added open mosaic habitat using only waste materials from within 2 miles. Adding biodiversity to our everyday infrastructure in very urban places is so well suited to Open Moscaic Habitat and in turn brings all these ideas up close to people.
Most importantly, all the new habitat and planting was designed and implemented without compromising the aesthetic or function of the parking lot. Wildlife is very happy in well-designed places.
Conclusion
The creative use of gabion baskets in landscaping to help cost effectively management waste, while also creating low or no maintenance habitat to support biodiversity, is still very much in its infancy. There is a virtually limitless range of design possibilities to use these structures in urban and rural settings and much more that we can due to improve their biodiversity potential.
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John Little the founder of the Grass Roof Company, established in 1998, John has been experimenting at Hilldrop, his 4-acre garden in Essex, UK with new ideas and incorporating brownfields sites on a smaller scale, into public spaces and onto roofs for over 30 years.
For more information on the Grass Roof Company visit their website.
For an interview with John Little, see here.
