Case Study

What do we do with this empty land?

Between the scope and scale of the RRZ, the diversity in land use, potential for further liquefaction, and minimal topological or hydrological information available, making decisions about the future of this land became extremely challenging.

CCC had minimal information about the changes in land use, ecological growth and development, or elevation changes over time for this piece of land.

It was proposed to map the RRZ areas with our multispectral drone, capable of providing high tech images of the landscape; stitching the entire RRZ into one map that can be monitored over time.

Multispectral imagery is able to read chlorophyl levels in plants, see soil moisture levels, assess plant health, and give more defined data to AI.

With the inclusion of AI, we are able to recognise existing plantings, provide species differentiation, and create shapefiles for use across multiple platforms.

Data captured during this project will be used by CCC to develop an app that informs species selection for planting projects within the RRZ.

Given the scope, volume of plants, and resources required to deliver this project, it seemed beyond the capability of a single contractor to deliver. Greater Wellington Regional Council set about to gauge interest from specialists within the ecological restoration industry.

The primary sites are spread across Queen Elizabeth, Belmont, and East Harbour regional parks. Some sites are exposed and, transitioning from retired pasture to natives, results in a period of high fire risk as the grass grows before native canopies are established.

A panel of experienced contractors was established in 2022 to deliver this visionary project.
In that same year, Red Tree conducted nine Enviroblanket® trials across the three regional parks to ascertain the viability of direct seeding in Wellington.

Eco-sourced seed was collected for direct seeding and propagation for traditional revegetation methods.

After being accepted onto the panel, Red Tree traditionally planted 120,000 natives during the winter of 2023.

The direct seeding trials were successful and resulted in Greater Wellington Regional Council scaling up and engaging Red Tree to apply 8.5 hectares of direct seeded Enviroblanket® in the winter 2023.

On one 2.5 hectare site, Waitangirua, Red Tree utilised an innovative eco-divot methodology. This is an approach developed from the Enviroblanket principles of ecological succession and biomimicry.
The method involves blending eco-sourced seed from pioneering native plants with locally sourced compost. Ground disturbance is created by earthmoving equipment and the blended seed mix is dispersed either by drone or by hand.

Following a natural period of winter stratification, seedlings have emerged en masse to colonise the disturbed ground.

Weed management and monitoring of nutrient levels are undertaken to achieve the correct balances during the maintenance phase.

This project was labor intensive therefore required a high level of staff motivation and effective project management to ensure planting quality. The challenge was to work around heavy machinery, as the motorway was being built. The lead contractor was HEB’s construction.

Using reliable and reputable nurseries, we ensured high quality and robust plants. With a large planting team, we were able to effectively complete the planting in the short seasonal time frames.

Ecological succession is a race for domination; a process by which species best adapted to local environmental conditions succeeds. Exotic weeds metabolise faster than native species and without intervention, gain the upper hand; weed competition is the greatest hurdle to successful native restoration.

Four years ago, the Enviroblanket® began with small scale trials, effective on vertical faces and hard to access areas; however, as we scaled up and diversified into wetlands and riparian margins, it became clear that versatility and resource optimisation was needed to achieve a cost-effective outcome.

Red Tree developed innovative and unorthodox herbicide application methodologies to overcome the exotic weed competition by combining boom spraying, weed wiping and drone technologies. These breakthrough weed management practices have facilitated effective knock down of competing species and has allowed native wetland plants to emerge.

The resource optimisation process required to upscale the Enviroblanket® refined biological blends and optimised sewing timings, cultivation techniques, herbicide use, species selection and order of delivery.

The topography was the major challenge Red Tree faced in this project; the elevated gradients and unstable terrain of the volcanic rim resulted in strenuous working conditions. Vigorous health and safety protocols had to be upheld in order to mitigate the risk to the multiple contractors onsite. In addition, a high population of possums within the restoration area posed a significant risk to native establishment.

In order to deliver the traditional planting phase of the project, native plants had to be brought onsite and distributed along the hillside. The difficult access and steep terrain made this very challenging for our team. At first, Red Tree Plant Technicians carried plants manually up the slopes; however, we quickly learned that the risk of physical stress and fatigue had to be mitigated.

A land stabilization Enviroblanket® was applied pneumatically across the exposed area below the catch-bench for rapid establishment of exotic grass species. Compost was used to boost substrate nutrients, provide erosion control, and to filter sediment runoff. This process required anchor points to facilitate rope access across the work site and to scale vertical faces between regions.

Following on from the Enviroblanket® application, Red Tree was contracted by CCC to traditionally establish ~25,000 plants along Sumner Rd. Teams of Red Tree Plant Technicians, trained in rope access, completed the planting and worked closely with McConnell Dowell, Golder Associates, and Boffa Miskell for traffic management, rockfall risk mitigation, and biosecurity respectively.

Geovert installed a rockfall risk mitigation fence below the working areas to act as a third line of defence in preventing rocks falling onto the road below. This meant the road could remain open while Red Tree undertook ongoing planted maintenance.

Challenging access and the necessity to reduce fatigue required Red Tree to come up with an innovative method of transporting native plants up the hillside. After considering various options, it was decided that the plants would be airlifted. Way2Go Heliservices commenced the airlift, delivering the plants in one tonne customised bags and positioning them along the hillside ready for planting.

Scope of work for the post-quake landscape remediation involved the maintenance and management of 7.6 hectares of planted Port Hills Red Zone sites, in the rim locations of Governors Bay, Lyttelton and the hill suburbs through from Sumner to Cashmere.

The challenge for Red Tree was to establish native plantings and binding ground covers on tough clay substrates, gradients and North-facing aspects to revegetate and stabilise the land.

Establishing native plants were forced to compete with invasive weed infestations of Fat Hen, Californian Thistle and Mallow, utilising organic weed control in high density residential zoning.

Nature abhors a vacuum and in ecological terms that translates to, “ bare earth will not be tolerated”. In short order, Mother Nature covers exposed earth, as without protecting vegetation the earth surface is highly susceptible to wind and water erosion. Downstream sedimentation is the consequence!

Red Tree utilized a clover plant companion technique; attractive to insects and bees, this versatile legume, with its distinctive flowers and cheerful foliage, belies a mass of rubbery roots that work to fix nitrogen into the soil as it creates a tenacious mat to bind the earth.

Clover species are numerous and by introducing the variety of clover containing the most appropriate attributes to the disturbed urban hillside sites, we were effectively able to suppress the existing bank of less helpful weeds and in conjunction with jute matting, quickly stabilize the cut faces.

In Nature nothing is wasted, everything is recycled. Red Tree Plant Technicians then hand release the natives, cutting out weeds around the stems and using the recycled biomass as a mulch around the plants. Topping using bush cutters was employed to prevent seed dispersal. On tough sites, it is essential that valuable biomass is recycled and able to enhance soil structure.

Through observing challenging site conditions and mainstream methodologies, Red Tree began conducting research in direct-seeding natives and compost-based revegetation technologies. With the intent to improve outcomes in harsh environments, the Enviroblanket® development was underway.

In support of the new technology’s potential, LINZ awarded an entire Red Zone site for Red Tree to trial the Enviroblanket®. Applied alongside traditional planting for comparison, the direct-seeding technology proved to be extremely successful.

NCTIR (North Canterbury Transport Infrastructure Recovery) was an alliance established to tackle the recovery efforts of both the road and surrounding areas.

An army of people, trucks, and diggers created multiple permanent stockpiles and engineered batters using the slip material removed from significant slips within the transport corridor. These stockpiles and batters were devoid of vegetation, topsoil, and nutrients, presenting a challenge to re-establish flora onto these degraded clay and mineral substrates.

Eco-sourcing plants to add aesthetic value to the newly established safe stopping areas and to stabilise engineered stockpiles and batters was a challenge due to the short timeframes and large volumes required.

Red Tree specializes in using eco-sourced native seed in post-natural disaster ecological restoration projects and was engaged to undertake a combination of traditional planting and Enviroblanket® applications along the damaged coastline.

A prescriptive coastal Enviroblanket® was designed to withstand the harsh environmental conditions presented in Kaikōura and to facilitate remediation of degraded substrates.

In 2018, Red Tree, in collaboration with other local nurseries, collected eco-sourced native tree and shrub seed within the Kaikōura ecological district. Invasive pest plant management was then undertaken in 2019 to prepare sites for planting and direct seeding.

In 2020, Red Tree traditionally planted more than 55,000 native plants and pneumatically installed approximately 4 hectares of Enviroblanket® across multiple sites within the corridor. In order to remediate a particular inaccessible slip site, Red Tree also developed and applied an aerial Enviroblanket® via helicopter.

The first commercial large scale Enviroblanket®, effectively an on-site nursery; could it be done?

Native direct seeded Enviroblanket® technology, developed by Red Tree Environmental Solutions (Red Tree), is essentially disruptive in that it bypasses the nursery system, interacting directly with disturbed substrates in a responsive time frame. Letting nature lead and assisting with biomimicry and self-design principles, Red Tree aims to replicate the life-giving function of the forest floor.

An undisturbed soil profile provides established networks of root systems, microorganisms, and mycorrhizal creating nutrient pathways, aeration, and drainage. Once the natural soil structure is disturbed and modified, there is a significant loss of soil ecology. This disturbance and compaction of engineered soils produced a major challenge to seed germination and healthy plant growth on this site.

Exposed to the elements, this large and open area is continually subjected to environmental extremes such as high wind velocity, sun exposure in the summer, and sinking cold during the winter with the attrition of browsing pest animals such as rabbits and hares.

Adjacent to a traditionally planted area, a one hectare dry forest Enviroblanket® was applied in August 2019 around the perimeter of the wetland basin. Nature provides direct feedback as to which species are best suited to variance within specific microclimates; species best suited to environmental conditions display higher germination rates with success being reflected in strong growth and plant resilience. Biomimicry and self-design capacity that the Enviroblanket® provides, gives nature the best opportunity to select species best suited to adapt and thrive in local environments.

During site preparation, mechanical ripping was undertaken to address compaction, improve poor soil structure and drainage. Biological additives were applied to the Enviroblanket® post-application to assist biogeochemistry health. Microorganisms and fungal networks rebuild microbial activity in the soil which in turn creates a symbiotic relationship between plant communities, builds resilience, and improves growth.

As this site is widely exposed to the elements, Red Tree utilised a fast-growing native nurse crop to provide protection and cover during the first year of establishment for the slower growing natives to emerge through.

Mitigation of pest browsing effects was undertaken in conjunction with Excell Biosecurity, implementing pest reduction controls and perimeter fencing in the most challenged areas.

Loess is comprised of platelets which carry a negative charge facilitating ion exchange once saturated and is therefore extremely partial to erosion. During precipitation onto the Sumner Road catchment, high velocity sheet flow was running down slopes above the vertical cuts and eroding the loess faces.

Sumner Road above LPC was still under construction after being closed following the Christchurch earthquake sequence. Being directly above the port operations and below the new road construction, this site was extremely high profile.

Coordination and communication between these two large civil construction projects was a challenge that required high levels of compliance and health and safety. Once windows of ingress were coordinated, gaining access to the steep slopes above the vertical cuts was also a challenge. Rope access teams were required to move across the slopes and work on the eroding cut faces.

A series of Enviroberm®’s and an Enviroblanket®, delivered via Canterbury Woodchip’s industrial high tech pneumatic applicator, was considered as an effective solution for the vertical cut faces and steep gradients above.

Trapezoidal Enviroberm®’s with dimensions 300mm high and 600mm wide were installed perpendicular to the gradient on the steep slopes above the eroding loess cut face. Enviroberm®’s bisected the slopes; constructed at intervals to interrupt sheet flow and facilitate infiltration. Rilling etched into the landscape from previous water flow indicated how best to work with the hydrology of the slope.

To remediate continued loess erosion, Red Tree Rope Access Teams securely pinned a dense three-dimensional reinforcement mat onto a portion of the vertical cut and managed the pneumatically applied Enviroblanket® onto the interface. Specific species of clover and drought tolerant grasses were selected and seeded over the Enviroblanket® to stabilise and vegetate the cut face.

The landscape design and planting required functionality and high amenity value.

As the project backs onto native bush, this site is a hotspot for goats, deer, rabbits, and hares. The pests meandering down the valley and browsing the plantings has been a significant challenge in this project, with some of the bigger tree species becoming victimised by young stags shedding their velvet.

Moved by the sculptural ribbon like topography, Red Tree’s in-house Landscape Designer allowed the plantings to accentuate the contour of the land and water course, creating corridors of visual passage across the plantings. Kowhai, ribbonwoods, lancewoods, mountain flax, pittosporum, carex virgata, and silver tussocks were all part of the plant palette.

In consultation during the conceptual design phase, Red Tree’s horticultural team anticipated the presence of pest plants and recommended ideal plant spacing and full mulch coverage at ~75 mm depth. For ease of mind, our clients engaged with our three year maintenance and monitoring package, which allows Red Tree to guarantee 95% establishment success and protection of their investment.

Plant losses due to pest browsing were detected early in the maintenance phase. Pest management was then undertaken and the unharmed plants were caged, with replacement plants being installed the following planting season.