Granto

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.