Ecological restoration at Drury Quarry

Over the past five years, Stevenson Aggregates has delivered a number of programmes to foster ecological restoration across the Drury quarry site.  These programmes are part of our commitment to protect, restore and create indigenous habitat.  Stevenson Drury quarry works closely with Envoco, an ecological consultancy, to implement and monitor our programmes. 

Tree planting

Stevenson Aggregates has planted approximately 85,500 eco sourced native seedlings and is in the fourth year of an eight-year ecological restoration programme. The scale of the programme is significant, and once completed more than nine hectares will be under managed planting, much of it along riparian edges.

Planting proceeds in two stages: pioneer and enrichment. The pioneer stage involves planting fast-growing, light-dependent and hardy species. The enrichment stage occurs after the pioneer plants have grown enough to provide some shade and leaf litter to more sensitive forest species (usually after a few years), and includes species representative of local ecosystem types, eg taraire, kahikatea, matai, nikau and pūriri. 

The planting connects existing forest fragments, and will provide critical habitat for native lizards, birds and insects. Over time as plantings mature, new species will appear via bird and wind dispersal.

Landscape buffer

The noise bund is an important landscape buffer between quarry works and neighbouring properties that is aimed at reducing noise and dust. It also creates an ecological link for native wildlife. The western aspect of the bund is highly visible from the entrance of Stevenson Drury quarry and is well maintained for its amenity and ecological values.

Pest plant and animal control

Pest plant control is also a key focus.  Working with Envoco, Stevenson Aggregates has removed weed infestations over large areas prior to planting and carries out ongoing control in planting areas and forest fragments.  Pampas grass, privet, woolly nightshade and gorse are heavy seeding, fast growing plants that can easily outcompete native vegetation if not contained.  

Pest control, through fence planting and pest containment and eradication, is a significant focus of the ecological restoration work. As an indication of scale, between June 2019 and June 2021 Envoco caught 992 pest animals. Hedgehogs, mustelids, rats and possums pose a serious threat to native wildlife and plants, and are controlled via trapping and poison baits.  The team has also deployed live-capture traps for feral cats, and bait stations targeting rabbits and hares. There has been an increase in observations of native bird species, such as kererū and tui, and of native seedling germination, demonstrating the impact of pest control in improving the local ecosystem.


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Fifteen years ago an extension at Waingaro quarry prompted a restoration that not only created an award winning wetland environment for our indigenous species, but also a legacy for future generations.

More than 8,500 eco-sourced indigenous trees were planted and a fish passage was installed. A programme was put in place to control pests including rats, possums and stoats.

Quarry staff have monitored the area ever since and the data shows an increase in both size and population of the native fish species and bird life. Perhaps most encouraging though is the long-tailed bat, or pekapeka. In danger of extinction, our predator control programme has seen the local population stabilise, with the pekapeka frequently visiting the stream and wetlands at night to feed.

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