Restoring Wetlands on Cobden Island

Department of Conservation —  22/11/2016

At the mouth of the Grey River/Māwheranui is an island that has been restored thanks to the efforts of DOC staff, the local community, and the Grey District Council.

In 2011 Biodiversity Ranger Henk Stengs began the Cobden Island Restoration Project with a strong vision of creating new inanga (Galaxias maculatus) habitat and spawning sites at Cobden.

Grey District mayor Tony Kokshoorn joined community ranger Lauren Roberts and volunteers on a recent planting day.

Grey District mayor Tony Kokshoorn joined community ranger Lauren Roberts and volunteers on a recent planting day

But the project has ‘migrated’, as Henk explains. “It’s been amazing! What started out as a vision to restore inanga spawning sites at Cobden wetlands has expanded to include predator control, recreational development and use of the area for educational activities by local schools.”

The project has been an excellent partnership between DOC and the Cobden community, including the Cobden Aromahana Sanctuary and Recreation Areas Inc.

It also involves a healthy partnership with the Grey District Council who administers the land, and Conservation Volunteers New Zealand who provide volunteers for the bulk of the long-term work, especially hand weeding and planting.

Restoration work involved four kilometres of channel being excavated and planted – they are now teeming with inanga and other fish species.

A digger was brought in to excavate the channels in stages – once a year for the past four years.

A digger was brought in to excavate the channels in stages – once a year for the past four years

With increased nursery habitat, the hope is that the restoration will help boost numbers of inanga that grow up to spawn as well as provide safe places for eggs during spawning seasons.

DOC and the community have planted over 10,000 native plants, mostly flax which was split from plants already on the site when work began.

Volunteers hard at work planting newly excavated banks. It will grow to provide shelter for inanga.

Volunteers hard at work planting newly excavated banks. It will grow to provide shelter for inanga

“One of the big challenges,” Henk explains, “is keeping people interested in helping out after all the major planting has been done and hands are turned to the less glamorous task of weeding.”

Broom and gorse seeds are present in the excavated soil and pop up regularly. If allowed to grow, they can shade out grass and other plants needed to provide spawning habitat.

The project has proven that once weeded for 2-3 years, preferred vegetation becomes established and the need to weed is significantly reduced. Conservation Volunteers NZ and offenders doing community service have been an integral part of the project’s long term success by doing this all important weeding work.

They’ve also had a successful rodent and mustelid trapping programme. Since March 2013 they’ve caught 209 rats and 60 mustelids on the island. This work is largely carried out by volunteer Denis Skates, who checks the traps once a week.

In addition to increasing conservation values and biodiversity, Henk sees Cobden Island as a valuable educational resource.

It has already been visited by several school and scout groups who’ve done planting and weeding, as well as high school geography classes from Christchurch learning about sustainability.

It’s available for any group to visit and learn about native fish species and habitat, how a small group of dedicated people can make a big difference for the environment, and how to be good stewards of our unique natural resources.

One response to Restoring Wetlands on Cobden Island

  1. 

    This has been a wonderful community project in conjunction with DOC – great teamwork and what a result. A real asset for the community. Well done to all involved.