• By Rod Brown

CO2e sequestration: Another benefit of Bay of Islands volunteer reforestation projects

The capital cost of planting is a key factor in reforestation.

This is where volunteer social enterprises such as Kerikeri's Shade House have been vital to reforestation efforts in Northland. The Shade House grows inexpensive plants to support other conservation groups that do not have a nursery and only limited funding available for plant acquisition. They usually have keen volunteer planters ready and willing to do the job.

The Shade House volunteers have grown about 300,000 native plants for habitat restoration so far. These plants have been distributed to many conservation groups and trusts in Northland.

The Shade House was runner-up in the 2010 Northland Trust Power Awards and in 2018 for the Northland environment award.

The volunteer run nursery raises native plants from seed collected by volunteers. Seedlings then go through several potting stages before being ready for distribution and planting by project volunteers.

These volunteer reforestation programs have been primarily focused on improving the habitat for micro-organisms, invertebrates, birds and the micro-climate. However, as climate change has moved into 'real time', the CO2e sequestering value is adding another critical dimension to these efforts.

Among the numerous projects which the Shade House supports is Project Island Song. Since 2003, 36,000 native plants have been planted on about 20 hectares on the eastern islands of the Bay of Islands. Typically, for the islands, native forest is created from kikuyu pasture. Apart from providing new habitat for native fauna, this forest land will sequester an estimated 300 Tonnes of CO2e annually.

Volunteers unload Shade House plants on Moturua Island in The Bay of Islands. These plants were distributed to sites for planting.

A public planting day on Urupukapuka Island 2016

Much of Kerikeri’s environment is degraded by weeds, often garden plants such as Jasmine that have spread, uncontrolled, into surrounding areas of bush and bare land.

Restoring the habitat along the Wairoa Stream is a significant project. It has multiple aims of; creating public access to the stream banks via a walkway, weed eradication and, linking remnant patches of bush with native plantings to form a continuous lowland forest and wildlife corridor.

Since 2012, the stream is progressively being transformed into a near continuous urban forest (it is only a 5 minutes walk from the town centre). The project has been inexpensive as it is maintained and planted by volunteers of The Friends of Wairoa Stream. 5,700 volunteer hours have been expended on the project since it started back in 2012.

The project has resulted in a number of existing trees being removed. These are invasive species such as; Tobacco Weed, Brush Wattle, Taiwan Cherry, Black Wattle and Acmena. In addition, some Eucalypts that presented a danger to walkers were also removed. It is acknowledged that these trees were already sequestering CO2e and that removal can temporarily set back sequestration rates. However, 11,100 native plants have already been planted and any set-back will be relatively short lived. Over time, these more extensive native plantings are expected to deliver a much greater volume of sequestration. Some of the earlier plantings already have canopy closure. With canopy closure plantings become self-sustaining with less human maintenance although vine species do remain a threat.

Before and after pictures of an area on the Wairoa Stream. The picture above was taken in 2016 when volunteers attempted to determine the scope of the task for weed clearance and replanting of an area near Sammaree Reserve. The weed species were almost impenetrable.

That same area in 2019 (below) now has a walking track and native plantings which are establishing well.

This Autumn a further 2,700 trees and shrubs will be planted in 10 places adjacent to the 3 km track that has been built to date. These and further future plantings will add to the CO2e sequestration and bio-diversity enhancement process.

The number, species and location of the trees have been documented in detail for the two projects referred too. In recognition of the growing significance of CO2e sequestration, we are now starting to extend our documentation to measuring growth rates for the different species so that we can calculate the CO2e sequestration rates at different stages of forest maturity and ultimately calculate, with a greater degree of accuracy, the CO2e sequestration value of each project.

An example of plantings that have reached 'canopy stage' (trees on right of track)

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