Advancing Blue Carbon in New Zealand's Coastal Wetlands
What is Blue Carbon?
Blue carbon sequestration is the removal and storage of CO2 by oceanic and coastal ecosystems such as saltmarshes, mangroves and seagrass meadows. By restoring degraded wetland habitats, we lift their capacity to remove carbon from the atmosphere and store it in their soil layers.
The Potential of Blue Carbon
The Nature Conservancy (TNC) in New Zealand is partnering with New Zealand Councils, iwi and coastal communities to overcome the barriers to effective climate and biodiversity solutions through blue carbon projects.
By restoring coastal wetlands ecosystems so that they capture and store carbon dioxide from the atmosphere, TNC aims to address the dual crises of climate change and biodiversity loss. To achieve this, TNC is investing in research and mapping, running pilot projects and providing policy advice on blue carbon.
Coastal wetlands are globally vulnerable to agricultural use and coastal development, leading to greenhouse gas emissions, biodiversity, amenity and resilience loss, and limiting their potential as carbon sinks. In addition, the survival of remaining coastal habitats is increasingly endangered by sea level rise.
Scientists have shown blue carbon ecosystems can store, or ‘sequester’, significantly more carbon than forests.
According to the Global Mangrove Watch, mangrove swamps can store four times more carbon—which is why halting their destruction and restoring and protecting them has become an international priority.
TNC has a track record of developing blue carbon projects across Central and North America, China, Indonesia, Papua New Guinea and Australia, typically using mangroves, tidal marshes and seagrass habitats. Some of these projects have already begun generating blue carbon credits on the voluntary carbon market.
Restoring coastal wetlands at scale could offer multiple win-wins for climate, biodiversity and people. Here in Aotearoa New Zealand, our Blue Carbon project is making progress as it builds the evidence base (i.e., total emission reduction benefits) and demonstrates how these projects can be designed and delivered using a partnership model.
Why Are Wetlands Important?
Coastal wetlands provide unique habitats for many native species including plants, fish, macro-invertebrates and birds. Many of these species have evolved to thrive in wetland habitats and are threatened by extinction when wetlands disappear.
Wetlands are part of the earth’s natural flood defences—acting as a giant sponge to soak up water, filter pollutants out of our freshwater and prevent sediment from reaching the sea. They are also efficient carbon stores and can play an essential role in mitigating climate change.
Coastal communities can reap benefits from healthy coastal wetlands in the form of increased flood protection, enhanced biodiversity, cleaner water and opportunities for eco-tourism. They can also enjoy the improved social and cultural outcomes from living in a healthy functioning ecosystem.
Coastal Wetlands and Voluntary Carbon Markets
Restoring a wetland’s carbon storage capacity (as well as its natural habitat and biodiversity) generates carbon credits which can have a tradeable value on the voluntary carbon market in New Zealand. Carbon credit prices on the voluntary carbon market range widely depending on the quality of the credit and associated co-benefits.
Blue carbon restoration principles can be applied to a range of sites, including degraded or modified land that was previously a coastal wetland. Restoration work can involve simply restoring tidal flows or may require more advanced intervention and engineering.
Several approaches can be employed ranging from:
- Passive actions for re-introduction of tidal flow e.g., improving management practices; or
- Softer-engineering where drainage canals are filled in, stop banks/bunds are removed or culverts are installed to allow tidal flow back onto the land.
Unlike growing forests, saltmarsh plants might only take a couple of years to re-establish, provided that the site conditions are favorable for re-establishment.
What We're Doing
Our TNC New Zealand Blue Carbon team undertook a feasibility assessment to explore whether blue carbon projects like the ones that have been successful overseas are technically feasible here in Aotearoa New Zealand. We’ve also done some early restoration potential mapping for Te Tauihu/the top of the South Island and have begun site selection for pilot studies. This involves data collection, hydrological modeling and economic assessments, including quantification of additional co-benefits resulting from the restoration such as coastal resilience, improved water quality and biodiversity enhancement. This will help to assess the site’s suitability for blue carbon credits under a voluntary carbon credit scheme.
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