Coastal Wetlands Restoration, Carbon, and the Hidden Role of Groundwater

 

Coastal wetland restoration offers major carbon benefits, and understanding groundwater processes helps explain how these ecosystems store carbon over the long term.

by Mahmood Sadat-Noori 9 February 2026

Associate Professor Martin Andersen (UNSW, Sydney) and Dr. Mahmood Sadat-Noori (JCU) collecting samples to measure dissolved greenhouse gases (CO and CH₄) in groundwater at Tomago Wetlands, NSW, Australia. Credit: Kate Waddington (UNSW, Sydney)

Editors’ Vox is a blog from AGU’s Publications Department.

Coastal (tidal) wetlands are low-lying ecosystems found where land meets the sea, including mangroves, saltmarshes, and seagrass meadows. They are shaped by tides and support a mix of marine and terrestrial processes. However, agricultural and urban development over the past century have drained, modified, or degraded many of these coastal wetland ecosystems and now require restoration efforts.

A new article in Reviews of Geophysics explores how subsurface hydrology and biogeochemical processes influence carbon dynamics in coastal wetlands, with a particular focus on restoration. Here, we asked the lead author to give an overview of why coastal wetlands matter, how restoration techniques are being implemented, and where key opportunities lie for future research.

Why are coastal wetlands important?

Coastal wetlands provide many benefits to both nature and people. They protect shorelines from storms and erosion, support fisheries and biodiversity, improve water quality by filtering nutrients and pollutants, and store large amounts of carbon in their soils. Despite covering a relatively small area globally, they punch well above their weight in terms of ecosystem services, making them critical environments for climate regulation, coastal protection, and food security.

What role do coastal wetlands play in the global carbon cycle?

Coastal wetlands are among the most effective natural systems for capturing and storing carbon.

Coastal wetlands are among the most effective natural systems for capturing and storing carbon. This stored carbon is often referred to as “blue carbon”. Vegetation in these ecosystems, such as mangroves, saltmarsh, and seagrass, take up carbon dioxide from the atmosphere through photosynthesis and transfer it to sediments through roots. These plants can store carbon 40 times faster than terrestrial forests. Because coastal wetland sediments are often waterlogged and low in oxygen, this carbon can be stored for centuries to millennia. In addition to surface processes, groundwater plays an important but less visible role by transporting dissolved carbon into and out of wetlands. Understanding these hidden subsurface pathways is essential for accurately estimating how much carbon wetlands store and how they respond to environmental change.

How has land use impacted coastal wetlands over the past century?

Over the past century, coastal wetlands have been extensively altered or lost due to human activities. Large areas have been drained, filled, or isolated from tides to support agriculture, urban development, ports, and flood protection infrastructure. These changes disrupt natural water flow, reduce plant productivity, and expose carbon-rich soils to oxygen, which can release stored carbon back into the atmosphere as greenhouse gases. In many regions, groundwater flow paths have also been modified by drainage systems and groundwater extraction, further altering wetland function. As a result, many coastal wetlands have shifted from long-term carbon sinks to sources of emissions.

How could restoring wetlands help to combat climate change?

Restoring coastal wetlands can help combat climate change by re-establishing natural processes that promote long-term carbon storage.

Restoring coastal wetlands can help combat climate change by re-establishing natural processes that promote long-term carbon storage. When tidal flow and natural hydrology are restored, wetland plants can recover, sediment accumulation increases, and carbon burial resumes. Importantly, restoration can also reconnect groundwater and surface water systems, helping stabilize (redox) conditions that favor carbon preservation in sediments. While wetlands alone cannot solve climate change, they offer a powerful nature-based solution that delivers climate mitigation alongside co-benefits such as coastal protection, biodiversity recovery, and improved water quality. Getting restoration right is key to ensuring these systems act as carbon sinks rather than sources.

What are the main strategies being deployed to restore coastal wetlands?

Common restoration strategies include removing or modifying levees and tidal barriers, reconnecting wetlands to natural tidal regimes, re-establishing natural vegetation through improving the hydrology of the site, and managing sediment supply. Increasingly, restoration projects are recognizing the importance of subsurface processes, such as groundwater flow and salinity dynamics, which strongly influence vegetation health and carbon cycling. Successful restoration requires site-specific designs that consider hydrology, geomorphology, and long-term sea-level rise.

What are some remaining questions where additional research efforts are needed?

Despite growing interest in wetland restoration, major knowledge gaps remain. One key challenge is quantifying how groundwater processes influence carbon storage and greenhouse gas emissions across different wetland types and climates. We also need better long-term measurements to assess whether restored wetlands truly deliver sustained carbon benefits under rising sea levels and increasing climate variability. Finally, integrating hydrology, biogeochemistry, and ecology into predictive models remains difficult but essential. Addressing these gaps will improve carbon accounting, guide smarter restoration investments, and strengthen the role of coastal wetlands in climate mitigation strategies.

—Mahmood Sadat-Noori (mahmood.sadatnoori@jcu.edu.au; 0000-0002-6253-5874), James Cook University: Townsville, Australia

Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.

Citation: Sadat-Noori, M. (2026), Coastal wetlands restoration, carbon, and the hidden role of groundwater, Eos, 107, https://doi.org/10.1029/2026EO265003. Published on 9 February 2026.

This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s).

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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Tagged: beaches, coasts, & shorelines, climate, Climate Change, groundwater, Health & Ecosystems, Reviews of Geophysics, Sustainable Development Goals (SDGs), wetlands

 Challenges of institutional adaptation

Nature Climate Change volume 15, page 683 (2025)Cite this article

Environmental change requires substantial adaptation efforts across scales and sectors — from infrastructure development and technological upgrades to emergency responses and individual behaviour change. Institutions that shape decision-making, resource allocation and collective action during the adaptation process play a vital role in moving efforts forward. For example, during extreme weather events, meteorological departments provide early warnings, health services assist the injured, and power, water and transport sectors work to restore essential services. As climate-related hazards are becoming more complex and frequent, institutional coordination and workload challenges are also intensifying¹ and existing institutions are unable to meet the demands of effective climate adaptation. This indicates that institutions themselves need to adapt in order to respond appropriately to environmental change. However, institutional adaptation remains an underexplored frontier in climate science and faces challenges in practice. In an Article in this issue of Nature Climate Change, Branda Nowell and colleagues highlight an increasingly complex task environment (such as increasing competing jurisdictional priorities and interests) for institutions that are responsible for managing wildfire incidents in the USA.

Credit: Jan Schliebitz / Alamy Stock Photo

The increasing frequency, duration and scale of hazards under climate change is putting strain on institutional capacities. However, the challenges of institutional adaptation are rooted in the complexity of the physical and ecological processes impacted by climate change. These processes are interconnected and often unpredictable, making it difficult for institutions to anticipate, plan for and respond to emerging risks. For example, the impacts of wildfires on forests depend on local conditions, with cool, wet forests more vulnerable to the changes in microclimate caused by fire compared with warm, dry settings². It is thus difficult to manage the associated risks and damages effectively through traditional institutional frameworks that are often plagued by inertia and weak coordination. A practical scientific understanding of these complex biophysical processes is a necessary first step towards informing effective institutional adjustments and policy responses.

In addition, biophysical processes are often intertwined with socioeconomic processes, further complicating the management of adaptation efforts. For example, deltas face multiple natural hazards under climate change, and are additionally impacted by anthropogenic activities such as dam construction. This confluence of environmental and anthropogenic factors makes anticipating the full impacts of a decision difficult for the responsible institutions and stakeholders. In a Comment, Sepehr Eslami and colleagues underscore the need for integrated systems understanding, coordinated efforts and holistic decision-making in adaptation, with particular focus on the smaller scales at which implementation is more likely.

Constraints also emerge from the institutional landscape itself. Governance systems responsible for either a particular event or adaptation initiatives more broadly are rarely streamlined. Instead, they are often fragmented, characterized by overlapping jurisdictions, misaligned priorities and institutional inertia. For example, authority for managing wildfires is fragmented across a mosaic of local, state, federal and tribal jurisdictions³, and evidence from Nowell and colleagues’ work indicates the overall increased jurisdictional complexity of US wildfires. Emergency management frameworks, forest service protocols and inter-agency coordination mechanisms often struggle to cope with multi-jurisdictional fires, simultaneous outbreaks across regions, and the long-term health and ecological consequences. Also, trade-offs between short-term political gains and long-term resilience, and between centralized control and local agency, may hinder adaptive decision-making among the departments. Social hierarchies and resource disparities further complicate efforts, by creating unequal capacities, priorities and access to decision-making processes⁴.

The challenges of institutional adaptation could be particularly acute in marginalized regions that face heightened environmental stress — through deforestation, biodiversity loss, water scarcity and extreme events — yet often lack the cohesive institutional architecture needed to respond effectively^5,6. The critical limitations include the lack of regulatory enforcement, political resistance in implementation, lack of processes for sharing resources among institutions, lack of equity consideration and inadequate financial resources⁷. Here, institutional adaptation is also constrained by a lack of awareness that institutions themselves must evolve along with climate change. Climate change adaptation in these regions should be closely aligned with socioeconomic development and capacity-building efforts. A coordinated policy framework is necessary to navigate trade-offs among competing priorities.

Adaptation is often framed as a technical or behavioural challenge, rather than one of governance. Institutional adaptation will not be easy and there will not be a one-size-fits-all solution, but it is necessary. It needs to evolve in line with the changing climate and be grounded in the local environmental and governance contexts.

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Cite this article

Challenges of institutional adaptation. Nat. Clim. Chang. 15, 683 (2025). https://doi.org/10.1038/s41558-025-02388-w

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• Published08 July 2025

• Issue DateJuly 2025

• DOIhttps://doi.org/10.1038/s41558-025-02388-w

   

  Further Information

  Social strategies to engage video gamers in climate action Jennifer Carman, Marija Verner & Marina Psaros Comment | 20 June 2025 Nature Climate Change 15 | doi:10.1038/s41558-025-02369-z

  A systems perspective for climate adaptation in deltas Sepehr Eslami, Gualbert Oude Essink, Amelie Paszkowski, Katharina Seeger, Philip S. J. Minderhoud et al. Comment | 07 July 2025 Nature Climate Change 15 | doi:10.1038/s41558-025-02368-0

Lanz und die Runde, Klimathema ab ca. 47'

 https://www.zdf.de/gesellschaft/markus-lanz/markus-lanz-vom-17-august-2022-100.html

Ab ca. 47 Minuten kommt Harald Lesch dran ...  Sehr interessant und hörenswert - Alle Dächer mit PV bestücken, wir brauchen ca. 5000 km² PV-Fläche, die Häuser könnten ca. 1500 km² beisteuern. 

Es gibt aber noch einige Probleme:

* die Module (PV-Module) fehlen
* Es fehlen sogar zeitweilig die alu-basierten Haken für die Montage der Module
* Altbauten könnten rein statische Probleme bieten

Aber es gibt aber auch Positives zu berichten:

* Im Agrarbereich könnten PV-Module ca. 4 m hoch gebaut werden, so dass Traktoren einfach Platz darunter finden, um ihrer Arbeit tun zu können. Es scheint sogar so zu sein, dass in trockenen Zeiten die Flächen unter diesen Modulen fruchtbarer sind als sonstwo.

* Ein weiteres Projekt könnten Gründungen von Energiegenossenschaften sein, die z.B. von den Kommunen gegründet werden und nur Dachflächen benötigen, private und öffentliche ... 

Also: hier werden sehr interessante Ideen ausgebreitet ...

Blog 2022-01-15 - Thoughts on climate change - is mankind guilty?

(light mod. 2022-01-26).


It's about guilt, maybe responsibility, definitely guilt.

It's about climate change. A climate change largely caused by humans. The "human cause" can be proven very clearly ...

But that's not the point at the moment. Whoever is to blame, we - the people, and only we the people - must reverse climate change. One possibility might be renunciation. Not driving, not eating meat, and much more. But it doesn't look as if people's hunger for energy will be curtailed. Renunciation is honorable, but I fear we must also renounce that honor. At least largely. I'm not saying that we shouldn't practice conserving energy.

But it is not enough to practice renunciation. We need new technologies - technologies that are free of fossil fuels: Photovoltaics to generate electricity, "machines" that produce "green" gasoline, wind energy for the electricity hunger and much more. But we also urgently need technologies that will enable us to remove CO2 from the air. Nevertheless: we also have to produce less CO2 and fewer other greenhouse gases. We can "compensate", i.e. "capture" the emitted CO2 again. But it is not that simple!

Planting trees, renaturing dry moors, all of this is a method of compensating – methods that are strongly favored at the moment, but as far as trees are concerned, they can burn and we have gained little, maybe nothing at all. The devastating forest fires worldwide and this century in different parts of the world show that it seems almost too late. A planted tree stores CO2 due to pho40 tosynthesis. One tonne of wood stores (roughly) one tonne of CO2. But only until the wood has been burned or rotted away. A zero-sum game in the long run. And there may not be enough peatlands to significantly affect the climate.

So we have to get the CO2 out of the air faster than it comes in. And we should only do that up to a certain limit. Because when there is no more CO2 in the air and no other greenhouse gases either, then the earth becomes a lump of ice, as has happened several times in the history of the earth when there was a so-called snowball earth. Quite apart from that, our plants need the CO2 to grow! The CO2 reduction limit should be around 280 ppm CO2 or CO2e (this is the actual climate gas value, which includes the other climate gases such as methane, socalled-CO2 equivalents). Possibly a bit more than that because it is rather difficult to reduce that gas at the moment. About 40 - 50 Gt of CO2 are generated annually by mankind.

There is also a fundamental problem here: If there should one day be a biologically effective method for getting the CO2 out of the air relatively quickly, such as improved photosynthesis, as discovered on a laboratory scale at the Max Planck Institute in Marburg (CETCH cycle), then do we have a chance. An internal publication of this institute spoke of a 20-fold effectiveness of this cycle compared to natural photosynthesis.

If this is successful, then care must be taken to ensure that the process is implemented fairly quickly on the one hand, and on the other hand that this process can be strictly controlled so that the 280 ppm limit is not exceeded.

The authors of this study (including Prof. Tobias Erb from the MPI for Terrestrial Microbiology) also believe that this could make it possible to create more food for a growing world population: Erb says that he and his colleagues hope to further expand their facility and modify the process in order to make other organic compounds that are even more valuable than glycolate, such as drug molecules. They also hope to convert captured CO2 more efficiently into organic compounds that plants need to grow. That would open the door to manipulating the genes for this novel photosynthetic pathway in crops to create new varieties that grow much faster than current varieties - a boon for agriculture in a world with a booming population.