NOTEBOOK FEATURE: How floating wetlands could transform restoration in California’s Delta – Maven’s Notebook

Floating Wetlands: A Potential Solution for Delta Restoration

Floating wetlands, although they may sound like something out of a fairy tale, are real and possess qualities that border on magic. These buoyant mats of peat and tall marsh plants called tules historically broke off from marshes in the Sacramento-San Joaquin River Delta, and were so large that they were often referred to as floating islands. In fact, during California’s Great Flood of 1862, one of these floating wetlands even bore a herd of livestock to safety. Today, researchers are exploring the potential of floating wetlands to restore the Delta and support imperiled native fish species, such as the Delta smelt.

The Challenge of Food Availability in the Delta

One of the main reasons why fish populations are declining in the Delta is the lack of available food. The region, often referred to as a “food desert,” has lost most of its tidal marshes, which were once abundant with zooplankton, a vital food source for fish. The conversion of marshes into agricultural land has limited the availability of suitable sites for tidal marsh restoration.

Furthermore, the islands in the central Delta, where tidal wetlands could potentially be established, have experienced extreme soil loss over the years. The peat soil, which is crucial for marsh growth, has subsided due to the drainage of these islands for agriculture. As a result, the land surface is now below the water level, preventing the establishment of new marshes through tidal flows.

Restoring Food, Shelter, and Cooler Water for Fish

To address these challenges, researchers have turned to floating wetlands as a potential solution. These wetlands, which are independent of land, can mimic the benefits of tidal marshes for fish. By creating floating wetlands using peat blocks from restored marshes, researchers have observed promising results.

A study led by Steven Deverel and his team found that floating wetlands had a significantly higher density of zooplankton compared to the adjacent river. This increase in food availability can support fish populations and contribute to their overall health and growth. Additionally, the tangle of roots under the floating wetlands provides shelter for baby fish, offering them a safe environment to grow.

Another advantage of floating wetlands is their ability to shade the water, reducing its temperature by 2⁰C. This cooling effect can be crucial for fish survival, especially during temperature spikes in the Delta.

Scaling Up Floating Wetlands for Restoration

The success of the pilot floating wetland has inspired researchers to explore larger-scale implementation. The team envisions expanding the floating wetlands to as much as half an acre in a wide channel, using a boom to keep them in place. However, the availability of peat blocks for this expansion remains a challenge. Permitting processes may also pose hurdles, but the presence of nearby restored marshes provides hope for obtaining the necessary resources.

Enhancing Delta Smelt Production

Shawn Acuña and his team at the Metropolitan Water District of Southern California are particularly interested in the potential of floating wetlands for enhancing Delta smelt production. These rare fish species have been reintroduced into the wild through a hatchery, but the current production capacity is limited. By utilizing ponds and floating wetlands, the team aims to increase the production of Delta smelt in a cost-effective manner.

Preliminary experiments have shown promising results, with Delta smelt thriving in the ponds and experiencing significant weight gain. The availability of abundant fish food in the ponds contributes to their growth and overall health. The team plans to anchor Delta smelt cages near floating wetlands to further enhance fish production.

Potential Challenges and Future Opportunities

While ponds offer opportunities for fish production, they also present challenges. Fish in ponds are more vulnerable to environmental conditions, particularly heat. Ponds can become much hotter than rivers in the Delta, potentially impacting fish survival. Researchers are exploring various methods, such as shade balls or groundwater pumping, to optimize pond conditions for Delta smelt.

Despite these challenges, the potential of floating wetlands for Delta restoration and fish production is promising. The ability to create habitats, enhance food availability, and provide shelter and cooler water for fish can significantly contribute to the recovery of imperiled native fish species in the Delta. With further research and implementation, floating wetlands have the potential to transform restoration efforts in California’s Delta.

SDGs, Targets, and Indicators

SDGs Addressed:

1. SDG 14: Life Below Water
2. SDG 15: Life on Land

Targets Identified:

1. Target 14.2: By 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans.
2. Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity, and, by 2020, protect and prevent the extinction of threatened species.

Indicators:

• Indicator 14.2.1: Proportion of national exclusive economic zones managed using ecosystem-based approaches.
• Indicator 15.5.1: Red List Index.

The issues highlighted in the article, specifically the potential of floating wetlands to restore the Delta and benefit native fish species, are connected to SDG 14 (Life Below Water) and SDG 15 (Life on Land). These SDGs focus on the conservation and sustainable management of marine and terrestrial ecosystems, including the protection of biodiversity and the restoration of degraded habitats.

Based on the content of the article, the specific targets that can be identified are Target 14.2, which calls for the sustainable management and restoration of marine and coastal ecosystems, and Target 15.5, which aims to reduce habitat degradation, halt biodiversity loss, and protect threatened species.

The article mentions indicators that can be used to measure progress towards these targets. Indicator 14.2.1 measures the proportion of national exclusive economic zones managed using ecosystem-based approaches, which aligns with the focus on sustainable management and restoration of marine and coastal ecosystems. Indicator 15.5.1, the Red List Index, measures the extinction risk of species and can be used to assess progress in preventing species extinction and protecting biodiversity.

SDGs, Targets, and Indicators Table:

Source: mavensnotebook.com