Restoration and management of an Indigenous aquaculture system helps mitigate climate change impacts to estuarine fisheries – Nature

Executive Summary

This report details a study on the resilience of Indigenous aquaculture systems (loko iʻa) in Hawaiʻi against the impacts of climate change, directly addressing several Sustainable Development Goals (SDGs). The study assessed how rising water temperatures affect loko iʻa productivity and evaluated mitigation strategies, including nutrient flow restoration and fish restocking. Key findings indicate that while climate change poses a significant threat, biocultural restoration practices can substantially enhance fish populations and social-ecological resilience. These efforts align with SDG 2 (Zero Hunger) by improving local food security, SDG 13 (Climate Action) by modeling and mitigating climate impacts, and SDG 14 (Life Below Water) by promoting sustainable fisheries and marine ecosystem health. The study concludes that a combination of global emissions reduction and local restoration actions is crucial for the long-term sustainability of these vital food systems.

Introduction: Aligning Indigenous Aquaculture with Sustainable Development Goals

Indigenous aquaculture systems in Hawaiʻi, known as loko iʻa, represent a historical model of sustainable food production. These systems are central to achieving several SDGs by integrating cultural heritage with ecological management. However, their productivity is threatened by modern challenges, primarily climate change.

Biocultural Restoration and its Role in Sustainable Development

• SDG 2 (Zero Hunger) & SDG 14 (Life Below Water): Historically, loko iʻa produced approximately 900,000 kg of fish annually, forming a cornerstone of local food security. Today, restoration efforts aim to revive this productivity, contributing to sustainable food systems and the conservation of marine resources.
• SDG 11 (Sustainable Cities and Communities) & SDG 15 (Life on Land): The practice of biocultural restoration strengthens the connection between people and their environment, fostering resilient communities and promoting sustainable management of interconnected land and sea ecosystems.
• SDG 13 (Climate Action): Loko iʻa are highly vulnerable to climate-induced stressors such as rising water temperatures and altered precipitation patterns, which impact fish physiology and nutrient flows. This study addresses the urgent need for climate adaptation strategies to protect these systems.

Methodology: A Collaborative Approach to Climate Resilience Modeling

This study employed a co-production methodology, exemplifying SDG 17 (Partnerships for the Goals). Researchers collaborated with Paepae o Heʻeia, the Native Hawaiian stewards of Heʻeia Fishpond, to develop research questions and refine ecosystem models. This approach ensures that scientific inquiry is grounded in local and Indigenous knowledge, enhancing the relevance and application of the findings.

Modeling Scenarios for Sustainable Management

An ecosystem model of Kāneʻohe Bay was used to project the impacts of various environmental and management scenarios on fish populations. The model incorporated:

1. Climate Change Scenarios (SDG 13): Three greenhouse gas emissions scenarios (SSP1-2.6, SSP2-4.5, and SSP3-7.0) were used to project the effects of rising water temperatures on fish and phytoplankton physiology.
2. Nutrient Flow Scenarios (SDG 14 & SDG 15): The model tested how different levels of nutrient inputs, simulating watershed restoration, affect fish populations and fisheries harvest.
3. Restocking Scenarios (SDG 2 & SDG 14): The viability of restocking juvenile fish to supplement natural population growth was assessed as a direct intervention to boost food production and ecosystem health.

Results: Assessing Climate Impacts and Mitigation Strategies for SDGs

The study’s findings highlight the complex interplay between climate change, ecosystem function, and human intervention, providing critical data for achieving sustainable development targets.

Climate Action (SDG 13): Impact of Emissions Scenarios on Marine Ecosystems

• Under high emissions scenarios (SSP3-7.0), fish biomass in both the loko iʻa and the surrounding bay is projected to decrease by the end of the century.
• Fish populations within the loko iʻa demonstrated greater resilience to warming waters compared to those in the bay, experiencing a smaller relative decline in biomass. This resilience is likely due to the temperature-regulating effects of freshwater inputs.
• Long-term population trends were primarily dictated by the emissions scenario, underscoring the critical importance of global climate action for local ecosystem health.

Life Below Water (SDG 14) & Zero Hunger (SDG 2): Enhancing Fisheries Productivity

• Nutrient Restoration: Increased nutrient inputs, simulating the effects of watershed restoration, substantially enhanced fisheries harvest potential. Higher nutrient levels supported greater fish biomass, allowing for maximum sustainable harvest at a lower fishing effort.
• Restocking Interventions: Restocking juvenile fish significantly accelerated the recovery of fish populations to their carrying capacity. With sustained restocking over 4-5 years, the loko iʻa population reached carrying capacity up to 95% faster than without intervention.
• Fisheries Management: The model confirmed that fishing pressure is a primary determinant of fish density. Sustainable management of fishing effort is essential to complement restoration benefits and maintain healthy stocks.

Integrated Solutions for Sustainable Development (SDGs 2, 13, 14)

• A combination of nutrient restoration and restocking was highly effective at mitigating the negative impacts of climate change.
• Under this combined strategy, fish density was nearly double that of non-restored scenarios, even under high emissions projections.
• This demonstrates that local management actions can significantly bolster ecosystem resilience and food production, contributing directly to climate adaptation and the sustainable use of marine resources.

Discussion: Biocultural Restoration as a Pathway to Achieving the SDGs

The study’s results strongly support biocultural restoration as a powerful strategy for advancing multiple SDGs simultaneously. By integrating Indigenous knowledge with scientific modeling, communities can develop targeted, effective interventions.

Key Implications for Sustainable Development

1. Enhancing Food Security (SDG 2): Restoring loko iʻa through nutrient management and restocking can substantially increase local seafood availability, contributing to food sovereignty and zero hunger.
2. Building Climate Resilience (SDG 13): Local-scale actions, such as restoring freshwater flow to regulate temperature and enhance nutrients, are vital adaptation strategies that build resilience against climate change. However, these local efforts must be paired with global emissions reductions for long-term success.
3. Conserving Marine Life (SDG 14): The restoration of loko iʻa not only increases the target fish population but can also have positive spillover effects on the surrounding estuary, enhancing the overall health and productivity of coastal ecosystems.

Conclusion and Recommendations for Sustainable Action

This study demonstrates that the restoration and sustainable management of Indigenous aquaculture systems are critical for mitigating climate change impacts on estuarine fisheries. The findings provide a clear pathway for action that aligns with the 2030 Agenda for Sustainable Development.

Recommendations

• Support Biocultural Restoration: Invest in community-led, biocultural restoration projects that integrate traditional ecological knowledge with modern science to enhance both ecological and social resilience. This directly supports SDGs 2, 11, 13, 14, and 15.
• Implement Integrated Management: Adopt a holistic management approach that combines watershed restoration (to manage nutrient and freshwater flows), sustainable fisheries regulations, and restorative aquaculture techniques like restocking.
• Prioritize Global Climate Action (SDG 13): Acknowledge that while local actions are effective, long-term ecological stability is ultimately dependent on global efforts to reduce greenhouse gas emissions and limit warming.
• Foster Collaborative Partnerships (SDG 17): Continue to build and support partnerships between Indigenous communities, scientists, and policymakers to co-produce knowledge and implement effective, place-based solutions for a sustainable future.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The article on the restoration and management of Indigenous aquaculture systems (loko iʻa) in Hawaiʻi connects to several Sustainable Development Goals (SDGs) by addressing issues of food security, climate change, ecosystem management, and cultural heritage.

• SDG 2: Zero Hunger: The article’s core focus is on the productivity of loko iʻa, which “historically produced abundant seafood.” It explores methods to enhance fish production, directly contributing to local food security and sustainable food production systems.
• SDG 6: Clean Water and Sanitation: The study emphasizes the critical role of water management, discussing how “changes in freshwater flow” and “nutrient flow” impact the productivity of loko iʻa. It highlights the importance of watershed restoration to improve water quality and quantity.
• SDG 11: Sustainable Cities and Communities: The article addresses the protection of cultural heritage through “biocultural restoration.” This approach “emphasizes Indigenous and local community knowledge” and strengthens “cultural identities and connections of people to place,” aligning with the goal of safeguarding cultural heritage.
• SDG 13: Climate Action: A central theme of the study is assessing how “climate change may affect loko iʻa productivity” through rising water temperatures. It models different emissions scenarios and evaluates mitigation strategies, directly addressing climate change adaptation and resilience.
• SDG 14: Life Below Water: The research is fundamentally about marine and coastal ecosystems. It examines the health of fish populations, the impacts of fishing pressure, and the restoration of estuarine systems, all of which are central to the sustainable use of marine resources.
• SDG 15: Life on Land: The article connects the health of the aquatic loko iʻa system to terrestrial management practices. It mentions “watershed restoration, through an Indigenous biocultural lens, including invasive species removal, native species restoration,” linking the conservation of land-based ecosystems to the health of coastal waters.

2. What specific targets under those SDGs can be identified based on the article’s content?

The article’s content aligns with several specific targets under the identified SDGs:

1. Target 2.4: By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production… and that progressively improve land and soil quality.
   • The study directly addresses this by assessing how to maintain the productivity of loko iʻa (a food production system) under climate change stress. It explores “nutrient flow restoration and restocking” as strategies to offset negative effects and “substantially increase short- and long-term estuarine and loko iʻa fish density.”
2. Target 6.6: By 2020, protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes.
   • The entire research project is an example of an effort to restore a water-related ecosystem (loko iʻa and the surrounding estuary). The article discusses how “watershed restoration” is a powerful way to restore the salinity and nutrient conditions that made these systems historically productive.
3. Target 11.4: Strengthen efforts to protect and safeguard the world’s cultural and natural heritage.
   • The article frames the restoration of loko iʻa as “biocultural restoration,” which it defines as an approach that conserves “both biophysical and sociocultural components of an ecosystem.” This directly contributes to safeguarding the Indigenous cultural heritage of Hawaiʻi embodied in these aquaculture systems.
4. Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.
   • The study’s objective is “to assess how climate change may affect loko iʻa productivity, as well as how nutrient flow restoration and restocking may mitigate some of these effects.” By modeling these scenarios, the research identifies pathways to enhance the “social–ecological resilience” of these systems in the face of rising water temperatures.
5. 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.
   • The research is a direct application of this target. It models the restoration of an Indigenous aquaculture system and demonstrates that these efforts “can substantially increase both short- and long-term estuarine and loko iʻa fish density,” contributing to the health and productivity of the coastal ecosystem.
6. Target 14.4: By 2020, effectively regulate harvesting and end overfishing, illegal, unreported and unregulated fishing and destructive fishing practices…
   • The study models the impact of different fishing pressures, stating that “Fisheries harvest was the primary factor determining fish density.” By comparing scenarios with no fishing, bay fishing, and fishing in both the bay and loko iʻa, it provides insights necessary for regulating harvesting to maintain sustainable fish stocks.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, the article mentions and uses several quantitative indicators to measure the state of the ecosystem and the effectiveness of management interventions, which can be used to track progress towards the SDG targets.

• Fish Density and Biomass: This is the primary indicator used throughout the study to measure ecosystem health and productivity. The results are reported in terms of “fish density” and “fish biomass” under various scenarios. For example, the study found that “increased emissions scenarios led to decreased fish biomass by the end of the century.” This indicator directly measures progress for targets related to ecosystem health and food production (Targets 2.4, 14.2).
• Fisheries Harvest and Catch Per Unit Effort (CPUE): The article explicitly models and presents results on “bay fisheries harvest and CPUE.” It shows how these metrics change with different levels of nutrient inputs and fishing effort. This is a standard indicator for measuring the sustainability of fishing practices (Target 14.4).
• Nutrient Input Levels: The study models the effect of different nutrient inputs, testing “50%, 100%, 150%, and 200% of the current nutrient levels.” The level of nutrient flow is used as an indicator of both a driver of productivity and a potential pollutant, making it relevant for measuring progress in water resource management (Targets 6.6, 14.1).
• Water Temperature: Sea surface temperature is the key climate change indicator used in the model. The study uses “dynamically downscaled climate projections” for different emissions scenarios (SSP1-2.6, SSP2-4.5, and SSP3-7.0) to drive its ecological model. Monitoring water temperature is a direct way to track climate change impacts and the need for adaptation (Target 13.1).
• Fish Restocking Quantity and Duration: The study quantifies restocking efforts in terms of biomass added (“1, 2, and 3 g/m²”) and duration (“annually for up to 5 years”). These metrics serve as indicators of the scale of restoration intervention needed to achieve desired outcomes in fish population growth (Target 14.2).

4. Table of SDGs, Targets, and Indicators

Source: nature.com