8.3 Nature-based solutions for disaster risk reduction

Nature-based solutions (NbS) are innovative approaches to disaster risk reduction that work with nature, not against it. By harnessing the power of ecosystems, NbS protect communities from hazards like floods, landslides, and coastal erosion while providing numerous co-benefits.

From restoring wetlands to planting mangroves, NbS offer sustainable alternatives to traditional infrastructure. They not only mitigate disaster risks but also boost biodiversity, support livelihoods, and enhance climate resilience. However, challenges like limited awareness and resource constraints must be addressed to fully realize their potential.

Nature-based solutions for disaster risk reduction

Definition and applications

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• Nature-based solutions (NbS) protect, sustainably manage, and restore natural or modified ecosystems to address societal challenges (disaster risk reduction, climate change adaptation, and human well-being)
• NbS can be applied to mitigate the impacts of various hazards
  • Floods
  • Landslides
  • Coastal erosion
  • Droughts
• NbS harness the natural functions and services provided by ecosystems
• Examples of NbS for disaster risk reduction
  • Wetland restoration for flood control
  • Mangrove plantation for coastal protection
  • Afforestation for landslide prevention
• NbS can be implemented as standalone measures or integrated with traditional engineering solutions (gray infrastructure) to create hybrid approaches
  • Enhances the overall resilience of communities and infrastructure

Integration with gray infrastructure

• NbS can be integrated with traditional engineering solutions (gray infrastructure) to create hybrid approaches
  • Combines the benefits of both natural and engineered systems
  • Enhances the overall resilience of communities and infrastructure
• Examples of hybrid approaches
  • Integrating wetland restoration with levees for flood protection
  • Combining mangrove plantation with seawalls for coastal defense
  • Incorporating green roofs and permeable pavements with stormwater drainage systems in urban areas
• Hybrid approaches can provide more comprehensive and adaptive solutions to disaster risk reduction
  • Capitalizes on the strengths of both NbS and gray infrastructure
  • Addresses the limitations and uncertainties associated with relying solely on either approach

Examples of nature-based solutions

Flood mitigation

• Restoring floodplains to provide natural storage and conveyance of floodwaters
• Creating urban green spaces (parks, gardens) to reduce surface runoff and enhance water infiltration
• Implementing permeable pavements (porous concrete, interlocking pavers) to allow water to percolate into the ground and reduce surface runoff
• Constructing bioswales and rain gardens to collect, filter, and infiltrate stormwater runoff

Coastal protection

• Establishing or restoring mangrove forests to attenuate wave energy, reduce coastal erosion, and provide a buffer against storm surges and sea-level rise
• Restoring salt marshes to dissipate wave energy, trap sediments, and stabilize shorelines
• Protecting and rehabilitating coral reefs to reduce wave energy, minimize coastal erosion, and provide habitat for marine biodiversity
• Implementing dune restoration and stabilization to prevent coastal erosion and protect inland areas from storm surges

Landslide prevention

• Reforesting slopes to stabilize soil, reduce erosion, and minimize the risk of landslides
• Implementing terracing to reduce slope steepness, control runoff, and prevent soil erosion
• Promoting sustainable land management practices (contour plowing, strip cropping) to conserve soil and prevent landslides
• Establishing vegetated buffer zones along rivers and streams to stabilize banks and reduce the risk of slope failures

Drought mitigation

• Implementing rainwater harvesting systems (rooftop collection, cisterns) to enhance water storage capacity and provide water for irrigation and domestic use
• Promoting agroforestry (intercropping trees with crops) to improve soil moisture retention, reduce evapotranspiration, and provide shade for crops
• Restoring wetlands to enhance water storage capacity, regulate water flow, and support water-efficient agriculture
• Implementing conservation agriculture practices (no-till farming, cover cropping) to improve soil structure, increase water infiltration, and reduce evaporation

Urban heat island mitigation

• Increasing urban green spaces (parks, gardens, green corridors) to reduce surface and air temperatures, improve thermal comfort, and mitigate the impacts of heatwaves
• Implementing green roofs to reduce building energy consumption, mitigate urban heat island effect, and provide habitat for biodiversity
• Planting trees and increasing tree canopy cover to provide shade, reduce surface temperatures, and improve air quality
• Using cool pavements (reflective materials, permeable surfaces) to reduce heat absorption and mitigate the urban heat island effect

Co-benefits of nature-based solutions

Ecosystem services

• NbS provide multiple ecosystem services that contribute to the overall health and well-being of communities and the environment
  • Water purification: Wetlands and riparian buffers filter pollutants and improve water quality
  • Carbon sequestration: Forests and other vegetated areas absorb and store atmospheric carbon dioxide
  • Nutrient cycling: Healthy ecosystems regulate the flow of nutrients, supporting soil fertility and productivity
• Ecosystem services provided by NbS can reduce the need for costly infrastructure and maintenance
  • Natural water treatment by wetlands can reduce the need for expensive water treatment plants
  • Coastal protection by mangroves and coral reefs can reduce the need for expensive coastal defense structures

Biodiversity conservation

• Implementing NbS can enhance biodiversity by creating and restoring habitats for various species
  • Wetland restoration provides habitat for waterfowl, fish, and aquatic plants
  • Reforestation supports forest-dwelling species and improves ecological connectivity
• NbS promote ecological connectivity by creating corridors and stepping stones for species movement
  • Facilitates gene flow and supports the resilience of populations to environmental changes
• NbS support the conservation of threatened or endangered species
  • Mangrove restoration provides critical habitat for endangered species (sea turtles, migratory birds)
  • Coral reef protection supports the survival of endangered marine species (dugongs, whale sharks)

Sustainable livelihoods

• NbS can support sustainable livelihoods by providing opportunities for eco-tourism, sustainable agriculture, and the sustainable use of natural resources
  • Mangrove restoration can support sustainable aquaculture and fisheries
  • Agroforestry can provide diverse income streams from crops, timber, and non-timber forest products
• NbS contribute to local economic development and poverty alleviation
  • Eco-tourism associated with protected areas can generate income for local communities
  • Sustainable agriculture practices can improve crop yields and income for smallholder farmers

Human health and well-being

• NbS can improve human health and well-being by providing recreational spaces, improving air and water quality, and reducing exposure to environmental hazards
  • Urban green spaces provide opportunities for physical activity, relaxation, and social interaction
  • Vegetation in cities can filter air pollutants, reducing the risk of respiratory diseases
  • Wetlands and riparian buffers can improve water quality, reducing the risk of waterborne diseases
• NbS can reduce the psychological stress associated with environmental hazards
  • Green spaces in cities can provide a sense of tranquility and reduce stress levels
  • Coastal vegetation can provide a sense of security and reduce the fear of coastal hazards

Climate change mitigation and adaptation

• NbS can contribute to climate change mitigation by sequestering carbon in vegetation and soils
  • Forests and other vegetated areas act as carbon sinks, absorbing atmospheric carbon dioxide
  • Wetlands and peatlands store significant amounts of carbon in their soils and vegetation
• NbS can enhance the resilience of ecosystems and communities to climate-related hazards
  • Mangroves and coastal wetlands protect against sea-level rise and storm surges
  • Agroforestry and conservation agriculture practices improve soil moisture retention and crop resilience to droughts
• NbS can regulate local and regional climate by influencing temperature, humidity, and precipitation patterns
  • Urban green spaces can reduce the urban heat island effect and improve thermal comfort
  • Forests can influence rainfall patterns and moderate temperature extremes

Challenges of nature-based solutions

Limited understanding and awareness

• Limited understanding and awareness of the potential benefits and effectiveness of NbS among decision-makers, practitioners, and the general public can hinder their adoption and implementation
  • Lack of knowledge about the multiple co-benefits of NbS beyond disaster risk reduction
  • Perception that NbS are less reliable or effective compared to traditional engineering solutions
• Insufficient communication and education about the value and importance of NbS
  • Inadequate dissemination of research findings and case studies demonstrating the success of NbS
  • Limited public engagement and participation in the planning and implementation of NbS projects

Scientific uncertainties and risks

• Insufficient scientific evidence and data on the long-term performance, cost-effectiveness, and scalability of NbS can create uncertainties and risks in their application
  • Lack of long-term monitoring and evaluation of NbS projects to assess their effectiveness and resilience over time
  • Limited understanding of the complex interactions and feedback loops between NbS and the surrounding environment
• Difficulty in quantifying and valuing the multiple benefits of NbS
  • Lack of standardized metrics and valuation methods for ecosystem services and co-benefits
  • Challenges in incorporating non-monetary values (biodiversity, cultural significance) into decision-making processes
• Uncertainties related to the performance of NbS under changing environmental conditions
  • Potential impacts of climate change on the effectiveness and resilience of NbS
  • Risks associated with the introduction of non-native species or the alteration of natural ecosystem dynamics

Cross-sectoral collaboration and coordination

• Implementing NbS often requires cross-sectoral collaboration and coordination among various stakeholders, which can be challenging due to conflicting interests and priorities
  • Involvement of multiple government agencies with different mandates and jurisdictions
  • Engagement of local communities, NGOs, and the private sector with diverse needs and expectations
• Lack of institutional frameworks and governance mechanisms to facilitate collaboration and coordination
  • Absence of dedicated policies, regulations, and funding mechanisms to support NbS implementation
  • Insufficient platforms for stakeholder dialogue, knowledge sharing, and conflict resolution
• Resistance to change and the adoption of new approaches
  • Preference for familiar and proven solutions among decision-makers and practitioners
  • Reluctance to invest in NbS due to perceived risks and uncertainties

Resource constraints and investment barriers

• NbS may require significant upfront investments and long-term maintenance, which can be a barrier for resource-constrained communities and organizations, particularly in developing countries
  • High costs associated with land acquisition, restoration activities, and monitoring
  • Limited access to finance and funding mechanisms for NbS projects
• Lack of economic incentives and market-based mechanisms to support NbS implementation
  • Absence of payment for ecosystem services schemes or other financial instruments
  • Insufficient recognition of the economic value of ecosystem services and co-benefits
• Competition for land and resources with other development priorities
  • Pressure to allocate land for agriculture, infrastructure, or urban development
  • Conflicting demands for water resources between ecosystems and human activities

Site-specific limitations and extreme events

• The effectiveness of NbS can be influenced by local environmental conditions, which may limit their applicability or require site-specific adaptations
  • Variability in soil type, topography, and climate across different regions
  • Need for tailored design and implementation strategies based on local ecological and socio-economic contexts
• NbS may have limited capacity to mitigate the impacts of extreme events or high-magnitude hazards
  • Potential for NbS to be overwhelmed or damaged by severe floods, storms, or droughts
  • Need for complementary risk reduction measures, such as early warning systems and emergency response plans
• Potential trade-offs between the benefits and costs of NbS in different locations
  • Balancing the priorities for disaster risk reduction, biodiversity conservation, and human well-being
  • Addressing potential conflicts between the needs of upstream and downstream communities in watershed management