2024-11-10-世界银行-国家财富的变化——用红树林建设沿海复原力_自然防洪对国家财富变化的贡献（技术报告）（英）_77页_3mb

Summary: Building Coastal Resilience with Mangroves

This technical report analyzes the flood protection services provided by mangroves globally and assesses changes in their economic and social value between 1996 and 2020. Using a quantitative "Averted Damages Approach," the study combines storm models, hydrodynamic simulations, and socioeconomic data to quantify the reduction in flood risk from mangroves, measured as annual benefits.

Key Findings

• Global Flood Risk and Benefits:

  • From 1996 to 2010, flood risk increased faster than mangrove benefits due to climate change and mangrove loss.
  • From 2010 to 2020, despite slower mangrove loss, flood risk and benefits both increased, with benefits growing faster in some cases. This is partly due to population and capital growth in mangrove-proTECTED areas.
  • The present value (at a discount rate) of global flood reduction benefits from mangroves (100-year assets) was $855 billion in 2020.

• Country-Level Variation:

  • Highest Values: China, Vietnam, Australia, US, and India had the greatest present value of mangroves for flood reduction.
  • Greatest Increases: Vietnam, China, and Bangladesh saw the largest annual increases in flood risk reduction benefits.
  • Risk Changes: Countries like Grenada, the Gambia, and Equatorial Guinea showed minimal risk increases despite mangrove gains, indicating some resilience due to geographical factors.

• Equity Considerations:

  • Lower-middle-income countries gained significantly more protection per person living in mangrove areas, underscoring marginalization effects; high-income countries had higher per-hectare values but the poorest nations saw greater proportional benefits.

• Data and Modeling: Used updated global mangrove data from GMW 3.0, high-resolution flood models, population grids (GHS_POP), and capital stock data. Limitations include uncertainties in bathymetry and socioeconomic data homogeneity.

Discussion and Recommendations

The report underscores that mangroves provide significant, yet often unaccounted, economic value for flood risk reduction. Mangroves' effectiveness depends critically on spatial extent and siting rather than just coverage. While continued loss is alarming, slowdowns offer opportunities. However, if mangrove degradation accelerates, the increase in flood risk could be severe. Recommendations include:

• Conservation and restoration to enhance flood protection and climate adaptation.

• Economic valuation to integrate into disaster risk management, insurance, and finance mechanisms.

• Combining natural defenses with engineered infrastructure for sustainable coastal protection.

• Generally, incorporating the value of mangroves into policy and investment decisions can support cost-effective adaptation to climate change and coastal development.