2017年-世界发展银行全球_Simulating_the_Macroeconomic_Impact_of_Future_Water_Scarcity_21页_927kb

Summary of "Simulating the Macroeconomic Impact of Future Water Scarcity"

Core Content

This paper by Roberto Roson explores the macroeconomic implications of future water scarcity under different socioeconomic scenarios, specifically the Shared Socioeconomic Pathways (SSPs). It uses a global general equilibrium model and data from the Global Change Assessment Model (GCAM) to simulate how water scarcity could affect economic growth and development in various regions of the world.

Main Points

1. Water Scarcity and Economic Growth

• Economic growth occurs in all regions, but the level of income per capita varies significantly depending on the water availability and how regions manage water resources.
• In 2050 and 2100, water demand is projected to exceed sustainable supply in most regions, with the exception of North America, South America, and Western Europe.
• The Middle East and South Asia (India and neighboring countries) already exceed sustainable water consumption, suggesting the need for nonrenewable water resources, such as groundwater, which may be unsustainable.

2. Model and Methodology

• The paper uses the GCAM model to estimate water supply, which includes yearly runoffs from all countries in a macro-region, averaged over three GCM climate scenarios (CCSM, FIO, and GISS).
• Water demand is calculated using water-intensity coefficients derived from base year (2004) data and economic growth projections.
• The model considers 14 macro-regions and 20 industries, including agriculture, industry, and municipal sectors.

3. SSP Scenarios

• SSP1 (Sustainability): Characterized by high economic growth, reduced inequalities, and rapid technological progress towards environmentally friendly processes.
• SSP3 (Regional Rivalry): Features moderate economic growth, a rapidly growing population, and slow technological change in the energy sector, leading to high emissions and reduced trade.

4. Water Demand and Supply Projections

• Table 1 provides projections of water demand and percentage changes relative to the base year (2004) for the years 2050 and 2100 under the two SSPs.
• In 2050, the demand gap is significant, especially in regions like the Middle East and South Asia, where water consumption exceeds availability.
• By 2100, the gap is even more pronounced, with many regions facing severe water shortages, suggesting that current water regimes may not support projected economic growth.

5. Policy Scenarios for Water Scarcity

• Three policy scenarios are explored to address the water demand gap:
  • NO-WR (No Water Reallocation): No reallocation of water between industries, leading to uniform production cuts.
  • MILD (Mild Reallocation): Partial reallocation of water between industries, assuming some efficiency improvements.
  • STRONG (Strong Reallocation): Significant reallocation of water, where water is moved to sectors with higher value and water efficiency is increased.
• The assumption is that efficiency gains can cover up to 75% of the demand gap, while the remaining 25% may require production cuts or other policy interventions.

6. Water Scarcity and Economic Implications

• Under business-as-usual scenarios, future global water supply is insufficient to meet demand, potentially leading to production shortfalls.
• The paper highlights that water scarcity is not adequately considered in the definition of the Shared Socioeconomic Pathways, which could lead to inconsistencies in economic projections.
• Regions with high water demand and low availability may experience reduced economic growth and increased vulnerability to climate change.

Key Information

• Water demand is projected to exceed sustainable supply in most regions by 2100, with significant variations in the degree of excess depending on the SSP scenario.
• Water is a critical factor in economic growth, and its scarcity could lead to substantial changes in production, trade, and economic structure.
• Efficiency improvements are essential to mitigate the impact of water scarcity, but they may not be sufficient to fully address the demand gap.
• Adaptation strategies include shifting production to less water-intensive sectors, increasing water efficiency, and importing water-intensive goods.
• The paper emphasizes the need for radical changes in water management policies to address future water scarcity effectively.

Conclusion

The study concludes that water scarcity will significantly impact future economic growth, particularly in regions where water demand exceeds sustainable supply. It underscores the importance of integrating water considerations into economic models and policy planning to ensure sustainable development and avoid economic setbacks due to water shortages.