战略与国际研究中心-The-UN-Climate-Change-Report--Transform-Global-Food-Systems-or-Trigger-a-Crisis_200页_6mb

Summary of Climate Change, Water and Food Security

Core Content

This report explores the anticipated impacts of climate change on water availability for agriculture and the implications for food security. It outlines the need for improved understanding, adaptation strategies, and policy alignment to manage these challenges effectively.

Main Views and Key Information

1. Introduction

• Water availability is a critical factor in the future of agriculture and agricultural water management.
• Climate change will increase water demand and reduce water availability, especially in areas where irrigation is most needed.
• Adaptation measures are necessary to ensure water security and resilience in agricultural systems.
• The report emphasizes the importance of aligning water and agricultural policies and implementing 'no-regrets' strategies.

2. Setting the Scene

• Climate change will affect all aspects of the hydrological cycle, leading to more frequent and severe droughts and floods.
• The IPCC 4th Assessment and the Stern Review highlight the impacts of climate change on food security and the environment.
• Agricultural systems that rely on water management, such as rainfed agriculture, irrigated agriculture, inland fisheries, livestock grazing, and forested land, are particularly vulnerable.
• Economic competition for water resources is a growing challenge, especially in the context of climate change.
• Climate change projections vary, and predictive models are not yet fully reliable for rainfall and runoff events.

3. Baseline and Trends in Agricultural Water Demand

• Irrigation areas are expected to grow significantly, with an estimated 11% increase in water withdrawals to meet future biomass production needs.
• Global and regional trends in irrigation and agricultural water use are analyzed, showing the expansion of irrigation in many regions.
• Emerging trends in agricultural water management include improved efficiency, technological innovations, and changes in crop patterns.
• The economic drivers of future investments in water management are discussed, highlighting the importance of cost-benefit analysis and policy support.

4. Specific Climate Change Impacts on Agricultural Water Management

• Temperature rise increases crop water demand, reduces productivity, and alters evapotranspiration rates.
• CO₂ fertilization may increase crop yields, but the negative impacts of pests and diseases are also expected to rise.
• Water supply and demand are affected by changes in precipitation, runoff, and groundwater recharge.
• Regional impacts vary, with Mediterranean, semi-arid, and glacier-fed river basins being particularly affected.
• Wetlands and coastal deltas are vulnerable to rising sea levels and increased salinity.
• Adaptive strategies at the farm, irrigation system, and basin levels are essential to address these challenges.

5. Prospects for Adaptation

• On-farm adaptation includes crop selection, water management practices, and irrigation technologies.
• Irrigation system-level adaptation involves water allocation, system performance, and policy measures.
• National and basin-level adaptation requires policy coordination, drought and flood management, and aquifer recharge strategies.
• Adaptive capacity depends on policies, institutions, and investment choices.
• Institutions and long-term investments are critical to enhancing resilience and sustainability in agricultural water management.

6. Prospects for Mitigation

• Greenhouse gas emissions from agricultural water management are a concern, with methane and nitrous oxide being significant contributors.
• Mitigation strategies include organic agriculture, carbon sequestration, and methane management.
• Forest-related mitigation has hydrological implications, such as increased water retention and reduced runoff.
• Agricultural water management can also contribute to hydropower generation, offering a potential climate change mitigation opportunity.

7. Conclusions and Recommendations

• Investment in climate change-related water management is essential to ensure irrigated agriculture and food production remain resilient.
• Understanding and integrating agronomic science with water management and hydrology is crucial for effective adaptation.
• Regional and national approaches are necessary to address climate change impacts.
• International support and collaboration are key to developing and implementing adaptive strategies.
• The report calls for action to address knowledge gaps, improve policy alignment, and enhance resilience in developing countries.

Key Figures and Tables

• Figure 2.1: Illustrates the range of scenario predictions for GHG emissions and global warming.
• Figure 4.1: Shows the agricultural production cycle as impacted by climate change.
• Table 2.1: Estimates the number of people at risk of hunger in 2080.
• Table 3.1: Shows the expansion of irrigation area from 1961 to 2050.
• Table 4.2: Typology of climate change impacts on water management in major agricultural systems.

Acronyms and Abbreviations

• AEZ: Agro-ecological zones
• AOGCM: Atmosphere-Ocean (coupled) Global Climate Model
• AQUACROP: Crop model to simulate yield response to water
• AQUASTAT: Global database on water use in agriculture
• AR3/AR4: Third and Fourth Annual Assessment Reports of the IPCC
• COP: Conference of Parties
• CROPWAT: Crop Water Model
• DSSAT: Decision Support System for Agrotechnology Transfer
• ETo: Reference evapotranspiration
• IPCC: Intergovernmental Panel on Climate Change
• IWMI: International Water Management Institute
• SRES: Special Report on Emissions Scenarios
• SRI: System of rice intensification
• SUA: Supply utilization accounts

Units Used in the Report

• Gt: Gigatonne (10⁹ t)
• ha: Hectare
• kg: Kilogram
• km³: Cubic kilometre (10⁹ m³)
• m: Metre
• m³: Cubic metre
• Mt: Megatonne (10⁶ t)
• ppm: Parts per million
• tonne: Tonne

Summary

Climate change will significantly affect water availability, crop productivity, and agricultural systems. Irrigation is the largest user of raw water and will be most impacted by these changes. Adaptation and mitigation strategies are needed to ensure food security and water sustainability, especially in developing countries. The report emphasizes the importance of policy alignment, institutional support, and investment in resilient water management systems.