2023-03-15-兰德-迈向低碳未来-估算加利福尼亚州西部水域的温室气体排放（英）-2023_73页_2mb

Growing Toward a Low-Carbon Future: Estimating Greenhouse Gas Emissions in California’s Westlands Water District

1. Research Questions & Approach
The study focused on greenhouse gas (GHG) emissions from Westlands Water District’s agricultural practices using a cross-sectoral model. It addressed:

1. Sources of GHG emissions and their variability.
2. Effects of climate change on emissions.
3. Trade-offs and emissions reduction potentials under policy levers (e.g., no-tillage solar expansion).

2. Key Findings

• Baseline Emissions (2020–2050 Average):

  • Total agricultural emissions: 665,929 MtCO₂eq/year.
  • Net emissions offset by solar: 263,889 MtCO₂eq/year (without solar offset).
  • Westlands currently a net negative emitter, transitioning to positive emissions by 2033 due to declining grid carbon intensity.

• Major Emission Drivers:

  • Highest per-acre emissions: Cotton (due to energy use), Fruits and Vegetables, Tree Crops.
  • Fallow land and Almonds/Pistachios (due to high acreage) are top contributors to aggregate emissions.
  • Processing Tomatoes, Corn, and Hay sequester more carbon than they emit.

• Climate Change Effects:

  • Climate uncertainties (e.g., precipitation, temperature) introduce ~200,000–900,000 MtCO₂eq/y fluctuations in emissions.
  • Reduced water availability in dry years increases fallowing, leading to temporary emission spikes.

• Alternative Practices:

  • Solar Conversion: Converting 15,548 acres to solar by 2025 reduces net emissions to -337,329 MtCO₂eq/y and delays net positive emissions until 2043.
  • No-Tillage: Cuts net emissions by 75% (to 70,123 MtCO₂eq/y) with no water trade-offs.
  • Renewable Energy for Pumping: Switching wells to grid-renewables reduces emissions by 20% (208,188 MtCO₂eq/y).

3. Implications

• Westlands: Conversion to solar by 2025, no-tillage adoption, and well electrification offer scalable, cost-effective减排路径。
• California Policy: Promote solar land conversion on idle lands and incentivize low-carbon farming practices, such as no-tillage and organic fertilization, to meet decarbonization targets.
• Natural Resources: Land-use policies must balance emissions reduction with water security, particularly in water-stressed regions.