Coding

Geoskill: Grassland Degradation Monitor

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Monitor grassland degradation and recovery trends from multi-temporal vegetation cover, phenology, bare ground and climate baselines. Outputs management zones for restoration prioritization. Use when assessing grassland health, identifying degraded areas, evaluating restoration effectiveness, or generating management recommendations.

What it does

Monitor grassland degradation and recovery trends from multi-temporal vegetation cover, phenology, bare ground and climate baselines. Outputs management zones for restoration prioritization. Use when assessing grassland health, identifying degraded areas, evaluating restoration effectiveness, or generating management recommendations.

The skill document

Grassland Degradation Monitor

Identifies grassland degradation and recovery trends from multi-temporal remote sensing data. Separates climate-driven from management-driven vegetation change and outputs management zones with restoration priorities.

Trigger

Use when the user wants to:

  • Identify degrading grassland areas from multi-temporal imagery
  • Evaluate restoration effectiveness (e.g., grazing exclusion, reseeding)
  • Separate climate-driven from management-driven vegetation change
  • Generate management zone maps with restoration priorities
  • Conduct BACI (Before-After-Control-Impact) analysis for management assessment
  • Monitor grassland health trends over years to decades

CLI Usage

# Basic analysis with default parameters (10 years, Theil-Sen, climate normalized)
python scripts/grassland_degradation_monitor.py --output-dir ./gdm-output

# Custom years and trend method
python scripts/grassland_degradation_monitor.py \
  --years 15 \
  --trend-method ols \
  --output-dir ./gdm-output

# Without climate normalization (raw trend only)
python scripts/grassland_degradation_monitor.py \
  --years 10 \
  --no-climate-normalize \
  --output-dir ./gdm-output

# With custom degradation schema
python scripts/grassland_degradation_monitor.py \
  --years 10 \
  --degradation-schema references/degradation_schema.json \
  --output-dir ./gdm-output

Parameters

ParameterDefaultDescription
--input-ndviNoneInput NDVI time series GeoTIFF (multi-band, optional)
--years10Number of years for analysis
--trend-methodtheil-senTrend estimation: theil-sen, ols, mann-kendall
--climate-normalizeTrueApply climate normalization (residual trend)
--no-climate-normalize-Disable climate normalization
--degradation-schemabuilt-inCustom degradation schema JSON
--output-dir./gdm-outputOutput directory

Output

FileDescription
degradation_status.tifRaster map of degradation/recovery status codes
trend.tifRaster map of trend slopes
priority_areas.geojsonPoint features for priority restoration areas
management_summary.csvArea statistics and recommendations per class
timeseries.csvMean NDVI, precipitation, temperature per year
request.jsonAnalysis request metadata
output-manifest.jsonOutput file inventory and area statistics
qa.jsonQuality assurance checks

Degradation Status Codes

CodeNameDescriptionRecommendation
3severe_degradationNDVI declining >0.02/yr, 3+ yearsImmediate restoration
2moderate_degradationNDVI declining 0.01-0.02/yr, 3+ yearsPriority restoration
1light_degradationNDVI declining 0.005-0.01/yr, 3+ yearsPreventive management
0stableNo significant trendSustainable use
-1light_recoveryNDVI increasing 0.005-0.01/yr, 2+ yearsMonitor and maintain
-2moderate_recoveryNDVI increasing 0.01-0.02/yr, 2+ yearsContinue current practices
-3significant_recoveryNDVI increasing >0.02/yr, 2+ yearsSuccess case, replicate

Key Algorithms

Climate Normalization (Residual Trend)

Regresses NDVI against precipitation and temperature anomalies, then computes the trend of residuals. This separates climate-driven variation from management-driven change.

Trend Estimation

  • Theil-Sen: Robust non-parametric slope (median of pairwise slopes). Recommended for noisy remote sensing data.
  • OLS: Ordinary Least Squares. Efficient for clean data.
  • Mann-Kendall: Normalized Kendall tau. Non-parametric trend strength.

Degradation Classification

Combines three factors:

  1. Trend slope: Direction and magnitude of change
  2. Persistence: Minimum consecutive years meeting threshold
  3. Absolute state: Current NDVI level (very low NDVI escalates severity)

BACI Analysis

Before-After-Control-Impact design for management effectiveness: BACI = (treat_after - treat_before) - (ctrl_after - ctrl_before)

Exit Codes

CodeMeaning
0Success
2Argument error
3Dependency missing
6Data validation failure
7Processing failure

Limitations

  • Grazing intensity data typically unavailable
  • Grassland type differences complicate threshold transfer
  • Remote sensing productivity proxies do not replace field biomass measurement
  • Climate normalization assumes linear climate-vegetation relationship
  • Short time series (< 5 years) reduces trend reliability

References

  • Fensholt & Proud 2012, Remote Sensing of Environment (residual trend)
  • Ivits et al. 2013, Remote Sensing (European grassland trends)
  • BGC ChinaGrass dataset for grassland classification

数据下载

本 skill 可自动从 Microsoft Planetary Computer 下载数据 (无需 API key):

python grassland_degradation_monitor.py --bbox 116,39,117,40 --date-range 2024-06-01,2024-06-30 --output-dir 
  • --bbox W,S,E,N: WGS-84 边界框 (西, 南, 东, 北)
  • --date-range START,END: 日期范围 (YYYY-MM-DD,YYYY-MM-DD)
  • --aoi-file : 替代 --bbox 的 GeoJSON 多边形
  • --cache-dir : 缓存目录 (默认 ~/.geoskill_cache)

当用户只给 --bbox + --date-range (没有 --image) 时,skill 自动下载数据。 当用户给 --image 时,走原文件路径 (向后兼容)。

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