Nitrogen Fertilizer Pollution maps the estimated environmental pollution caused by the application of nitrogen-based fertilizers in agriculture. Nitrogen (N) is the most widely applied macronutrient in global farming systems and, while essential for crop growth, a substantial fraction of applied nitrogen is lost to the environment through leaching to groundwater, volatilization as ammonia (NH₃), surface runoff, and microbial denitrification producing nitrous oxide (N₂O).
This indicator is critical for biodiversity monitoring because excess reactive nitrogen is one of the most pervasive drivers of ecosystem degradation worldwide. Nitrogen deposition in aquatic ecosystems triggers eutrophication — the excessive growth of algae and aquatic plants — which depletes dissolved oxygen (hypoxia), collapses food webs, and creates "dead zones" in rivers, lakes, and coastal waters. In terrestrial ecosystems, nitrogen deposition alters soil chemistry, favours fast-growing nitrophilous species at the expense of specialist flora, reduces plant diversity, and degrades habitats for dependent fauna such as pollinators and soil invertebrates. Additionally, N₂O emissions from fertilized soils are a potent greenhouse gas with a Global Warming Potential 298 times that of CO₂, linking fertilizer pollution directly to climate change and its cascading effects on biodiversity.
The data come from the NPKGRIDS dataset (v1.08), a global gridded inventory of nitrogen, phosphorus, and potassium fertilizer application rates at ~10 km resolution (5 arc-minutes), published by the University of Minnesota / Global Landscapes Initiative. The variable Nrate represents the total nitrogen application rate in kg N/ha/year, aggregated across all 175 crop classes present in the dataset. A 50% loss fraction is applied to estimate the portion of nitrogen that becomes environmental pollution, based on established estimates of nitrogen use efficiency in global agriculture.
The indicator is derived through the following processing steps:
xarray. The variable Nrate (kg N/ha/year) is extracted for each grid cellN_pollution = Nrate_total × 0.50
gnuplot2 colormap is applied with a PowerNorm normalization (gamma=0.4) to enhance visibility of lower pollution values. The colormap range spans from 0 to 9,720 kg/haBuffer: 25,000 m (25 km) around the polygon, to account for the coarse native resolution.
| Code | Name | Provider | Resolution | Availability |
|---|---|---|---|---|
WRD_NPKGR_20 | NPKGRIDS v1.08 | Nature Scientific Data / University of Minnesota | ~10 km (5 arc-min) | 2020-01-01 — 2020-12-31 |
| Indicator | Unit | Range | Inverted |
|---|---|---|---|
fertilizer_pollution_n | kg N/ha/yr | [0, 50, 100, 200, 500, 1000] | Yes |
Inverted = Yes: lower values of nitrogen pollution indicate less environmental contamination and conditions more favourable for biodiversity and ecosystem health.
| Level | kg N/ha/yr | Interpretation |
|---|---|---|
| A (Excellent) | 0 – 50 | Minimal nitrogen pollution — near-natural conditions, low eutrophication risk |
| B (Good) | 50 – 100 | Low nitrogen pollution — moderate agricultural influence, limited ecological impact |
| C (Moderate) | 100 – 200 | Moderate nitrogen pollution — noticeable pressure on aquatic and terrestrial ecosystems |
| D (Poor) | 200 – 500 | High nitrogen pollution — significant eutrophication risk, groundwater contamination likely |
| E (Critical) | > 500 | Very high nitrogen pollution — intensive agriculture, severe ecosystem degradation |
gnuplot2 colormap with PowerNorm (gamma=0.4) compresses the upper range, improving differentiation at low-to-moderate pollution levelsThe Fertilizer Pollution N map shows nitrogen (N) pollution using NPKGRIDS v1.08. Nitrogen application rates are summed over 175 crop classes. A 50% loss fraction is applied (leaching, NH3 volatilization, N2O denitrification, runoff). Data is bilinearly interpolated from ~10 km to ~1.7 km and displayed with gnuplot2 colormap (PowerNorm gamma=0.4).