Failed indices permit both signs of a warmth and nitrogen contrast in high butterfly indices in four British samples, 1986-2012

We tested whether failed annual indices fix the sign of a summer warmth and nitrogen contrast in British butterflies. We used 333,501 source records in two regions and two periods in 1986-2012. The outcome is an index above the observed species median. Each failed index can have either binary label. We held usable outcomes, thresholds, rows and model terms fixed. All four coefficient bounds permit negative and positive values. Bounds range from -13.12 to 14.15 percentage points per C, per 5 kg N/ha/year and per unit lower host nitrogen score. These are attainable finite-record bounds, not confidence intervals or causal effects. They do not show that missing outcomes caused bias. Static pollution, coarse weather, species traits and absent source rows limit use. The package includes exact inputs, endpoint assignments, source hashes, code and numerical checks.

butterflies · nitrogen deposition · summer temperature · missing outcomes · partial identification · observation bias