UK Biodiversity Indicators 2024. Spring Index
JNCC, 10/12/2024
The Spring Index - published 10th December 2024
The Spring Index is calculated from Nature's Calendar data. It combines the annual average dates for the following spring events:
- first flowering of hawthorn
- first flowering of horse chestnut
- first appearance of orange tip butterfly
- first sighting of a swallow
The Spring Index has high year-to-year variability, but since 1998 the annual mean observation dates have been 8.6 days in advance of the average dates in the first part of the 20th century. The advancement of spring events is strongly linked to warmer temperatures in March and April.
Swallow (John Bridges/WTML)
Orange-tip (John Bridges/WTML)
Horse chestnut (Rosana Ballentine/WTML)
Hawthorn (John Bridges/WTML)
