Two hundred and fifty years of people recording the timing of natural events – so-called ‘citizen science’ - has helped demonstrate that Britain’s plants are flowering five days earlier for every one degree C rise in temperature.

That’s the conclusion of a major analysis of data collated by Nature’s Calendar, a national survey co-ordinated by the Woodland Trust in partnership with the Centre for Ecology & Hydrology (CEH).

Data collected across 405 species of flowering plants in Britain from 1753 to date by everyone from Victorian vicars to modern day dog walkers – and tens of thousands of BBC Springwatch viewers - has been combined to powerful effect to produce a robust, simple index of how the natural world is responding to climate change.

Significantly, the last 25 years have seen the greatest advance in first flowering date, on average two to 12 days earlier than recorded in any previous consecutive 25-year period.

Data consisted of some 400 thousand records of first flowering dates right across the UK. Unlike many previous analyses of data for a single location or time period, the index uses a novel statistical approach to combine data across multiple sites from numerous different time periods. Although many studies have revealed phenological responses to climate change, no long-term community-level indices have been developed.

Report co-authors are from the National Institute for Agro-Environmental Sciences - Japan, the University of Cambridge, Poznan University of Life Sciences and the Woodland Trust.

Richard Smithers, Woodland Trust Senior Conservation Adviser, said: “The findings are a wonderful endorsement of the power of citizen science in helping fathom issues that demand data collection on a vast scale.”

“And we have still barely scratched the surface of the power of the internet as a mechanism to harness people power to further our understanding of the natural world in ways that have previously been beyond our grasp.”

Tatsuya Amano, co-author, added: “This is a perfect synergy between citizen science and the application of modern statistical methods. There is a wealth of similarly useful but unexplored data on a wide range of species around the world and this approach may open the door to creating a global index.”

Nature’s Calendar (The UK Phenology Network) was started in 1998 by Tim Sparks while at CEH and by 2000, when the Woodland Trust began promoting web-based recording, there were 300 recorders. Within three months of going online there were 3,000 recorders and in 2005 when the project was promoted by the BBC’s Springwatch and Autumnwatch programmes, 93,888 people submitted records.

The index is to be published by the Proceedings of the Royal Society B: Biological Sciences on 7 April and discussed at an international biodiversity conference in Japan in October.

Read the report in full at http://rspb.royalsocietypublishing.org