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Earlier flowers signal climate warming

Posted on 31 May 2002

Many of Britain's plants are now flowering two weeks or more earlier than they did a decade ago, a new paper in the journal Science has shown. The authors believe this is one of the clearest signs as to how powerfully climate warming is now affecting the natural world.

The finding comes from the analysis of a unique data set by father-and-son team Richard and Alastair Fitter. Richard Fitter recorded the first date on which over 500 different plant species flowered in each year for 47 years from 1954 – 2000 near his home in Oxfordshire. Alastair Fitter has now analysed these data to discover how the plants have responded to climate warming.

Richard Fitter is one of Britain's leading naturalists and natural history writers, and has been active in national and international conservation bodies. Alastair Fitter is Professor and Head of the Biology Department at the University of York.

"Nearly one in six of the species studied are now flowering significantly earlier than they did before the 1990s, which has been the warmest decade on record," said Alastair Fitter. "Some plants have responded dramatically, for example, white dead-nettle, a common roadside plant, flowered 55 days earlier in the 1990s compared to the period 1954 – 1990. And it can now often be seen flowering right through the winter."

"Spring-flowering species have advanced most, and plants pollinated by insects, which also have started to fly earlier in the year, have changed much more than those pollinated by wind - mainly trees and grasses."

The results also revealed that many species have responded much less and a few are actually flowering later. As a result, in any habitat some species are flowering much earlier but others are not, which may make some species disappear through increased competition or allow new ones to invade.

There could be effects on evolution too, leading to significant changes in the flora and countryside of Britain. Some species can form natural hybrids but do not usually do so because they do not flower at the same time. If they begin to flower at the same time they may form hybrids, and eventually new species.

The study dramatically illustrates the importance of long-term studies of the natural world, and of the central role that naturalists still play in modern science. Few professional scientific bodies can afford to obtain long series of data such as those used here, but their scientific value is enormous.

Notes to editors:

  • The value of amateur naturalists' records of the timing of natural events (a subject known as phenology) is now well recognised. There is a website ( where individuals can record their own findings and contribute to the science of phenology.
  • Scientists believe that evidence for climate warming is now incontrovertible: the 1990s were the warmest decade on record, and the spring of 2002 was the warmest world-wide since records began.
  • Biology at York is one of the largest and most successful departments in the UK University system, having been ranked 5 in the Research Assessment Exercise and 24/24 in Subject Review of teaching. Research in global change ecology is an important part of the Department's portfolio.

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David Garner
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