Analysis in the scientific journal Global Change Biology combines data on a diversity of taxa from marine, freshwater and terrestrial environments. The collaborative study,involving scientists from 12 UK research institutions, universities and conservation organisations, is the most comprehensive and rigorous assessment so far of long-term changes in the seasonal timing (phenology) of biological events across marine, freshwater and terrestrial environments in the UK.

Led by Dr Stephen Thackeray  (left) and Professor Sarah Wanless (right) of the Lancaster based Centre for Ecology & Hydrology, the research gathers together more than 25,000 long-term phenology trends for 726 species of plants and animals.

More than 80% of trends from 1976 to 2005 indicate earlier seasonal events. The study looks at  a diverse array of organisms including plankton, plants, insects, amphibians, fish, birds and mammals. On average, the seasonal timing of reproduction and population growth has become earlier by more than 11 days over the whole period, but change has accelerated in recent decades.

Research shows there are large differences between species in the rate at which seasonal events have shifted. Changes have been most rapid for many organisms at the bottom of food chains, such as plants and the animals that feed upon them. Predators have shown slower overall changes in the seasonal timing of their life cycle events.

However, seasonal timing of reproduction is often matched to the time of year when food supply increases, so that offspring receive enough food to survive. A key question is whether animals higher up the food chain will react to the faster rates of change in the plants and animals they feed upon, or will fail to do so becoming less successful at rearing offspring.

Dr Thackeray said, “This is the first time that data have been analysed with enough consistency to allow a meaningful comparison of patterns of changing seasonal timing in the UK among such a diverse range of plants and animals.”

“It is important to realise that this analysis doesn't identify which predator-prey relationships are most at risk of disruption due to changes in timing," says Professor Wanless. "What it does do is highlight that the recorded changes need urgent investigation, particularly for species with high economic or conservation importance.”

Co-author Richard Smithers (left) of the Woodland Trust said, “Phenology is ‘the canary in the cage’. The results of this new study make real our changing climate and its potential to have profound consequences for the complex web of life.”

Habitats for hope of conservation
Rugged, hilly landscapes with a range of different habitat types can help maintain more stable butterfly populations and thus aid their conservation, according to new findings published in the journal Ecology Letters.

Carried out by scientists from the Centre for Ecology & Hydrology, Butterfly Conservation and the University of York, the research has implications for how landscapes might be better designed to help conserve species.

Using UK Land Cover Map data (from satellite images) to collect information on the topography and diversity of habitats in the landscape,  they found sites with a greater diversity of habitat types (as wood, grass, and heathlands) and more varied terrain tended to have more stable butterfly populations  over time.

(Right: A rare Scandinavian butterfly Camberwell Beauty in Nethybridge in the Scottish Highlands regarded as yet another sign of global warming.)

Lead author, Dr Tom Oliver (left) from Centre for Ecology & Hydrology: “More stable insect populations are better for conservation because it means that, in years with extreme weather (eg. drought years), populations are less likely to go extinct. Our research shows that populations of species such as the Brown Argus and Dingy Skipper butterfly are more stable when they are located in hilly landscapes with a range of habitat types.”

Thirty-five British butterfly species were included in the analysis using records collected by volunteers of the UK Butterfly Monitoring Scheme from 166 transect sites across UK. The research team compared stability of butterfly populations over an 11 year period, with the diversity of habitats in the surrounding landscape up to 5km from monitored sites.

Their conclusion was that landscapes with a greater range of habitats harboured more stable butterfly populations. Landscapes with a greater range of topographic aspects (eg. north, south, east and west facing slopes) were also better for the insects.

Co-author Dr Jane Hill (right) of the Department of Biology at the University of York said, “Our findings show that more diverse landscapes may provide a greater range of resources and microclimates, which can buffer insect populations from declines in difficult years.”

A surprising result from the study was that, for some butterfly species, the diversity of habitats up to 5km away from monitored sites affected the populations. Dr Tom Brereton, (left) head of monitoring at Butterfly Conservation and also co-author said, “Our results highlight the importance of taking a landscape perspective for species conservation.