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Women in Science: ‘It’s great up north! Studying range shifts by species due to climate warming.’

butterfly 300x199 Women in Science: ‘It’s great up north! Studying range shifts by species due to climate warming.’

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Jane Hill is a professor of ecology at the University of York. She studies the impacts of climate change on biodiversity – including northwards and uphill shifts by species to track climate changes. Habitat loss is preventing many species from shifting their ranges: she studies where and which species will disappear as conditions become unsuitable – and if there is anything we can do about it. She has worked at the University of York since 2001. Her group works mainly on insects, including butterflies, moths, dung beetles and ants. Jane took part in Soapbox Science 2013, on 5th July where she stood on a soapbox on London’s Southbank and spoke to the public about her work and to help promote the role of women in science.www.soapboxscience.org

Butterflies fluttering around and nectaring on flowers is a sure sign of summer. As with other insects, most butterflies generally do better when its warm and sunny. So we might expect British butterflies to be benefiting from climate warming, and some of them have done so and have expanded their ranges northwards to track climate warming. However, many of them are not doing well and are declining – but more of that later.

There is considerable variation in how the global climate is changing, and since the 1970s there has been about 1 degree C of warming in Britain. Of course many people tend to remember the wash out summer last year, even though 2012 was globally one of the 10 warmest years on record, and most people have already forgotten the devastating heat wave that hit Europe in summer 2003. More recently, it is becoming apparent that we are experiencing unprecedented extremes of temperature with many records being broken around the world. Our research is examining how the biodiversity of Britain is responding to these climate changes.

Over the past 20 years, we have been studying the responses of species to climate change and we have been recording shifts in species’ ranges, particularly in butterflies which are a great group to study. Britain is a particularly good place to undertake these studies because many butterflies reach the northern limits to their global distributions in Britain (it currently gets too cold and wet for many butterflies in northern Britain), making it possible to examine changes in the locations of their range limits and rates of expansion northwards. Also, many people enjoy watching butterflies and there is a long history of butterfly recording in Britain, and we have millions of records of butterfly distributions going back decades in Britain. By analysing this ‘citizen science’ information we can track butterfly changes over the past few decades, and we have found that range shifting is greatest in locations where the climate has warmed most, where there is more habitat available, and by species with the greatest flight ability.

We know that range shifting is not a new phenomenon, and that our native butterfly species colonised Britain because they were able to respond to post-glacial warming and reach Britain from refuges further south after the last ice age. So does that imply that species will be able to cope with current warming? Probably not. Modern landscapes in Britain are very different from those historically.

The new challenge that butterflies face is that they are having to shift their ranges across landscapes that have been greatly modified and degraded by us. So there is often very little natural habitat left and there are many barriers to their range expansion. The larvae of most butterflies are very specific to certain plants, and often to certain parts of plants, and even when they feed on common plants, these plants may not occur everywhere. Few butterflies do well in intensive agriculture or urban landscapes and these types of landscapes form barriers to range expansion. This makes it difficult for species to spread their ranges northwards. And even within their current ranges, many butterflies are declining as their habitat deteriorates. Thus we know that many species that should be benefiting from climate warming are in fact declining because any benefits from climate are greatly outweighed by deterioration in local habitats. So there are relatively fewer ‘winners’ from climate change.

The amount of warming in Britain over the past few decades corresponds with a shift in isotherms of about 120 km northwards. Few butterflies, with the possible exception of the comma butterfly, are capable of speeding northwards so quickly. Thus we know that many species are lagging behind climate warming, mostly because of habitat loss. New locations are too isolated and are beyond the reach of most colonists. We are examining the best ways to promote range expansion at northern range margins. For example, we are looking to see if suggestions to create new habitats to form corridors might be effective, and the best locations to create new habitat to improve connectivity.

This research owes a huge debt of gratitude to the people who have devoted their time to recording butterflies across the length and breadth of Britain, and to colleagues at Butterfly Conservation and at the NERC Centre for Ecology and Hydrology who collate this vast amount of data and help in its analysis.

People are vary of weather forecasts predicting hot summers. But let’s hope for good weather and a good summer for British butterflies.

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