standard Climate-driven species migration: from source to sink and back

The Iberian brown bear was one of a wide range of species that retreated into southern Europe since the Last Glacial Maximum 21,000 years ago. Photo: iberianature.com

Dr Ralf Ohlemüller and Brett Cherry report on recent research at IHRR on the influence of climate on species migration.

If you want to understand where plant, animal and other kinds of species came from and where they are going, climate is one of the most important factors that affect species migration.  Climate sets the tone for how species colonise and persist across landscapes.  Research into how suitable climate space for species changes over time has been shown to influence where they move and how far.  For example, some species have been found to be moving north and to higher latitudes because of the changing climate in different parts of the world (see Climate change causes species to move north and to higher elevations).  Many of them are running out of suitable climate space, which could mean risk of extinction, but there is also the possibility that others could thrive because new suitable climate conditions are becoming available.

Modelling the spread of species from source to sink climate spaces can help reveal how species will migrate in the future during a changing global climate.  This is an important tool not only for learning more about the global impact of climate change on biodiversity, but also how species respond to climate in general and how people can adapt to their responses.  An abundance of fossil and genetic evidence shows that animal, insect and plant species from different regions across the continent of Europe have shifted their range following changing climatic conditions over thousands of years.  Even over more recent and shorter time periods, there is now ample evidence that species have shifted their distributions in response to warming climate conditions over the last 50-100 years.

A recent study at Durham led by researchers based in IHRR and the School of Biological and Biomedical Sciences looks at how climate conditions have shifted across Europe since the Last Glacial Maximum (LGM), 21,000 years ago when ice sheets were at their maximum extent.  Mapping these climatic shifts can help to understand how species might have responded to changing climatic conditions since the LGM.  This is done using past climate simulations to quantify and map source and sink areas for potential species re-colonisation in Europe since the LGM.  Researchers are interested in the routes and distances species travelled since the LGM because there is currently limited knowledge of the source locations where species lived and the ‘sink’ areas with analogous climate conditions that they travelled to.  Regions of the world with climatic conditions analogous to LGM conditions were new homes to species that migrated because the climate was warming rapidly.  For example, species that lived in southern Europe, such as parts of Spain and France, were able to move north after the LGM because of widespread warming throughout the continent.

For instance, in the image below all of the areas in black currently have a similar climate to the location marked with an X in Italy during the LGM.  Species that survived the last ice age in the climatic conditions of location X could find large areas where the climate today is similar to that of location X at the LGM.  In the present study, this location X would be considered a source location because the climate of that location at the LGM is today found in large areas of Europe, therefore potentially species that survived the LGM in this location could have re-colonised large parts of Europe since the LGM.

Before warmer climates became widespread after the LGM, many temperate species survived the cold temperatures of the last glaciation in warmer regions in southern Europe from where they then re-colonised Europe as the climate warmed.  This image shows all areas that at the LGM had a climate similar to that of location X in Russia today.  In the present study, this location X would be considered a sink location because large parts of Europe during the LGM had a climate similar to the climate found at that location today and potentially many species that survived the LGM in these areas could today be found in location X.

The climatic conditions suitable for a species (its ‘climate niche’) in Europe have generally shifted from south to north since the LGM.  But for species that lived in cold conditions in central and northern Europe during the LGM, they were forced to move to higher altitudes such as mountain ranges as the geographic extent of their climate niche became much smaller.  Species moved from glacial source areas which they lived during the LGM to climate change refuges further north which were analogous to the climates they once inhabited.

Some species may have had to travel long distances in order to find current climate conditions similar to LGM conditions, these include isolated areas such as the Spanish highlands and around the Baltic Sea.  Whether you could manage to travel these great distances in search of a suitable climate depended on what you are and where you were.  This makes mapping the location and extent of these refuge areas incredibly important for determining biodiversity patterns throughout continental Europe.

But there is one problem: for cold-loving species adapted to LGM conditions, climate spaces are disappearing.  This could also be the case for species that are adapted to present climatic conditions, but will not have any climate space in the future or will have to travel great distances to find it.  The study found that locations between latitudes 35 and 45° N are the largest potential post-glacial sinks areas that LGM adapted species travelled to, along with well-known post-glacial climate refuges in the southern European peninsulas.  Since the LGM, species in Western Europe and South of the Alps would have had to travel more than 2,000 km to reach these sink areas.

There are of course other factors to account for when studying the movement of species besides climate, including human activities that threaten biodiversity for example, but also a variety of environmental factors such as photoperiodism – the ability of species to adapt to variation in season including length of day and quality of light.  Yet research into the influence of climate on species is clearly important for developing adequate responses to environmental change, because climate is a primary mover that influences species both directly and indirectly in ways that people could prepare for and adapt to as climates throughout the world change over time.

References and Further Reading

Potential source and sink locations for climate-driven species range shifts in Europe since the Last Glacial Maximum. Global Ecology and Biogeography

Species are running out of suitable climate space. IHRR Blog

Climate change causes species to move north and to higher elevations. IHRR Blog

Mapping future climate space. IHRR Blog

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