Glacial Refugia

Recent climate change may be causing species to migrate northwards but this is not the first time in the long history of our earth that changes in the climate have caused mass migrations. It seems that species have been able to adapt to climate variations in the past in the exact same way as now – by migrating to areas of the earth that are more suitable in terms of temperature and habitat. The most well-known example of this is Glacial Refugia. During the Last Glacial Maximum (LGM), many species in the Northern Hemisphere had to migrate southwards in order to escape the cold temperatures and increasing ice cover that was occurring in the higher latitudes [1]. Evidence for this migration can be found by investigating the biodiversity and genetic variation of species in refugia sites. Refugia sites were found in Europe and Asia, where temperatures were warmer, and the effects of glaciation were less apparent. These sites are sometimes referred to as ‘hybrid zones’ as migration of different species (previously in allopatry) allowed interbreeding and introduced hybrid species [1].

I’ve just finished reading an article on the glacial refugia of marine fish by Kettle et al. In the paper they have looked at migration during the LGM and at various other points throughout the Holocene in order to understand and predict future migration due to climate change. Identified fish remains, leftover from human consumption, is the main proxy used in this study in order to determine the past ranges of different species. Studies like this have great importance for the future of the fishing industry, however, like the science of climate change they are still very vague and migration is difficult to predict. Patterns from the past show possible migration to areas of low oxygen concentration and high sea ice despite these conditions being seen as too severe for certain population (i.e. Salmon and cod) to inhabit [2].

Investigations of past species migration are important to gain an understanding of climate induced movement – however, as with all studies that are based on proxies and occurred thousands of years ago, there is a large grey area of uncertainty which reflects the future of our planet through climate change. On top of this, migration during the LGM may have been easier as there were less areas of habitat fragmentation preventing movement.

References:

1. Feliner 2011, 'Southern European glacial refugia: A tale of tales', Taxon, 60, 365 - 372.
2. Kettle et al 2011, 'Refugia of marine fish in the northeast Atlantic during the last
glacial maximum: concordant assessment from archaeozoology and palaeotemperature reconstructions', Climate of the past, 7, 181 - 201.