Two Recent Studies Document Northward Migration of Animals

  Note:  An update to this topic was posted in November of 2011.  

Two recent reports add to the growing evidence of animal migrations due to climate change.  While wild animals provide a number of benefits to mankind such as the pollination of crops and control of pests, the introduction of new species can include pest species and can result in the spread of invasive plant seeds, spread damaging fungus and agricultural and human diseases, and alter existing predator/prey relationships.  The arrival of new species can either positively or negatively impact agriculture, human health and the economy.

Researchers from the University of Michigan, Michigan State University and Miami University of Ohio described(1) a rapid migration of common forest species, with southern species, with a declining abundance of the displaced northern species.  The study included opossums and 8 rodent species such as mice, flying squirrels and chipmunks at 16 sites with long-term field studies, and museum records in Michigan.  The researchers evaluated over 14,600  records  for these nine species and found that all four southern species had expanded their range or increased their abundance, while all five northern species showed declines. Interestingly, repeated resampling at some sites showed that the southern species were actually replacing the northern species, not just being added.  Upon examination this south to north expansion of species presence and abundance the researchers found that the  observed changes were consistent with predictions from climatic warming but not with predictions based on recovery from logging or changes in human populations.  The evaluation of climatic records for 1900 – 2007 showed that the most significant change was an increase in annual minimum daily temperatures.

In Great Britain The BBC announced (2) that the Butterfly Conservation is reporting the spread of moth species northward, and the arrival of new species from mainland Europe.  Moths are  good "indicator species" since they are sensitive to environmental changes.  The collection and observation of moths is long-standing and popular hobby in Great Britian.   In fact, observations during the beginning of the industrial revolution of moth coloration patterns changing to mimic soot-covered buildings and stone walls are still used as the classic example of animal adaptations to a changing environment. 

The Butterfly Conservation is beginning to analyze their database of over 5 million records, with early results show that some species have migrated over 150 to the north in the past 30 years.  The records, collected from thousands of volunteers, also show that since the year 2000,  28  species have been seen in Great Britain for the first time.

These two diverse reports, one studying  Michigan mammals, the other British moths, are a typical sample of research reports from around the world, all reaching the same conclusion:  animals are migrating poleward due to climate change.  For some species such as the American Pika, a high elevation species in the North American west and which has no place to migrate but upwards until the mountain tops are reached, and the polar bear of the Arctic, which has nowhere else to go, the result will be extinction.  Other species will be able to migrate into new territory, either adding to, or displacing the current fauna.  Whether the benefits to mankind will be positive or negative is largely unknown; but, the changes are likely to be profound.


1.)  Philip Myers, Barbara L. Lundtigan, Susan M. G. Hoffman, Allison Poor Haranubac, Stephanie H. Seto. Climate-induced changes in the small mammal communities of the Northern Great Lakes Region. Global Change Biology, 2009; 15 (6): 1434-1454.

2.)  BBC NEWS. Published: 2009/05/20 00:48:48 GMT

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