Habitat Fragmentation

Habitat fragmentation is when a natural habitat is disrupted or divided, leaving an area of that habitat that is hard/impossible for certain species to cross.  Examples of these include rivers, roads, deforested areas, damns, crop fields etc.  Humans are constantly changing the natural environment by adding these features which then have a negative effect on species in the habitat.  Habitat fragmentation is especially important with migrating species (i.e. birds) and those species that have started to shift polewards due to climate change.  Shifting northwards is not always possible for species as they depend on food sources and certain habitat conditions, however those species that are able to adapt to other conditions are being prevented from moving north due to habitat fragmentation.

For example, the Bog turtle (America's smallest turtle) may be prone to extinction in the near future as it has very specific habitat requirements (bogs and wetlands) which are not only scarce but are often sandwiched in between main roads and areas of housing [1].  These act as barriers for the slow ground moving turtle, making it very hard to migrate to any other areas.

Another example is bird populations.  A study by Melles et al analysed the range expansion of bird species in the last 20 years.  It was found that fragmentation (such as deforestation and treeless areas) caused expansion rates to be slower than in areas without fragmentation.  The main reason for this lag in expansion is due to low breeding success and smaller populations (of species and their prey) existing in fragmented areas [2].

HOWEVER scientists have recognised this problem and there is a lot of research and conservation work being done on habitat fragmentation and assisted migration of species.  In California, mountain lions are being tagged in order to observe and understand their movements around fragmented areas (i.e. areas with roads, housing, water and concrete) [3].  A study like this can aid scientists with the knowledge on how to build wildlife corridors, allowing migration and range expansion of species in the light of climate change.  Currently there are lots of conservationists working on the idea of assisted migration as a means to save endangered species globally.

References:


[1] http://news.nationalgeographic.com/news/091211-ten-threatened-species-animals-global-warming-pictures/#/bog-turtle_10582_600x450.jpg
[2] Melles, S.J., M.J. Fortin, K. Lindsay and D. Badzinski (2011), 'Expanding northward: influence of climate change, forest connectivity, and population processes on a threatened species' range shift', Global change biology, 17, 17 - 31.
[3] http://www.newscientist.com/article/mg21028094.000-on-mountain-lion-patrol-in-the-california-wilds.html