Modelling eco-systems with Google search tool
August 7, 2008
The Google PageRank formula can be used to model changes to the structure of food webs in an eco-system.
Eco-systems often contain many different species which depend on each other in complex ways. Working out how population changes and extinctions affect the food web is difficult. But finding out which species are key predators and prey in these webs is vital if species or eco-systems are to be protected.
Nature reports how Google tool identifies linchpin species (2008-08-06).
Stefano Allesina is working on the reverse engineering of ecological networks, to work out “extinction risks”. He is using a modified version of Google’s Page Rank™ algorithm to model the relationships between species.
PageRankanalyses the connections between web pages to discover the importance of the pages. Allesina’s modifications allow him to model the importance of species by calculating their connectivity.
I wonder about how well the modelling works for eco-systems where the species – never mind their relationships – aren’t known in detail or even at all…?
Another Nature news item on the same day indicates that there are lots of viruses in the oceans which haven’t been discovered, and these viruses may play an important part in the life cycle of plankton (‘Virophage’ suggests viruses are alive).
- For a technical paper on PageRank, which underpins the Google search engine: [PDF format] The $25,000,000,000 Eigenvector: The Linear Algebra Behind Google, Bryan, K., and Leise, T., in the education section of SIAM Review, August 2006.
- Allesina’s research institution: National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara.
- Image source: from project page - Reverse Engineering of Ecological Networks.