Wednesday, May 21, 2008

Population growth, population decline

We talked about how populations can respond to release from predators or competition with exponential growth. We can also consider the opposite scenario: population growth/decline when a novel predator or parasite is introduced/added to the system. Unfortunately we have many examples and the results aren’t pretty. Today on NPR’s program “Day to Day” they aired a short segment on the Emerald Ash Borer – a species of beetle accidentally introduced from China only about a decade ago. In that relatively short time, the beetles have killed over 25 MILLION (!) Ash trees in the US Midwest. Good-bye baseball bats? Anyway, today’s story was of added interest in that one of the attempts to stop the local extinction of ash trees is to employ genetic engineering techniques – inserting DNA from beetle-resistant ash species into the native ones.

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