I have just started reading The Sixth Extinction: An Unnatural History by Elizabeth Kolbert. There have been five previous massive extinctions in the past. Over at the Wonk Blog they have an interview with the author. I have read chapter 1 and it concerns the extinction of amphibians world wide. The fact that amphibians were disappearing was noted more than a decade ago. The cause remained a mystery until recently. It is the result of human activity but has nothing to do with climate change. In his book 1493: Uncovering the New World Columbus Created Charles Mann documents how plants and animals from the New World altered the planet and our diets. This only increased in the 20th century with air travel and large ocean freighters. The impact was not always positive which brings us back to the amphibians.
The first clue to the mysterious killer that was claiming frogs from Queensland to California came— perhaps ironically , perhaps not— from a zoo. The National Zoo, in Washington , D.C., had been successfully raising blue poison-dart frogs, which are native to Suriname, through many generations. Then, more or less from one day to the next, the zoo’s tank-bred frogs started dropping. A veterinary pathologist at the zoo took some samples from the dead frogs and ran them through an electron scanning microscope. He found a strange microorganism on the animals’ skin, which he eventually identified as a fungus belonging to a group known as chytrids. Chytrid fungi are nearly ubiquitous; they can be found at the tops of trees and also deep underground. This particular species, though, had never been seen before; indeed, it was so unusual that an entire genus had to be created to accommodate it. It was named Batrachochytrium dendrobatidis— batrachos is Greek for “frog”— or Bd for short. The veterinary pathologist sent samples from infected frogs at the National Zoo to a mycologist at the University of Maine. The mycologist grew cultures of the fungus and then sent some of them back to Washington. When healthy blue poison-dart frogs were exposed to the lab-raised Bd, they sickened. Within three weeks, they were dead. Subsequent research showed that Bd interferes with frogs’ ability to take up critical electrolytes through their skin. This causes them to suffer what is, in effect, a heart attack.
Kolbert, Elizabeth (2014-02-11). The Sixth Extinction: An Unnatural History (Kindle Locations 198-209). Henry Holt and Co.. Kindle Edition.
As it turns out one explanation of the spread is the wide scale importation around the world of North American Bull Frogs (for food) and the African Clawed Frog (used for pregnancy tests). Both carry but are resistant to the fungus and their spread would not have been possible without air transport.
I have personally witnessed this 6th extinction. Just 5 or 6 years ago the Pacific Tree Frog was common here on the West Coast. Their chirping or croaking was a way of life. If you were unfortunate enough to have one outside your bedroom window in the summer you probably wouldn’t get a very good nights sleep. Three or four years ago they simply disappeared. The North American Bull Frog was not indigenous to this area but had been introduced several years ago – a possible explanation.
There are many similar examples. The introduction of the European earth worm nearly destroyed the North Eastern hardwood forests before the Revolutionary war is is still causing problems in the entire northern half of the United States. The Fox and Eastern Gray squirrels are spreading across the country from the North East probably hitching rides on trucks and trains. The result is the Western Gray squirrel is threatened. When debris from the earthquake and tsunami in Japan started washing ashore here on the west coast the major concern was not radiation but invasive species.
I guess the question is can human beings survive the 6th extinction they are responsible for?