On Invasives 1

The Boston Globe published an article on invasive species Sunday that has elicited some comment. It is a not very well written example of sensationalizing journalism-sort of like all those articles that spotlight the one scientist (usually paid by an oil company) that is predicting a new Ice Age rather than global warming. Going to the abstracts of the underlying scientific journal articles we find the 19 scientists featured in the Globe opposed by an article signed by 141 other scientists. The Globe article is no longer easily available online, but since it was in the Globe, it will probably do much damage to the effort to control invasives. I intend to blog my views on this article tomorrow since invasive species control is a subject that has interested me for almost twenty years.

Today, I want to present an an interesting article from Scientific American that also relates to invasive species science. No scientists in the invasive species debate doubts the potential impact of introducing a new species onto an island. The arrival of Old World mammals and snakes to Pacific islands like Guam, Hawaii and New Zealand has had devastating effects on local bird populations, The cited article details scientific experiments that document the impact of bird extinction on the pollination of native flowers.

What caught my attention was the mention of passenger pigeons, which used to exist in America by the billions, until they were shot into extinction by hunters. These missing birds were mast feeders eating hickory nuts, beech nuts, and chestnuts and spreading these seeds in their guano. What effect has the loss of the passenger pigeon had on our forests? The author of the article suggests the extinction might have contributed to forest loss, but I think this might be an unfair extension of the research featured in the article. In areas where flocks of passenger pigeons flew, they would often darken the sky with their numbers for hours according to early observers. Thus, it's unlikely that other mast distributors like chipmunks or squirrels have taken up the slack from their loss. However, to attribute forest loss to the passenger pigeon extinction is probably inaccurate. Forest loss was almost exclusively caused by the spread of agriculture. With agriculture's decline the forests are coming back, but with the absence of the passenger pigeon it's accurate to speculate that the composition of the forest has changed. One thing we know for certain-no one is getting their heads covered with poop from billions of pigeons!