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Lecture 1:

Listen to part of a lecture in an ecology class.

So we’ve spent a lot of time in this class studying ecosystems sand. Now I wanna talk about a specific instance of an ecosystem changing over time, changing significantly. And um, unexpectedly, uh, I’m talking about the illusion islands, um, off the coast of alaska. the illusion islands up until the 18th century were grassland ecosystem. now the grasslands on some of the islands have disappeared. And what we have there now is tundra, primarily low scrubby vegetation. and and this started happening in the 18th century. Okay, so why jeffum excuse. me professor. I thought. tundra referred to frozen ground. Wouldn’t all the islands have that? okay, right. tundra often refers to a region where the underground soils permanently frozen. and and the primary vegetation is moss, lichen, and maybe a few dwarf shrubs. But it’s the vegetation that classifies a region as tundra, not the temperature of the soil. anyway, in the 18th century, traders introduced foxes on to the islands, and those fox’s preyed on the ground nesting sea birds. you’re saying that change the entire ecosystem. oh, yes. And drastically introducing a single species can gradually transform an entire ecosystem. and a study that was done on the illusion island shows one way this can happen. um.

So all right, the foxes were introduced and the most obvious impact was a decrease of the sea bird population. that’s a direct impact. Right? the fox is preyed on the sea, birds, and they started to disappear. well, there were indirect effects to changes in the soil and vegetation. And these effects weren’t obvious. For a long time. They were much harder to detect. so this study, um, a biologist LED a team of researchers to the aleutian islands, where they noticed significant differences in the islands that had foxes and the islands that didn’t, especially in the vegetation. it was so thick on the islands without foxes that they could barely get through it. But on the islands with foxes, it was only up to their ankles. and the biologist had a theory about this. can anyone guess what it might be? hum. So the foxes are eating the sea. Birds may be the um, the sea birds were using up the grass, like for nesting materials or something. well, think about what that would mean. oh, right. and what the biologist thought was, but he thought it might have something to do with the soil nutrients. so these researchers to investigate this theory, they analyzed the soil on these islands. they wanted to determine the nutrient content to see if it played some kind of role in transforming the vegetation from grassland to tundra.

well, what they found was, I think, very interesting.

Now, first the soil on the aleutian islands is volcanic soil, nutrient poor soil that formed from volcanic rock. and what the researchers learned was that the islands without foxes were receiving regular doses of fertilizer from the droppings of the sea birds. The fox’s preyed on the sea, birds eat fish, and they were bringing ocean derived nutrients to the islands in the form of droppings. When they came there to nest. now the islands with foxes weren’t getting this fertilizer because the birds were disappearing. so now we see the indirect effects of the foxes. Right? The fox is because of their impact on the sea. Birds deprive the soil of fertilizer, which caused the grasslands to disappear and be replaced by tundra. tundra vegetation does well in nutrient poor soil. now that’s a pretty huge impact and one that no one predicted. so what can we do about it?

Well, we want to bring back the sea birds, and we’re doing that. We’re removing the foxes, and we’ve been successful. most of the foxes are off the islands now, and the sea birds are starting to come back. but see birds, most sea birds that is have only one offspring a year. well, we’ve learned that there are now only half the number of breeding sea birds on the islands that had the foxes as there are on the islands that didn’t. and there were major changes in the vegetation, and the foxes were there for a long time. so does this mean that non native species should never be introduced into an ecosystem? well, not necessarily. a scientists introduced species in many different places around the world. And for a number of reasons, we’ll talk more about that over the course of the semester. it does point out the dangers of unforeseen consequences, though, and it certainly suggests the need for careful planning and for further studies of the effects in habitats such as these, where new species have already been introduced.

nd for all the same reasons.