托福听力_考前小试牛刀（四）

【Lecture 3】

Environmental science

Narrator

Listen to part of a lecture in an environmental science class.

Professor

When land gets develop for human use, the landscape changes. We don’t see as many types of vegetation, trees, grasses and so forth. This in turn leads to other losses: the loss of animal that once lived there. Err…but these are the obvious changes, but there are also less obvious changes like the climate. One interesting case of this…of…of changes in the local land use causing changes in climate, specifically the temperature is in Florida. Now what comes to mind when you think of the state of Florida?

Student A

Sunshine, beaches.

Student B

Warm weather, oranges…

Professor

Yes, exactly. Florida has long had a great citric industry; large growth of oranges, lemons and the like. Florida’s winter is very mild; the temperature doesn’t often get below freezing. But there are some areas in Florida that do freeze. So in the early 1900s, farmers moved even further south in Florida, to areas that were even less likely to freeze. Obviously, freezing temperatures are danger to the crops. A bad barrier of cold weather, a long spell of frosts could ruin a farm and the entire crop, anyway, before these citric growers moved south, much of the land in south Florida, was what we called wetlands. Wetlands are areas of marshy, swampy land, areas where water covers the soil, or is present either at or near the surface of the soil for large part of the year. Wetlands have their own unique ecosystem, with plants and animals with special an interesting adaptation. Very exciting, but it’s not what we are talking about today. Emm…where was I?

Student A

Farmers moved south?

Professor

Oh, yes. Farmers moved south. But the land was not suitable for farming. You can’t grow orange in wetland, so farmers had to transform the wetlands into lands suitable for farming. To do that, you have to drain the water from the land, move the water elsewhere, and divert to the water sources such as rivers. Hundreds of miles of drainage canals were built in the wetlands. Now these areas, the new areas the farmers moved to, used to be warm and unlikely to freeze, however, recently the area has become susceptible to freezes. And we are trying to understand why.

Student B

Is it some global temperature change or weather pattern like El Ni?o or something?