新托福考试必备：新托福TPO（1-24）听力原文文本TPO11

　　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?

　　Professor
　　Well, there are two theories. One idea is as you suggested that major weather
　　patterns, something like El Ni?o, are responsible. But the other idea and this is
　　the one that I personally subscribe to, is of the changes in the temperature
　　pattern had been brought about by the loss of wetlands.

　　Student A
　　Well, how would the loss of wetlands make a difference?

　　Professor
　　Well, think about what we’ve been studying so far. We discussed the impact of
　　landscapes on temperature, right? What affects does the body of water have
　　on an area?

　　Student A
　　Oh, yeah. Bodies of water tend to absorb the heat during the day, and then
　　they release the heat at night.

　　Professor
　　Yes, exactly. What you just said is what I want you all to understand. Bodies of
　　water release heat and moisture back into the environment. So places near
　　large bodies of water are generally milder, err...slightly warmer than those
　　without water. And what I, another think is that the loss of the wetlands has
　　created the situation where the local temperatures in the area are not slightly
　　different, slightly colder than they were 100 years ago, before the wetland were
　　drained.

　　Student B
　　Emm…do we know what the temperature was like back then?

　　Professor
　　Well, we were able to estimate this. We have data about South Florida’s
　　current landscape, emm…the plant cover. And we were able to reconstruct
　　data about the landscape prior to 1900. Then we enter those data, information
　　about what the landscape look like before and after the wetlands were drained.
　　We enter the data into a computer weather model. This model can predict
　　temperatures. And when all the data were entered, an overall cooling trend
　　was predicted by the model.

　　Student B
　　How much colder does it get now?

　　Professor
　　Well, actually the model shows a drop of only a few degrees Celsius. But this is
　　enough to cause dramatic damage to crops. If temperatures over night are
　　already very close to the freezing point, then this drop of just a few degrees
　　can take the temperature below freezing. And freezing causes frosts, which kill
　　crops. These damaging frosts wouldn’t happen if the wetlands were still in
　　existence, just as the tiny temperature difference can have major
　　consequences.