1Are you just leaving the library now?
2I saw you get there at 8 am!
3Yeah, I've been there all day.
4What for?
5They hired a cute new librarian or something?
6I wish.
7No, it's the presentation that I will give in Environmental Science the day after tomorrow.
8What's it about?
9I heard you were really excited about the class.
10And Dr Schnee also calls you for the "arcane" questions, as he calls them.
11It's about environmental damage in the Yucatan.
12Excuse me, what?
13Or is that where?
14Yucatan.
15It's a state in Southeast Mexico.
16So what's happening there?
17Agriculture is having a really adverse impact on the environment.
18There are too many farmers doing too much farming.
19It's really destroying the forests and ruining the soil.
20Deforestation is a major problem there now.
21How did you learn about this?
22I don't recall Dr Schnee saying anything about it in lecture.
23Yes, but my brother went there last month,
24you know, to look at the old cities like the Mayan Indians built.
25That's what first got me interested.
26Your brother Tom?
27No, Dick, Harry's twin.
28Anyway, he told me how few trees there were now and how much empty ground that grows almost nothing.
29He said the place looked more like the desert than jungle in some parts.
30It brought environmental damage.
31So I started looking for materials in the library.
32Here, look at this magazine.
33What's in it?
34It's an old issue of "National Geographic".
35It includes interviews with tourists who've been there in the past few years.
36It's pretty bad. See the photos?
37I see the photos, but one or two photos don't prove anything.
38Then read what the article says. Right there.
39The first thing it points out is how soil samples show it's hard for anything to grow there.
40It says how an area of 21,000 square kilometres has lost most of its forest in the past ten years.
41See, there are graphs.
42As the number of farmers increases, the acres of forest have decreased.
43It's an inverse relation.
44So how big is that state?
45I'm sorry, but I've never really learned the metric system.
46It's bigger than the state of Massachusetts!
47That's shocking!
48Anything else?
49There's lots of else.
50Scientists say there's a "growing area" of about 10.5 square kilometres where nothing can grow at all.
51It's like the beginning of a desert.
52Oh yes.
53What Dr Schnee called "desertification".
54But, why can't anything grow there?
55I've never really studied soil chemistry.
56I'm just starting to look into that subject,
57but my sister Marie is a geologist
58and she says the problem is that the soil has too much saline,
59with no plants helping to adjust the chemistry.
60Apparently, that's a common problem with soil types throughout the areas with rainforest.
61Once you lose the plant cover, it's difficult to bring it back.
62Reforestation is almost impossible, even if the land is not being used for other purposes.
63Wait a minute. What is "saline"?
64Saline is salt dissolved in water.
65Scientists who've gone there have taken measurements.
66They do this by gathering a sample of the soil and running a simple test that shows the ionisation of the solution.
67The Geology Department in our own university has reviewed the soil at the site, too.
68They're right. It looks pretty bad.
69The level of salinity is going up.
70But the plants that would solve that problem can't be planted in soil like that.
71There is a narrow spectrum of salinity in which the plants will grow.
72And once you pass the threshold, there is no way to put the problem right?
73Exactly. It's possible that no one can do anything to stop the trend now.
74All because of human greed!
75Wait a second.
76How do you know these "scientists" can be trusted?
77What kind of reputation do they have?
78Are they reliable?
79Oh they're definitely reliable.
80They include four members of the faculty from the Geology Department right here at MIT.
81Here, study these photographs and check the damage yourself.
82That's what Dr Horst who wrote the book here did.
83He's newly appointed, but Dr Schnee says that he's brilliant.
84So, where are you going now?
85I'm headed over to the Geography Department to borrow a map for my presentation.
86You know, this whole problem could have been avoided!
87The farmers there in the Yucatan...
88Uh, Pete??
89What?
90Go take a break! Leave some studying for the rest of us.