2 
00:00:02,050 --> 00:00:07,580 
Vegetation can have 

3 
00:00:09,980 --> 00:00:15,170 
a strong impact on water scarcity. 

4 
00:00:15,170 --> 00:00:19,550 
Because when you have vegetation, it tends 
to mine the groundwater 

5 
00:00:19,550 --> 00:00:24,680 
and drive it to evaporate, and then 
recycle to perpetuate rainfall. 

6 
00:00:25,720 --> 00:00:28,490 
And then when the vegetation is 
gone, the 

7 
00:00:28,490 --> 00:00:32,650 
the water from rainfall just runs off, 
instead of re-evaporating. 

8 
00:00:32,650 --> 00:00:35,710 
And so vegetation 

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00:00:35,710 --> 00:00:39,000 
can provide a kind of tipping 
point... 

10 
00:00:39,000 --> 00:00:42,710 
where things can hang on, under water 
stress, 

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00:00:42,710 --> 00:00:45,140 
then the vegetation dies, 

12 
00:00:45,140 --> 00:00:48,080 
and it takes even more water to get 

13 
00:00:48,080 --> 00:00:51,170 
back out of the drought than you had 
originally. 

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00:00:52,520 --> 00:00:55,740 
Some examples of rainforests that 

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00:00:55,740 --> 00:01:00,710 
are vulnerable include Queensland, 
Australia,

16 
00:01:00,710 --> 00:01:03,180 
where the high altitude rainforest

17 
00:01:04,200 --> 00:01:09,490 
is expected to get chased off the 
surface of the Earth as the climate zones 

18 
00:01:09,490 --> 00:01:11,430 
warm, because you can't go any higher up 

19 
00:01:11,430 --> 00:01:14,050 
in the mountains to get to a cooler 
climate. 

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00:01:14,050 --> 00:01:19,090 
That's vulnerable under fairly
modest amounts of warming. 

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00:01:19,090 --> 00:01:23,250 
The big rainforests, the Amazon, and 
Indonesia,

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00:01:23,250 --> 00:01:25,972 
are in the three degree chapter in 

23 
00:01:25,972 --> 00:01:28,560 
Lynus's book. 

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00:01:28,560 --> 00:01:31,260 
it's very speculative and model dependent 
whether 

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00:01:31,260 --> 00:01:33,980 
these rainforests could actually collapse 
or not. 

26 
00:01:33,980 --> 00:01:35,540 
But it's certainly a possibility. 

27 
00:01:37,460 --> 00:01:42,160 
We know that because the Sahara used to be 
a rainforest during a time 

28 
00:01:42,160 --> 00:01:45,850 
in the early interglacial time 
called 

29 
00:01:45,850 --> 00:01:49,470 
the African humid period, about 8,000 years 
ago. 

30 
00:01:49,470 --> 00:01:51,900 
And it abruptly collapsed, 

31 
00:01:51,900 --> 00:01:59,150 
as diagnosed from pollen 
records in sediment cores of Africa. 

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00:01:59,150 --> 00:02:02,880 
Nebraska used to be sand dunes; it looked 
like the Sahara. 

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00:02:02,880 --> 00:02:05,930 
It's a place now called The Sand Hills. 

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00:02:05,930 --> 00:02:08,780 
And these date from medieval time when it 
was so 

35 
00:02:08,780 --> 00:02:14,010 
dry in the other parts of the 
American west. 

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00:02:14,010 --> 00:02:16,530 
These things are definitely open to 
change. 

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00:02:18,025 --> 00:02:22,290 
One scary possibility is that the 
end game 

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00:02:22,290 --> 00:02:27,370 
for some jungle like the Amazon would 
probably involve fire. 

39 
00:02:27,370 --> 00:02:30,660 
If the conditions are just wrong and 
the plants 

40 
00:02:30,660 --> 00:02:34,300 
are not thriving and everything dries out, 
you could have 

41 
00:02:34,300 --> 00:02:38,190 
big fires that could suddenly release CO2 
to the atmosphere 

42 
00:02:38,190 --> 00:02:43,154 
as well as carbon monoxide, and soot,

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00:02:43,154 --> 00:02:51,860 
announcing, and punctuating 
the demise of such a rainforest.