The Cloud, Mountain, Fog, Forest Connection
Contributed by Dr. Lincoln Brower 

1.Listen to Dr. Brower describe "fog drip." >>

2. Illustrate how "fog drip" works by drawing a series of pictures

TRANSCRIPT (and Teacher Tip):

If you look at the south side of the Sierra Chincua when there’s a lot of moisture in the air, these big, beautiful clouds form right on the top of the mountains.

If you happen to be up there in the butterfly colony it will become foggy. What happens is that the moisture in the air condenses to form clouds. Then, as those clouds push through the colony, it’s like a very wet fog coming through. The needles of the fir trees actually cause the droplets of water to condense on the leaves. If you’re inside the colony it can actually be raining on you. But it’s "fog drip," it’s not really rain.

In the absence of the trees there’s nothing for the moisture to condense on. So, if you cut a tree you’re actually resulting in the failure of this fog-drip mechanism the result of which is it begins to dry out. So having the forest there in tact whenever you get this cloud formation on top of the mountains then it’s adding moisture to the colony during the very dry season which is extremely important for the butterflies.

If you come down to this area in the summer time you’ll find that the whole oyamel forest is surrounded in clouds because during the wet season this formation of clouds on the high mountain tops goes on frequently. (I mean, possibly every day for weeks on end.) This is condensing moisture and keeping that area wet and dripping down on the ground.

In California in the redwood forests, something like 40% of the precipitation in some of these coastal forests results from fog drip. Nobody has ever measured this in the Sierra Chincua but it needs to be done. I’m absolutely convinced based on what happens in California and other forests that are subjected to fog banks moving through (or cloud banks just like they do here in Mexico moving through) that this is a major contributor to the total accumulated rainfall in the area. (But it’s not rainfall. It’s precipitated fog drip.)