Air Date: Week of September 28, 2007

Aerial view of clouds forming over native vegetation (Photo: Udaysankar S. Nair)

In an attempt to stop the westward spread of crop-consuming wild rabbits, Australia put a fence across an almost 2,000 mile stretch of the outback. The fence didn’t stop the rabbits, but it’s caused an interesting phenomenon: the weather is different on each side of the fence. Host Bruce Gellerman speaks with Udaysankar S. Nair of the University of Alabama, who conducted research on how land use affects the weather.

Transcript

[MUSIC: Bugs Bunny in “What’s Opera Doc” (Looney Tunes/Warner Bros.—1954)]

GELLERMAN: It’s Living on Earth. I’m Bruce Gellerman.

[ELMER FUDD SAYING ‘WABBIT TWAPS’]

GELLERMAN: Back in 1907, wabbits—uh, rabbits—were invading western Australia.
The government decided the bunnies had to go.

[ELMER FUDD SINGING: ‘KILL DA WABBIT, KILL DA WABBIT, KILL DA WABBIT!’]

GELLERMAN: Instead of killing the rabbits, Australia decided to build a bunny
Fence--- 2,000 miles long to keep the rabbits out of the outback. The fence didn’t work but scientists began noticing something strange: on the side of the fence where farmers planted crops there were fewer clouds and it rained a lot less than the side that had native vegetation. The effect the bunny fence had on weather has baffled researchers, until now.

Udaysankar Nair of the University of Alabama in Huntsville is in western Australia where he’s investigating the fence phenomena. Thanks for joining us, professor.

NAIR: You’re welcome.

GELLERMAN: I’m looking at a photo that’s in your research paper. It was taken of the fence from an airplane and the image is really dramatic. Right down the fence line on the left side it’s very dark and there are clouds over the field. And then on the right side of the fence there’s not a single cloud. That’s the farmed land. Why is that?

NAIR: We believe what’s happening is that like you mentioned it’s darker on one side where there is native vegetation. It absorbs more solar radiation that comes down to the ground which means that it will put more heat into the atmosphere and heat transferred from the ground to the atmosphere is one of the essential ingredients and that’s the reason why you are seeing more clouds on the darker native vegetation side.

GELLERMAN: And the farmed side is lighter in color so it’s not absorbing the radiation, it’s just bouncing back into the atmosphere.

NAIR: It is not absorbing as much. It is actually absorbing the radiation but it’s slightly less than what’s being absorbed on the other side.

GELLERMAN: So, it’s not the fence. It’s what we do with the land that can affect the weather.

NAIR: Yes. What’s happening here is the fence is a barrier that demarcates between these two areas. And you know you can see that from space.

GELLERMAN: So Dr. Nair are you seeing this effect anywhere else on the planet?

NAIR: Yes, we have been researching deforestation in Costa Rica. And what we found out was that in upwind locations of mountains when you deforest the air going up into the mountains are more dry and more warm. What this implies is that there is less water available for cloud forest for example in Monte Verde. And another region where this might have an impact is for example Kilimanjaro where there have been recent concerns about glaciers melting. And this could also have an impact in such regions because when you deforest lowlands the air going up the mountains are going to be altered and it could be more dry and more warm.

GELLERMAN: So the farmers around Mt. Kilimanjaro could actually be leading to the shrinkage of the snow cover of the mountain.

NAIR: Yes, they could be contributing to the effects that are being seen in Kilimanjaro now.

GELLERMAN: I’m wondering what the implications of your research would be here in the United States. You know farmers are being told to plant corn for ethanol from fence post to fence post.

NAIR: One of the interesting questions that this study raises is that when you clear more and more areas for farming—would you reach a point where you clear too much land that you are going to reduce the rainfall and you get to a point of diminishing returns?

GELLERMAN: Dr. Nair, how is the weather there by the way?

NAIR: It was actually really nice today. It was very warm. It’s actually been cold for the last couple of days and it has really warmed up today.

GELLERMAN: Which side of the fence are you on?

NAIR: Actually we are staying on the agricultural side but we also have a site that’s set up on the native vegetation area.

GELLERMAN: So are there clouds over the agricultural side?

NAIR: Actually today we found clouds that formed over the native vegetation area early in the morning and it stayed that way until about the afternoon. So, clouds were preferentially forming over the native vegetation area today in the morning.

GELLERMAN: So, it’s consistent with your research.

NAIR: Yes, we saw what we were looking for today so that was very good.

GELLERMAN: Udaysankar Nair is a research scientist in the Earth System Science Center at the University of Alabama in Huntsville. He joined us from the Lake King area in southwest Australia. Dr. Nair, thanks a lot. Enjoy the weather.

NAIR: I definitely will.

 

Links

For a summary of the findings along the rabbit-proof fence, click here.