Why Soil Matters: A 4th Grade Lesson on Earth's Growing Capacity
Watch as a farmer breaks down the math of how much usable soil we actually have on Earth. Using a simple apple and fractions, you'll see why protecting the small amount of soil we farm on is critical for feeding 8 billion people today and 10 billion by 2050.
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0:00 So if this apple represents the whole globe, what percentage of our globe is covered with water?
0:12 You know, yes, 75%. Gold star for you. Yes, 75% or 3/4s of the world is covered with water, so we're going to take this and we
0:29 Will cut this into fourths. Okay, so here is water. So this we can all agree that this is what's left for the land, right? 25%. Okay, so out of the 25% of the world that is land, we have half of.
0:55 It okay we have half of it. I didn't do a great job of cutting that exactly half, but you'll have to pretend with me. Half of it is covered with deserts and snow, you know, Antarctica, the polar ice caps, all of that. So this is not usable for growing anything. So what fraction am I...
1:16 Left with here I had a fourth and I cut it in half so that is no we started with the fourth and we cut it in half 1/8 okay so 1/8 so out of this let going see if we can do this without cutting my fingers go from this.
1:36 Way we cut this in half again, okay, so now I've got I had an eighth and I cut it in half, so now I've got 1/16th right on each one. So half of this we can't use it because it is either too dry or too cold or the soil's already been worn out.
2:00 You know this is land and it's not deserts or mountains but it might be swamps, it might be really rocky, any number of different things that say we can't use this for growing any food. So now we've got a 16 and we're going to cut this in half one.
2:17 More time giving us what fraction. I take a 16th and we cut it in half. Go ahead, 1/32nd. So we got 1/32nd of the Earth's because this other half this.
3:00 Down to 132nd of the whole earth. Okay, this is what we're left with. Okay, how many people are in the world right now? What is there, 78 billion something like that? This has to provide food for.
3:21 Everyone, but that's not exactly correct. Okay, hold on, we're not done yet because really all of our food is grown on the very top few inches of the earth. So really, what all of our life.
3:45 Depends upon is this. We started with this—this is all we have to feed you and me and the other 8 billion people. And they say by the year 2050 there's going to be like 10 billion people and we're not making any more.
4:05 Earth, okay, we have to take care of what we have. And so because there is such a relatively small amount of soil that everybody has to depend upon to survive, we have to really take care of it because when we leave it uncovered and the wind blows it away, we're not getting that back.