Comparing the Earth to an Apple
On the left we see the Earth (click it for a larger image). This image, dubbed by NASA as the “blue marble,” is the most detailed true-color image of the entire Earth to date. Using a collection of satellite-based observations, scientists and visualizers stitched together months of observations of the land surface, oceans, sea ice, and clouds into a seamless, true-color mosaic of every square kilometer (.386 square mile) of our planet. These images are freely available to educators, scientists, museums, and the public, click here.
On the right we see an ordinary apple (small fuji variety).
The diameter of the earth at the equator is 7,926.41 miles (12,756.32 kilometers) http://heasarc.gsfc.nasa.gov/docs/cosmic/earth_info.html
Suppose the Earth were the size of an apple, about 3 inches across. The biosphere, consisting of the ocean, land surface, and lower atmosphere in which all life exists, would be no thicker than the apple's skin.
OK, NOW IMAGINE THIS: if the Earth were the size of an apple....
(This exercise is based on a handout circulated by the non-governmental organization called Zero Population Growth, 1400 16th St. N.W. Washington, D.C. 20036; the activity is copied here in modified version with permission from Zero Population Growth).
1. Think of the earth as an apple./ Slice an apple into quarters and set aside three of the quarters. These three pieces represent the oceans of the world. The fourth quarter roughly represents the globe's total land area.
2. Slice this "land" in half. Set aside one of the pieces. The portion set aside represents the land area that is inhospitable to people (e.g., the polar areas, deserts, wetlands, very high or rocky mountains). The piece that is left is land where people live, but do not necessarily grow the foods needed for life.
3. Slice the 1/8 piece into four sections and set aside three of these. The 3/32 fraction set aside represent those areas too rocky, wet, cold, steep, infertile to actually produce food. They also contain the cities, suburban sprawl, highways, shopping centers, schools, parks, factories, parking lots, and other places where people live, but don't grow food.
4. Carefully peel the 1/32 slice of the apple. This tiny bit of peeling represents our arable land, the land upon which we depend for our food. Estimates suggest that we loose 25 billion tons of precious topsoil each year from erosion, yet we must feed an additional 71 million people each year on this diminishing resource.
I do the "apple demonstration" to draw attention to the precious stock of arable land on our planet. The larger message is to draw attention to biophysical concerns about growth. We need to broaden the conception and theory-building agenda of "globalization and planning" to include an integrated focus on natural, manufactured, and human capital. Most attention focuses on economic restructuring and its socio-political ramifications. We need a more integrated mico-meso-maco perspective that draws into view the interdependencies linking natural capital (e.g., ecosystems, wetlands, biodiversity), manufactured capital (e.g., produced assets such as machines, buildings, infrastructure), and human capital (e.g., labor, social systems, networks, knowledge and learning capacities).
A more detailed version of this demo is on-line at:
Excerpts copied below, with acknowledgement to the Florida Solar Energy Center (FSEC).
PART I: FARMLAND
|Whole Apple - Planet Earth
||1/8 - Habitable Land
|¾ - Water
||3/32 - Habitable, but Unarable Land
|¼ - Land
||1/32 - Arable Land
1/8 - Uninhabitable & Unarable Land(poles, deserts, swamps, mountains)
|1/32 - Peel - Topsoil
- Hold the apple out so the class can see it.
"This apple represents our planet."
- Cut the apple into quarters. Hold out ¾ in one hand and ¼ in the other.
"What do these ¾ represent? (Water.) So, only ¼ of the Earth's surface is land."
- Set the ¾ representing water aside. Slice the remaining ¼ representing land in half, lengthwise. Take 1/8 in each hand, and hold out one of them.
"1/8 of the Earth's surface, or half of all land, is inhospitable to people and to crops: these are the polar regions, deserts, swamps, and high or rocky mountains."
- Set that 1/8 aside and hold out the other.
"This 1/8 of the Earth's surface, the other half of all land, represents the total area on which people can live, but can't necessarily grow food."
- Slice the 1/8 lengthwise into four pieces. Hold out 3/32 in one hand and 1/32 in the other.
"Each of these pieces represents 1/32 of Earth's surface. These three represent land that never was arable because it's too rocky, wet, cold, steep or have soil too poor to produce food. They also contain land that was once arable but I no longer because they've been turned into cities, suburbs, highways, shopping centers, schools, parks, factories, parking lots and other forms of development that makes them incapable of growing food."
- Set 3/32 aside and hold out 1/32.
"So, only 1/32 of the Earth's surface has the potential to grow the food needed to feed all the people on Earth."
- Carefully peel the 1/32 slice of Earth, and hold this peel up so they can see it.
"This tiny bit of peeling represents the topsoil, the dark, nutrient-rich soil that holds moisture and feeds us by feeding our plants. The U.S. currently loses an inch of topsoil every 16 years. Because it takes nature 500 years to build one inch of topsoil,(1) it is considered a non-renewable resource."
Part II: WATER
|¾ - Water
1/8 - Food-Producing Areas
3/32 - Coastal Areas
1/32 - N. American Pacific Coastline: world's most productive ocean region
1/32 Peel - Photic Zone: top 100 meters, habitat of most marine life
Sliver of Peel - Freshwater: only .003% of all Earth's water
- Return to the ¾ of the original apple that represents ocean.
"Some of our food comes from the sea-fish provide about 16% of animal-protein consumed by humans, and a little over 5% of our total protein intake.(2) But despite its vastness and seeming uniformity, many regions of the ocean are unproductive due to a lack of life-supporting nutrients. Its capacity to produce food is therefore finite.
- Set aside 2/4. Cut the remaining ¼ in half. Set 1/8 aside and hold out the other 1/8.
"This 1/8 represents the productive zones of the ocean along the equator and the western margins of continents. Currents cause upwelling which brings nutrients to the surface. These nutrients support large numbers of marine plants and animals.
- Slice the 1/8 lengthwise four equal pieces (4/32) and hold them all up.
"3/32 represent coastal areas around the world where fishermen earn their livelihoods. The last 1/32 represents the most productive area along the Pacific Coast of North America, historically one of the riches ocean regions in the world."
- Peel the skin from the last 1/32.
"This peel represent the photic zone, the top 100 meters (330 feet) of the ocean which light can penetrate, supporting photosynthesis. Since the marine food chain depends on photosynthesizing plants, especially phytoplankton and algae, almost all ocean life is concentrated in this narrow photic zone. 100 meters down, the amount of light is only 1% of what it is at the surface."(3)
- Cut a very small wedge from the apple skin. Hold it out.
"Fresh water is another precious and finite resource that is essential to all life on this planet, including human life. Although ¾ of the Earth is covered by water, only a tiny portion of it is readily available for human use. It is what we drink, cook with, bathe in, and water crops with when rain doesn't provide enough moisture. Freshwater is supplied by groundwater, rivers, lakes, and streams. Although this sliver isn't exactly to scale, it represents the 3/100 of 1% of the Earth's water that is fresh."
- John Robbins, Diet for a New America (Walpole, NH: Stillpoint Publishing, 1987) p.357.
- L. Brown et al., State of the World 1995 (New York: W.W. Norton & Company, 1995) p. 21.
- "Apple Ocean." Project O.C.E.A.N., 1988.