| In geography, arable land (from arado, plough in Portuguese) is a form of
agricultural land use, meaning
land that can be (and is) used for growing crops. David Ricardo incorporated the
idea of arable land into economic theory.
Of the earth's 57 million square miles (148,000,000 kmē) of land, more than 12 million square miles (31,000,000 kmē)
is arable.
Most of the arable land on earth is around the largest rivers on earth. Some examples are: the Nile River, the Tigris and Euphrates Rivers, the Yellow River, the Amazon River, and the Rhine River. These
rivers flood regularly, overspilling their banks. When the flood is over, the rivers recede, leaving behind rich silt. This silt is excellent fertilizer for crops. Even if the land is overfarmed, and all the
nutrients are depleted from the soil, the land renews its fertility when the next
flood comes. Rivers and streams can make desert land arable.
The closest thing to a natural habitat that human beings have is the large river valleys of the world. The temperature is
comfortable there, and it has plenty of fresh water, food, fish, and thirsty wild animals attracted to the water. This is why all
the great ancient civilizations began on the banks of great rivers. Lots of food can be grown there, feeding the largest
populations.
Unarable land
On unarable land, farming is nearly impossible unless more advanced methods of agriculture are used. Unarable land usually has no source of fresh water, and is often too hot (desert), too
cold (arctic), too rocky, too mountainous, too salty, too rainy, too snowy, or too cloudy. Clouds block the sunlight plants need
for photosynthesis (making sunlight into food). The plants starve
without light. Starvation and nomadism
often exist on unarable land. Unarable land is sometimes called 'wastes', 'badlands', 'worthless' or 'no man's land'.
Sometimes, unarable land can be turned into arable land. New arable land makes more food, and can prevent starvation, saving lives. This also makes the country more self-sufficient and politically independent, because the country doesn't have
to buy food from other countries. Making unarable land arable often involves digging new irrigation canals and new wells,
aquaducts, desalination plants, planting trees for shade in the desert,
hydroponics, fertilizer, nitrogen fertilizer, pesticides, reverse osmosis water processors,
mylar insulation or other insulation against heat and cold, digging ditches and hills for
protection against the wind, and greenhouses with internal light and heat for protection against the cold outside and to provide
light in cloudy areas.
Some examples of infertile unarable land being turned into fertile arable land are:
- Aran Island: This island off the west coast of Ireland, (not to be confused with the Isle of Arran in Scotland's Firth of Clyde), was unarable because it was too rocky. The people covered the island with a shallow
layer of seaweed and sand from the ocean. This made it arable. Today, they grow crops there.
- Israel: Israel was mostly unarable desert until desalination plants were built on the coast. The plants turn salt water into fresh water for farming,
drinking, and washing. They created their own large fresh water source.
Some examples of fertile arable land being turned into infertile unarable land are:
- Droughts like the 'dust bowl' of the Great Depression in the U.S. turned farmland into desert.
- Rainforest Deforestation: The fertile tropical forests turn into infertile
desert land.
- Romans' destruction of Carthage: At the
end of the Punic Wars, the victorious Romans sowed the earth with salt, to
symbolize total victory. The Roman symbol meant that Carthage would never grow back - their civilization ended. Crops won't
generally grow in salty soil. This is why salt water from the ocean can't be used to water crops.
- Each year more arable land is lost to desertification and erosion from human
industrial activities. Irrigation of farm land also increases the sodium, calcium, and magnesium in the soil. This
process steadily concentrates salt in the ground, decreasing productivity for crops that are not salt-tolerant.
- Urban sprawl: In the United States, about 2.2 million acres (8,900 kmē)
of land was added to urban areas between 1992 and 2002, much of it farm land now paved.
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