A Moment of Science

Why Is Rain Forest Soil So Poor After Trees Are Cut Down

Rain forests are full of abundant vegetation and life. So, why does the soil change when the trees are cut down?

A rain forest with many lush, green trees

Photo: blambert555 (Flickr)

The rain forest is full of lush, dense greenery. But, when the forest is cleared for farming, the soil changes dramatically.

Deep, green forests, thick with plants and ringing with the sounds of wildlife. When we think of the rain forest we usually think of abundant life. In fact, rain forests contain the world’s greatest abundance and variety of life.

Diversity In The Wild

One research station in a Peruvian rain forest counted six hundred species of birds. That’s about as many species of birds as there are in all of North America. And the diversity of plants is even greater than it is for animals.

In an area where everything grows so prolifically, you’d think a farm would also flourish. But when tropical, lowland rain forest, like what fills the Amazon basin of South America, is destroyed, the soil is generally to poor to grow anything for more than a year.

Why Is Rain Forest Soil So Poor?

One reason the rain forest soil is so poor is that most of the nutrients are stored in the plants themselves.

In any forest, dead organic matter falls to the ground, providing valuable nutrients for new growth. In cooler or drier climates, the nutrients build up in the soil.

But in a rain forest, with its abundance and variety of life, those nutrients are reabsorbed almost as fast as they’re deposited. Also, the trees in tropical rain forests are often evergreens and so very few leaves actually fall to the ground.

Destroying Nutrients In The Soil

When a rain forest is burned to raise crops or cattle, most of the nutrients are destroyed along with the vegetation. Grass may grow for a year, but as the grass is turned into beef, the few remaining nutrients are depleted.

Since land in the rain forest is often cheaper than fertilizer, farmers often clear new fields each year, leaving the old ones to turn into desert.

  • http://twitter.com/CoryCeciliaY Cory Cecilia Y

    hi.. :) can i use this photo for my assignment? :)

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