The Big Culprit Behind
Land Deterioration Agriculture
(Page 4)

<< Page 3



By Professor Nils Nykvist

How fire worsens the problem (continued)

During the rainy season the vegetation is green, and only the low-growing trees with thick bark give a hint that the tree growth could be much higher. During the dry periods, when the trees shed their leaves and the sun can dry out the plant residue on the soil, fires easily occur with or without human involvement.


When slash and burn agriculture is practiced, the plants cannot build up enough nutrients in the biomass for a good harvest of agricultural crops, if the fires are too frequent.

In some areas of Zambia the soil has therefore been enriched before cultivation by adding plant nutrients in biomass from surrounding areas.

In an area approximately 4 hectares in size, all branches and shrubs are cut down [7]. After drying, the cut-down biomass is gathered together into a smaller plot about 0.4 hectares in size and burnt before the rain. In the ash-fertilized plot, beans, millet, groundnuts, and cassava may be grown and harvested after a few years.

After this period the inorganic nutrients in the soil have decreased so much that it is no longer profitable to cultivate it for the following 20–30 years. If this period is shorter, the harvesting of biomass from surrounding areas to fertilize the plot prior to cultivation has to be larger.

The vast open grasslands of Africa, with its mostly annual fires, are additional very obvious evidence of fire’s large impact on vegetation (Fig. 7). Unlike the National Parks of East Africa, the burning is not systematic with many gentle fires. Instead, the grass grows until it is set on fire in the dry season by lightning or by people, accidentally or deliberately.

The great biomass of grasses that grow during the rainy season makes the fires very fierce and difficult to master when the grass dries out during the dry season. Modern weapons and shooting ranges at the fire-front have also drastically reduced the great abundance of wild game which by grazing decreased the grass biomass and thus also the fire intensity. When people use counter-fires to try to protect the villages and cultivations, they contribute even further to the distribution of savannah areas.

And the problem becomes entrenched

In many savannah areas of Congo people have begun to accept fires as inevitable and decide in advance which day they shall set fire to the grass. This gives people time to protect their villages and cultivations and to prepare for the hunt of animals forced to flee from the fire.

Many people even believe that the fires are not harmful at all, because the smoke causes rain. The sad thing is that they often seem to be right, as the rainy season usually comes fairly regularly after the dry season.


For the relatively few people living on the large grasslands of Congo, agriculture is the most important way of life. Because of increased soil erosion after burning and long cultivation without fertilization, the soils are so depleted of plant nutrients that only cassava (manioc) can be grown in certain areas. This crop contains a great deal of starch, but is poor in proteins, leading to severe deficiency diseases in humans.

When slash and burn agriculture is practiced, the plants cannot build up enough nutrients in the biomass for a good harvest of agricultural crops, if the fires are too frequent.

In some areas of Zambia the soil has therefore been enriched before cultivation by adding plant nutrients in biomass from surrounding areas.

In an area approximately 4 hectares in size, all branches and shrubs are cut down [7]. After drying, the cut-down biomass is gathered together into a smaller plot about 0.4 hectares in size and burnt before the rain. In the ash-fertilized plot, beans, millet, groundnuts, and cassava may be grown and harvested after a few years.

After this period the inorganic nutrients in the soil have decreased so much that it is no longer profitable to cultivate it for the following 20–30 years. If this period is shorter, the harvesting of biomass from surrounding areas to fertilize the plot prior to cultivation has to be larger.

The vast open grasslands of Africa, with its mostly annual fires, are additional very obvious evidence of fire’s large impact on vegetation (Fig. 7). Unlike the National Parks of East Africa, the burning is not systematic with many gentle fires. Instead, the grass grows until it is set on fire in the dry season by lightning or by people, accidentally or deliberately.

The great biomass of grasses that grow during the rainy season makes the fires very fierce and difficult to master when the grass dries out during the dry season. Modern weapons and shooting ranges at the fire-front have also drastically reduced the great abundance of wild game which by grazing decreased the grass biomass and thus also the fire intensity. When people use counter-fires to try to protect the villages and cultivations, they contribute even further to the distribution of savannah areas.
Figure 7. Savannah in the Democratic Republic of Congo (former Zaire).

In savannah areas with few trees and shrubs in Congo, people use grass biomass from the surroundings to increase the amounts of plant nutrients in cultivations. The grass from approximately one square meter is cut during the dry season, collected in small heaps, covered with a thin layer of soil and burnt.

In the burnt heaps, beans, groundnuts, and cassava are sown or planted when the rainy season begins (Fig. 8). The pods are first harvested, thereafter the peanuts, and after a few years the cassava roots. This cropping system helps the individual farmers temporarily, but does nothing to reduce the large depletion of plant nutrients in the soil, which is the result of burning and overly intensive cultivation over long period.
Figure 8. To increase the amounts of plant nutrients when cultivating in savannahs, grass and soil is hoed up from the nearest surroundings and gathered in heaps that are burnt during the dry season. When the rainy season starts, beans, peanuts, and cassava are sown or planted in the burnt heaps. Democratic Republic of Congo (former Zaire).

Until the late 1800s, people with the help of fire created a lot of large open areas of grassland that in Africa are called savannahs, in Argentina pampas, and in Brazil cerrados. North of the tropics the grasslands are called steppes or in North America prairies. In some countries, these grasslands are now under cultivation or used as pasture for large herds of cattle. In other areas, particularly in Africa, grasslands are largely untapped.

See the references for this article.


Return from this page on The Big Culprit Behind Land Deterioration – Agriculture (Page 4) to The Land Degradation Series

Return from this page on The Big Culprit Behind Land Deterioration - Agriculture to All Recycling Facts Homepage





Sign up for
Love4Gaia Newsletter
to receive free green living information and environmental news.

Enter Your E-mail Address
Enter Your First Name (optional)
Then

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you Love4Gaia Newsletter.

Get eco-friendly and organic products at reasonable prices (over 100 quality brands):

  • eco-friendly cleaning products
  • natural personal care items
  • green cosmetics
  • organic food items
  • organic baby care products
  • organic supplements

To receive a FREE $5 DISCOUNT COUPON through your email, simply fill in your details here.