Avoid monocultures during the combat of desertification
A monoculture is the cultivation of one species (e.g. one variety of trees). Limited to only one variety, this type of planting has a very bad influence on ecology. If there is only one variety, only a few animals can live from it, and naturally complex lifecycles become impossible. This often results in plagues and infestations, as the system lacks natural enemies which normally balance excessive (and damaging) populations of other fauna (e.g. larger animals, smaller pathogens, etc.).
The current practice of planting large areas (i.e. 10's of 1000's of hectares) as a monoculture (e.g. only Eucalyptus, or only Acacia), will become a bigger disaster for the environment than savannas now are! In the case of monocultures, it is better to have a 'barren' desert than a 'green' monoculture desert.
Solution
The establishment and productivty of forests can be much greater if we choose for a mix of ecologically and economically interesting trees:
- Ecologically interesting trees on areas where harvesting is difficult (i.e. gaps, ravines, escarpments, really poor soils);
- Economically interesting trees in combinations (e.g. fruit, nuts, wood products, varieties supporting wildlife, etc.);
- High-growing trees in combination with low-growing bushes and/or shrubs producing fruit;
- High-growing trees with 5 - 10 varieties all having naturally symbiotic growing qualities;
- High-growing trees divided into different rates of growth (e.g. fast, slower and very slow growing). First harvesting the fastest, and finally, the slowest growing varieties;
- The slowest-growing should ideally be high-growing varieties, which enables other trees to grow below them.
Suitable trees for combined growing
The following is a list of trees suitable to prevent monocultures (Source document ‘Wood Energy’ FAO – Unisylva - editor T.M. PASCA):
Species | Ecosystem | Fw* | Ti* | L.f.w.* | Other uses | Method of propagation | Annual rainfall and climatic/soils conditions |
1. Acacia arabica |
Windbreaks |
XX |
X |
Pods as fodder |
Direct seeding on mounds, strip or line |
Alluvial or loamy soil; moist conditions |
|
2. Albizzia falcataria |
Shade trees |
XX |
XX |
X |
Direct seeding or seedlings raised in nursery |
Wide range of soils, but prefer loamy soil and good rainfall |
|
3. Bamboo (several spp.) |
Live fencing |
X |
X |
XX |
Raw material for cottage industries |
Rarely from seeds |
Loamy or clayey soil; moderate to high rainfall |
4. Calophyllum inophyllum |
Shade trees for amenity (roadsides, around houses, public gardens) |
XX |
Burning oil |
Seedlings to be raised in nursery |
Loamy/clayey soil; moderate to very moist conditions |
||
5. Cassia siamea |
Shade trees in plantations |
XX |
X |
Direct sowing of seed in lines |
Heavy rainfall (poor growth in dry climate) |
||
6. Casuarina equisetifolia |
Agri-forestry systems |
XX |
XX |
X |
Tannin bark |
Seedlings raised in nursery. Planting (1.5- to 2-m spacing) or if too close, early thinning needed |
Sandy soil; stand rainfall between 800 and 5 000 mm |
7. Combretum quadrangulare |
Rice field dikes |
XX |
X |
Medicine |
Seedlings raised in nurseries. Direct seeding possible |
Loamy soil; slower growth on sandy soil; average rainfall 1500 2 000 mm over 5/6 months |
|
8. Cordia alliodora |
Agri-forestry systems |
XX |
X |
Direct seeding (mixed success) |
Moist, well-drained sites; rainfall 1500-2000 mm |
||
9. Glyricidia spp. |
Shade trees in plantations or as living stakes |
X |
X |
Direct seeding or stumps |
Alluvial or clayey soil; high rainfall or moist conditions |
||
10. Grevillea robusta |
Shade trees in tea and coffee plantations |
XX |
Seedlings from nursery |
Sandy soils; 700 to 1 500-mm summer rainfall |
|||
11. Leucaena glauca |
Windbreaks |
XX |
X |
Fodder |
Direct seeding or cuttings |
Neutral or alkaline soils, poor growth on acidic houses soil; rainfall 600-1 700 mm |
|
12. Morus indica (M. alba) |
Regular plantations for silkworm raising |
X |
X |
Fruit leaves for silkworm raising |
Direct seeding or branch cuttings |
Light sandy soil. Moderate to high rainfall (18002 500 mm) or canal planting |
|
13. Pithecellobium saman |
Shade/amenity trees |
XX |
X |
Fodder |
Direct seeding or seedlings from nursery |
Clayey or loamy soil; high rainfall; moist conditions |
|
14. Prosopis spp. |
Plantations for fuelwood |
XX |
X |
Fodder |
Direct seeding (if irrigated) or stump planting |
Dry soil, not excessive moisture; grows on rocky and saline soils |
* Firewood, timber, light farm wood.
Downloads and links
Read some articles about the negative effects of monocultures: