Reading on land degradation: meaning, effects on agriculture and biodiversity, and measures

(i) What land degradation is. It is the decline in land's capacity to produce food and support life, caused mainly by misuse. Soil is eroded, salted, waterlogged or poisoned until crops fail, and in the end the land can become wasteland. The passage says nearly a quarter of the world's land is already in this state.

(ii) How it affects agriculture and biodiversity.

Agriculture:

• Loss of topsoil makes soil less fertile and reduces how much water it can hold.
• Over-irrigation brings salts to the surface, where crops cannot grow, and waterlogs the topsoil so that roots suffer.
• Ever more chemical fertiliser poisons the soil.
• The passage's warning follows from this: billions of people depend directly on agriculture, so the damage reaches every person through the food supply.

Biodiversity:

• Eroded topsoil washed into water clogs lakes, raises turbidity and leads to loss of aquatic life.
• Land degraded by pollution adds to habitat loss, which, with fragmentation, is the most important force driving plants and animals to extinction.

(iii) Measures to prevent land degradation.

• Keep the soil covered. Develop vegetative cover on non-arable land so that rain does not strike bare soil.
• Slow the water. Use contour trenches, ponds and live check dams of grass, shrubs and trees across gullies.
• Farm with the soil. Rotate crops to raise fertility and reduce erosion, and work crop residue back into the soil to add organic matter.
• Use irrigation and chemicals with care. Avoid over-irrigating, so that salts and waterlogging do not build up, and limit chemical fertilisers.
• Stop toxic dumping. Keep highly toxic industrial and nuclear wastes off land, because such land is lost as a renewable resource.

The passage also points to the opportunity: restoring two billion hectares of degraded land could raise productivity, store carbon and preserve biodiversity, so prevention and restoration should go together.