Lesotho cannot wait for the world to come up with ideas to feed its hungry population, so it has developed some of its own. The mountain kingdom in southern Africa with a population of barely two million sits on a plateau mostly above 1,800 metres altitude, so the growing season is short and its vulnerability to climate change is acute. With the country struggling with one of the world's highest HIV prevalence rates, many of its able-bodied workers have either died or been crippled by disease. And in what is one of the poorest states in Africa, even the slightest increase in the cost of food or commodities hits painfully hard. They are now thriving on what have become known as "keyhole gardens". They are round gardens of about two metres in diameter and raised to waist-height to make them easy for the sick and elderly to work. Inside, the garden-beds are layered with tin cans, dirt and ash which together provide the nutrients to make the gardens extraordinarily productive. Ntsie Tlali from CARE, the NGO behind the gardens, believes they are revolutionary. A typical family has three keyhole gardens and that's more than enough to supply a family of 10 of with all the vegetables they need, and with some left over to sell. Because they are protected by the stonework, the rich soils are safe from erosion. They retain moisture far more effectively than land farmed by traditional farming methods, and they are compact enough to turn the tiniest plot of land into productive agriculture. Lesotho's vast highland plains are spectacular places for tourists. Broad and treeless, they offer stunning views of the mountains looming over shimmering gold grasslands. But they are terrible for farmers. Decades of intensive agriculture have stripped the land of trees, and exposed soils to wind and rain. Erosion has created countless miniature canyons that split the plains everywhere you look. The already thin mountain soils have lost virtually all their productive nutrients. In many respects, Lesotho is a microcosm of the problems facing so many parts of the developing world.