Cement, Vṛikṣhāyurveda and Sikkim

Cement is the chapter's hardest example, because there is no easy answer.

We cannot imagine life without it: houses, schools, hospitals, bridges, roads and airports all need cement.

Yet making it is listed as one of the most polluting industries. It releases fine dust that gets into the lungs of people and animals and harms them, settles on leaves and lowers plant yields, and pollutes soil and water.

So two things are being done at once. The Central Pollution Control Board has made guidelines for cement factories to reduce or stop the pollution. And other materials are being developed: traditional stone and mud, new plant-based materials, and recycled materials made from waste plastic.

The Jaisalmer fort, a mud building from the 12th century, and a modern Auroville building made of mud with special techniques, are on the same page for a reason: an old material, a new method.

That leads to Vṛikṣhāyurveda: an ancient Indian science of studying and caring for plants and trees. From Sanskrit: vṛikṣha means tree, and ayurveda means the science of life or health.

It goes back several thousand years and was written down in order in texts such as Surapala's Vṛikṣhāyurveda around the 10th century CE. It covers:

• which plants suit which soils;
• collecting and keeping seeds;
• watering by plant type and season;
• natural pest repellents and planting helpful plants together;
• crop rotation and mixed cropping;
• even how to plough so the soil keeps its moisture and its fungi, bacteria and earthworms.

The Sikkim example shows these ideas working today. Pema's family farm had falling yields and debts from buying chemicals. When the state promoted organic farming, they switched to compost, neem and garlic pest repellents, and several crops. Yields dropped at first while the soil recovered. After about five years the farm was thriving, and she sold cardamom, ginger and traditional vegetables at higher prices. In 2016 Sikkim became a 100 per cent organic state: biodiversity returned, tourism rose, and farmers' incomes grew by 20 per cent on average.