Every year, China plants trees over an area the size of Ireland. The country may be the biggest polluter on Earth, but its reforestation efforts are enough to make Saint Greta look twice. In the last decade, the ‘Great Green Wall’ project has cost more than £73 billion, and the country aims to expand its forest cover to 24 per cent by the end of 2025 (the total area of the five largest European countries combined).