Hayley Smith, of Balclutha School, asks :-

What can you make with trees?

John Walker, of the School of Forestry at the University of Canterbury, responded.

While most things can be made out of wood, it is probably true to say that the dominant interest is in meeting the needs of the middling rich and the poor.

The great surprise is that the largest use of wood is as a fuel. Developing countries use wood and charcoal for cooking. Even in the United States more than half the commercially gathered wood is burnt. Thus in a chemical pulp mill, such as Carter Holt Harvey's Kinleith operation at Tokaroa, wood is chemically broken down into fibres (for paper) and carbon-rich lignin which is recovered and burnt to provide sufficient energy to power the entire mill. (Every two tonne of wood yields a little over one tonne of paper.)

You can make the most wonderful yacht out of solid wood, or plywood, or fibreglass, or aluminium, or steel. We always have a choice. The wealthiest of yachts often have teak decking because this wood is durable, stable and beautiful.

The first re-entry modules in the American space programme had their cones lined with plywood as it is light and a very good thermal insulator. (The ceramic foam panels of the Shuttle haven't proved to be more reliable!) Liquified natural gas tankers used to be insulated with balsa wood as balsa has a very high crushing strength, despite its low density, and very low thermal conductivity (less evaporation when shipping the gas from North Africa to markets in Europe).

Few large public buildings are built of wood these days. But all buildings incorporate timber as a feature or in its furnishings.

Finally, in countries like New Zealand we should not forget the risk of earthquakes. I have no doubt that when the big one strikes I'd rather be asleep in a timber-framed house than any other.