Wood and trees: timber is the only building material that, properly used, positively benefits the planet and our relationship to it. Wood is indeed good and we should explore as many ways of using it in building as possible.

Our existence on the planet is ecologically intimately bound to the life of trees. The effect of forests on the atmosphere is undoubted, yet their role as the lungs of the world is sometimes exaggerated. Natural forests are close to environmental equilibrium: allowing for growth and decay, their net timber increment is negligible, and so is their contribution to the balance of oxygen and carbon dioxide in the atmosphere.

Indeed, it is sometimes argued by market-orientated ecologists that grassland prairie has just about the same properties in relationship to climate as natural forest. So it does not matter, they suggest, that large parts of the South American and Indonesian tropical forests are being destroyed to make way for grazing land. But managed forests can be made to become net absorbers of carbon dioxide by harvesting timber before the decay sequence sets in. In fact, most felled trees, particularly in tropical forests, are used as fuel by the poor, which immediately returns carbon back to the atmosphere, increasing the greenhouse effect and the planet's gradual overheating. Yet if the trees are used in building, the carbon they contain is constructively locked into a stable form that can last for many centuries. It is very important to realize that building with wood is a positive benefit to the planet.

Wood as a building material has the further advantage of being low in the consumption of energy needed in its processing, and hence in its overall impact on the biosphere. The conversion of a tree into kiln dried and preservative treated building timber takes 5.3 megajoules a kilo, but 35 MJ/kg are needed to produce a kilo of steel, and a staggering 145 for aluminium. Wood has roughly the same structural properties as steel or reinforced concrete, yet producing a cold rolled steel section equivalent to a 50mm x 300mm solid untreated softwood section of the same stiffness requires 19 times as much energy. Structural hardwood would show an even greater difference because a smaller section would have the same stiffness. Even in large-span structures, wood construction needs less than a quarter of the energy of concrete.

But before we become too starry-eyed about the wonders of wood, and the marvels of the managed forest, we must for a moment think of their problems. Boreal and tropical forests are being catastrophically destroyed, even in Scandinavia and Malaysia, in both of which there are official policies of replacing a felled tree by at least one newly planted sapling. Mono-cultures result from this process, greatly reducing the natural abundance of species of animal and plant life. It is clear that we need to preserve the great diversity of the natural forests, not least for our own interests. By destroying nature's abundance, we are irretrievably losing hundreds if not thousands of species, all of which could be useful to humanity.

Since the invention of plywood possibly millennia ago, we have been using adhesives to make wood go further and to exploit its natural strengths in untraditional ways. But the veneers used in plywood are too often from relatively large logs, and plywood made from hardwood veneers is one of the main uses of tropical timber, a cause of destruction of rain forests. (Though in fact it is probably less destructive than for instance Japanese chopsticks, which are used only once, then thrown away and are supposed to be, at least by many Australian environmentalists, one of the major reasons for the horrendous destruction of the Queensland forests.)

The concept of whole tree utilization, in which the trunk, branches and even roots of felled trees can all be made available in building, has become an important measure of our use of wood and our relationship to the forests. Admittedly, many of the products that stem from whole tree utilization and related approaches: laminated veneer lumber, wafer-board, mdf, orientated strand board and the like, are not very attractive to see and touch. Almost all of them lack the empathic qualities of natural wood, but they can perform essential tasks in construction and, as long as they are used in places you cannot touch and see, they should be employed whenever possible.

Wood is the only building material that has empathic qualities: we identify with wood from the cradle to the coffin. It is the only really sustainable building material. It is the only one which, properly managed and abundantly used, can actually improve the quality of life on the planet because of its ability to lock up carbon. We have a duty to use it, and to continue to do so with the highest degree of silvicultural, technological and architectural innovation and imagination.