Wood is good for the world

This is an extraordinary book. From the elegantly written preface to the summary 400 pages later, Colin Tudge has written about trees with an infectious enthusiasm. It is a book that works on many levels, and it will be of great interest and educational value to everyone from sixth-form biology students through to amateur gardeners. There are many "wow" moments, as when Tudge notes that it takes 4,000kg of leaves from white mulberries to make a silk blouse (plus a few worms), and when we learn that Jatropha bean oil is so pure that it needs only to be pressed and filtered before it is ready to be put in the fuel tank of a vehicle.

However, this book is relevant to all our lives, and there are a great many people in the wider public who should read it. On many occasions, Tudge shows how biology, politics and socioeconomics form a very tangled web; he advocates not "trying to change the minds of our leaders" but "changing our leaders". If this is perceived as provocative, then it is nothing compared with the suggestion that teak rafters in the World Trade Centre buildings would have resisted the onslaught of the plane crashes far better than steel.

Tudge defines a tree as "a big plant with a stick up the middle". With this definition, the book covers perhaps one quarter of all land plants, yet it covers many principles of biology, too. Tudge is quite right to describe biology as a "perpetual dialogue" between the constituent parts. His account of pollination syndromes is especially interesting because it shows how little we know about biology and, therefore, how difficult it is to build models for the future behaviour of biology in a changing world. The more we look, the more we find - and the more we find that we do not understand. Tudge uses the words "often" and "may" many times because "all generalisations are dangerous".

As one would expect from Tudge's background, the author does not shy away from tackling cutting-edge science, even where the edge is not defined or is moving very fast. Nowhere is this truer than in our understanding of the evolutionary relationships between extant groups of plants. As he says, the phylogeny is not finished and is "still fluid", and the "evolutionary history of all groups are full of loose ends".

Tudge is very modest about this book; he goes so far as to describe it as a "whimsical account", yet this modesty makes the book even more beguiling.

About one third is taken up with a description of the main groups of trees.

At times this reads like the catalogue that it is, but, as Tudge points out, we must compile an inventory of the world if we are to conserve it.

Either side of this encyclopedic centre is a great deal of common sense.

Tudge is quite right to promote the agro-forestry that has been neglected in the second half of the past century. The fig, olive, almond and carob orchards of the Algarve, along with the nearby cork woods, are just two examples of sustainable production systems.

Tudge has written much of the book from first-hand encounters with trees, and in him they have a passionate advocate. At times the style is reminiscent of Bill Bryson, and science needs advocates as eloquent as Tudge. Towards the end, the narrative begins to enter the slough of despond as he describes the plight of so many wooded areas. Yet he pulls us back from the brink with his account of the inspirational Green Belt Movement in Kenya. As he concludes, "we are creatures of the forest still".

Timothy Walker is director, Oxford University Botanic Garden.