One response to this challenge is the concept of ecologically sustainable forest management, the attempt to harvest products without diminishing the capacity of the forests to sustain wildlife, yield clean water and protect the soils in which they grow.

Although the broadening of foresters’ intellectual horizons is to be welcomed, the world-weary among us may still ask what will actually change. Cynics may claim that the new ecologically sensitive practices have been advanced as a ploy to justify exploitation of the remaining unlogged forest patches in a region. For example in the Pacific Northwest there are only a few patches of old growth remaining, such has been the long history of logging.

Given our voracious demand for forest products, no large areas of forest, such as those in the tropical and boreal zones (see “Death by a thousand cuts”, New ĐÓ°ÉÔ­´´, 11 February 1995) are likely to remain unexploited. Therefore we can’t afford to dismiss ecologically sustainable practices because they may provide the solution to a serious global problem.

The whole subject has become such an academic growth industry that Gary Hartshorn, a tropical ecologist with the World Wildlife Fund in Washington DC, has felt forced recently to comment that although such practices are certain to generate more than enough research publications, he hoped that sight of the fundamental goal – that forests must be sustained – would not be lost. Applications and techniques for forestry must, he suggested, be tested, demonstrated and documented.

A critical question remains: how can forestry be conducted in an ecologically sustainable manner? My view is that the answer will be found by applying the scientific method: management by hypothesis. This is a very practical and field-based approach that can be applied immediately.

The complexity of forest ecosystems means that sustainable forestry management systems must be tailored to suit specific situations: one size cannot fit all. Managing by hypothesis will require foresters to state what they think they know about a particular forest system and what they think their proposed practice will achieve.

This would also allow others, such as environmentalists, to scrutinise and challenge the scientific basis of management regimes. The longevity of trees means that the outcomes of different systems can only be accurately judged by future generations. Stating management hypotheses will enable people to judge in a distant future the outcomes of various forms of forestry.

Two examples will help to illustrate how this approach could be used to tackle some serious impediments to sustainable forestry. In the late 1960s, it was discovered that several Australian tropical rainforest trees that produced valuable timbers would not grow in close proximity to other trees of their kind: these species were called “nongregarious”.

Further attempts to develop plantations of these trees were abandoned when it was realised that they could only grow in multi-species plantations, which were seen as economically less attractive than monocultures. Until the operational details of multi-species plantations are worked out, the only source of these timbers is natural forest. Trials are required to determine what sort of mixed species planting will allow the growth of these trees.

Even more challenging is the maintenance of the specific habitat requirements of forest wildlife. In Australia it is now recognised that some old-growth forest mammals, such as the rare Leadbeater’s possum (Australia’s version of the American spotted owl), need not only old eucalyptus trees with hollows for nest sites, but also specific fire regimes that favour the growth and regeneration of food plants in the forest understorey.

The challenge here is to design forestry operations in which the appropriate mix of trees is retained and maintained in the understorey and the canopy. Much remains to be learnt about how to design logging operations to provide forest wildlife with unlogged refuges and escape routes – the so called “migration corridors” – to ensure that animal populations avoid inbreeding and local extinction. Although computer modelling provides insights into this complex problem, there seems no alternative but to carry out long-term field experiments.

This idea – of seeing forestry operations as a collection of landscape experiments – is different from the popular concept of “adaptive management”, which simply boils down to learning from mistakes. And it involves more than monitoring changes in forests, which too often means taking periodic ecological censuses for no stated hypothesis. By building from the results of landscape experiments, it should ultimately be possible to achieve sustainable forestry. It may seem to be a costly proposition to view all forestry activities as experiments; but these costs are small given that some forest systems will be irreparably damaged by forestry operations. Badly managed forests will be an unwelcome inheritance for future generations.

It could be argued that foresters have always managed by framing hypotheses and used the scientific method to solve specific problems, such as the reasons for poor growth of forests. To some degree this is true; but if it were entirely true, why have manifestly negative forestry practices, such as massive clearfelling, been carried out for decades? And why else is there now the need to champion a “new” ecologically sustainable forestry?

Conservation biologists are desperately struggling with the aftermath of
human destruction, but they are few in number and relatively poorly funded.
For example, the research effort into biodiversity is far less than that
dedicated to the huge project to map the human genome – the US alone this year
set aside $127 million dollars for that project. The situation is both
tragic and ironic, because biodiversity is to all life on Earth what the human
genome is to you and me.

Few people know that the Austrian quantum physicist Erwin Schro¨dinger
anticipated the discovery of DNA’s fundamental role in heredity in a beautiful
little book called What is Life? In it he suggested that life was ultimately a
code-script contained in a complex molecule. Perhaps we need another book to
be written, What is Biodiversity? I believe the author would conclude that
biodiversity is a code-script contained on a planet. The science with the
tools to read this planetary code-script – the patterns of distribution of
plants and animals – is biogeography.

Life forms are not randomly grouped together on the planet, there are
distinct repeated patterns. These patterns of life occur at all spatial scales
from the global to the microscopic. Just as there are latitudinal gradients in
plants from the tropics to the poles, so there are gradients of mosses up the
trunk of a tree. Our knowledge of the geography of life is based on at least
200 years of study. There are now well established techniques to identify the
underlying environmental cause of spatial patterns, but they have only been
applied to a fraction of the Earth’s land and oceans. Much basic work remains
to be done. For example, there is still no complete explanation of the fact
that there is more biodiversity in the tropics than in the temperate zone.

Climatic change, shifts in sea level, mountain building, volcanic activity
and chance events have all influenced the distribution and abundance of life,
as has the evolution of new species. Fortuitous geological and fossil
discoveries only provide us with limited insights into evolution, but the
distribution of life forms can help fill in the gaps.

A knowledge of biogeography was critical in developing the theory of
evolution – the distribution of finch species on the Galapagos Islands
provides an excellent example. The British naturalist Alfred Russel Wallace
wrote in 1863 that the distribution patterns of species may be looked upon as
“individual letters which go to make up one of the volumes of our Earth’s
łóľ±˛őłŮ´Ç°ů˛â”.

Given the incomplete fossil and geological evidence of the origin and
evolution of Earth, the loss of biodiversity is certain to restrict,
fundamentally and irreparably, our understanding of our planetary home.
Wallace grasped this point when he wrote in 1863: “a few lost letters may make
a sentence unintelligible, so the extinction of numerous forms of life which
the progress of cultivation invariably entails will necessarily obscure this
valuable record of the past” (see C.H. Smith’s Alfred Russel Wallace: An
Anthology of his Shorter Writings, Oxford University Press, 1991).

Equally, without intact landscapes ecologists will not be able to
understand broad-scale natural ecological processes. Because of the rapid
destruction of habitats throughout the world I believe we urgently need to
embark on a biogeographic project of comparable scope to the human genome
project. The primary aim would not be merely the compilation of lists of
species and detailed taxonomic research as ends in themselves, but rather the
discovery of why biodiversity varies in space and time. Given the rapidity
with which humans have transformed ecosystems throughout the world, there is
only a short time left to embark on such a project before the Earth has been
robbed of many of its evolutionary treasures. The message contained in the
distribution of life forms may turn out to be trivial or redundant (see, for
example, the writings of Australian ecologist Btian Walker, Conservation
Biology, volume 6, pp 18-23, 1992), in which case the loss of biodiversity
will be of little concern for our future. On the other hand, the forces which
have given rise to the variation of other species may substantially impact on
the future of our own. Can we afford to ignore the text?