Biodiversity means biological diversity, the range and mix of biological species. Global biodiversity is shrinking, and any significant further erosion could seriously threaten human welfare. But what is the importance of biodiversity and why is global diversity shrinking?
Mother Nature is unsentimental about her biological species. The geological record shows many large-scale extinctions of life on Earth caused by changing environmental conditions. It is estimated that 99 per cent of all living species that ever existed on Earth became extinct.
Before humans arrived, the history of the natural world unfolded unconsciously. However, we now understand much about how the world works. Human activities are changing the environment and we have an inescapable obligation to manage the world for the well-being of humanity and of other living creatures.
There are perhaps 50 million living species on Earth. This number is steadily decreasing because of pressures exerted by human activity, notably deforestation, various industrial activities, and modern agricultural practices. Different habitats have different levels of biodiversity. The tropical rain forests are richest in biodiversity. One hectare of rain forest harbours 275 species of trees, whereas one hectare of European forest contains only six species at most. Rain forest is disappearing at an alarming rate. The Amazon rain forest is being steadily cleared to create poor-quality grazing for cattle and poor-quality cropland of low biodiversity.
All human food is supplied by various other biological species. The earliest human hunter-gatherer societies harvested other edible species of life as they found them in the environment. he predictability of food supplies is low in hunter-gatherer society. About 10,000 years ago a major development aimed at ensuring a predictable food supply arrived, the birth of agriculture. Eight species of plants known for their desirable properties (e.g. palatability, food value, hardiness, etc) were chosen for cultivation.
As human numbers grew, more land was cleared for cultivation and these few cultivated food species spread. This process has continued and intensified to the present day. For a long time human numbers remained relatively small and the spread of food crops did not press significantly on global biodiversity. But the population explosion this century, combined with the modern industrial agriculture necessary to feed these numbers, has changed all that.
World population has grown more since 1950 than in the previous four million years, from 2.5 billion to 5.8 billion. Today about 20 plant species provide 90 per cent of our vegetable food and only three, maize, rice and wheat, account for over half of all harvested crops.
The dedication of vast tracts of land to a handful of crops has allowed some plant species to become extinct and makes world food supplies dangerously vulnerable to disease. If some plant pathogen mutated into a very virulent form against which our current rice plants have no defence, this would wreak havoc on food supplies in large areas of the world.
Biodiversity has a fourfold value. It plays a vital role in maintaining the physical conditions of the planet. Second, biodiversity represents our total global bank of genetic variety. Third, it is a straightforward economic asset. Fourth, biodiversity is essential for the well-being of the human psyche. Many physical aspects of the planet are determined by living organisms (biota). The gaseous composition of our atmosphere, the circulation of moisture from Earth to atmosphere, global climate patterns etc are all significantly affected and regulated by the web of life on Earth. The effect of the biota on the physical nature of the planet is determined by the pattern of biodiversity. If this pattern was changed it would cause significant changes in planetary physical conditions. We live comfortably under the conditions produced by current biodiversity, but who knows how we would fare under altered conditions.
The vast array of genetic information in biodiversity is available to be used by human ingenuity. Although the basic genetic blueprint for all life is the same, many species secrete unique chemicals. Science is familiar with only a small fraction of these chemicals and an even smaller fraction has been tested for useful properties in medicine or in other applications. About 25 per cent of pharmaceuticals are presently derived from plants. It is probable that chemicals capable of curing all the major human diseases are waiting to be discovered in the Earth's rich biodiversity.
The genetic library in biodiversity is also an insurance policy against a disastrous failure in a major food crop. If a major crop type was wiped out by disease it should be possible to substitute a wild-type cousin plant for the crop that failed.
Biodiversity has a direct commercial value. Regions rich in biodiversity could be harvested in a sustainable manner and it is estimated that rain forests thus "farmed" would yield an income to the farmer at least as great as that temporarily available by clearing the forest.
Biodiversity is an essential aesthetic value. This would quickly become apparent if we severely impoverished the biodiversity of the Earth. In that event the consequent psychic pain experienced by humanity would be almost unendurable. Humankind evolved throughout most of its history amongst unfettered biodiversity. In our core we are in tune with wild fecundity and the natural contours of the Earth.
Why else does the sight of forest and stream strike us as beautiful, whereas a concrete jungle strikes us as ugly? Which of us would like to see large advertising hoardings dotted around our favourite beauty spot? And yet, would that not be less of a blow to our spirit than if we caused a living species to die in that beauty spot? Biodiversity not only feeds the body, it also feeds the soul.
William Reville is a senior lecturer in bio-chemistry and director of microscopy at UCC