A Matter of Life and Death

Biodiversity is the blanket term for natural biological wealth - that vast array of nonhuman organisms on the planet that underpin human life. Paul Ehrlich, Professor of Biological Science at Stanford University, California, and his wife Anne, warn that "extrapolation of current trends in reduction of biodiversity implies a denouement of civilisation within the next 100 years comparable to a nuclear winter". They view it as the most serious single environmental peril facing civilisation. Worldwatch Paper No. 108 says:

Biodiversity is the variety of the world's organisms, including their genetic diversity and the assemblages they form. It is the blanket term for natural biological wealth that undergirds human life and wellbeing.

The breadth of the concept reflects the interrelatedness of genes, species and ecosystems. Because genes are the components of species, and species are the components of ecosystems, altering the makeup of any level of this hierarchy can change the others... Species are central to the concept of biodiversity.

Biodiversity has so far been viewed as a subject in its own right - an attitude which does not reflect the importance of understanding how humans have affected biodiversity in the past, and how they might affect it in the future. Human activities and impacts are being treated from a narrow biological perspective as interferences with biophysical systems, rather than as continuing human intervention over many thousands of years. Viewing the subject in this broader context of human ecology promotes understanding of the complex interactions between natural and human systems.

The International Convention on Biodiversity signed in June 1992 at the Earth Summit in Rio is based on the narrower view. Emphasis is on documenting species and habitats, and on understanding better the biological functions and values of biodiversity. This will do little more than document in more detail the disappearance of species and destruction of habitat, according to Nelson and Serafin, writing in Ambio.

Biodiversity cannot be maintained just by a limited number of parks and wilderness areas. Assessments and monitoring must document the different ways people value, use, manage and affect biodiversity in their day-to-day lives. Conservation efforts must be based on long-term support and participation of people and governments.

Paul and Anne Ehrlich emphasise that plants, animals and organisms help to supply human beings with an array of "free ecosystem services", without which civilisation could not survive. These include climate and water; soils, nutrients and wastes; biochemical cycles; and pest control and pollination. The Erlichs maintain that it is indisputable that life has played a major role in shaping conditions near Earth's surface; that Earth itself is alive is indisputably wrong.

Biodiversity is a resource for which there is no possible substitute. Its loss is irrevocable in any timescale relevant to human society.

As the Erlichs point out, soils are among the most threatened ecosystems worldwide, and the most needed by living creatures. Soils are complex ecosystems. "The living components of soil ecosystems are crucial to their fertility... Earthworms are vital as they loosen soil and allow oxygen and water to penetrate it." Other creatures that help give soils their texture and fertility include insects, mites and millipedes. In the soils under each square metre of forest in North Carolina were found 35,000 tiny creatures invisible to the human eye. A gram of forest soil may contain 100,000 yeast cells and 50,000 bits of fungus; and a gram of fertile soil over 2.5 billion bacteria.

It is not the number of soil organisms that is important, so much as the roles they play in soil ecosystems. These include conversion of the nutrients nitrogen, phosphorous and sulphur into forms useable by the higher plants people depend on. Organisms help to create soils - a process that starts with the weathering of underlying rock. Small organisms decompose organic matter like leaves and animal droppings, releasing carbon dioxide and water into the soil, and leaving a residue that makes up the key elements of compost.

Organisms are crucial to the maintenance of soil fertility and soil conservation. Agricultural chemicals kill organisms and cause sterile soils and loss of natural fertility.

To biologists, perhaps the most ominous concern arising from the extinction of species is the human impact on the planet's total supply of energy produced in photosynthesis - global net primary production (NPP). NPP is the energy fixed by photosynthesis, minus that required by the plants themselves. Almost 40% of all potential NPP generated on land is directly consumed, and forgone, because of human activity. People reduce potential NPP by converting highly productive natural ecosystems into less productive ones: tropical forests to pastures; prairies to farms; and farms to urban development.

Since probably over 95% of species exist on land, the 40% use of NPP by humans goes far to explaining the extinction crisis. The amount of energy available to support the millions of other kinds of animals on Earth has thus been drastically reduced. Plant diversity is also being reduced, from the loss of land with suitable soils and climate.

The amount of NPP available on land to support further growth and development is now close to its limits. As the Ehrlichs warn: "If anything remotely resembling the Brundtland population/economic growth scenario is played out, we can kiss goodbye to most of the world's biodiversity, and perhaps civilisation along with it."

This article draws on Paper 108, 'Life Support: Conserving Biodiversity', Worldwatch Institute and Ambio, May 1992.