What is the concept behind the word "biodiversity"? Although relatively recently coined in the early 1990s from combining the words biological and diversity it is already in extensive use, not only in the halls of natural sciences academia but also in the political arena and the public domain.
Probably the most significant political definition of biodiversity to date is the definition of biological diversity found in the United Nations Convention of Biological Diversity, proposed in 1992 and ratified in 1993. In its definition of terms section, it defines biological diversity as "the variability among living organisms from all sources and the ecological complexes of which they are part". It gives an inter alia list of sources and closes by clarifying that this diversity occurs within as well as between species and of ecosystems.
Various ecological and environmental scientists however, give us a variety of definitions for biodiversity. The following are a few of the more prominent.
Kupecek defines biodiversity as the "variety of life on Earth and the natural patterns it forms" in an E&D File he compiled for the United Nations Non-governmental Liaison Service in 1995. His clarification of this embodies the commonly accepted genes, species and ecosystems model, which could be considered to follow logically from the closing phrase of the UN's CBD definition. He has however, now limited biodiversity to life on Earth; the CBD definition was open to extraterrestrial life, whether intentionally or not. Becher in 1998 essentially sticks to this concept, defining biodiversity in terms of genes, taxonomic species and ecological (ecosystem) diversity.
Gaston and Spicer, also in 1998, in their "Introduction to Biodiversity" recognize the UN CDB definition as the most important of the 12 formal published definitions then extant. They expand the concept of biodiversity being the variety of life to include a time element; all organisms that have ever lived as well as those that do now. They also recognize and highlight the arbitrariness of the genes, species and ecosystems model, discussing the nested hierarchical structure of the biological world. They suggest as an example, that a chosen three levels could as easily have been nucleotides, populations and biomes.
Grumbine in 1992 placed more emphasis on the macro rather than the micro, recognizing genes and species as elements but focusing more on the higher levels of the hierarchical structure: communities, ecosystems, landscapes and the whole biosphere. He writes in terms of ecosystem components, structures and functions and has made the statement that "to understand biodiversity, one has to think like a mountain."
In "The Life Industry" published in 1996, Baumann, Bell, Koechlin and Pimbert perceive biodiversity as much more than just genes, seeing it as a "web of relationships" that ensures balance and sustainability in ecosystems. They stress that it is one of the planet's life-support systems, promoting its importance to human continuance.
Perlman and Adelson in "Biodiversity: exploring values and priorities in conservation" published in 1997 reject the genes, species and ecosystems model on the basis of both practicality and theory. They refer to the complexity and extensiveness of the Human Genome Project to show the impossibility of measuring the genetic variation in a cubic meter of forest, let alone the biosphere in its entirety. They would prefer to label that as "Life on Earth" and apply the term biodiversity to specific, quantifiable uses.
They consider this to already be the case in practicable terms, an example they give is that conservation decision makers use biodiversity when they are speaking of a specific subset of life for a specific purpose. This use of biodiversity would however, seem to move more towards the political than the scientific, using the term as a catchphrase to attract public attention and support. On the theoretical side, like Gaston and Spicer after them, they refer to the arbitrariness of selecting genes, species and ecosystems, offering alleles, populations and landscapes as equally valid.