By Ranil Senanayake –

Dr. Ranil Senanayake

The word biodiversity is gaining both interest and currency worldwide as a result of the Convention on Biological Diversity (CBD), an internationally binding set of agreements ratified by most nations on this planet. The articles of the CBD are legally binding and used today to address many aspects of nature and the role that biodiversity plays in natural processes. Thus it is critical to appreciate the true nature of biodiversity and what role it has in our future.

Biodiversity is often expressed as ‘the measure of the variability of living organisms at any spatio-temporal point’, i.e. the number of different species at any place at any given time. It does not mean wild, endemic, rare or even native, it is merely a measure of diversity of life at any place. This measure has various meanings, from indicating a potential for conservation to indicating changes in the environment. It also significant in affecting the way natural cycles of substances such as carbon, oxygen or water function in the biosphere. The conservation of biodiversity refers to the sustaining  these patterns of life.

But in considering the management of biodiversity on any landscape, it has to be evaluated on the stated goals for that land. If conservation is the goal, exotic species are an anathema and have to be removed. If production or human habitation is the goal, exotic species are an important component of the local biodiversity. Therefore, biodiversity on any landscape must be measured as two distinct states, natural and anthropogenic

Natural biodiversity exists as a product of a long history of interactions between organisms, landscape and climate at any given place. It is high in some ecosystems and low in others. The natural biodiversity of stable ecosystems provide the indicators and measurements that define the sustainable state for that ecosystem. A loss of biodiversity, means a loss of the variety of organisms that comprise that ecosystem and suggests disturbance and unstable states.

Anthropogenic ecosystems are those influenced by humans in such a manner that their natural evolutionary processes are massively disrupted. Most rural land other than natural ecosystems are regions where exotic species replace native species to some degree. However all agricultural and other anthropogenic land use systems, also have a biodiversity measure or value as represented by its biological components. If the frequency or intensity of disturbance in any area is high there is a loss of biodiversity. If the frequency and intensity of disturbance is low there is a corresponding gain in biodiversity. This gain is obtained through a hybrid population of natural and exotic organisms. In traditional societies there is often a sophisticated knowledge of the use of native biodiversity. There is a correlation between the increase in biodiversity and establishment of stability in traditional systems.

This relationship also holds in anthropogenic ecosystems such as modern agricultural fields where the development of biodiversity demonstrates clear links to the development of sustainability.

Thus, biodiversity provides a very effective summary of the prevailing ecological condition. Studies on agricultural diversity suggest that high measures of diversity are often correlated with environmental stability. A rapid loss in biodiversity, for instance, suggests a loss in ecological stability. Therefore, the measure of biodiversity is a useful indicator of the health of an ecosystem.

The pattern of increasing ecological stability with increasing diversity in land use is also corroborated by studies of traditional land managers, whose management systems are sustainable and conserve a much higher level of biodiversity than conventional responses. High levels of diversity in the agricultural field produce positive effects of biological control, spread the risk in marketing and production, as well as distributing labor needs to fit with a single family unit. These traditional methods of land management have much to contribute to biodiversity management.

A major problem in the setting of biodiversity or measuring  the number of species at a given point is the question of scale. For instance, alpha diversity will tend to show a series of peaks and troughs if an ecosystem is measured along a scalar gradient. A clump of grass extracted from a forest meadow provides an illustration. If roots of  the clump are examined microscopically it will yield  high biodiversity values, in bacteria, actinomycetes, fungi etc. As we expand scale to reflect the plants in the clump at the scale of the grass plant, it will have low biodiversity value, again at the scale of the meadow the grass will be a component of a system with high biodiversity with other plants, while at a landscape scale, of forest and meadow, the system can have low diversity.

This suggests the need for an index that accommodates the phenomenon of scale, perhaps a measure of some indicator species that confirm the condition of the cascade of smaller ecosystems which is needed by that particular species for its survival may be of utility. Finally, all ecosystems are temporal in composition. They are constantly changing in time depending on the organisms that comprise it and their well-being. Thus, all ecosystem or biodiversity values attributed to a place, must be time bound.