The earth supports approximately five to ten million species of plants and animals (IUCN, 1980), which have been the result of three billion years of evolution, including mutation, recombination and natural selection. Humans have been in existence for some two million years. Our prehistoric ancestors were a hunter of animals and gatherer of plants. As compared to the history of man, agriculture is a very recent innovation. It was only about 12 000 years ago that women probably started collecting plants from the wild and began cultivating them, leading to the birth of agriculture. For its continued growth, however, we have to protect the basic life support systems consisting of soil, water, flora and fauna and the atmosphere.

Walter G. Rosen coined the term biodiversity (or biological diversity) in 1985, and it refers to the variety of life forms and habitats found in a defined area. The Convention on Biological Diversity (CBD) defines biodiversity as ‘variability among living organisms from all sources, including inter alia, terrestrial, marine and other aquatic ecosystems; this includes diversity within species (intraspecific) as well as among species (interspecific) and ecosystems’.

Plant genetic resources are the most precious but very vulnerable and irreplaceable natural assets of a nation. They have evolved through thousands of years of natural and human selection—both conscious and subconscious. However, certain developments of relatively recent times are posing great threats to the basic life support systems that protect rich plant diversity.

Threats to Biodiversity

The chief causes for the disappearance of plant species are as follows: