Biodiversity or biological diversity is variety and variability among living organism and ecological complexes in which they occur. This concept can be subdivided into three levels.
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(i) Genetic diversity: Biodiversity includes the genetic variation within species. It is among separated population and among individuals within single population.
(ii) Species diversity: Biodiversity includes the full range of species on earth. It is from micro organism through the multi-cellular kingdom of plants, animals and fungi.
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(iii) Ecological diversity: Biodiversity includes variations in community level or in ecosystem level in which living organism exist.
Direct threats to’ biodiversity includes:
(1) Loss of genetic variation:
Variations in the genes or organisms lead to differences within the species and between the species. These variations are fundamental to the future evaluation of all species, creating biological diversity. Today the genetic Varity within species is being eroded at an alarming rate over increasing number of species rich ecosystems are disrupted, mutilated or destroyed. This is due to shifting cultivation, forest clearance, direct exploitation of forest, construction of road and railways. The conservation of population needs the conservation of genetic variation.
(2) Loss of individual species:
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Threats may also be at the individual species level due to loss, disruption or destruction of habitats. Many terrestrial species and declining seriously. The change in the practice of agriculture by the use of herbicides and fertilizer there is a decline in farmland plants.
(3) Native species, their conservation:
The native and endemic species are threatened to a small region land found nowhere else. Many of such species are on the verge of extinction.
(4) Loss of biodiversity by monocultures:
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Biodiversity discourages the use of monocultures since these are highly susceptible to attack pests and diseases as compared to natural forest ecosystem. Extinction of plant and animals occur after a long period of decline. A combination of natural breeding and monoculture is required for conservative of species.
(5) Loss of habitats:
Habitat in which the species live and the loss of such habitat world result in rapid decline of the species. Such habitats reduced its quality through the pollution change, disturbance, neglect, over-exploitation, introduction of non-native species, and the use wastelands.