The variety of living organisms existing on the Earth is called biodiversity.The following consequences can occur if biodiversity of an area is not preserved:It can result in environmental disasters such as floods, forest fires and hurricanes.It can bring about soil erosion and desertification as a result of deforestation.It can bring about large scale habitat losses and extinction of vulnerable animal and plant species.The continued loss of forests and the destruction of watersheds reduces the quality and availability of water supplied for household use and agriculture. It results in sudden climatic changes and instability in the functioning of the ecosystem. 
If biodiversity is not preserved we can lost some special variety ....which may cause complete disappearance of that variety