Rosen when he organized what is now known as the National Forum on Biodiversity which was held in 1986 in Washington DC. In 1987, the US Office of Technology Assessment (OTA) released a report titled 'Technologies for Maintaining Biological Diversity' in which they begin with the question "What is biological diversity?" “Biological diversity refers to the variety and variability of living organisms and the ecological complexes in which they are found.” In fact, they also defined diversity as “the number of different elements and their relative frequency”. They also wanted to highlight the fact that diversity varies within ecosystems, species and genetic levels. In fact, ecosystem diversity, species diversity, genetic diversity can vary in many different ways. In the OTA report, they provide the example of ecosystem diversity by stating that a landscape interspersed with grasslands, cropland, and woodland, for example, has more diversity than a landscape with most of the woodland converted to grassland and farmland cultivated. From this example we can see that biodiversity is a complex concept and for this reason it is difficult to explain. Aware of this, we will conclude this section by giving a very broad definition of biodiversity as "life on Earth, the variety of living organisms, their habitats and the interaction between them" (DAC, 2010) knowing that no definition can fully cover the complex concept that is