Decrease in species diversity in tropical countries is mainly due to
(a) Urbanization
(b) Pollution
(c) Deforestation
(d) Soil erosion

Hint: The various types of species are present in different areas according to their nature of the habitat. They mostly live in the areas that are surrounded by the trees which are getting depleted due to the continuous cutting of trees.

Complete answer:
The species diversity is the large number of variable species found in a particular area or the community. This species diversity is now decreasing at a very high rate due to the deforestation that is taking place in the forest area which is the natural habitat of many species.
- The species diversity includes a large number of variable species. species richness, and diversity in the phylogeny and the taxonomy of the species.
- The species richness refers to the number of different species present in an area.
- The genetic relationship between different species can be studied through the taxonomic and the phylogenetic diversity of species.
- The process of deforestation refers to the clearing of the land by cutting the forests leading to the land which is of no use and this results in urbanization.
- The deforestation will result in a decrease in soil fertility, destruction of the natural habitats of several species.
- It is done to construct buildings, form ranches, etc which will lead to an increase in pollution.
- Its extremity may lead to desertification, changes in the climatic conditions, loss of biodiversity, etc.
- The Nature Scientific published their reports and stated that if deforestation continues at this rate for the next 20 - 40 years then it will lead to the extinction of the humans on the earth.
So, the correct answer is ‘Deforestation’.

Note: Urbanization is the process of increasing the amount of population in the urban areas and the amount of population is decreasing in the rural areas leading to the change in the lifestyle and environment. Pollution is the process of the addition of harmful contaminants in the natural environment which leads to the change in the environment and causes a great loss of biodiversity. Soil erosion is the process of the degradation of the upper layer of soil making it unfit for the cultivation of crops.