Distribution and abundance of life in the tropics
According to my college textbook, ecology is the scientific study of the interactions that determine the distribution and abundance of organisms. This is a really interesting subject and it becomes even more interesting when you ask why most of the species on earth are concentrated in the tropics. The discussion can start by the fact that geographic areas has a fundamental role over biodiversity, and that’s why species diversity in the tropical zones is so much greater in respect to the temperate regions. It’s sad to realize that even when we want to, richness is not distributed equal.
The geographic area influences directly with variables such as temperature, humidity and luminosity that determine the tolerance limits of the species. We can also find that the tropics hosts a huge array of biodiversity because these variables are more stable in the majority of cases. Also life has been able to diversify in the tropics due to the abscense of great geological perturbations, like the glaciations that affect the temperate zones. When a glaciation strikes, it leaves almost nothing and life has to start again with processes of primary succession.
Now from studies in ecology we know that most species have a very narrow distribution, and that they’re not abundant. The contrary is true for widespread species that have high population densities. For a mundane example, rats are superabundant and you can find them everywhere (chances are there is one of them watching you right now)
I mention this ecological observation so you can understand better what is happening in the tropics. We have tons of different species, but they are distributed in really specific areas. That is why deforesting say, 10 hectares of tropical rain forest is devasting. You could easily have lost some species in that process, because they’re distribution is so limited. Deforestation in a tropical rain forest is a genocide to nature.