The photo above is from the Refugio Amazonas Lodge, Puerto Maldonado, Peru.
Home to the highest concentration of life on Earth, the Amazon Rainforest covers around 2,300,000 square miles (6,000,000 square km) with the majority situated in Brazil (60% of the total) and the next highest amounts in Peru (14%) and Colombia (10%).
The highest diversity is in the western part of the Amazon Rainforest, in Ecuador, Peru, Colombia and western Brazil. In this area, the highest records of diversity are from the Yasuni National Park in Ecuador, which sits on the world’s largest untapped oil reserve threatening this remaining Eden. In 2006, half of Ecuador’s extracted oil went to the United States of America. To read more on the western Amazon Rainforest, see the article on the Peruvian Amazon Rainforest.
In the forests surrounding Iquitos (Peru), the world record for tree diversity was set by Alwyn Gentry in 1988 where he recorded 300 species of tree in one hectare of forest. Although its trees that seem to make up the rainforest, it’s really the flowering plants that make up the largest diversity component followed by the lianas (vines). In the animal kingdom, the beetles are the most species rich but it’s the ants that are most abundant.
The secrets of diversity are only now starting the be understood. Plants and trees in tropical rainforests have many species with overlapping living conditions. Usually, dominant species simply drive other species out of the area. The reason this doesn’t happen to a high extent in tropical forests has been linked to the existence of disease. Varying amounts of disease and tolerance in different areas means some usually-dominant plants are affected by disease to different degrees. This means some plants allow other species to grow that would otherwise be out-competed and erased.
The origin of vertebrate diversity in the Amazon Rainforest has been linked to a few different theories. These include landscape changes, frequent movements of rivers across evolutionary time creating population barriers, forest areas becoming isolated due to dry climatic periods during the Tertiary and Quaternary periods (Refuge theory), competitive interactions and isolation of species during the Pleistocene, and then steep environmental gradients occurring across a species’ distribution (parapatric speciation).
Global diversity is being threatened by several main drivers of change you can read in the article on biodiversity loss, but the main causes are habitat loss and over harvesting. The causes of biodiversity loss are all increased with population growth.
Examples of Diversity
Amphibian numbers are plummeting worldwide making people think the entire group is heading towards extinction. This is not helped by the lack of information on the species that exist in the Amazon and especially the eastern part of the rainforest, such as Brazil. Although, research by Azevedo-Ramos & Galatti (2002) indicates that unique and threatened species may be low in the Brazilian Amazon Rainforest.
As examples for amphibian diversity in the western Amazon from Peru, the Tambopata National Reserve and Manu National Park accessed from Puerto Maldonado have a little over 90 species in each protected area and there are just over 40 species in Bahuaja-Sonene National Park. Researchers found non-protected areas contained many different species and sometimes contain animals that are not present within the reserves themselves, which showed a need for formation of more protected areas within the Amazon Rainforest.
Within the mammals, it’s the rodents that dominate in terms of diversity. In total, they make up about 40% of all living mammal species. They are exceptionally adaptable. The above species, the pictured yellow crowned brush rat (Isothrix bistriata), is actually more closely related to guinea pigs than the usual rats we think of, the black rats (Rattus rattus), which can hold many different infectious pathogens in their blood stream.
We are currently a part of the sixth extinction event. Although climatic events have played a major role, the fact that mass extinctions have occurred on every continent humans have colonized shortly after human arrival cannot be ignored. Given the impressive devastation we have had and continue to have on the world’s habitats, especially tropical forests, it’s easy to see how humans are responsible for significant fractions of extinctions. To read updated stats and figures on Amazon deforestation in Brazil (containing the largest fraction of the Amazon), you can head over to Mongabay’s article on the Brazilian Amazon.
Would you know we are in an extinction event by watching television or reading the news? If you’re after a project, you could find out declining species estimates from site like the IUCN Redlist (International Union for Conservation of Nature list of endangered animals) and compare this with how often wild animals are mentioned in the news on television or in newspapers. See if you think public awareness should be increased or if it’s about right.