In the 10 short minutes it takes you to step off the canoe and walk up to the lodges, you’ll likely have passed over 300 species of plants and insects and heard the calls of dozens of varieties of birds.
Welcome to the Amazon.
There are more species of butterflies here in Tambopata than all of North America and Europe combined. One tree may contain over a thousand species of insects, many of which are new species to science. And it just takes one look at the “Birds of Peru” book to realize we are in an area with more species of birds than anywhere else in the world. This is one of the most biodiverse places on earth- but scientists are still trying to figure exactly out why.
There are a multitude of effects that have interacted for millions of years to create the Amazon as it is today and we are just beginning to understand them. One of these that you’ll be quick to notice: the weather. It is hot, and it is humid. Warmth and ample access to water allow organisms to spend less time acquiring resources (i.e. looking for water or warmth), and more time reproducing and interacting with each other. These complex interactions are part of what can cause new species to specialize and form over time.
Additionally, studies have shown that the higher average temperature here causes a slightly higher rate in genetic mutations. These mutations are fundamental to creating variety within a species, which, over time and with a little help from geology or natural selection, can result in one species having two forms that are so unalike that they have become two. In one study, tropical plants were found to evolve twice as fast as colder weather plants, meaning they had twice the opportunities for evolving into new species.
Recent studies have also shown that fungi and plants in the Amazon actually contribute to creating more rainfall via a nighttime release of certain salts into the air. Meaning, the diversity of organisms that benefit from rainfall are actually causing more rainfall. This rain helps as not only a supply of one of life’s essential ingredients but also helps erode the fertile, volcanic Andes Mountains, sending a steady supply of fertilizing minerals into the Amazon basin by way of rivers.
Another concept that scientists think plays a role in high biodiversity is that rainforests are known to be ‘harborers,’ not just creators, of biodiversity: they have remained relatively unchanged as hot, humid incubators of diversity for millions of years. Other environments that could go through large historical changes in climate may wipe out species that can’t adapt well, but rainforests tend to keep many species around for the long-haul.
Within this blanket of forests lie differences in the soil composition, the altitude, the seasonal flooding, and other factors that allow one area of the Amazon to be quite different to another, increasing diversity again. But if you take a closer look, you’ll see that within these broad scale habitats there are seemingly endless microhabitats. From a pool of water in a bromeliad, to the a hole in the side of a palm tree, to even the fur on the back of a sloth, high rates of evolution have allowed species to become extremely specialized in where, and how, they live. This again is a major factor in the high biodiversity: where one tree in North America may have dozens of species living on it, high rates of evolution and specialization allow on tree in the tropics to potentially have thousands.
This specialization of species is one of the major factors that makes the Amazon so impressive on one hand, and vulnerable on the other. Wiping out a unique area of forest may potentially cause several entire species to go extinct. Human-created changes in the forest may cause specialized species to be exposed to conditions that are starkly different than what they have experienced over the last several million years, leaving them in a non-ideal environment that would give them a lower likelihood of survival.
So, while we enjoy the biodiversity that surrounds us, better understanding the causes that have interacted over millions of years will allow us to respect it, and hopefully protect it, too.