The rainy season in tropical forests
18 December 2020 (751 visits)The climate of South America’s rainforests, including the forests in southeastern Peru where we operate our ecotourism itineraries, is characterized by year-round heat and humidity, and it is rainfall that defines seasonal variation in the Amazon’s forests.
Across the year, temperatures in the lowland forests of Peru’s Madre de Dios region average around 25 centigrade (77 Fahrenheit). As its name implies, there is no true dry season in the rainforest. It can rain at any time of year, and seasons are defined by the frequency and intensity of rainfall.
When we speak of the “dry season” and “rainy season” in the lowland forests of the Amazon basin, what we are really talking about is the seasonal variation that creates those times of the year when the rainiest and least rainy months are experienced.
In the biologically diverse Madre de Dios region where we operate our ecotourism tours within our own Tambopata Ecolodge Private Conservation Area and the protected Tambopata National Reserve, the southern hemisphere summer months, from mid-December to late March, are when the heaviest rains are experienced. During this period, afternoon downpours are common, with the heaviest rains coming in January and February. However, tropical rainstorms tend to be short-lived, meaning that even during the rainiest months it is unusual for ecotourism excursions and wildlife observation activities to be canceled due to rain.
While many travelers choose to visit the rainforests of Peru from April to December, during those months when less rainfall is experienced, and which also coincide with the northern hemisphere summer vacation season, there are many reasons to visit tropical forests during the rainier months of the year. When the heaviest rains arrive, many tree and plant species produce their fruits, and this in turn leads to greater activity among many species of birds and mammals, including monkeys.
It is the incredible abundance and diversity of rainforest plant species that has enabled the emergence of all the many thousands of insect, mammal, reptile and other species that inhabit these forests. And while trees and other plants play an essential role as the planet’s lungs, through oxygen production and CO2 absorption, those same species of flora also regulate the climate of the rainforest, creating the “dry” and “wet” season cycle upon which life in tropical forests depends.
Biologists have found that in rainforests, with their dense foliage and big trees that soar to heights in excess of thirty meters, transpiration, the process through which plants and trees release moisture into the atmosphere, accounts for much of the water that falls back onto the forest understory.
In addition to studies –aided by satellite technology- of the converging winds that influence seasonal variation in the equatorial region, experts have also determined that forests use increased leafage as a mechanism to trigger seasonal variation in the rainforest. Leaf increment in the dry season leads to an increase in water vapor that rises and cools to form clouds. In this way, the moisture released as water vapor from trees acts as a kind of continent-wide pump, providing the water required to maintain consistent rainfall patterns across the entire Amazon basin. In this way, trees might be said to be creating and maintaining their own annual rainy season, along with the climatological stability that has enabled the world’s rainforests and the countless species they harbor to evolve for more than 120 million years.
