Nature and Biodiversity

These trees in the Amazon make their own rain

An aerial view shows the Amazon rainforest at the Bom Futuro National Forest near Rio Pardo in Porto Velho, Rondonia State, Brazil, September 3, 2015. The town of Rio Pardo, a settlement of about 4,000 people in the Amazon rainforest, rises where only jungle stood less than a quarter of a century ago. Loggers first cleared the forest followed by ranchers and farmers, then small merchants and prospectors. Brazil's government has stated a goal of eliminating illegal deforestation, but enforcing the law in remote corners like Rio Pardo is far from easy. REUTERS/Nacho Doce   TPX IMAGES OF THE DAYPICTURE 1 OF 40 FOR WIDER IMAGE STORY "EARTHPRINTS: RIO PARDO" SEARCH"EARTHPRINTS PARDO" FOR ALL IMAGES   - RTX1UUU2

Academics believe that the Amazon rainforest goes one step further than transpiration. Image: REUTERS/Nacho Doce

John McKenna
Senior Writer, Forum Agenda
Share:
Our Impact
What's the World Economic Forum doing to accelerate action on Nature and Biodiversity?
The Big Picture
Explore and monitor how Future of the Environment is affecting economies, industries and global issues
A hand holding a looking glass by a lake
Crowdsource Innovation
Get involved with our crowdsourced digital platform to deliver impact at scale
Stay up to date:

Future of the Environment

In the Amazon rainforest, the rainy season begins two to three months before everywhere else in Latin America.

This phenomenon puzzled scientists.

Now one team of researchers in the US believe they have the answer: the trees make their own rain.

Transpiration is a well-known part of photosynthesis, where moisture is drawn up by plant roots, gathers on leaves and then evaporates into the atmosphere.

However, academics at the University of California believe that the Amazon rainforest goes one step further: the sheer amount of moisture released into the atmosphere by transpiration helps make it rain.

Trees pump so much moisture into the air that it changes the atmosphere, triggering a shift in wind patterns that brings in more moisture from the ocean.

This means it can start raining in the Amazon rainforest as much as three months before the arrival of the weather system known as the Intertropical Convergence Zone (ICZ), which is responsible for the region’s rainy season.

Image: REUTERS/Bruno Kelly

Viewed from space

University of California climate scientist Rong Fu and her colleagues used NASA’s Aura satellite to observe water vapours over the Amazon rainforest.

She told Science magazine that the satellite showed vapours consistent with transpiration, rather than evaporation.

This is because the differences in the processes means the water from transpiration is heavier than that from evaporation.

Another clue that transpiration was behind the heavier vapours was that they were most prevalent at the end of the dry season, when photosynthesis is at its strongest.

As the tree-induced rain clouds release their own rain, they warm up the atmosphere. This encourages circulation, which in turn brings in more moisture from the ocean.

Vital climate

With previous research having shown that the Amazon rainforest also releases aerosols that encourage the formation of rainclouds, it is clear that plants are anything but a passive recipient of moisture in the atmosphere.

This adds yet more credibility to the battle against deforestation.

Scientists and environmental campaigners have long championed rainforests like the Amazon as the lungs of the planet, breathing in carbon dioxide and breathing out oxygen.

This helps cut the amount of carbon dioxide in the atmosphere, which is one of the greenhouse gases responsible for trapping the sun’s heat and warming the planet.

Research by Fu and others shows that rainforests not only have an indirect effect on planet temperatures, but can also directly cool their immediate environment.

The cutting down of these rainforests to make way for agricultural land has been described as one of the greatest challenges facing humanity.

Image: REUTERS/Nacho Doce

Unfortunately, data released earlier this year showed that deforestation in the Amazon is again on the rise.

The Brazilian government is bringing together businesses and non-profits in an attempt to reverse the trend.

This collaboration is also being carried out on a global scale through initiatives such as the Tropical Forest Alliance 2020.

Have you read?
Loading...
Don't miss any update on this topic

Create a free account and access your personalized content collection with our latest publications and analyses.

Sign up for free

License and Republishing

World Economic Forum articles may be republished in accordance with the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License, and in accordance with our Terms of Use.

The views expressed in this article are those of the author alone and not the World Economic Forum.

Related topics:
Nature and BiodiversityClimate Action
Share:
World Economic Forum logo
Global Agenda

The Agenda Weekly

A weekly update of the most important issues driving the global agenda

Subscribe today

You can unsubscribe at any time using the link in our emails. For more details, review our privacy policy.

The Amazon is close to the point of no return. COP16 is a critical opportunity to act

Kirsten Schuijt and Maria Susana Muhamad González

October 11, 2024

About us

Engage with us

  • Sign in
  • Partner with us
  • Become a member
  • Sign up for our press releases
  • Subscribe to our newsletters
  • Contact us

Quick links

Language editions

Privacy Policy & Terms of Service

Sitemap

© 2024 World Economic Forum