TROPICAL RAINFORESTS: Disappearing Opportunities
 Home
 What's New
 About
 Rainforests
   Mission
   Introduction
   Characteristics
   Biodiversity
   The Canopy
   Forest Floor
   Forest Waters
   Indigenous People
   Deforestation
   Consequences
   Saving Rainforests
   Amazon rainforest
   Borneo rainforest
   Congo rainforest
   Country Profiles
   Statistics
   Works Cited
   For Kids
   For Teachers
   Photos/Images
   Expert Interviews
   Rainforest News
  Forest data
   Global deforestation
   Tropical deforestation
   By country
   Deforestation charts
   Regional forest data
   Deforestation drivers
 XML Feeds
 Other Languages
   Chinese
   French
   German
   Japanese
   Portuguese
   Spanish
 Pictures
 Books
 Links
 Newsletter
 Education
 Mongabay Sites
   Kids' site
   Travel Tips
   Tropical Fish
   Madagascar
 Contact



About this site
Providing tropical forest news, statistics, photos, and information, rainforests.mongabay.com is the world's most popular rainforest site. [more]



Weekly Newsletter
Enter your email:
Mongabay will never distribute your email address or send spam.





Share

Rainforest canopy in the late afternoon. (Photo by R. Butler)

GLOBAL CONSEQUENCES

Tropical rainforests play a vital role in the functioning of the planet's natural systems. The forests regulate local and global weather through their absorption and creation of rainfall and their exchange of atmospheric gases. For example, the Amazon alone creates 50-80 percent of its own rainfall through transpiration. Cutting the rainforests changes the reflectivity of the earth's surface, which affects global weather by altering wind and ocean current patterns, and changes rainfall distribution. If the forests continue to be destroyed, global weather patterns may become more unstable and extreme.



CLIMATIC ROLE OF FORESTS

As previously discussed, tropical rainforests play a vital role in local climate regulation by their interaction with water cycles. However, rainforests also have a significant effect on global weather. Rainforests, like all forms of vegetation, affect the "surface albedo" or reflectivity of a surface by absorbing more heat than bare soil. Norman Myers (1997) explains,
    Much of the energy that converts surface moisture into water vapor comes from the sun's radiational heating of the land surface. The energy thus depends on surface albedo, or relevant degree of reflectant "shininess" of the land surface (Gash and Shuttleworth 1992). In turn, the albedo depends on the vegetation, which absorbs more heat than does bare soil. Over thick vegetation, vigorous thermal currents take moisture (provided by the same plant cover) up into the atmosphere, where it condenses as rain. Because of its influence on convection patterns and wind currents, and hence on rainfall regimes, the albedo effect constitutes a basic factor in controlling climate.
The loss of forest vegetative cover means less heat absorption translating to less moisture being taken up into the atmosphere.

Rainfall is also affected when forest-clearing fires create air pollution and release tiny particles, known as aerosols, into the atmosphere. While aerosols can both heat and cool the air, depending on their size, shape, and color, high concentrations of biomass-burning aerosols directly impact local climate by increasing cloud formation but decreasing rainfall, according to research by NASA. In areas with lots of smoke, "cloud droplets form around the aerosol particles, but may never grow large enough to fall as rain," say researchers with NASA's Goddard Space Flight Center who studied the effect. Thus large forest fires have the effect of further reducing rainfall, leaving burned areas more prone to dryness and future fires.

In the long run, these changes explain why deforested regions may experience a decline in rainfall.

Tropical deforestation can also affect weather in other parts of the world. A 2005 study by NASA found that deforestation in the Amazon region of South America influences rainfall from Mexico to Texas and in the Gulf of Mexico, while forest loss in Central Africa affects precipitation patterns in the upper and lower U.S Midwest. Similarly, deforestation in Southeast Asia was found to impact rainfall in China and the Balkan Peninsula.

Soybeans may worsen drought in the Amazon rainforest
Expansion of agriculture in the Amazon may impact climate
Amazon drought extends into second year
Will Amazon drought worsen in 2007?
Changes in forest cover could significantly affect climate
Temperate forests may worsen global warming


Review questions:
  • Why does local rainfall decline with deforestation?

[print version | spanish | french | portuguese | chinese | japanese]


Continued: Atmospheric Role of Forests


This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.




Other pages in this section:
Consequences of Deforestation
Erosion
Loss of Renewable Resources
Atmospheric Role
- - - - -
References
References
References
References
References
Local Climate Regulation
Loss of Species, Disease
Climactic Role
Extinction
- - - - -
Kids version of this section
- Why are rainforests important?
- Climate
- Home to wildlife
- Water cycle
- Erosion control
- Extinction




Recent news

Fossil fuel subsidies "bringing us closer to irreversible climate change"
(11/06/2009) The Green Economy Coalition is urging G20 finance ministers to rapidly put an end to fossil fuel subsidies. In a letter to the ministers the coalition argues that these subsidies are contributing directly to climate change and making it difficult for the world to transition to a greener economy.


NASA satellite image reveals extent of drought in East Africa
(11/05/2009) A new image from NASA shows the severity of the drought in East Africa, which impacted Tanzania, Kenya, Ethiopia, and Somalia.


Governments, public failing to save world's species
(11/04/2009) According to the International Union for the Conservation of Nature's (IUCN) 2008 report, released yesterday, 36 percent of the total species evaluated by the organization are threatened with extinction. If one adds the species classified as Near Threatened, the percentage jumps to 44 percent—nearly half.


Emissions from deforestation overestimated; 12% rather than 17%
(11/04/2009) Greenhouse gas emissions from deforestation are lower than previously believed, according to a new study published in Nature Geoscience. The findings mean that developing countries may see less money under Reducing Emissions from Deforestation and Degradation, a proposed climate change mitigation mechanism.


Gucci drops APP in pledge to save rainforests
(11/03/2009) One of the world's largest and most prestigious fashion brands has stated it will stop sourcing paper from Indonesian forests and will drop Asia Pulp and Paper (APP) as a supplier, which has become notorious for tropical deforestation. The move comes after pressure from the Rainforest Action Network (RAN) on the fashion industry to stop sourcing paper from threatened rainforests for their shopping bags.



More news on climate change


More rainforest news
what's new | rainforests home | for kids | help | madagascar | search | about | languages | contact



Copyright Rhett Butler 1994-2009

"Rainforest" is used interchangeably with "rain forest" on this site. "Jungle" is generally not used.