<p>For rain to fall, water vapour must exist in sufficient quantities in the atmosphere. The main source of atmospheric water vapour is evaporation from oceans. However, evaporation from large bodies of water such as lakes and dams also contributes. Another <a href="http://rainforests.mongabay.com/0906.htm" rel="nofollow">significant contributor</a>, on a local level, is <a href="http://water.usgs.gov/edu/watercycletranspiration.html" rel="nofollow">transpiration</a> from <a href="http://blog.cifor.org/10316/make-it-rain-planting-forests-to-help-drought-stricken-regions" rel="nofollow">forests</a>.</p>

<blockquote>
  <p>the Amazon alone creates 50-80 percent of its own rainfall through transpiration</p>
</blockquote>

<p>Removing forests has </p>

<blockquote>
  <p>the biggest impact on cross-continental transport of water vapour</p>
</blockquote>

<p>Removal of trees from an area of forest immediately stops transpiration in the that area. This causes less rain to fall in that area. It changes the way light is reflected from the Earth's surface, which changes the heating characteristics of the ground, which changes air movements. It will also have an influence on ground water levels and depending on local geology can bring salt to the surface causing salt scars and eventually desertification.</p>

CC BY-SA 3.0
2015-05-06T04:24:31.163Z
Trees can also emit particulates or VOCs around which water vapor coalesces into rainfall.
cphlewis
CC BY-SA 3.0
2015-05-06T09:16:56.267Z
So the historical saying that "Forest bring rain" is not totally false?
Sab
CC BY-SA 3.0
2015-05-06T12:08:22.163Z
It is not just forests. Large fields of corn cause a lot of evaporation (transpiration) - I have heard it said that it is no coincidence that "tornado alley" and the corn belt have such overlap...
Floris
CC BY-SA 3.0
2015-05-06T14:48:11.850Z
Also now there is research showing that pollen can influence cloud formation.  http://onlinelibrary.wiley.com/doi/10.1002/2015GL064060/abstract
f.thorpe
CC BY-SA 3.0
2015-05-06T02:07:00.710Z
2016-01-08T21:40:28.883Z
2016-01-08T21:40:28.883Z
Fred
<p>I know that forests can change the local temperature, but what about rainfall?.  Do forests affect rainfall in their region? I have read that if a forest is very big, it can cause minor changes to local rainfall and temperature.  How does that work?</p>

<climate><land-surface><forest><rainfall>
Do forests affect local rainfall and climate significantly?
Sab
# Do forests affect local rainfall and climate significantly?

(Asked by: username_0 on 2015-05-05)

I know that forests can change the local temperature, but what about rainfall?. Do forests affect rainfall in their region? I have read that if a forest is very big, it can cause minor changes to local rainfall and temperature. How does that work?

**Tags:** climate, land-surface, forest, rainfall


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## 1 answers

### Answer by username_1 on 2015-05-06. Score: 11 | Accepted answer

For rain to fall, water vapour must exist in sufficient quantities in the atmosphere. The main source of atmospheric water vapour is evaporation from oceans. However, evaporation from large bodies of water such as lakes and dams also contributes. Another [significant contributor](http://rainforests.mongabay.com/0906.htm), on a local level, is [transpiration](http://water.usgs.gov/edu/watercycletranspiration.html) from [forests](http://blog.cifor.org/10316/make-it-rain-planting-forests-to-help-drought-stricken-regions).

> the Amazon alone creates 50-80 percent of its own rainfall through transpiration

Removing forests has

> the biggest impact on cross-continental transport of water vapour

Removal of trees from an area of forest immediately stops transpiration in the that area. This causes less rain to fall in that area. It changes the way light is reflected from the Earth's surface, which changes the heating characteristics of the ground, which changes air movements. It will also have an influence on ground water levels and depending on local geology can bring salt to the surface causing salt scars and eventually desertification.

> **Comments:**
> **username_2**: Trees can also emit particulates or VOCs around which water vapor coalesces into rainfall.  
> **username_0**: So the historical saying that "Forest bring rain" is not totally false?  
> **username_3**: It is not just forests. Large fields of corn cause a lot of evaporation (transpiration) - I have heard it said that it is no coincidence that "tornado alley" and the corn belt have such overlap...  
> **username_4**: Also now there is research showing that pollen can influence cloud formation.  http://onlinelibrary.wiley.com/doi/10.1002/2015GL064060/abstract  

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