The Effect of Deforestation on the Climate and Environment


Deforestation is caused by the growing demand for forest products and the conversion of forest to agriculture as the human population continues to expand. In 1750 cropland and pastureland occupied 6-7% of the global land surface; by 1990 cropland and pastureland occupied 35-39% of the global land surface. It is estimated that the world is currently losing over 9 million hectares per year which is an area the size of Portugal. Deforestation not only affects the climate by increasing the atmospheric level of carbon dioxide but also affects the environment by inhibiting water recycling, triggering severe flooding, aquifer depletion, soil degradation and the extinction of plant and animal species.

Trees remove carbon dioxide from the atmosphere through photosynthesis (see my posting entitled The Carbon Cycle). Cutting down forests will cause a decline in photosynthetic activity which results in the atmosphere retaining higher levels of carbon dioxide. Forests also store an enormous amount of organic carbon which is released into the atmosphere as carbon dioxide when forests are cleared by burning. Clearly, deforestation contributes to global warming and ocean acidification (see my two postings entitled Solar Activity, Greenhouse Gas Levels and Climate Change on Our Earth and Atmospheric Carbon Dioxide Levels and Ocean Acidification).

Water recycling is the movement of rain from the forest to land masses further inland. When rain falls on forests the water is intercepted by the forest canopy. Some of this intercepted water is returned to the atmosphere by evaporation and transpiration (release of water vapor into the atmosphere through stomata on tree leaves) while the rest is returned to the ocean as river runoff. In a healthy forest about three fourth of the intercepted water is returned to the atmosphere as moisture laden air masses which move inland, cool and are converted to rain. Land cleared by deforestation returns only about one fourth of the rain water to the atmosphere. This air mass has less moisture and delivers less rain further inland. Deforestation inhibits water recycling and converts inland forest to dry land and potential waste land.

Severe flooding is a result of deforestation because removal of the forest leaves little vegetative cover to hold heavy rains. The inability of land void of forest to hold heavy rain water will also trigger mudslides like the ones that have occurred in recent years in California, China and other parts of the world. Severe flooding and mudslides are extremely costly because they devastate homes and communities.

The excess water from land cleared of forest becomes runoff water and enters the ocean instead of seeping downward into the soil to recharge aquifers. Aquifer depletion is already becoming a serious problem in certain areas of the planet and as the human population continues to grow so will the demand for fresh water.

Deforestation also results in soil degradation. Forests store nutrients that are required for all plant life. In the tropics almost all nutrients are stored in the vegetation because tropical soil has little organic matter and almost no nutrient storage capacity. If tropical forests are cleared for cropland, the land will yield crops for only a few years and when the nutrients are depleted they become waste land.

Raj Khamkar
5/28/2012 6:56:37 AM

I need your personal opinions on these questions, even if they are big please spare some time and give your complete answers and you can also mail them to me. Thank you! :D • Do you think that deforestation results in a climate change? o If yes, how? o If no, how? • How has the climate in the Amazon forest changed in the past few decades? • In Amazon (rainforest) is it possible that deforestation is ruining habitat indirectly? o If yes, why? o If no why? • Is it possible to blame only the authorities for the deforestation? o If yes, why? o If no why? • Do you think it’s possible to regain the trees and the original climate? o If yes, why? o If no why? Note: e-mail ID:

Richard Hilderman, Ph.D.
1/21/2011 8:41:19 AM

Roy Fritz--It will not take 50 to 75 years for the world to see water problems--there are various parts of the world are already having water shortage. As the world population grows (estimated to be up from 6.9 billion today to 8 billion by 2050)water will become a much more serious issue. Another point--as sea level continues to rise there will be serious contamination of aquifers by salt water. We need to start stabilzing the human population--most experts feel do this families need to be limited to two children. We also need to serious start converting from a carbon-base energy economy (coal,oil and natural gas) to carbon-free renewable energy sources.

1/20/2011 11:54:48 PM

Within the next 15 to 20 years we will be fighting for clean water. We have polluted the land in such ways that it is only starting to show up. Take Dallas the polution that has been sent into the ground will take 3oo to 400 years to clean it's self. It is showing up 275 miles away in the ground water. Soon we will be haveing the cities start looking for the off grid people to take our land and our living will become harder to keep. Within the next 75 years we will have more people than the planet can provide food for. This will not stop until mass deaths fill our land. Only then will we seek the wisdom we need today and then it may be to late to save ourselves.

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