How rainforests help regulate Earth's Climate and Temperature
Mist rising from a rainforest keeps the rain cycle going
Rainforests regulate both the water and the atmosphere
Rainforests serve as part of the lungs of the world as well as moisture and temperature regulators. They are separate from the oceans and the algae that also serve as part of the worlds lungs, producing the oxygen that we require to breath. However, as the oceans become increasingly polluted, the dependence upon the rainforests around the world increases. Another concern that exists is if it were not for rainforests the earth would end up as a drier and hotter place racked with temperature extremes and wild weather as the norm. With global warming, this trend would exaggerate the extremes we are seeing in action today from other influences. That we can say this is due to the fact that clear cutting and shrinking the extent of the world's rainforests has actually reduced the quantity of rain cloud formation, leading to drying and increasing desertification within the Amazon region in Brazil. On top of this, the temperature of the areas affected has increased, further drying out the affected regions. All of this causes the poor to clear-cut more forest to create marginal agriculture.
The regions in question are the Amazon basin, the African rainforests and interestingly enough, the rainforests of the Pacific Northwest. The forests that are by far the most sensitive to this are the Amazon and African tropical rain forests. There is much concern for the Pacific Northwest due to the destruction brought by the spruce pine beetle that has devastated about 90 percent of the BC interior forests. The region has evolved to a dry and dead region with the total disappearance of many species. Brazil and the Congo lie on the equator and effect both the north and south hemispheres. The local weather patterns moderated by the forests have a profound influence on the rest of the planet.
Everyone knows that on hot summer days, clouds which pass between us and the sun, have an immediate cooling effect. Lack of clouds means that heat has a chance to accumulate and build. Everyone who has endured a heat wave in a concrete city welcomes the cooling clouds and rain that bring an end to it. We also know that on winter days, clouds tend to act as a blanket and keep things warmer. Vast rainforests that once existed acted as a huge carbon and moisture sink. In the days where the forests dominated in the Amazon and the Congo, there was a daily weather cycle that started in the early morning as bright and sunny. As the day progressed and the jungle heated, clouds built up over the rainforest due to the moisture released from all the plants. The moisture condensed as clouds and prevented everything below from reaching extreme heat. When cool enough, the clouds released torrents of rain to water and cool everything below. By evening, the clouds were once more dispersing and becoming sparse. Winds blew some of the clouds from the rainforest to other regions that were also watered and cooled. In the Amazon, this is especially important due to prevailing wind from the west. Typically, moisture is lost in the mountains and the lee side becomes semi-arid. This was not the case for the Amazon rainforest, but is becoming increasingly so. Some of these clouds from the Pacific Ocean fed rivers and glaciers in the mountains. The clouds reflect more sunlight when plentiful and help regulate the Earth's temperature. Fewer clouds mean more sunlight reaches the darker earth and thus heats it up. More clouds mean cooling overall. When the winds mix up the hot and cool regions, the temperature is averaged out planet wide. Less rainforests eventually translates into less cloud cover and more heat. This is but one part of the complex issue of global warming.
Rainforests also absorb a lot of carbon dioxide from the atmosphere, thus functioning as a carbon trap and release oxygen, thus removing this greenhouse gas from the atmosphere and acting as the world's lungs, giving us life giving oxygen. Global wind patterns mix everything up so that the air with less carbon dioxide moves out and air with more has a chance to contact the carbon hungry rain forests to be cleared of excess greenhouse gasses. Rainforests thus serve a triple function to increase global cloud cover, to subtract and trap carbon dioxide and add oxygen. Now water vapor is a greenhouse gas when it is not in the form of clouds and it lends it influence as humid heat. But when the moisture condenses into clouds, the cloud tops reflect incoming sunlight, increasing the albedo of the earth and the regions under the clouds are allowed to cool.
For many decades and up to the present, rainforests were and are still being clear cut for agricultural growing regions, usually to produce cash crops for export and profit, in particular feed lots for beef. The soil tends to be thin and is quickly exhausted as it lacks a lot of nutrients for heavy feeding crops and beef. The loss of the forest canopy means that soil is more quickly leached of nutrients. When it is exhausted after a few crops, farmers usually abandon the now unproductive fields, which turn to desert, cut down more rainforest to clear land for agriculture. Such has been the case and continues in the Amazon basin, where enough forest is cleared in a year to rival France in area. Clear cutting is affected by cut and burn techniques, which release carbon dioxide into the atmosphere while at the same time subtracting oxygen that we need to, breathe. Climatologists have noticed that as the clear cuts expand and the rainforest shrinks, that the local climate dries up and gets hotter. Regions already clear cut and exhausted turn to desert and are generally unrecoverable in the short term. Less rainforest remains and less daily cloud cover occurs and this threatens even the diminishing the forest cover that remains. The outer regions that used to see daily rains now see little cloud cover, scant rains and get scorching hot. This affects the groundwater level to the point where people and animals are forced to migrate due to increasing drought. The loss of the rain forest that used to exist, has led to an unknown loss by way of species across the biological spectrum. We can say this due to discoveries of new species in what is still left. Once great rivers ran to the ocean, but now some of them are drying up and water coming in from other regions never reaches the sea.
Carbon dioxide that is not absorbed by rainforest is absorbed by the oceans instead, acidifying the oceans and dissolving calcium carbonate from shells and coral and releasing trapped carbon dioxide into a vicious increasing cycle in the sea water. In addition, the increasing acidity is lowering the oceans ability to capture oxygen and creating oceanic dead zones. The extra greenhouse gasses heat the ocean as well as the atmosphere. This places the ocean species that are temperature and chemistry sensitive at risk and the potential for the collapse of the other part of the Earth's lungs, the photo plankton. Massive die off of coral has already been noted. Though heating of the oceans contribute to evaporation and cloud formation, it does nothing to lock away carbon either as calcium carbonate or in plant material. It does escalate the scenario for super storms that brew over heated oceans and make landfall as intense hurricanes as the weather seeks to balance extremes of heat and cold.
Increasing dry hot areas jacks up the average world temperature and some of this heat reaches far enough north and south to melt the polar ice caps and high enough to melt mountain glaciers. The Earth is heating up for a number of reasons and one of them is the decrease of rainforest cover. Less carbon is recycled and fewer clouds mean hotter days overall as we move closer to catastrophe, flooding and hot dry conditions. Growing seasons in temperate climates are growing in length on both ends of the season. This causes changes of bird migration habits. The loss of the rainforests spells an increased risk for catastrophe for the entire planet. As the rainforests shrink, a crucial temperature regulator is reduced and at threat of being completely lost. We are moving inexorably toward a tipping point where the whole ecosystem will go through catastrophic change. When temperatures get hot enough, photosynthesis shuts down and the process reverses, injecting more carbon dioxide into the atmosphere while taking up oxygen. No one is sure where this tipping point is that will lead to a total break down of the rainforest regulator, but when it does, the result will be catastrophe.
There is a lot of interest to stop the destruction of the rainforest, but as long as we run business as usual and do nothing about regional poverty that is driving much of the destruction, the result seems inevitable. We are all at risk; rich and poor alike and must seriously act to avert catastrophe.