Scientists have come around to the view that the impact of forests in climate change spreads much further than carbon storage. Rainforests especially play diverse roles that include regulating climate at multiple levels – continental, regional, and local– by producing rainfall and atmospheric moisture, and regulating temperature.
Broadly divided, forests affect the climate in 3 major ways. One is by absorbing CO2, the major greenhouse gas, and help cool the climate in the process. The second is by evaporating water that forms clouds. The third is by absorbing sunlight with their dark green leaves, thus warming the planet.
For these reasons, forests should be considered the primary contributor to global climate change adaptation and mitigation, with carbon storage, considered an additional benefit.
Forests provide numerous climate and water-related services. That includes precipitation recycling, infiltration, water purification, groundwater recharge, and cooling.
These services are just as important as the traditional benefits of providing food, fiber, and fuel, as well as facilitating carbon storage.
Forests Are Inextricably Linked To Water Availability And Rainfall
The availability of water depends heavily on healthy forests. They positively impact the quality, quantity, and even the cost of filtration and purification of water.
Over 6% of the tree cover in the major watersheds of the planet was lost in the first 14 years of this century. 31% of the watershed area of the planet is covered by forests.
The quality of water is most affected when wind, rainfall, and runoff lead to the detachment of soil particles and radically worsen the quality of water. The health of the forests is an essential factor in keeping pollution out of the water.
While strong roots anchor loose soil against erosion, materials on the forest floor help the trees absorb sediments and nutrients. These sediments end up in the streams and other waterways when the forests are disturbed and degraded.
Forests also control the water cycle through the regulation of evaporation, precipitation, and water flow. Multiple layers of the forest canopy, the roots, and branches, store and release water vapors, which lead to rainfall on their own. Forests also slow down the flow of runoff by slowing down and even blocking stormwater.
The process of deforestation slows down and weakens this process. This leads to irregular rain patterns such as flooding and droughts. Deforestation is never a local process as far as the effect is concerned. For instance, deforestation in Central Africa has led to a decrease ranging from 5% to even 35% in rainfall in the US MidWest.
Texas alone saw a decrease in rainfall of 25% after the Amazon rainforests underwent deforestation. It affected the productivity in multiple sectors around the globe.
The cost of water treatment is exorbitantly high, especially when the natural process of cleansing is disturbed due to the disappearance of forests. Expensive water filtration infrastructure becomes more expensive and even unreliable when erosion increases beyond a certain level.
We always need to rely on forests as the frontline soldiers in the fight to maintain the quality of water. Traditional forests bring down the cost of water cleaning infrastructure and also provide additional benefits like fishing infrastructure, wildlife habitats, and recreational spaces of green.
The water of New York City, for instance, is stored in the Catskills. This conserves the forest and also the natural landscapes while saving on filtration costs. An investment of $1.5B by the authorities protects over a million acres of overwhelmingly forested land. It has over time led to a saving of $6B to $8B on the expenses of building an artificial filtration facility.
Cooling Globally And Locally With The Help Of Forests
Global and local temperatures are under the influence of forests which regulate the movement of heat. Each fully grown tree can give off hundreds of liters of water a day. Just 100 liters of transpired water is equal to the cooling power plant for AC units for two average households per day. Forests can also increase the level of low clouds and increase local cooling.
In contrast, in colder regions, forests may help add to warming. They also stimulate cloud formation that traps radiation beneath.
Regulating Water Supply Through Forests
Forests help to regulate the supply of water in multiple ways. Forests in high altitudes trap cloud droplets and fog and contribute as much as 75% of the total catchment overflow in the area. Removing such forests causes the moisture in the clouds to shift to other regions with forest cover. This could lead to a severe depletion of water supply to downstream areas.
Loss of forest cover leads to degradation of the soil. This reduces its capacity to retain war and reduces soil infiltration. This in turn diminishes the reserves of groundwater that help maintain the base flow during the dry season.
From the above reason, it is apparent that retaining forest cover over a region has a positive effect on keeping the region cool and also providing for the storage and recycling of substantial quantities of water, and moderating the flow of water that helps control floods in the catchment area.
In this context, it is worth mentioning that forests comprising mixed species of trees are more effective than monoculture forests in regulating the supply of water and helping cool down the region and the planet. Mixed-species forests help more in erosion control and water infiltration. Multiple species of trees help each other with water uptakes.
There are multiple reasons why tropical rainforests help cool down the atmosphere. Vast areas of forest land remain along the equator where the sunlight is at its highest and has the most potential to transform that energy.
But tree cover is the most affected in the tropics and deforestation of the Amazon rainforest has led to the warnings reaching a ‘critical threshold.’ Crossing this would mean a spike in global temperature. Advocates of the destruction of the rainforests such as President Bolsonaro of Brazil have argued that the Amazon rainforests act against economic progress. But a study conducted showed that clearing of forest land directly led to the loss of vast expanses of soy crops due to extreme rises in temperatures.
Tree-clearing is also expected to expose the people living in the Brazilian Amazon.