Science estimates the world population in 1800 was one billion people and is currently over seven and a half billion. Scientific efforts have been undertaken to determine the population carrying capacity of planet earth based upon the availability of resources earth can provide. Estimates tend to fall between nine and ten billion people being the upper limits for Earth’s capabilities. The U.S. Census Bureau predicts our world population will reach ten billion in just 30 years. Certainly, no one should find it difficult to understand the difficulties we will face in providing the resources that will be required. The food requirements alone will necessitate clearing forest covered lands for agricultural purposes. There are no new lands to be discovered on our planet so, highly populated countries like China are already looking to acquire lands on less populated continents, to deforest for agricultural reasons. Population expansion is a serious problem and will require accelerating the deforestation of our remaining forested lands and increase levels of CO2 and toxic pollution to our atmosphere!
The result will be continued significant changes to our climatic conditions therefore, we need to take a closer look at how deforestation impacts climate. First, we must understand there are three different forest types; boreal, temperate and tropical, each having somewhat different effects upon climate conditions. We also need to understand different kinds of surfaces reflect the incoming solar energy in different ways which is called, “albedo”. It is defined as the ratio of the radiation reflected from the surface to the total radiation falling on the surface. The lower the albedo the more solar energy is absorbed. Forest cover has a very low albedo thus, absorbing high levels of heat from the solar energy.
Boreal forests have a large influence on local temperatures and have the largest influence on global mean temperatures of the three forest types. This results in warmer temperatures throughout the year when compared to surrounding areas that are void of trees. Boreal forests are found in colder climates with shorter growing seasons thus, producing smaller trees. This results in only moderate intake of CO2 and a low rate of evapotranspiration. Deforestation of boreal forest cover will result in reduced evapotranspiration and cooler temperatures along with lower humidity. Deforestation of boreal regions would, overall, increase the surface albedo leading to cooler temperatures and increase in snow and ice cover, which would enhance the cooling.
Temperate forests tend to cool the air during the leaf-on period and warm the air during leaf-off periods. During warm seasons with sufficient moisture, local cooling is caused by evapotranspiration and shade. The surface roughness of forest cover, contributes to increased rainfall and surface warming. Trees in temperate forests grow larger and faster thus, absorbing increased levels of CO2 and a higher rate of evapotranspiration. Another mechanism by which forests affect local weather is by aerodynamic roughness. The rough surface of forests causes a drag on the air flow resulting in reduced wind speeds and enhances the exchange of heat and moisture from the forests into the air. This causes convection which increases cloud formation and increased rainfall. Deforestation of temperate forests will result in significant increases in surface temperatures, reduced moisture and leads to desertification. What can we expect as we approach ten billion people on planet Earth?
The tropical forests are very different from the other two zones. These forests grow in very warm moist conditions and are considered carbon sinks using over fifty percent of the CO2 available within the atmosphere. They are frequently referred to as the lungs of Earth producing almost thirty percent of the oxygen required to support life on our planet. Rainfall averages 70 to 100 inches annually with a very high evapotranspiration rate. Over 50% of the currently identified living organisms are found in these forests. Scientists believe there are millions of species yet to be identified in the tropic ecosystem. These forests are the center of bio-diversity, the single most important element in Earth’s ability to support the life systems on our planet. Forest communities in the tropical zone, can contain 400 to 500 different plant species as compared to a temperate community which seldom exceeds 15. Plants from these forests are being used for medicine, beauty produces and food, but are being threatened by deforestation for lumber and agriculture. The past 50 years has resulted in the loss of 17% of tropical forest acreage. Today, tropical forests are experiencing habitat alteration and species extinction on a large scale and more rapid rate than any other ecosystem.
Loss of tropical forest cover will have a major impact on global warming and climate change. We can expect significant reductions in transpiration resulting in reductions in rainfall, increased temperatures due to reduced transpiration and significant increases in atmospheric levels of CO2. As temperatures raise, many species will become extinct and climatic conditions will change over the entire planet.
Understanding the forest ecosystems hopefully, will create a better appreciation for the impact we humans are having on our natural world and encourage us to make the needed adjustments for the future! As our population grows, deforestation will accelerate and we will rapidly move closer to the limited carrying capacity of Mother Earth!