A line from The Lorax, an infamous book by Dr. Seuss, states, “I am the Lorax who speaks for the trees which you seem to be chopping as fast as you please” (41). Trees and forests exist as vital components of the biosphere. Diverse species of trees and forest ecosystems reside across the globe. In the last thirty years deforestation rapidly increased as society chopped trees as fast as pleased. This resulted in habitat loss, changes in ecosystems, and alterations in chemical cycles. Trees remain vital in the biosphere due to diverse functions and roles on earth.
One important function of trees is photosynthesis. Reece et al. states in the Campbell Biology 10th edition textbook, “Photosynthesis nourishes almost the entire living world directly and indirectly” (185). The world consists of autotrophs and heterotrophs. Autotrophs sustain themselves without consuming materials from other living organisms. Autotrophs produce organic molecules and are sources of organic compounds for heterotrophs. Majority of all plants are autotrophs or photoautotrophs that utilize light energy to produce organic materials. In photosynthesis, “the chloroplast in plants and other photosynthetic organisms capture light energy…from the sun and convert it to chemical energy that is stored in sugar and other organic molecules” (Reece et al. 185). Photosynthesis has a magnitude of intricate processes, such as the light reactions and Calvin cycle reactions. To summarize the complex series of chemical reactions that occur in this process, photosynthesis condenses into one chemical equation. Overall, the reactants consist of six carbon dioxide molecules, twelve water molecules, and light energy. These three reactants form a molecule of glucose, six oxygen molecules, and twelve water molecules as products (Reece et al. 188).
An important characteristic of trees as photosynthetic plants is, “on a global scale, photosynthesis is the process responsible for the presence of oxygen in our atmosphere” (Reece et al. 205). The oxygen produced in photosynthesis by plants is also required for human life. Humans inhale oxygen, which is taken to the lungs, and diffused into the blood from the alveoli. This oxygenated blood traveled to the rest of the body as it diffused out of the blood and into the cells. The cells then utilize oxygen in cellular respiration to produce ATP, a necessity for human bodily function. While oxygen comes into the body, carbon dioxide diffuses out of cells, into the blood taken back to the lungs and exhaled out. Photosynthetic plants, like trees, perform the process of photosynthesis and use the carbon dioxide exhaled from the respiratory system.
The exhalation of carbon dioxide into the environment is also apart of the carbon cycle. The carbon, an essential element for life, forms a framework of crucial organic molecules. As discussed with photosynthesis, plants use carbon dioxide to convert into organic forms like glucose. Consumers or heterotrophs then use glucose for metabolic processes. Plant biomass is a major reservoir of carbon. The photosynthetic process performed by plants “removes substantial amount of atmospheric CO2 each year” (Reece et al. 1245). The forest of the Amazon basin absorbs around 8% of the total carbon dioxide emitted by the world (Bunyard 34).
A key process on Earth is the water cycle because water is essential for all living organisms. Solar energy evaporates liquid water, which then condensates into water vapor in the clouds. The water vapor in the clouds then precipitates. Then surface and groundwater flow back into the ocean for evaporation to occur again. Trees, along with other terrestrial plants, perform evapotranspiration in the water cycle to move large amounts of water in the atmosphere (Reece et al. 1244). Trees are vital in the water cycle as the water vapor transpired from trees precipitates back. To maintain the continuity of the water cycle, forests are needed.
A vital component in Earth’s biosphere is ecosystems. An ecosystem “is the sum of all the organisms living in a given area and the abiotic factors with which they interact” (Reece et al. 1233). Ecosystems can include vast areas such as a forest, or space under a fallen log. Either way, trees are important components of ecosystems. Ecosystems have two key processes: energy flow and chemical cycling. A primary source of energy that enters most ecosystems is sunlight. Photosynthetic plants utilize sunlight in photosynthesis as the organic compounds produced are passed to heterotrophs. Carbon, nitrogen, and phosphorus are chemically cycled through the ecosystem. These chemicals are nutrients needed by an organism to carry out life processes. These chemicals, unlike energy, are recycled through decomposition and reused again (Reece et al. 1234). Trees are paramount in Earth’s biosphere because trees perform photosynthesis, are factors in the carbon and water cycle, and a major component of ecosystems. Trees are also homes to an abundance of wildlife as well as provide food and shelter for living organisms. The function of trees and forests are diverse and essential for life on Earth.
While trees are functionally diverse, the world is also composed of diverse species of trees. These diverse species of trees form various forest ecosystems across the globe. The tropical rain forests are located in equatorial and subequatorial regions. These regions include Central Africa, Amazon, and Southeast Asia. Tropical rain forests are composed of evergreen or semi-deciduous broadleaf species. Also in this region montane forests, flooded forests, and mangroves are found. Characteristics of rain forests include tall stature (above 30 m), tightly closed canopies, and high diversity (200-300 species per hectare) (Runyan & D’Odorico 7).
Another forest ecosystem is tropical dry forests. This ecosystem differs from tropical rain forests because dry forests “occur in frost-free areas experiencing a 4- to7-month period with limited or no rainfall” (Runyan & D’Odorico 7). Also, the trees in tropical dry forests are shorter with smaller basal areas than trees in tropical rain forests. Majority of tree species in this ecosystem are deciduous. The annual evapotranspiration in dry forests usually exceeds the annual precipitation received. Tropical dry forests are found in northern Australia, Africa, India, Central and South America, and Southeast Asia (Runyan & D’Odorico 9).
Temperate forests are another forest ecosystem found in mid-latitude regions of the Northern Hemisphere and smaller areas in the Southern Hemisphere. Places temperate forests are found in the Southern Hemisphere include Chile, New Zealand, Tasmania, South Africa, and Australia. Unlike in tropical dry forests, in temperate forests, the average annual precipitation exceeds the average annual evapotranspiration. The genera of trees found in temperate forests are pine (Pinus), oak (Quercus), beech (Fagus), maple (Acer), and eucalypts (Eucalypts) (Runyan & D’Odorico, 9). The evergreen eucalypts dominate in Australia (Reece et al 1167).
Deciduous broadleaf trees dominate temperate forests in eastern North America, western Europe, and northeast Asia. Mountains regions with warm summers and cold winters have coniferous forests. In Mediterranean regions like the Mediterranean Basin and the Pacific coast of North America, temperate forests are mixed with coniferous evergreen and broadleaf trees. The Pacific North America temperate forests contain coniferous redwoods, Douglas fir, hemlock, and Sitka spruce (Runyan & D’Odorico 9).
The last forest ecosystem is boreal forests. The boreal forest expands across northern North America and Eurasia to the edge of the arctic tundra. The boreal forest is also called the Northern Coniferous forest and is Earth’s largest terrestrial biome (Reece et al, 1169). Boreal forests contain coniferous spruce (Picea), pine (Pinus), larch (Larix), fir (Abies), and deciduous birch (Betula) and poplar (Populus) (Runyan & D’Odorico 10).
These various forest ecosystems across the globe are subjected to deforestation. Deforestation is the clearing of trees or forests for non-forest uses such as road construction. The tropical rain forests are the primary target subjected to deforestation. Tropical forests account for the highest portion of net global forest loss with 58% (86 Mha). Boreal forests account for 27% (40 Mha), temperate with 8% (12 Mha), and subtropical with 8% (11 Mha) (Runyan & D’Odorico 10). Over 15 million hectares of tropical rain forests were cleared annually from 1980-90. From 1990-2000, deforestation of tropical rain forests slowed to 12 million hectares a year (Barbier 1347). As of 2005, nine soccer fields are destroyed every minute just in the Brazilian Amazon (Bunyard 34).
One process of deforestation is the slash and burn technique. The area is cleared as trees are cut down. The vegetation left in the cleared area is then burned. The burning causes large proportions of nutrients to remain in the ashes (Salati & Vose 133). The slash and burn technique is primarily used to deforest land eventually used for agriculture. These ashes provide nutrients to help fertilize crops grown on the land. Another process of deforestation is logging. Since the 1850s logging primarily occurred in temperate and boreal forests. From the 1950s to 1980s though, logging rates increased from less than 2 Mha per year to 8 Mha per year. In the 1970s, logging in tropical forests surpassed logging rates in temperate and boreal forests (Runyan & D’Odorico 25).
A specific form of logging is selective logging. Selective logging was considered harmless because it left a larger portion of the forest unaltered. This deforestation process occurs when the most valuable log is removed instead of a mass area. Selective logging though does more harm than it first appears. The construction trails, log yards, thick vines connect to neighboring trees factor into selective logging. About twenty trees are damaged or knocked down for every one harvested (Wood & Porro 10). Illegal logging is also an issue in terms of deforestation. Around 80% of mahogany was illegally harvested from the Brazilian Amazon in 1997. Greenpeace International investigated the mahogany trade from Brazil by tracking with UV-visible paints (Bunyard 33).
Primary drivers of deforestation are cattle ranching and agriculture. As the global population increases so do the food demand. This led to an increase in beef, soybeans, and palm oil. The main driver of deforestation in South America is agriculture. From 1990-2005, 88.5% of land deforested was converted for agriculture. Around 71.2% was used for pastures and 14.0% for commercial crops. Commercial crops doubled the annual rate of deforestation in the early 2000s. In Brazil, Argentina, Paraguay, and Bolivia the main drivers of deforestation are large ranches and commercial crops. In Andean countries, such as Peru, Colombia, and Venezuela, smallholder and mixed agriculture were major drivers (Sy et al.10).
In 2003 Brazil exported over $8 billion worth of soy and $1.5 billion of beef (Bunyard 32). Soybean cultivation and cattle ranching attributed to a 23% acceleration of net forest loss from 1990 to 2000s in Brazil (Kim et al. 3497). Soybeans have become the most important harvest crop in Brazil since the 1990s because of the increase in global demand. From 2001 to 2006 over one million hectares of soybean fields expanded in the Amazon. In the Amazon, nearly 30% of soybean expansion caused deforestation (Gibbs et al. 377).
Palm oil is a rapidly increasing crop in the world today. The production of palm oil increases globally by 9% every year. Palm oil is grown across 13.5 million hectares of the tropical rain forest. The two major producers of the world’s palm oil are Malaysia and Indonesia. These two countries produce over 80% of the world’s palm oil. Also, Malaysia and Indonesia contain over 80% of Southeast Asia’s remaining primary forests. In Malaysia, the area of palm oil increased from 1.8 million hectares to 4.2 million hectares from 1990-2005. This resulted in roughly 1.1 million hectares of tropical rain forest lost in Malaysia. In Indonesia between 1990-2005, the area of palm oil increased from 4.4 million hectares to 6.1 million hectares. This resulted in 28.1 million hectares of tropical forest loss in Indonesia because of palm oil. Deforestation from palm oil plantations continues expansion in southern Thailand, Papua New Guinea, and Myanmar. It is estimated that 410-570 million hectares of forested land in Southeast Asia, Latin America, and Central Africa could be deforested for palm oil production (Fitzherbert et al. 538-539).
Infrastructure and urbanization also drive deforestation. Infrastructure and urban expansion directly contributed to 1.7% of deforestation in South America from 1990-2005. As an indirect driver, urbanization significantly affects deforestation as consumption patterns change and increase the demand for agricultural products. In Peru, illegal mining was an important driver of deforestation. Venezuela had large infrastructure projects, such as dams, which largely contributed to deforestation in the country (Sy et al. 11).
The rapid increase in deforestation because of cattle ranching, agriculture, infrastructure, and urbanization had lead to detrimental impacts on nature. With deforestation, fewer trees are available to perform evapotranspiration in the water cycle. In the Amazon Basin about 50% of rainfall evapotranspires into the atmosphere as water vapor. Then 48% of that is precipitated back. As tree density declines in the Amazon Basin and less evapotranspiration occurs, precipitation will decline to lead to droughts. Less water vapor transpires back into the atmosphere to cycle back in precipitation. In the Amazon basin, precipitation declined by 34% from deforestation. Also, precipitation declined in the Congo basin (26%), Southeast Asia (8%), and Indonesia and New Guinea (17%) (Hoffman et al. 6).
In addition to declined precipitation, the continuation of large-scale deforestation will lead to increased soil erosion and water runoff with initial flooding in the lower Amazon (Salati & Vose 129). Fewer tree canopies and disrupted soil causes a higher probability of flooding in the Amazon. Tree canopies in forests intercept 20% of rainfall. The loss of canopies causes 4,000 tones of water per hectare a year hit the forest floor, which leads to soil erosion (Bunyard 34). Forests hold more water and prevent enriched runoff from contaminating water sources. Disturbed soil has reduced water absorption and shorter retention times compared to forest soil (Salati & Vose 131). In deforested areas, nutrient enriched runoff increases along with flooding, soil erosion, and contamination of water sources.
Along with the water cycle, the nitrogen cycle was also altered by deforestation. Around 88.5% of deforested area in South America was converted to agriculture (Sy et al. 7). Deforestation affects the nitrogen cycle because a majority of deforested land was converted for agricultural purposes. A negative result of the slash and burn technique is the result of poor nutrient soil. After the land is burned, the soil is only valuable for crop growth for 2 to 3 years. Once the crop yield declines the cultivator moves to another area of land (Salati &Vose 133). After two years this area of land is no longer beneficial farmland. Extensive agriculture causes the natural storage of nutrients in the soil to become exhaustive (Reece et al. 1270). So, then a new area of land is deforested, used for agriculture for about two years, and the same process occurs again.
Plowing soil causes mixing and increases the decomposition of organic matter. Nitrogen is then released and removed as crops are harvested. Forests also cleared by burning results in a major loss of nitrogen too. Nitrogen retained in the ashes can be rapidly lost because of rain. Around 15% of nitrogen retained in ashes is lost from just the first rainfall (Salati & Vose 133). Since agricultural ecosystems lose nitrogen, fertilizers are applied to compensate. Plants are needed to uptake nitrates from the soil, without plants the nitrates are leached from the ecosystem (Reece et al. 1270). Also, the production of soybeans is a major driver for the conversion of forested land into agriculture. Soybeans are symbionts nitrogen-fixing legumes. Nitrogen-fixing legumes increase fixed nitrogen in the soil. As soybean cultivation increases in deforested land, the more fixed nitrogen increases in the disturbed soil (Reece et al. 1270).
Nitrogen levels continue to increase from human activities, such as fossil fuel burning. Too much nitrogen in the soil leaches into groundwater or runoff into water supplies causing contamination. Agricultural areas experience the highest increase in nitrate concentration in groundwater. Rivers contaminated with nitrate runoffs into the ocean and leads to eutrophication in lakes (Reece et al. 1270). The addition of nutrients in these bodies of water alters the ecosystem as organisms begin to die. An increase in agricultural land formation increases runoff from farmland that is rich in nitrates. This increases water contamination and eutrophication altering ecosystems.
Deforestation also alters the carbon cycle. A decline in trees reduces the use of carbon dioxide for photosynthesis. This results in higher amounts of carbon dioxide in the atmosphere. According to Reece et al, “…the average CO2 concentration in the atmosphere before 1850 was about 274 ppm. In 1958…the CO2 concentration was 316 ppm. Today, it is around 400 ppm, an increase of more than 40% since the mid-19th century” (1272). The increase in atmospheric CO2 associated with the increasing global temperature. Global models predict the CO2 concentration doubling by the end of the century as the global temperature rises 3°C. From 1990-2000, 351 teragrams of carbon (Tg C) was lost due to deforestation and conversion to agriculture. From 2000-2005, 445 Tg C was lost (Sy et al. 9). If every forest in the Amazon were deforested around 77 billion tones of carbon would emit into the atmosphere (Bunyard 34).
Ecosystems have altered because of deforestation. First, deforestation caused the depletion of forested ecosystems. As deforestation continues to occur at rapid rates, the less forested areas remain present on earth. Also, deforestation altered the water, carbon, and nitrogen cycles. Energy flow and chemical cycling are the two key processes of an ecosystem. As these processes change, changes in ecosystems occur too. Tropical rain forests have the highest animal diversity than any other terrestrial biome (Reece et al. 1167). Deforestation decreases diversity in forested ecosystems. Palm oil plantations hold less than half as many vertebrate species as primary forests. These plantations also have relatively lower species richness than logged or secondary forests. Fitzherbert et al. states, “Across all taxa, a mean of only 15% of species recorded in primary forests was also found in oil palm plantations” (540). These disrupted areas result in depleted resources for these species.
A disrupted forested area also increased the chances of large-scale forest fires. Logged and damaged trees allow sunlight to reach the forest floor. This causes the forest ground, covered in organic debris from logging, to dry out. As the forest ground dries out, “…the combined effects of severe droughts provoke forest leaf shedding and greater flammability” (Potter 776). The alteration of the water cycle in the Amazon results in less precipitation. A combination of drought and sunlight penetration on the logged deforested ground floor increases fires in the Amazon (Potter 776).
Experiments conducted in a journal by Hoffman et al. discovered increased forest fire occurrence in deforested areas. Simulations performed in the experiments calculated the McArthur Forest Fire Danger Index (FFDI), a quantitative formula that measures the fire risk related to probable fire occurrence and spread rate. Deforestation increased the FFDI in the Amazon, Congo, and Indonesia, and New Guinea. The FFDI increased by 41%, 56%, and 58% respectively in these areas. Also, the predicted occurrence of forest fires increased by 43.9% in the Amazon, 79.5% in the Congo, and 123% in Indonesia and New Guinea (Hoffman et al. 6). As logging occurs in tropical forests areas, the ground floor loses tree canopy protection. A result of logging caused increased sunlight penetration, dried out the ground, less evapotranspiration, and less precipitation. These effects of deforestation rippled into another effect of increased forest fires occurrence. With forest fires, the disruption of forested ecosystems and destroyed trees continues.
Deforestation rapidly increased in the last several decades. The major drivers of deforestation include cattle ranching and agriculture. The increase in human population resulted in increased production of beef, soybeans, and palm oil. There are numerous forested ecosystems composed of diverse tree species across the globe. The type of forest impacted the most by deforestation is the tropical rain forest. Deforestation creates detrimental impacts as trees play vital roles in the biosphere. Trees perform photosynthesis and play key roles in the carbon and water cycle. Various species rely on trees and forests for resources and survival. Deforestation altered important biochemical pathways changed ecosystems and caused habitat loss. Deforestation harmfully affected nature and the rapid rate must decline in order to help the planet. As a speaker of the trees, stop chopping trees down as fast as pleased.
