The Effects Of Deforestation

The economic and ecological effects of forest clearance are serious and growing. They fall most heavily on local communities who rarely see their share of benefits. But they also affect global climate and loss of biodiversity. We explain all the main adverse effects of deforestation, including: an increase in global warming, water supply problems, soil erosion, loss of biodiversity, loss of medicinal plants, spread of disease, and more.
Deforestation Effects: Mud slide, Sierra Leone
Deforestation led to a massive slide in Freetown, Sierra Leone (2017) killing hundreds. Image: Trocaire CC BY 2.0

Deforestation Affects Everyone

The effects of deforestation are not confined to forested areas, because they impact directly on global warming, whose rising temperatures influence climate events in every corner of the globe. Every time a tree is cut down and burned, less carbon dioxide is removed from the atmosphere and a whole lot is emitted. That’s bad news for Planet Earth and very bad news for the biodiversity of its living organisms, including us.

Make no mistake, deforestation is on the rise across the world. It has risen from an average loss of 18.3 million hectares (45 million acres) per annum, during the period 2001-2013, to 26.1 million hectares per annum (2014-2018) – an increase of 43 percent. 1 More than half of all forest loss is caused by cattle grazing, intensive farming (e.g. soybeans, palm oil), logging, and drilling, while slash-and-burn agriculture, wildfires and urbanization account for the rest. 2

To make matters worse, the world’s population is projected to increase by about 2.5 billion by 2050, causing a 50-90 percent rise in the global demand for food. 3 This will place huge pressure on land use, especially in developing countries where the majority of the world’s 800 million poor are concentrated. This poses a particular problem for the Congo Rainforest, where deforestation by subsistence farmers is predicted to mushroom in line with a fivefold increase in population.

On top of this, calorie consumption is on the rise around the world. For example, according to the IPCC’s Special Report on Climate Change and Land (August 8, 2019), consumption of food calories per person worldwide has increased by about one-third since 1961, and the average person’s consumption of meat and vegetable oils has more than doubled.

A recent report from the U.N. Food and Agriculture Organization states: “How to increase agricultural production and improve food security without reducing forest area is one of the great challenges of our times.” 4

In a nutshell, over the next few decades the demand for food (allied to the world’s insatiable appetite for more and more resources), will ramp up the pressure on the environment, in an attempt to seize more forest land for agricultural and commercial development.

Unfortunately, deforestation leads directly to more climate change and the immediate risk of catastrophic coastal flooding. It will also cause irreparable harm to rainforests 5, one of the most precious biomes in our planet’s ecosphere, as well as the probable extinction of thousands of Earth’s species. As you can see, there’s no easy answer. See also: History of Deforestation.

The 7 Bad Effects Of Deforestation

There are 7 particularly troublesome effects of deforestation, but its contribution to our climate crisis outranks everything else. This is because, in certain areas like the Amazon Rainforest, the amount of forest lost is approaching a climate tipping point that might trigger irreversible drying out, transforming the Amazon Basin into grassland. This would be catastrophic for our climate system and possibly our planet.

(1) It Leads To Global Warming

Forests Absorb CO2

Undoubtedly, one of the most worrying effects of deforestation is that less carbon dioxide is taken out of the atmosphere, thus adding to global warming. Forests play a vital role in the carbon cycle by acting as a ‘carbon sink’ – that is, they soak up carbon dioxide that would otherwise remain in the atmosphere, thus helping to dial down the greenhouse effect that leads to climate change.

The point is, trees take in significantly more carbon dioxide (CO2) from the atmosphere as a result of photosynthesis than they give out in respiration. Of the 39 billion tons of CO2 that human activity emits into the air each year, 28 percent is removed on land, mostly by forests. 6

Carbon sequestration by forests – in effect, a natural form of carbon capture and storage – is a key element in many nationally determined contributions (NDCs) made under the Paris Climate Agreement (2015). Nations rely on them for roughly a quarter of their planned emission reductions. 7

According to the World Resources Institute, tropical forests can provide 23 percent of the cost-effective climate change mitigation needed up to 2030, to meet goals set in the Paris Agreement. 8

Between the years 1990 and 2007, forests are estimated to have absorbed approximately 4 billion tons of carbon per year – equivalent to nearly 60 percent of the emissions caused by fossil fuels and cement manufacture combined. 9

Cutting Down Trees Releases CO2

The trouble is, when trees or plants are cut down, they stop absorbing CO2 and start releasing it into the atmosphere. According to the World Resources Institute, if tropical deforestation was a country, it would rank number three in global CO2 emissions, after China and the U.S.

The consensus is that forest clearance accounts for between 10 and 17 percent of all greenhouse gas emissions. Note: Higher estimates are not accurate. 10 11

Roughly 80 percent of the Earth’s above-ground terrestrial carbon and 40 percent of below-ground terrestrial carbon is in forests. 12 Were deforestation to continue unchecked, it is quite possible for the Amazon forest ecosystem to reach an irreversible tipping point, releasing huge quantities of carbon in the process, with unknown consequences for the planet’s biosphere.

Forest Trees Provide Cooling Cover

In addition to absorbing CO2 during photosynthesis, forest trees exert a cooling effect locally, in two ways: (1) by transpiration and (2) by shading the ground from excessive daytime heat while retaining some heat under the canopy at night. 8

By contrast, removing trees increases the difference between daytime and night-time temperatures (the diurnal temperature variation) and raises air temperatures. For example, it can raise local air temperature in the tropics and in the temperate areas by 1°C (1.8°F) and increase daily temperature variation by nearly 2°C (3.6°F) in the tropics and 2.85°C (5.13°F) in the temperate zone. Such temperature swings can be harmful to plants and animals. 13

7 Effects of Climate Change on Plants and Trees

Deforestation Can Lead To Harmful Change Of Land Use

Deforestation in the Amazon Rainforest is typically a means to obtain valuable timber after which, the land is cleared for livestock grazing. Unfortunately, cattle and other ruminants are the leading source of emissions of methane (CH4), a greenhouse gas which is thirty times more powerful than carbon dioxide. See also: Why are Methane Levels Rising?

(2) It Interferes With The Water Cycle

One of the worst effects of deforestation is the impact it has on water supplies. In the tropics, trees play a critical role in the local water cycle, because of a combination of heat absorption and transpiration. To begin with, their leaves are able to soak up more heat than ordinary soil. This heat warms the surrounding air which rises upwards.

At the same time the trees give off water by transpiration. Transpiration is the process whereby trees and plants draw moisture from the soil – via their underground roots all the way up to small pores (stomata) underneath their leaves, through which it is released into the air as water vapor.

This vapor exerts a cooling effect before being carried up into the atmosphere on the warm air rising from the trees, as described above. This condenses as rain in the atmosphere. The rainfall effectively recycles the water drawn up by the trees from the soil, providing moisture for the forest vegetation and soil. The process conserves rainfall in times of shortage and prevents surface run-off during heavy rainfall.

In addition, by assisting in the formation of clouds, trees help to reflect heat, thus contributing further to a reduction in temperature.

However, when the forests are cut down, less moisture is absorbed by plant roots, so less water is transpired into the atmosphere causing fewer rain clouds and thus less rain. Within a few years the area can become dried out as strong tropical sunlight bakes the scrub-land.

Concern is growing among scientists that widespread forest clearance could result in a significant decline in rainfall and trigger a positive-feedback process leading to increased desiccation throughout the bioregion. As the Arctic fires of 2019 demonstrate, dried out forests are extremely vulnerable to ignition by lightning. Indeed, similar fires occurred in 1997 in Brazil, Colombia, Central America, Indonesia, and other places. The droughts in the Amazon Basin in 2005 and 2010 are another case in point.

(3) It Increases Soil Erosion

One of the most widespread effects of deforestation is soil erosion. Forest trees hold onto the soil. When there are no trees the soil is much more easily washed or blown away. And when the soil disappears so do the plants and the vegetation and any crops. (For more about the value of soils, see: Why is Soil So Important to the Planet?)

Even if deforestation is followed by the replanting of trees and shrubs – for cash crops like soy, coffee or and palm oil – these types of trees will only cause more soil erosion because their roots will not be able to hold onto the soil.

The rate of soil loss after deforestation can be distressingly quick; a study conducted in the African Ivory Coast, for instance, compared the soil erosion of forested slopes with that of cultivated slopes. It showed that forested slopes lost 0.03 tons of soil per year per hectare (2.5 acres), compared to a loss of 90 tons per hectare experienced by cultivated slopes, while bare slopes lost a total of 138 tons per hectare.

In addition, the more soil is washed into the rivers, the more silt is deposited on the river bed, reducing river flow and decreasing local water quality. The impact of heavy siltation continues all the way to the sea, resulting in increased flooding as well as a decline in the health of coastal mangrove forests, coral reefs, and coastal fisheries.

Erosion is exceptionally painful for developing countries. Aside from the damage to local ecosystems, fisheries, and infrastructure, the loss of precious top soils costs billions of dollars every year. In the late 1980s, for instance, the Indonesian island of Java lost 770 million metric tons of topsoil every year at an estimated cost of 1.5 million tons of rice, enough to feed more than 10 million people. 14 For more about soils and the surface of the land, see: What is the Pedosphere?

(4) It Reduces Biodiversity

One of the most distressing effects of deforestation concerns the damage it causes to animal habitats. Roughly 80 percent of the world’s land-based biodiversity is found in forests – from pine forests of the northern taiga to the rainforests of the tropics. 15 The clearance and consequent degradation of forest land threatens the habitats of a great many species causing their numbers to dwindle to the point of extinction. 16 17 Indeed, some scientists consider that tropical rainforest deforestation is contributing to the ongoing Holocene mass extinction. 18 Hence the reason for the campaign to rename our present era the “Anthropocene epoch“.

IPBES Report On Biodiversity

According to a new report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2019), roughly 1 million animal and plant species are now threatened with extinction, many within decades, more than ever before in human history. In fact, the current rate of species extinction is tens to hundreds of times higher than the average over the last 10 million years, and the rate is accelerating. 19

The report states that more than 40 percent of amphibians, a third of all coral reefs and more than a third of all marine mammals are threatened. In addition, one third of all forests have been lost since 1800.

Despite these warnings, doubts have been cast on our understanding of the process of extinction, and whether it is sufficient to make predictions about the effects of deforestation on biodiversity with any great accuracy. 20 Most forecasts of forest-related biodiversity loss are based on area models, that assume that forest declines are accompanied by corresponding declines in species diversity. However, many of these forecasts have been shown to be wrong – loss of habitat does not always lead to large scale loss of species. 21

(5) It Leads To Fewer Medicines

Deforestation depletes the world’s store of medicinal plants. More than 50 percent of prescription drugs come from chemicals first identified in plants. Furthermore, almost five billion people still depend on traditional plant-based medicine as their primary type of health care. 22 So it’s hardly surprising that horticulturalists and pharmacologists are worried about the effects of deforestation on the development of new drugs.

In fact, one in five of all plant species is threatened with extinction, according to a recent report by experts at the Royal Botanic Gardens Kew. The report, entitled “The State of the World’s Plants”, says that one of the worst effects of deforestation is the threat it poses to future supplies of food and medicines.

The report – the first of what is intended to be an annual snapshot of the world’s plants highlighting critical issues and how they can be tackled. – reveals that of the 390,000 species of known plants, more than 30,000 are used by people.

Plants are fundamental to humankind, says Prof Kathy Willis, director of science at Kew, who led the new report. “Plants provide us with everything – food, fuel, medicines, timber and they are incredibly important for our climate regulation. Without plants we would not be here. We are facing some devastating realities if we do not take stock and re-examine our priorities and efforts.”

The report also stressed the importance of plants for the development of new medicines was revealed in the report, which found that of the 31,000 species in use, 57 percent were used in the manufacture of drugs. 23

The Amazon Rainforest – The World’s Largest Pharmacy

Approximately 1 in 4 of all drugs in use today are derived from plant species native to rainforests. 24 In addition, as many as 70 percent of the 3,000 plants identified by the United States National Cancer Institute as having potential anti-cancer properties are endemic to the rainforest ecosystem, notably in the Amazon Basin.

All this makes the Amazonian Rainforest the world’s largest medicine cabinet.

What’s more, it’s worth noting that of the millions of plants, insects and other creatures who live in the Amazonian biome, less than a fraction of 1 percent have been assessed for their pharmacological benefits.

Which is why all the big pharmaceutical corporations are bioprospecting in the Amazon region for plants that might be the next treatment for cancer, Alzheimer’s, malaria and other diseases.

(6) It Increases Tropical Diseases

One of the most insidious effects of deforestation is the spread of disease. Recent outbreaks of new viral diseases, including hemorrhagic fevers like Ebola and Lassa fever, are a case in point. As more humans enter and penetrate deeper into the rainforest, they are bound to encounter microorganisms with unique and undocumented behaviors. As these pathogens run out of primary hosts – through forest disturbance and degradation – they turn to humans.

Other diseases linked to land alterations that bring them into closer contact with humans include, malaria and snail borne schistosomiasis – whose growth is linked to the proliferation of artificial pools of water like dams, rice paddies, irrigation canals, and holes created by tractors and other machinery. Malaria is a particular problem in deforested and degraded areas, though not in forests where there are few stagnant pools to act as mosquito breeding grounds. Climate Models indicate that global warming might expand the distribution of malaria-ridden mosquitos.

Infectious diseases may arise in the tropics but they are by no means confined to them. For example, a European nurse infected with the Ebola virus from a patient, who flies back to Heathrow Airport, London, can land in London within 10 hours. The virus could spread rapidly among the city’s large population. Additionally, every person at the airport who was exposed to her can unwittingly transport the pathogen to their homes around the world. 25 In the aftermath of the COVID-19 pandemic, scientists are naturally concerned about the effects of deforestation on the emergence and transmission of tropical pathogens. See also: Effect of COVID-19 on Climate Change.

(7) It Disrupts Livelihoods

1.25 billion people around the globe (including 1 billion of the world’s poorest) depend on forests for shelter, livelihoods, water, fuel, and food. Roughly 750 million people actually live in forests. This figure includes 60 million indigenous inhabitants, who suffer the most from the effects of deforestation.

Some studies indicate that forests provide roughly 20 percent of income for local households in developing countries, either through cash income and/or by meeting their subsistence needs. Non-wood forest products (NWFPs) provide food, income, and nutritional diversity for an estimated one in five people around the world, notably women, children, landless farmers and others in vulnerable situations. 26

Sadly, deforestation activity disrupts the lives of these people, sometimes with devastating consequences. In the Greater Mekong delta in Vietnam and Cambodia, the effects of deforestation have sparked social conflict and migration. (See also: Deforestation in Southeast Asia.) Meantime, in Brazil, people have been lured from their villages to remote plantations and forced to work under slave-like conditions.

To counterbalance the pursuit of profit that drives deforestation – either by the large corporation or small farmer – new financial mechanisms are being introduced that may offer some hope. One of these is the Reducing emissions from deforestation and forest degradation (REDD+) program developed by Parties to the United Nations Framework Convention on Climate Change (UNFCCC). It creates a financial value for the carbon stored in forests by providing financial incentives for developing countries to reduce emissions from forested lands and invest in sustainable low-carbon forestry practices. Developing countries get results-based payments for results-based actions.

The key point is that REDD+ goes beyond simply limiting deforestation and incorporates conservation, sustainable management of forests and enhancement of forest carbon stocks. 8

For more about trees and climate change, see:
Tree-Planting: Is it the Easy Answer to Global Warming?

One commercial activity that should definitely help regions to switch from cutting trees to conserving them, is nature-based tourism. The eco-tourism industry is growing three times faster than the tourism industry as a whole, and now accounts for approximately 20 percent of the global market. 26


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