Negative Effects Of Deforestation On The Environment – Rainforest cleared for cattle ranching along the Trans-Amazonian Highway. This kind of cleaning is linked to the spread of infectious diseases such as malaria.
In 1997, a plume of smoke hung over the Indonesian rainforest as an area about the size of Pennsylvania was burned to make way for agriculture, fires exacerbated by drought. Shrouded in haze, the trees are unable to produce fruit, leaving the resident fruit bats with no choice but to fly elsewhere in search of food, bringing with them deadly diseases.
- 1 Negative Effects Of Deforestation On The Environment
- 2 Deforestation And Impacts On Our Health And Nature
- 3 Deforestation Is Leading To More Infectious Diseases In Humans
- 4 Deforestation Of The Amazon Rainforest
- 5 New Data Shows Deforestation In Peruvian Amazon Responsible For Sizable Carbon Emissions
Negative Effects Of Deforestation On The Environment
Soon after the bats took up residence in the trees in the Malaysian orchard, the pigs around them began to fall ill—probably after eating fallen fruit that the bats had bitten—as did the local pig farmers. By 1999, 265 people had developed severe brain inflammation, and 105 had died. It was the first known appearance of the Nipah virus in humans, which has since caused a series of recurring outbreaks across Southeast Asia.
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It is one of many infectious diseases normally confined to wildlife that have spread to people in areas undergoing rapid forest clearance. Over the past two decades, a growing body of scientific evidence shows that deforestation, by triggering a complex chain of events, creates the conditions for a variety of deadly pathogens—such as the Nipah and Lassa viruses, and the parasites that cause malaria and Lyme disease—to spread to many people.
As widespread burning continues today in tropical forests in the Amazon, and parts of Africa and Southeast Asia, experts have expressed concern about the health of people living on the border of deforestation. They also fear that the next serious outbreak could emerge from the forests of our world.
“It’s well established that deforestation can be a powerful driver of infectious disease transmission,” said Andy MacDonald, a disease ecologist at the University of California, Santa Barbara’s Earth Research Institute. “It’s a numbers game: The more we degrade and clear the forest habitat, the more likely we are going to find ourselves in this situation where an outbreak of an infectious disease occurs.”
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Malaria—which kills more than a million each year from infection by the mosquito-borne Plasmodium parasite—has long been suspected of going hand in hand with deforestation. In Brazil, while control efforts have dramatically reduced malaria transmission in the past—reducing 6 million cases a year in the 1940s to just 50,000 by the 1960s—cases have since risen steadily again in parallel with rapid deforestation and agricultural development. At the beginning of this century, there were over 600,000 cases a year in the Amazon basin.
Work in the late 1990s by Amy Vittor, an epidemiologist at the University of Florida’s Emerging Pathogens Institute, and others, suggested a reason why. Clearing forest patches appears to create ideal habitat along the forest edge for the Anopheles darlingi mosquito—the Amazon’s most important vector of malaria—to breed. Through careful surveys in the Peruvian Amazon, he found higher numbers of larvae in warm, semi-shaded pools, the kind that form on roadsides cut into the forest and puddles behind debris where water is no longer taken up by trees.
A man sprays to kill Aedes mosquitoes that carry the yellow fever virus in Matadi, Democratic Republic of Congo.
In a complex analysis of satellite and health data published recently in the journal Proceedings of the National Academy of Sciences, MacDonald and Erin Mordecai of Stanford University report the significant impact of deforestation across the Amazon basin on malaria transmission, in line with some previous research.
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Between 2003 and 2015, on average, they estimated that a 10 percent increase per year in forest loss led to a 3 percent increase in malaria cases. For example, in one study year, an additional 618 square miles (1,600 square kilometers) of cleared forest—equivalent to nearly 300,000 football fields—was linked to 10,000 additional cases of malaria. This effect is most pronounced in the interior of the forest, where few patches of forest remain intact, providing a moist fringe habitat that mosquitoes prefer.
With the ongoing burning of the Amazon, these results do not bode well; The latest data, released this week, reveals an area 12 times the size of New York City has been destroyed so far this year.
“I’m worried about what’s going to happen with shipping after the fire is over,” MacDonald said.
It’s difficult to generalize about mosquito ecology, which varies depending on the species and region, Vittor stressed. In Africa, studies have found little association between malaria and deforestation—perhaps because mosquito species there like to breed in sunlit waters and prefer open farmland to shady forested areas. But in Sabah, part of Malaysian Borneo, malaria outbreaks have also occurred in tandem with the eruption of forest clearing for palm oil and other plantations.
Deforestation And Impacts On Our Health And Nature
Mosquitoes are not the only animals that can transmit deadly diseases to humans. In fact, 60 percent of new infectious diseases that arise in humans—including HIV, Ebola, and Nipah, all of which originate from animals that live in the wild—are contracted by various other animals, most of them wildlife.
In a 2015 study, researchers at the Ecohealth Alliance, a New York-based nonprofit that tracks infectious diseases worldwide, and others found that “nearly one in three new and emerging disease outbreaks is linked to land-use changes such as deforestation ,” organization president Peter Daszak tweeted earlier this year.
Many viruses exist harmlessly with their host animals in the wild, because the animals have evolved alongside them. But humans can become unwitting hosts for pathogens when they explore or change forest habitats.
“We are completely changing the structure of the forest,” said Carlos Zambrana-Torrelio, a disease ecologist at the Ecohealth Alliance.
Deforestation Is Leading To More Infectious Diseases In Humans
For example, in Liberia the clearing of forests for palm oil plantations attracted hordes of rats that normally live in the forest, lured there by the abundance of palm fruits around plantations and settlements. Humans can become infected with the Lassa virus when they come into contact with food or objects contaminated with the feces or urine of virus-carrying rodents or the body fluids of an infected person. In humans, the virus causes dengue fever—the same type of disease caused by the Ebola virus—and in Liberia kills 36 percent of people infected.
Rats carrying the virus have also been detected in deforested areas in Panama, Bolivia, and in Brazil. Alfonso Rodriguez-Morales, a medical researcher and tropical disease expert at the Universidad Tecnológica de Pereira in Colombia, fears that their range will increase following the resurgence of fires in the Amazon this year.
Such a process is not limited to tropical diseases. Some of MacDonald’s research has revealed a curious connection between deforestation and Lyme disease in the Northeastern United States.
Borrelia burgdorferi, the bacteria that causes Lyme disease—is infected by ticks that depend on forest-dwelling deer to breed and get enough blood to survive. However, the bacteria is also found in the white-footed mouse, which happens to thrive in forests broken up by human settlement, MacDonald said.
Deforestation Of The Amazon Rainforest
Spillover of infectious diseases to humans is more likely to occur in tropical regions because the diversity of wildlife and pathogens is generally higher, he added. There, several animal-borne diseases—from blood-sucking bugs to snails—have been linked to deforestation. In addition to known diseases, scientists fear that some unknown deadly diseases are lurking in the forests that could be exposed as people encroach further.
Zambrana-Torrelio noted that the possibility of spillover to people may increase as the climate warms, pushing animals, along with the viruses they carry, into areas where they never existed before, she said.
Whether such a disease remains confined to the fringes of the forest or if it establishes itself in humans, unleashing pandemic potential, depends on its transmission, Vittor said. Some viruses, such as Ebola or Nipah, can be transmitted directly between humans, theoretically allowing them to travel around the world as long as there have been humans.
Century, could only travel the world and infect millions because it found a host in Aedes aegpti, a mosquito that thrives in urban areas.
New Data Shows Deforestation In Peruvian Amazon Responsible For Sizable Carbon Emissions
“I hate to think that another or some other pathogen could do such a thing, but it would be foolish not to consider it as a possibility to prepare,” Vittor said.
Ecohealth Alliance researchers have suggested that containing disease can be considered a new ecosystem service, i.e. benefits derived independently from natural ecosystems, such as carbon storage and pollination.
To make the case, their team worked in Malaysian Borneo to detail the exact cost of malaria, down to every hospital bed, and syringe used by doctors. On average, they found that the Malaysian government spends about $5,000 to treat each new malaria patient in the region—in some areas more than they spend on malaria control, Zambrana-Torrelio said.
Over time, that adds up, outweighing the profits that can be made by cutting down forests and making a compelling financial argument for leaving some forests standing, Daszak said.
The Impact Of Deforestation
He and his colleagues began working with the Malaysian government to incorporate this into land use planning, and are running a similar project with Liberian officials to
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