TROPICAL RAINFORESTS: Disappearing Opportunities
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Forest clearing in Peru. (Photo by R. Butler)

LOSS OF SPECIES FOR FOREST REGENERATION

A fully functioning forest has a great capacity to regenerate. Exhaustive hunting of tropical rainforest species can reduce those species necessary to forest continuance and regeneration. For example, in Central Africa, the loss of species like gorillas, chimps, and elephants reduces the ability of seed dispersal and slows the recovery of damaged forest. Loss of habitat in the tropics also affects the regeneration of temperate species. North American migratory birds, important seed dispersers of temperate species, declined 1-3 percent annually from 1978-1988.

INCREASE OF TROPICAL DISEASES

The emergence of tropical diseases and outbreaks of new diseases, including nasty hemorrhagic fevers like ebola and lassa fever, are a subtle but serious impact of deforestation. With increased human presence in the rainforest, and exploiters pushing into deeper areas, man is encountering "new" microorganisms with behaviors unlike those previously known. As the primary hosts of these pathogens are eliminated or reduced through forest disturbance and degradation, disease can break out among humans. Although not unleashed yet, someday one of these microscopic killers could lead to a massive human die-off as deadly for our species as we have been for the species of the rainforest. Until then, local populations will continue to be menaced by mosquito-borne diseases like dengue fever, Rift Valley fever, and malaria, and water-borne diseases like cholera.

Many emergent and resurgent diseases are directly linked to land alterations which bring humans in closer contact with such pathogens. For example, malaria and snailborne schistosomiasis have escalated because of the creation of artificial pools of water like dams, rice paddies, drainage ditches, irrigation canals, and puddles created by tractor treads. Malaria is a particular problem in deforested and degraded areas, though not in forested zones where there are few stagnant ground pools for mosquito breeding. These pools are most abundant in cleared regions and areas where tractors tear gashes in the earth. Malaria is already a major threat to indigenous peoples who have developed no resistance to the disease nor any access to antimalarial drugs. Malaria alone is cited as being responsible for killing an estimated 20 percent of the Yanomani in Brazil and Venezuela. Malaria—caused by unicelluar parasites transferred in the saliva of mosquitoes when they bite—is an especially frightening disease for its drug-resistant forms. Thanks to poor prescribing techniques on the part of doctors, there are now strains in Southeast Asia reputed to be resistant to more than 20 anti-malarial drugs. There is serious concern that global climate change will affect the distribution of malaria, which currently infects roughly 270 million people worldwide and kills 1-2 million a year— 430,000-680,000 children in sub-Saharan Africa alone.

Disease-Environment articles

  • Emerging (disease) markets
  • Clearing rainforest for cattle pasture drives surge in vampires
  • Ebola outbreaks may worsen with global warming
  • Demise of passenger pigeon may be linked to Lyme disease
  • Environmental damage linked to new diseases says WHO
  • Controlling Wildlife Trade Key to Preventing Disease Outbreaks, Study Says
  • Ebola, SARS battle requires new look at humans, livestock, and wildlife relationships
  • Now identified as likely origin of SARS, will bats be killed in China?
  • The outbreak of disease in the tropics does not affect only the people of those countries, since virtually any disease can be incubated for enough time to allow penetration into the temperate developed countries. For example, any Central African doctor infected with the ebola virus from a patient can board a plane and land in London within 10 hours. The virus could quickly spread, especially if airborne, among the city's population of 8 million. Additionally, every person at the airport who is exposed can unknowingly carry the pathogen home to their native countries around the world.

    According to the Centers for Disease Control (CDC) in Atlanta, deaths from infectious disease are on the rise. Infectious disease is the leading cause of death worldwide and the third leading cause of death in the United States. Though AIDS death rates are declining in wealthier countries, this infectious disease is still killing millions around the globe. Demographers predict several African countries may achieve zero population growth within a generation partly due to the toll from AIDS. Of even greater concern, according to the CDC, in 1994 10 percent of people who died before 50 did so suddenly and mysteriously, probably from some unidentified infection. Strangely, the U.S. invests only $42 million a year in infectious-disease surveillance, yet spends $225 million maintaining marching bands for the military (Crenson 1997). The times may be changing, though: in the fall of 1997, Congress allocated funds for the establishment of a world monitoring system to detect emerging infectious-disease outbreaks. Infectious disease have had a major role in human mortality throughout history. At least one-third of human deaths during World War I came from an infectious disease: influenza. In 1919, between 20 million and 100 million died from the flu—more than the number of total casualties from the war.


    Review questions:
    • How is deforestation linked to the emergence of disease?

    [print version | spanish | french | portuguese | chinese | japanese]


    Continued: Loss of Renewable Resources, Wildlife Conflict


    This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.




    Other pages in this section:
    Consequences of Deforestation
    Erosion
    Loss of Renewable Resources
    Atmospheric Role
    - - - - -
    References
    References
    References
    References
    References
    Local Climate Regulation
    Loss of Species, Disease
    Climactic Role
    Extinction
    - - - - -
    Kids version of this section
    - Why are rainforests important?
    - Climate
    - Home to wildlife
    - Water cycle
    - Erosion control
    - Extinction


    Recent news

    Birds found to be key protectors of forest in Tanzania
    (07/02/2009) Seed-eating birds play a critical role in maintaining forests in the Serengeti by keeping seed-killing beetles in check, report researchers writing in the journal Science. The finding is another example of ecological interdependency between species.


    869 species extinct, 17,000 threatened with extinction
    (07/02/2009) Nearly 17,000 plant and animal species are known to be threatened with extinction, while more than 800 have disappeared over the past 500 years, reports the International Union for Conservation of Nature (IUCN). While these numbers are substantial, they are likely "gross" underestimates since only 2.7 percent of 1.8 million described species have been assessed. The IUCN report warns that governments will miss their 2010 target for reducing biodiversity loss.


    A New Idea to Save Tropical Forests Takes Flight
    (06/29/2009) Every year, tens of millions of acres of tropical forests are destroyed. This is the most destabilizing human land-use phenomenon on Earth. Tropical forests store more aboveground carbon than any other biome. They harbor more species than all other ecosystems combined. Tropical forests modulate global water, air, and nutrient cycles. They influence planetary energy flows and global weather patterns. Tropical forests provide livelihoods for many of the world’s poorest and marginalized people. Drugs for cancer, malaria, glaucoma, and leukemia are derived from rainforest compounds. Despite all these immense values, tropical forests are vanishing faster than any other natural system. No other threat to human welfare has been so clearly documented and simultaneously left unchecked. Since the 1992 Rio Earth Summit (when more than 100 heads of State gathered to pledge a green future) 500 million acres of tropical forests have been cut or burned. For decades, tropical deforestation has been the No. 1 cause of species extinctions and the No. 2 cause of human greenhouse gas emissions, after the burning of fossil fuels. For decades, a few conservation heroes tried their best to plug holes in the dikes, but by and large the most diverse forests on Earth were in serious decline.


    Anti-HIV and anti-cancer drugs derived from Borneo rainforest progressing to final development stages
    (06/29/2009) Two drugs derived from rainforest plants in Sarawk (Malaysian Borneo) are now in their final stages of development, reports Bernama.


    Rainforest discovered via Google Earth to be protected
    (06/29/2009) Mozambique has agreed to protect a tract of highland forest discovered by scientists using Google Earth, reports The Guardian.



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    Copyright Rhett Butler 1994-2009

    "Rainforest" is used interchangeably with "rain forest" on this site. "Jungle" is generally not used.