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Human Impacts on Biodiversity | Ecology and Environment | Biology | FuseSchool

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comprehensive article on how humans affect biodiversity

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comprehensive article on how humans affect biodiversity

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The effects of overpopulation and overconsumption are not only felt locally or nationally. Pollution generated in one region can affect the air, water, vegetation or animals in another. The effect of global CO2 changes, loss of biodiversity and marine pollution do not respect political boundaries and ultimately affect everyone in the world.

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Written by Kari Norborg Carter

Biodiversity, the rich variety of living things that have evolved over millions of years to live in particular habitats, contributes to the beauty of natural ecosystems as well as to their resilience and stability. But certain stressors, most of them human-caused or human-influenced, threaten or reduce biodiversity. Because the creatures and plants in ecosystems are interdependent, the loss of even one species can have profound effects on the entire ecosystem, can affect other ecosystems and can endanger people as well. As biologist Edward O. Wilson said, "It is reckless to suppose that biodiversity can be diminished indefinitely without threatening humanity itself."

Overexploitation

Overexploitation means harvesting species more rapidly than populations can replenish themselves or to do so at unsustainable levels. All over the world, people collect or hunt wild plants, birds, mammals, amphibians, fish, reptiles and other animals or their eggs for purposes as varied as commercial fishing; fur, skin or feathers for fashion; meat; lumber; sport; scientific research; superstitious beliefs; medicine; the pet trade and zoos. Hunting threatens about one-third of threatened mammals and birds in the world and poses the most immediate threat to large animals that reproduce slowly, including elephants, antelopes, rhinoceroses, jaguars and primates. Animals that humans hunted or harvested to extinction include the passenger pigeon, great auk, dodo, Zanzibar leopard, Pyrenean ibex, Javan tiger, Falkland Island wolf, Caribbean monk seal, Tasmanian tiger, Carolina parakeet, Stellar's sea cow, West African black rhinoceros and sea mink.

Habitat Loss

Habitat loss and fragmentation due to development, ranching, agriculture and pollution has a huge impact on biodiversity as human populations continue to grow. Deforestation of tropical rainforests has had perhaps the most dramatic effect on biodiversity, both directly in the loss of species in these incredibly diverse ecosystems and indirectly through the increased threat of global warming. Tropical rainforests hold at least 50 percent of the world's species, and they are also known as the "lungs of the earth" for their role in producing oxygen and absorbing carbon dioxide. Today, less than half of the world's tropical rainforests remain from what existed a few thousand years ago, and that destruction continues at a rate of about 80,000 acres per day. More than 85 percent of all natural habitat in Europe has disappeared since the mid-Holocene, and more than 96 percent of native tallgrass prairie and 50 percent of wetlands in the United States have been destroyed since the arrival of Europeans. In addition, habitat fragmentation, the division of ecosystems and populations of species into smaller, isolated, sometimes unsustainable parcels, often causes loss of biodiversity by increasing vulnerability of some populations to disease and other stressors, leaving habitats too small for some species to survive. Pollutants such as acid rain, air pollution, fertilizers, herbicides and pesticides alter and destroy habitats and their species in numerous ways as well.

Invasive Species

Non-native, introduced, alien or invasive species are plants, animals, diseases or other organisms transferred unnaturally from one ecosystem to another, either intentionally or unintentionally. They can pose a threat to biodiversity when they possess adaptations that help them out-compete, prey upon or interbreed with native species in their new ecosystem, especially in isolated ecosystems such as islands or freshwater habitats. For example, humans introduced the Nile Perch for sports and subsistence fishing to Lake Victoria in Africa, where it has eaten many of the native species and very well might lead to their extinction. In North America, an exotic beetle carrying Dutch elm disease has destroyed most large elm trees, the exotic emerald ash borer has killed hundreds of millions of ash trees and purple loosestrife has choked out much native vegetation in wetlands, devastating the wetland ecosystems. Scientists estimate that introduced species have contributed to at least half of the species extinctions that have occurred since 1600.

Climate Change

Climate change is generally more gradual than habitat destruction, but it threatens ecosystem biodiversity because climate strongly influences the kinds of organisms that have adapted to each ecosystem. Average global temperatures are predicted to rise by up to 4°C by 2100, and most scientists argue that the increase in atmospheric carbon dioxide and methane from combustion and the burning of fossil fuels strongly exacerbates this. Overall climate pattern changes, including changes in precipitation, jeopardize food and water sources, negatively impact breeding and nesting habits, change species' geographic ranges, increase drought in some areas and flooding in others, alter competition patterns in species and pose other problems. Although climate change is relatively gradual compared to some factors affecting biodiversity, it is becoming more rapid and may be proceeding too swiftly for many native species to adapt.

About the Author

Kari Norborg Carter is a college English instructor and writer. She has a Bachelor of Science in biology and Master of Arts in English and has worked many years as an educator and as a writer and editor for academic, science and environmental publications. She has also published fiction and essays.

Photo Credits

Stockbyte/Stockbyte/Getty Images

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What Factors Influence the Biodiversity of an Ecosystem?

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Biodiversity, the rich variety of living things that have evolved over millions of years to live in particular habitats, contributes to the beauty of natural ecosystems as well as to their resilience and stability. But certain stressors, most of them human-caused or human-influenced, threaten or reduce biodiversity.

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Factors Affecting Biodiversity: Year 1 of OCR A level Biology

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Factors Affecting Biodiversity | A-level Biology | OCR, AQA, Edexcel