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Biology LibreTexts

47.3D: Climate Change and Biodiversity

  • Page ID
    14257
  • The global warming trend is recognized as a major biodiversity threat, especially when combined with other threats such as habitat loss.

    LEARNING OBJECTIVES

    Evaluate climate change and its impact on biodiversity

    KEY TAKEAWAYS

    Key Points

    • This warming trend is persistently shifting colder climates further toward the north and south poles, forcing species to move with their own adapted climate norms, while also facing habitat gaps along the way.
    • Climate shifts will move up mountains, resulting in the crowding of species higher in altitude and eliminating the habitat for those species adapted to those high elevations; indeed, some climates will completely disappear.
    • Global warming will also raise ocean water levels due to melted water from glaciers and the greater volume of warmer water; shorelines will be flooded, affecting many species; many islands will disappear altogether.

    Key Terms

    • anthropogenic: having its origin in the influence of human activity on nature
    • biodiversity: the diversity (number and variety of species) of plant and animal life within a region

    Climate Change

    Climate change, specifically, the anthropogenic (caused by humans) warming trend presently underway, is recognized as a major extinction threat, particularly when combined with other threats such as habitat loss. Scientists disagree about the probable magnitude of the effects, with extinction rate estimates ranging from 15 percent to 40 percent of species by 2050. Scientists do agree, however, that climate change will alter regional climates, including rainfall and snowfall patterns, making habitats less hospitable to the species living in them.

    Impact of Climate Change on Biodiversity

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    Grizzly-polar bear hybrid: Since 2008, grizzly bears (Ursus arctos horribilis) have been spotted farther north than their historic range, a possible consequence of climate change. As a result, grizzly bear habitat now overlaps polar bear (Ursus maritimus) habitat. The two kinds of bears, which are capable of mating and producing viable offspring, are considered separate species as historically they lived in different habitats and never met. However, in 2006 a hunter shot a wild grizzly-polar bear hybrid known as a grolar bear, the first wild hybrid ever found.

    The warming trend will shift colder climates toward the north and south poles, forcing species to move with their adapted climate norms while facing habitat gaps along the way. The shifting ranges will impose new competitive regimes on species as they find themselves in contact with other species not present in their historic range. One such unexpected species contact is between polar bears and grizzly bears. Previously, these two species had separate ranges. Now, with their ranges are overlapping, there are documented cases of these two species mating and producing viable offspring. Changing climates also throw off species’ delicate timing adaptations to seasonal food resources and breeding times. Many contemporary mismatches to shifts in resource availability and timing have recently been documented.

    Range shifts are already being observed. For example, some European bird species’ ranges have moved 91 km northward. The same study suggests that the optimal shift based on warming trends was double that distance, suggesting that the populations are not moving quickly enough. Range shifts have also been observed in plants, butterflies, other insects, freshwater fishes, reptiles, and mammals.

    Climate gradients will also move up mountains, eventually crowding species higher in altitude and eliminating the habitat for those species adapted to the highest elevations. Some climates will completely disappear. The rate of warming appears to be accelerated in the arctic, which is recognized as a serious threat to polar bear populations that require sea ice to hunt seals during the winter months; seals are the only source of protein available to polar bears. A trend to decreasing sea ice coverage has occurred since observations began in the mid-twentieth century. The rate of decline observed in recent years is far greater than previously predicted by climate models.

    Finally, global warming will raise ocean levels due to glacial melt and the greater volume of warmer water. Shorelines will be inundated, reducing island size, which will have an effect on many species; a number of islands will disappear entirely. Additionally, the gradual melting and subsequent refreezing of the poles, glaciers, and higher elevation mountains, a cycle that has provided freshwater to environments for centuries, will also be jeopardized. This could result in an overabundance of salt water and a shortage of fresh water.

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