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10: Threats to Biodiversity

Last updated

Sep 5, 2022
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- 9.6: Review
- 10.1: Extinction

Melissa Ha and Rachel Schleiger
Yuba College & Butte College via ASCCC Open Educational Resources Initiative

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Chapter Hook

The northern spotted owl (Strix occidentalis caurina) is a western North American owl species that prefers large swaths of pristine old growth forests (that typically take 150-200 years to mature) for nesting. Unfortunately, most western forests have been regularly harvested for timber since around the establishment of the Forest Service in 1905. Thus, this species preferred habitat has been largely destroyed and their populations have plummeted. Habitat destruction is the number one cause for species extinction globally. For some species that are very habitat specific, like the northern spotted owl, there are not as many conservation actions to choose from that can help reverse declining population trends.

Northern spotted own perched in a tree.

Figure $\PageIndex{a}$ Northern spotted owl perched in a tree. Image by USFS (licensed under CC-BY 2.0)

Biodiversity loss refers to the reduction of biodiversity due to displacement or extinction of species. The loss of a particular individual species may seem unimportant to some, especially if it is not a charismatic species like the Bengal tiger or the bottlenose dolphin. However, biologists estimate that species extinctions are currently many times higher the normal, or background, rate seen previously in Earth’s history. This translates to the loss of tens of thousands of species within our lifetimes. This is likely to have dramatic effects on human welfare through the collapse of ecosystems. Loss of biodiversity may have reverberating consequences on ecosystems because of the complex interrelations among species. For example, the extinction of one species may cause the extinction of another. To measure biodiversity loss, scientists assess which species are at risk of extinction as well as survey ecosystem decline.

The core threat to biodiversity on the planet is the combination of human population growth and the resources used by that population. The human population requires resources to survive and grow, and many of those resources are being removed unsustainably from the environment. The five main threats to biodiversity are habitat loss, pollution, overexploitation, invasive species, and climate change. Increased mobility and trade has resulted in the introduction of invasive species while the other threats are direct results of human population growth and resource use.

Attribution

Modified by Rachel Schleiger and Melissa Ha from Threats to Biodiversity and Importance of Biodiversity from Environmental Biology by Matthew R. Fisher (licensed under CC-BY)

Threats to Biodiversity

10.1: Extinction
Extinction is the global loss of a species. Five mass extinctions have occurred in geological history, and extinction rates were particular high during these events. Earth is currently experiencing a sixth mass extinction, which is driven by human activities. When mass extinctions are not occurring, extinction still occurs at a low rate, the background extinction rate. The local elimination of a species (extirpation) is also of conservation concern.
10.2: Measures of Biodiversity Loss
A common means of assessing biodiversity loss involves classifying species based on extinction risk. The Red List includes nine such categories. The species at greatest risk of extinction are called critically endangered, followed by endangered, vulnerable, and near threatened species. Biodiversity can also be gauged at the ecosystem level, both in terms of area and ecosystem diversity.
10.3: Habitat Loss
Habitat loss includes habitat destruction, altering the physical environment such that a species can no longer live there, and habitat fragmentation, which involves dividing a habitat into discontinuous patches.
10.4: Overexploitation
Overexploitation involves removing organisms at a faster rate than they can be replenished. Examples include the poaching of elephants, unsustainable hunting for bush meat, overfishing, and overcollection of slow-growing plants and fungi.
10.5: Pollution
Pollution is the release of harmful chemicals or other materials into the environment. Some types of air pollution results in acid deposition and climate change. Nutrient pollution of water bodies due to fertilizer overuse results in eutrophication.
10.6: Invasive Species
Invasive species are those occurring outside of their historical distribution that cause ecological and/or economic harm. Invasive species can overpredate or outcompete native species, sometimes causing their extinction or extirpation. Examples of invasive species include the Asian carp, zebra mussels, Bd (which causes a fungal disease in amphibians), purple loosestrife, and the European starling. Biological control employs other organisms to control invasive species and has had successes and fa
10.7: Climate Change
The release of greenhouse gases, like carbon dioxide and methane, when burning fossil fuels for energy causes climate change. Not only does climate change involve an increase in average global temperature, but it also results in unpredictable weather patterns. Climate change threatens biodiversity through a variety of mechanisms and can cause species range shifts, mismatched biotic interactions, sea level rise, and ocean acidification.
10.8: Data Dive- Threats to Biodiversity
10.9: Review

Chapter Hook

Attribution

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