extinction rate

Examples of extinction rate in the following topics:

• Present-Time Extinctions

  • Human activities probably caused the Holocene mass extinctions; many methods have been employed to estimate these extinction rates.
  • The background extinction rate is estimated to be about one per million species per year (E/MSY).
  • One contemporary extinction rate estimate uses the extinctions in the written record since the year 1500.
  • Taking these factors into account raises the estimated extinction rate closer to 100 E/MSY.
  • This work argues that the species-area relationship leads to an overestimate of extinction rates.

• Biodiversity Change through Geological Time

  • Biodiversity has been affected by five mass extinction periods, which greatly influenced speciation and extinction rates.
  • When speciation rates begin to outstrip extinction rates, the number of species will increase; likewise, the number of species will decrease when extinction rates begin to overtake speciation rates.
  • There are many lesser, yet still dramatic, extinction events, but the five mass extinctions have attracted the most research.
  • The Ordovician-Silurian extinction event is the first-recorded mass extinction and the second largest.
  • The end-Permian extinction was the largest in the history of life.

• Climate Change and Biodiversity

  • 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.
  • 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.
  • The rate of decline observed in recent years is far greater than previously predicted by climate models.

• Newly Discovered Eukaryotes

  • Of course we may never truly identify many eukaryotic species, since the rate of extinction has increased.
  • Many extant species may become extinct before they are described.

• Biodiversity of Plants

  • Plant biodiversity, vital to ecosystems, food crops, and medicine production, is threatened by habitat destruction and species extinction.
  • The explosion of the human population, especially in tropical countries where birth rates are highest and economic development is in full swing, is leading to human encroachment into forested areas.
  • Ebony and Brazilian rosewood, both on the endangered list, are examples of tree species driven almost to extinction by indiscriminate logging .
  • The number of plant species becoming extinct is increasing at an alarming rate.
  • They may become extinct before we have the chance to begin to understand the possible impacts resulting from their disappearance.

• Loss of Biodiversity

  • In fact, there were several factors that played a role in the extinction of perhaps 200 cichlid species in Lake Victoria.
  • Extinction, a natural process of macroevolution, occurs at the rate of about one out of 1 million species becoming extinct per year.
  • The fossil record reveals that there have been five periods of mass extinction in history with much higher rates of species loss.
  • The rate of species loss today is comparable to those periods of mass extinction.
  • However, there is a major difference between the previous mass extinctions and the current extinction we are experiencing: human activity.

• Managing Fisheries

  • Overfishing leads to fishery extinctions, loss of a food source, and affects many other species in ways that may be impossible to predict.
  • Resource depletion, low biological growth rates, and critically low biomass levels result from overfishing.
  • Fishery extinctions rarely lead to complete extinction of the harvested species, but rather to a radical restructuring of the marine ecosystem in which an abundant species is so over-harvested that it becomes a minor player, ecologically.
  • In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction.
  • In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction.

• Past and Present Effects of Climate Change

  • Results of climate change, past and present, have been documented and include species extinction, rising sea levels, and effects on organisms.
  • Global warming has been associated with at least one planet-wide extinction event during the geological past.
  • The Permian extinction event occurred about 251 million years ago toward the end of the roughly 50-million-year-long geological time span known as the Permian period.
  • On average, the sea is rising at a rate of 1.8 mm per year.
  • However, between 1993 and 2010, the rate of sea-level increase ranged between 2.9 and 3.4 mm per year.

• Overharvesting

  • Ecologists use the term to describe populations that are harvested at a rate that is unsustainable, given their natural rates of mortality and capacities for reproduction.
  • Overharvesting can lead to resource destruction, including extinction at the population level and even extinction of whole species.
  • In these cases (for example, whales) economic forces will always drive toward fishing the population to extinction.
  • In turn, the unchecked prey can then overexploit their own food resources until population numbers dwindle, possibly to the point of extinction.

• Population Trends

  • The world population growth rate was estimated at 1.1% per year as of 2011, a rate which has declined since its peak during the 1950s–1970s.
  • The demographic transition refers to the shift from high birth rates and death rates to low birth and death rates; this occurs as part of the economic development of a country.
  • The basic premises of the theory are as follows: in pre-industrial societies, population growth is relatively slow because both birth and death rates are high; as countries develop, death rates fall faster than birth rates do, resulting in large population growth; as development stabilizes, birth rates drop off and the population stabilizes .
  • Malthus argued for population control—policies intended to lower the birth rate—to avoid this happening.
  • Objections to this argument include that a huge number of plant and animal species would go extinct; terrible pollution would arise in some areas, and it would be difficult to abate; and moral problems would be created—great suffering for the people who do not have access to resources.