Evaluate different methods of estimating the current extinction rate. Do you think that humans will induce a mass extinction on the same scale as the Big Five? Introduction: There is consensus in the scientific community that the current massive degradation of habitat and extinction of many of the Earth’s biota is unprecedented and is taking place on a catastrophically short timescale.
Based on extinction rates estimated to be thousands of times the background rate, figures approaching 30% extermination of all species by the mid 21st century are not unrealistic, an event comparable to some of the catastrophic mass extinction events of the past. The current rate of rainforest destruction poses a profound threat to species diversity. Likewise, the degradation of the marine ecosystems is directly evident through the denudation of species that were once dominant and integral to such ecosystems.
Indeed, this colloquium is framed by a view that if the current global extinction event is of the magnitude that seems to be well indicated by the data at hand, then its effects will fundamentally reset the future evolution of the planet’s biota. Robert Whittaker recognized an additional kingdom for the Fungi. The resulting five-kingdom system, proposed in 1969, has become a popular standard and with some refinement is still used in many works, or forms the basis for newer multi-kingdom systems.
It is based mainly on differences in nutrition: his Plantae were mostly multicellular autotrophs, his Animalia multicellular, heterotrophs and his Fungi multicellular saprotrophs. The remaining two kingdoms, Protista and Monera, included unicellular and simple cellular colonies. Extinction rates in the fossil records: The time at which an organism is classified as becoming extinct is when the youngest fossil of its form is found. It is likely that there would have been later examples of the organism present, which were simply not preserved.
It is known that some genera have existed for long periods around this time without leaving any known fossil record by the phenomena of Lazarus taxa. It is believed that these organisms were simply not preserved during the time they are missing, or preserved in offshore sediments as yet undiscovered. This may also be the case with many other organisms creating the illusion they are becoming extinct before they are in reality. Ecological Evolutionary Factor affecting the past extinction: Many claim that human activity caused a large scale of plants and animals extinction.
The others claim that human caused extinctions are on a similar scale to those that occurred 65 million years ago at the boundary between the Cretaceous and Tertiary eras when most species perished including the dinosaurs. This causes two distinct worries: (1) The loss of species will harm humans (2) Quite apart from any harm to humans; there is a duty to prevent “ecocide”. According to Peter Raven (National Academy of Science) “We are confronting an episode of species extinction greater than anything the world has experienced for the past 65 million years.
Of all the global problems that confront us, this is the one that is moving the most rapidly and the one that will have the most serious consequences. And, unlike other global ecological problems, it is completely irreversible. ” Different people evaluate this duty differently. Since the purpose of these pages is establish the sustainability of material progress, I’ll take the view that although biodiversity is an important amenity, we are mainly concerned with the extent to which losses of diversity are a threat to human progress.
One interesting fact in the article concerns the effect of an increase in temperature on the north-south range of a plant species, especially of trees. It turns out that the northern limit of a species is determined by temperature. As that limit is approached the rate of growth goes to zero. However, the rate of growth of a species does not decline as it approaches the southern limit of its range but remains stable or even increases. What determines a species’ southern boundary is competition from other species that require high temperatures.
For this reason the southern boundary of a species is likely to change slowly as its territory is gradually invaded by species liking warm temperature. The invasion is likely to begin in gaps caused by logging and various kinds of die-off. According to Lord Robert May (FRS)-Chief Scientific Adviser to the British Government. “Hardly a day passes without one being told that tropical deforestation is extinguishing roughly one species every hour, or maybe even one every minute.
Such guesstimates are based on approximate species-area relations, along with assessments of current rates of deforestation and guesses at the global total number of species (which range from 5 to 80 million or more. ) While such figures arguably have a purpose in capturing public attention, there is a clear and increasing need for better estimates of impending rates of extinction, based on a keener understanding of extinction rates in the recent and far past, and on the underlying ecological and evolutionary causes.
” Scientists who worry about extinctions often agree that the world will reach a new equilibrium as temperature increases – assuming it does. However, they worry that the rate of increase of temperature is unprecedented and that species, especially of plants, will migrate northward too slowly and become extinct. Roughly 43 percent of the earth’s terrestrial vegetated surface has diminished capacity to supply benefit to humanity because of the recent, direct impacts of the land use.
This represents 10 percent reduction in potential direct instrumental value (PDIV), defined as the potential to yield direct benefits such as agricultural, forestry, industrial and medical products. Capitalizing on the natural recovery mechanisms is urgently needed to prevent further irreversible degradation and to retain the multiple values of productive land. Differences in extinction rates among groups: Estimated Future extinction rates from the species area relations: A better way of studying rates of complete biota extinction levels has been developed with the analysis of isotopic ratios of Carbon.
When life is abundant there is almost completely carbon-12 within the geological record. Enzymes within organisms, passing into organic matter faster, more efficiently accept this isotope, which becomes lithified into rock. At times of lowered biotic activity, such as at an extinction event when a lot of life has been killed, the ratio of carbon-13 within the rocks will be higher as a higher proportion of carbon will be being fixed as carbonates inorganically. Inorganic precipitation of carbon does not differentiate between the different isotopes of carbon as life does.
By analyses of carbon isotope ratios it is then possible to see, by peaks in the carbon-13, at what times there has been a reduction of biotic activity. This is independent of whether organisms present are being preserved or not, and shows at what rates the extinction is occurring. Estimated future extinction rates from IUCN red Lists: Recent extinction rates are 100 to 1000 times their pre-human levels well known, but taxonomically diverse groups from widely different environments. If all species currently deemed threatened become extinct in the next century, then the future extinction rates will be 10 times recent rates.
Although new technology provides details on habitat losses, estimates of future extinctions are hampered by our limited knowledge of which areas are rich in endemics. The 2004 IUCN Red List contains 15,589 species threatened with extinction. The assessment includes species from a broad range of taxonomic groups including vertebrates, invertebrates, plants, and fungi. However, this figure is an underestimate of the total number of threatened species as it is based on an assessment of less than 3% of the world’s 1. 9 million described species. Among major species groups, the percentage of threatened species ranges between 12% and 52%.
The IUCN Red List identifies 12% of birds as threatened, 23% of mammals, and 32% of amphibians. Although reptiles have not been completely assessed, the turtles and tortoises are relatively well reviewed with 42% threatened. Fishes are also poorly represented, but roughly a third of sharks, rays and chimaeras have been assessed and 18% of this group is threatened. Regional case studies on freshwater fishes indicate that these species might be more threatened than marine species. For example, 27% of the freshwater species assessed in Eastern Africa were listed as threatened.
Of plants, only conifers and cycads have been completely assessed with 25% and 52% threatened respectively. References: Robert M. May, John H. Lawton and Nigel E. Stork. “ Assessing Extinction Rates” “Extinction Rate Analysis” http://palaeo. gly. bris. ac. uk/Palaeofiles/Permian/rateanalysis. html “Restoring the value to the worlds degraded Lands” Gretchen C. Daily “The future of biodiversity “ Stuart L. Pimm, Gareth j. Russell, John L. Gittleman ,Thomas M. Brook “IUCN Red List of Threatened Species”http://www. iucn. org/themes/ssc/red_list_2004/GSAexecsumm_EN. htm References: IUCN 2001. IUCN Red List Categories and Criteria: Version 3. 1.
IUCN Species Survival Commission, IUCN, Gland, Switzerland and Cambridge, UK, pp. ii+30. Parr C. S. and Cummings M. P. 2005. Data sharing in ecology and evolution. Trends Ecol. Evol. 20: 362–363. Purvis A. and Rambaut A. 1995. Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data. Comput. Appl. Biosci. 11: 247–251. Sherwood, Keith and Craig Idso (2003) “The Specter of Species Extinction Will Global Warming Decimate Earth’s Biosphere? ” 2003 September John Lawton and Robert May “BIODIVERSITY AND EXTINCTION RATES” 17-May-2004) www-formal. stanford. edu/jmc/progress/biodiversity. html