This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.
Catastrophic events have had a dramatic effect on the environment of the Earth for billions of years. Past events are the key to predicting the future. Fossil record of glacial cores and oceanic sediments are fundamental for evidence of the four recent glacial-interglacial changes in climate over the past 2.5 million years. The historical timescale of life on Earth gives an insight into the physiological and morphological changes of organisms over evolutionary time. The degree of environmental changes throughout most of the Cenozoic era is crucial to predicting the future of biota in Britain over the next one million years. Many different theories of the forthcoming century will be discussed. One theory has been proposed by a religious Mayan tribe over many centuries, that the world will come to an end in 2012 (Montuori, 2010). Other theories of the future include the rising sea levels due to an increased temperature from global warming and the melting of the ice sheets in Greenland and Antarctica. Human impacts on Earth greatly affect the upcoming environmental conditions by adding to global warming; adding to the ozone (O3) in the troposphere and hence heating up the Earth. This will bring forth a fluctuation in climate by which humans will have to acclimatize to extreme environmental conditions in order to survive. Prevention of potential natural disasters is still currently undergoing in attempt to gain control over the possible spiralling environmental changes. One way to do this is through geoengineering. There are many possible outcomes for biota of Britain in the next ten decades. Relating back to their response to the environment over the past 2.5 million years allows various predictions to be put forward and the extent that each of the possible scenarios to be determined.
Firstly, the past events from 2.5 million years ago (mya) are considered. The past 2.5 million years includes the Quaternary period; Holocene and Pleistocene and also some of the Pliocene epoch. It is thought that the Earth becoming colder in the later Pliocene was the cause of the quaternary glaciations (Bintanja, 2008). Glaciations are also known as ice ages and have occurred over the past 2.58 million years according to...(ref). 2.5mya was a glaciation known as the Waltonian, by which lower Pleistocene glaciations follow. The lower Pleistocene was between 1.8-1.6mya and consists of 4 intermitting stages: 2 tree rich, temperate phases and 2 glacial episodes by which Britain supported tundra and very few tree species. Pines, silver fir and wing nuts were common during these Ludhamian and Antian temperate phases. In the middle Pleistocene, approximately 700kya there were temperate, cold, temperate sequences. Temperate stages supported mammals such as the straight tusked elephant and woolly rhinoceros. The three main glaciations which affected Britain are the Anglian, Wolstonian and the Devensian. The Anglian glaciation occurred around 480-430kya. From 430kya was a temperate stage called the Hoxnian, is cooler than the present. Biota in Britain at this time included aurochs, lions, mammoths, woolly rhinoceros, alder and oak trees. This is followed by a second major glaciation of Britain which is named Wolstonian, in the upper Pleistocene 380kya. Vostok Antarctic core data was gathered from this East Antarctica glaciation (Petit et al, 1999). The Ipswichian period occurred between 130-110kya and was warmer than at current and a higher sea level, giving rise to biota such as water chestnuts, brown bears red deer and spotted hyenas. Flooding occurred during this time at the land bridge between Britain and Europe. Next was the Devensian; another main British glaciation from 110kya towards the beginning of the Holocene, 10.5mya. Afterwards was another interglacial: Flandrian, 10.5mya to the present. Sea levels have increased during this phase due to melting of ice and marine transgression. From 10.5mya-9.6mya was the pre-boreal where there was decreasing rainfall and tundra vegetation as well as a hotter climate. Wild horses became extinct along with many other Scottish mammalians. Following was the Boreal between 9.6 and 7kya which became increasingly hotter in climate and migration in pollinating trees. 7-4.8kya was the Atlantic, further increase in rainfall and temperature resulting in rising sea levels and increased precipitation. The land bridge between Britain and Europe disappeared due to flooding. Approximately 4.8-3kya was the sub-boreal by which temperature began to fall and deforestation reaches its peak towards the Bronze Age around 3.7kya. Dutch elm disease in Ulmus species is a common feature of this phase. Sub-Atlantic is from 3kya up to the present and includes the continued forest clearance in the Iron Age which began around 2.5kya.
Within an interglacial there are four key phases, in order of occurrence: protocratic, mesocratic, oligocratic, and telocratic as shown in figure 1 (Birks, 2004). Glaciations are denoted as cryocratic phrases and these cold episodes are also known as stadials. These five phases form a glacial-interglacial cycle. Temperatures increase at the start of an interglacial as well as plant biomass (primary succession), fungi, litter decomposition and soil fertility; a higher release rate of nitrogen and phosphorus. Maximum plant biomass is reached between the mesocratic and oligocratic phases of interglacials. Fossil records of pollen grains give evidence that regressive succession occurs towards the later part of interglacial, in the oligocratic and telocratic phases when tree biomass and phosphorus levels of the soil decreases. The interglacial occurring at present; in the Holocene is proven by fossil evidence of pollen grains to have regressive succession towards the telocratic phase. Interglacial-glacial transitions have stabilized dramatically in Britain throughout the Holocene from the rapid fluctuations during the Pleistocene epoch. In cryocratic phrases during glaciation the temperature decreases becoming exceedingly cold and dry, plant biomass decreases greatly and there is very little species diversity. Also, soils become infertile due to the lack of phosphorus and increase in alkalinity.
Figure 1: The changes in glacial-interglacial stages. (Birks 2004)-ref properly!??
Carbon dating, continental deposits of fauna and flora, isotope manipulation of ice-cores and deep sea marine sediments provides evidence of Glacial-interglacial climate changes. Ice cores give access to palaeoclimate series that includes local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin. They are also unique with their entrapped air inclusions in providing direct records of past changes in atmospheric gas composition. Dust composition, ice volume, as well as CO2 and CH4 concentrations change during the glacial-interglacial periods. Plate tectonics also effect glacial-interglacial cycles as when mountains are formed, weathering occurs, this reduces CO2 levels in the atmosphere producing a gradual decrease in temperature. Ice forms in layers, by which old layers of ice trap air that can show indication of atmospheric conditions long ago. Records of CO2 in the atmosphere over the past 800kyr's are known. During glacial episodes lower levels of CO2 and CH4 were found than interglacial periods. Ratios of oxygen isotopes in deep sea cores of the North Sea are also good indicators of the seventeen cold cycles of the Pleistocene and Holocene.
Continental drift occurred in the tertiary period, causing increased sea levels from the resulting tectonic activity. The ocean is constantly circulating in a conveyer belt fashion and lasts roughly 170 million years before closing from the movement and deformation of the Earth's crust. Sea levels increase with increasing temperature due to the oceans thermally expanding and the melting of glacial sheets because of enhanced sunlight intensity which also causes greenhouse gases to rise. A permanent ice sheet composed of oceanic water developed across the Antarctic and Greenland towards the end of the tertiary period around 2.5mya (ref?). A gradual decrease in temperature towards the end of the tertiary period, led to the formation of glacial sheets. This was the first of eight glacial-interglacial stages that occurred throughout the quaternary. Each glacial-interglacial cycle occurred around every 100k years. During the warmer interglacial stages, the ice melts, leaving drifted deposits of sand, clay and gravel all over the land. According to Toghill (2002), the last glacial was the Devensian glacial which took place about 100kya and peaked to a maximum 18kya. He found that in Britain the ice reached 2km wide and the eustatic effect depressed the Earth's surface. Also, sea levels decreased due to the isostatic effect of the ice. Since the beginning of the Holocene, 10kya to the present is an interglacial stage. Therefore, it is estimated that the next glacial will be expected to occur in about 5k years time (Toghill, 2002).
Milankovitch cycles were named by Milutin Milankovitch in 1930 by his theory that the variations in latitude and seasons greatly affect the glacial-interglacial cycles. These cycles around the Earth cause variations in intensity of the sun on the Earth's surface as the sun orbits, causing climate changes which trigger glacial-interglacial variations.
The Homo genus first appeared in Africa as the Homo erectus according to Finlayson, (2004) about 1.9mya. Parfitt etÂ al (2010) explained that humans did not migrate into mainland Europe until ~1.8mya and that human activity was found in Happisburgh, Britain by fossil evidence around 780kya, towards the end of the lower Pleistocene. The human population was low because of the variation in climate at this time. Homo neanderthalansis emerged around 400kya and evolved into Modern humans (Homo sapiens) at the start of an inter-glacial 130kya when the climate changed faster than they could adapt (Finlayson, 2004). Homo neanderthalansis survived the many cold glaciations before migrating North during the rapid fluctuations in temperature during the upper Pleistocene. The Homo lineage have always been omnivores and they migrated North due to the vast supply in mammalian meat compared to other regions. Homo sapiens evolved from Homo neanderthalansis via allopatric speciation.
The fact is our Earth is enduring human impacts that produce many negative environmental effects, such as increased global warming from carbon emissions, melting polar caps, increased solar system phenomena, as well as wiping out many endangered species. The green house effect has continued to increase over the decades especially since the added influence of Homo sapiens from the mid-Holocene (5-6kya).
Green house gases include CO2, N2O, O3, CFC's and CH4. CO2 is released by respiring creatures, the burning of fossil fuels, deforestation and during ocean evaporation. Photosynthesising organisms of the planet like plants reduce the amount of CO2 in the atmosphere. CFC's are also known as chlorofluorocarbons and have increased over the past few decades. Examples of when these gases are emitted are caused by lightening, landfills, fossil fuels and coal mining. The more intense the sun's rays, the hotter the Earth's surface and the greater amount of energy emitted. Decreasing the UV-B rays hitting the Earth's surface would help prevent a further increase to the ozone layer. Also, preventing further increase in the human population by limiting reproduction and hence consumption. In addition, reflecting solar radiation via mirrors or aerosols because ice cover increases the albedo due to the more reflective, mirror-like surfaces. There are less greenhouse gases emitted into the atmosphere in cold periods, therefore increased temperature produces a greater amount of greenhouse gas emissions, adding to the ozone layer around the Earth.
Many measures have been taken in order to impede the effects of global warming and stop them from further developing including geoengineering. This aims to counteract the effect of global warming by, for example removing CO2 from the atmosphere in iron fertilization. This is due to phytoplankton developing well in iron rich surface waters. However, the problem is that many deep sea biota are unable to tolerate increased levels in oceanic CO2. Also, phytoplankton is unable to uptake CO2 when levels are high, producing more alkaline conditions and making less iron available. Another strategy includes humans reducing the usage of the limited supply of fossil fuels and use renewable sources of energy instead. Solar mediated technologies could be used such as wind turbines which decreases the emissions of greenhouse gases.
There is much evidence to indicate that CO2 and CH4 levels will continue to rise in the future...(ref...climate..change..book-not..British!...&no's/%s). Methane and nitrous oxide are commonly released during agriculture. Carbon dioxide, methane and nitrous oxide are all released by human induced deforestation. Agriculture originated polyphyletically around 8kya and provides food sources for humans in much of Britain's landmass today. Reduction in agriculture would increase global warming; therefore crop production and reforestation can be beneficial to the planet. The increase in carbon emissions from burning of fossil fuels and land use changes exceeds its decrease from the removable effects of geoengineering, and the process of photosynthesis like in plants. Examples of C3 and C4 plants are wheat and corn respectively. High CO2 levels are more ideal for C3 plants than C4 plants; hence C3 plants generally outperform C4 plants under these conditions. However, C4 plants are usually more tolerable to high temperatures. C4 plants productivity increased in the tertiary period when atmospheric CO2 levels declined. During the quaternary and at present, C3 plants dominate C4 plants due to the increasing atmospheric CO2. However, some C3 plants are not as responsive to high CO2 levels such as rice. Rice is in great demand as a food source for human agriculture. An increased population of people dependant on rice would cause sea levels to rise. During the Flandrian interglacial, 17k-7kya sea levels have risen by 120 metres (Toghill, P. 2002). Increased sea levels have the greatest impact on humans, as the effects of flooding are disastrous. It is predicted that sea levels will increase by approximately 0.5metres within the next century, according to the Intergovernmental Panel on Climate Change (IPCC) (1990). This is without the possible effects of the melting of Greenland's and Antarctica's glaciers, which would increase levels about 70metres higher than currently (Alley et al. 2005).
In extreme environmental conditions such as high or low temperatures, animals must undergo migration otherwise they will not survive as they are intolerable to temperatures outside a limited range. Therefore migration of species is common during glacial-interglacial cycles as temperatures change in the sequence warm, cold, and then warm again. As discussed previously, after each glaciation landforms are produced and form features during the melting part such as clays.
Conservation of endangered species attempt to prevent extinctions in the future. The process involves identifying the most threatened species. These are then ranked to produce a red list of endangered species, to allow the possible occurrences to be predicted and intervene on all the biota of the ecosystems, checking that they would be highly invasive. Conservationists value experiments such as those that involve capture and recapture of small mammals as they can help to give an estimate of the population size and biodiversity of different ecosystems. This is a good starting point to allow species most vulnerable to extinction to be highlighted. Fossil record and phylogenetic trees provide an insight to whether or not particular species succeeded well under different environmental conditions as well as a comparison of with and without anthropogenic effects. Fossil record in particular allows the responses of species to climate change over the Palaeocene epoch to be taken into account. Like oceans, organisms are present for a limited amount of time and will eventually become extinct. Fossil records give Conservationists evidence of the time frames of particular species on Earth. Therefore, it is more producible to conserve species that are expanding compared to those that have inhabited the Earth over a longer period of time. Careful consideration has to be given on how conserving one particular species may affect another. The species abundance over the rest of the world must also be thought about when deciding on species to conserve. The past and existing state of the planet provides clues to possible occurrences in the future, which is why conservation is very important as it could dramatically influence future events.
Implications and predictions of the future...
A prophecy that states that there will be an apocalypse on December 21st 2012 (Montuori, 2010). They believe in cyclical timescales by which the past will repeat in the present and that 2012 is the year that sunspots will climax.
There are many possibilities for the next century. The Earth's rotation could slow down, reducing seasonality. Increasing temperatures could cause volcano eruptions, heating up rivers, and killing fish due to the increase in bacteria levels.
Biota in Britain over the past 2.5 million years have responded to environmental changes by undergoing natural selection to conform to their environments as stated by Charles Darwin (1859). The impact on biota in Britain today is high due to the increase of CO2, temperature, precipitation, sea levels, UV-B rays and tropospheric O3. There are many consequences of human actions in Britain and all over the world. Global warming is one of them, with the addition of emissions natural occurrences to the O3 layer in the troposphere exceeds the gases removed from the atmosphere by photosynthesis and oceanic surface waters. Reducing emissions of greenhouse gases, geoengineering and the usage of fossil fuels are current strategies that are undergoing to attempt to help the planet in some way. Variations in rainfall have increased throughout the Holocene epoch and will continue to increase in the future. The fact that the sea level is already increasing makes it very likely that sea levels will continue to rise over the next century. Another ice age is likely to happen in the future to some extent, but within the 10 decades to a lower extent. Developments of the future may include extinctions of Homo sapiens all together or them diverging to a different lineage via geographical speciation. Fossil record is greatly relied upon for producing a picture of past occurrences however; it is unlikely for these events to appear as reoccurrences. An apocalypse is possible at some point in the future however; it is unclear if this will happen within the next century as proposed by the Mayan prophecy (Montuori, 2010). The real question is: to what extent are past events key to the future? They are probable, however, it is also feasible for a total different scenario to occur; one that is totally unique and has not happened before. The fact is predictions are merely ideas and a total different outcome may persist; this is something that only time can reveal.