The Oligocene Epoch (c. 34 to 23 mya) was relatively cold. In the 1960s, a , the recovered nearly 20,000 cores from Earth’s oceans, and scientists had paradigm-shift learning experiences from studying those cores. One finding was that Antarctica developed its ice sheets far earlier than previously supposed, and the cores pushed back the initial ice sheet formation by 20 million years, ; the first Antarctic glaciers formed as early as 49 mya. The evidence included in sediments, which meant icebergs. The event that led to Antarctic ice sheets was the formation of the , which began to form about 40 mya and was firmly established by 34 mya, when the Antarctic ice sheets grew in earnest. The current’s formation was caused by Antarctica’s increasing isolation from Australia and South America, which gradually allowed an uninterrupted current to form that circled Antarctica and isolated it so that it no longer received tropical currents. That situation eventually turned Antarctica into the big sheet of ice that it is today. It also radically changed global oceanic currents. formed, which cooled the oceans as well as oxygenated its depths, and it comprises more than half of the water in today’s oceans. began forming around the same time.
In recent years, Neogene temperatures have been the focus of intensive research. What appears to be the proximate cause of elevated temperatures was a dramatic change in global ocean currents. The final closing of the , the isolation of Antarctica, the creation of , and the opening and closing of land bridges, such as in the Bering Sea and ultimately the land bridge between North and South America, created dramatic changes in ocean currents and global climate. One result was fluctuating . Its production declined beginning about 24 mya, and its weakness lasted until about 14 mya. Consequently, Earth’s oceans were not stratified as they are today, and warm water extended far lower into the oceans than it does today. Also, it reduced the temperature gradient between the equator and poles, which drives global currents: the greater the differential, the more vigorous the currents. It was still an Icehouse Earth, but the “mid-Miocene climatic optimum” was relatively warm. The past three million years are the coldest that Earth has seen since the that ended 260 mya, but this . While the steadily declining carbon dioxide levels of the past 150-100 million years is the ultimate cause of this Icehouse Earth phase, relatively short-term and regional fluctuations have had their proximate causes rooted in other geophysical, geochemical, and celestial dynamics.
Since the most dramatic instances of speciation seem to have happened in the aftermath of mass extinctions, this essay will survey extinction first. A corollary to is that if any critical nutrient falls low enough, the nutrient deficiency will not only limit growth, but the organism will be stressed. If the nutrient level falls far enough, the organism will die. A human can generally survive between one and two months without food, ten days without water, and about three minutes without oxygen. For nearly all animals, all the food and water in the world are meaningless without oxygen. Some microbes can switch between aerobic respiration and fermentation, depending on the environment (which might be a very old talent), but complex life generally does not have that ability; nearly all aerobic complex life is oxygen dependent. The only exceptions are marine life which has adapted to . Birds can go where mammals cannot, , for instance, or being , due to their . If oxygen levels rise or fall very fast, many organisms will not be able to adapt, and will die.
For this essay’s purposes, the most important ecological understanding is that the Sun provides all of earthly life’s energy, either (all except nuclear-powered electric lights driving photosynthesis in greenhouses, as that energy came from dead stars). Today’s hydrocarbon energy that powers our industrial world comes from captured sunlight. Exciting electrons with photon energy, then stripping off electrons and protons and using their electric potential to power biochemical reactions, is what makes Earth’s ecosystems possible. Too little energy, and reactions will not happen (such as ice ages, enzyme poisoning, the darkness of night, food shortages, and lack of key nutrients that support biological reactions), and too much (such as , ionizing radiation, temperatures too high for enzyme activity), and life is damaged or destroyed. The journey of life on Earth has primarily been about adapting to varying energy conditions and finding levels where life can survive. For the many hypotheses about those ancient events and what really happened, the answers are always primarily in energy terms, such as how it was obtained, how it was preserved, and how it was used. For life scientists, that is always the framework, and they devote themselves to discovering how the energy game was played.
Mass extinctions always have critical geophysical aspects to them, and often geochemical. Continental shelves under shallow seas, which are home to most marine life, are vulnerable to sea level and oceanic current changes. Stagnant waters, or waters that have too many nutrients dumped into them, can lose their oxygen, which triggers anoxic events that kill complex life. A continental shelf exposed to the atmosphere by a falling sea level would obviously lose its marine life, and that marine life might have had nowhere else to go. Sea levels can rise or fall for different reasons. The most obvious reason has been advancing and retreating ice sheets, as water is removed from or added to the oceans, but the aggregate continental landmass has always grown (possibly sporadically), continents can rise and can fall during the journeys of their tectonic plates, and the ocean’s collective basin has fluctuated in size, as water was hydrated into rocks, and also falling when and rising again as they fragmented. Generally, when , the continental shelves lost their marine life, and , anoxic conditions often accompanied them. There is evidence that the ozone layer has been periodically damaged, which stressed all plants and animals that the Sun directly shined on. The positions of the continents, both in relation to each other and their proximity to the equator or poles, can have dramatic effects, including impacts on global climate. Global climate changes and moving continents can turn rainforests into deserts and vice versa.
Canals were competitive with railroads, sailing ships were competitive with steamboats, and watermills were competitive with steam-powered mills until around 1850. It for coal-powered steam to prevail against wind and water power. Water and wind power were not only geographically restricted, but they were also dependent on the weather. Calm air (and storms) and droughts (and floods) were the bane of wind and water power. Coal did not have those restrictions. American towns were built on hillsides above watermills to house the workforce. As coal-power made its ascendance, those mills and towns were abandoned. The pollution of industrial America’s cities could rival London’s. A visitor to Pittsburgh in 1841 described approaching the city as entering a dark cloud of coal smoke; the peoples and buildings inside it were blackened like some vision from hell. Far from an indictment, however, the visitor happily saw it as “progress” that would soon arrive at his home town of Cincinnati. The rivers of the Eastern Woodlands ran blue and clear before Europeans arrived. When I lived in Ohio, the Ohio River at Cincinnati in the 1990s had brown, stinking waters that nobody in their right minds would swim in. The Cuyahoga River that flows through Cleveland , and the 1969 fire finally led to environmental legislation that began to clean up the USA’s lakes, rivers, and air. The in the 1980s rivaled .
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This crisis is affecting not only low-developed parts of the world but also it affects high-developed countries, about one third of the humanity suffers from the scarcity of water (Molden 2010).
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India is one of the eight countries which are seriously facing a sharp increase in water crisis that threatens humans, while a huge percentage of the world has no access to sanitation and clean water....
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This essay will examine the water crisis specifically in China, because it is the country with the most serious water shortage problems in the world....