Impact – Tropical Forests

Impact – Tropical Forests

Jonathan Adams, Asst. Prof. Ecology @ Rutgers and Ning Zeng, Assc. Prof. Meteorology @ U of Maryland, ‘7

(Vegetation-Climate Interaction: How Vegetation Makes the Global Environment, p.215)
However, it is important to bear in mind that the plants themselves are generally bigger when they are C02-fertilized, and the extra amount lost to hungry insects in these experiments actually works out to be less as a percentage of the total leaf area. Also, insects which have to eat more leaf material to extract enough protein are generally placed in a difficult situation: it takes a lot of work for the insect to digest the extra material, and the insect may also have to take in extra amounts of poisons the host plant produces in the process of consuming more leaf. The insect may also have to spend more time feeding out on the leaf exposed to enemies when it cannot get enough protein. In fact, the evidence is that overall with C02 fertilization the advantage is tipped in favor of the plant, against the insect. It seems that insects on C02-fertilized plants not only consume a smaller proportion of leaf tissue, they grow more slowly and die more often. Most species in the world are herbivorous insects, and it is rather frightening to consider what effects this sort of change might have on insect biodiversity in the tropics and elsewhere. It is quite possible that a large change in nutrient content will push many species over the edge into extinction. It is widely considered by ecologists that a large part of the reason so many species of tropical trees can coexist in the tropical rainforests is that selective insect herbivores prevent each tree species from becoming too abundant. If we start to see these specialized herbivores dropping out of existence because of a direct C02 effect, many tropical trees may go extinct because the most competitive species among them are no longer so closely density-limited and can now push the others out.
Extinction.

David Takacs, Prof. Envt’l Humanities @ Cal State, ’96 (The Idea of Biodiversity, p. 200-201)

Impact – Biodiversity

Climate change will destroy biodiversity worldwide-most qualified scientists agree.

China Daily, 7/21/’6, http://english.people.com.cn/200607/21/eng20060721_285286.html
The Earth is on the brink of "major biodiversity crisis" fuelled by the steady destruction of ecosystems, a group of the world's most distinguished scientists and policy experts warn yesterday. Nineteen leading specialists in the field of biodiversity, including Robert Watson, chief scientist at the World Bank, and Professor Georgina Mace, director of the Institute of Zoology, are calling for the urgent creation of a global body of scientists to offer advice and urge governments to halt what they call a potentially "catastrophic loss of species". "All the scientific evidence points to the fact that whatever measure of vulnerability you take, whether it is local populations, species or ecosy stem, we know that the rate at which we are altering them now is faster than it has been in the past," Georgina Mace said in an interview. Mace, director of science at the Institute of Zoology in London, is one of the 19 scientists from 13 countries who signed a declaration published in the journal Nature explaining why an intergovernmental body is needed. Destruction of natural habitats and the effects of climate change are causing species to die out at 100 to 1,000 times faster than the natural rate, leading some scientists to warn we are facing the next mass extinction. Nearly one-quarter of the world's mammals, one-third of amphibians and more than one-tenth of bird species are threatened with extinction. Climate change alone is expected to force a further 15-37 per cent of species to the brink of extinction within the next 50 years. Writing in the journal yesterday, the experts, from countries ranging from China, Chile and Canada to South Africa, Germany and the United States, urge for the new body, the international mechanism of scientific expertise on biodiversity (IMOSEB), to be set up to force better biodiversity policies around the world. "We are on the verge of a major biodiversity crisis. Virtually all aspects of diversity are in steep decline and a large number of populations and species are likely to become extinct this century. Despite this evidence, biodiversity is still consistently undervalued and given inadequate weight in both private and public decisions," the authors say.
Warming kills all forms of biodiversity

Stern, 7- Head of the British Government Economic Service, Former Head Economist for the World Bank, Director of Policy and Research for the Commission for Africa, I.G. Patel Chair at the London School of Economics and Political Science (Nicholas, “The Economics of Climate Change: The Stern Review”, http://webarchive.nationalarchives.gov.uk/+/http://www.hm-treasury.gov.uk/independent_reviews/stern_review_economics_climate_change/stern_review_report.cfm)
Climate change is likely to occur too rapidly for many species to adapt. One study estimates that around 15 – 40% of species face extinction with 2°C of warming. Strong drying over the Amazon, as predicted by some climate models, would result in dieback of forest with the highest biodiversity on the planet. The warming of the 20th century has already directly affected ecosystems. Over the past 40 years, species have been moving polewards by 6 Km on average per decade, and seasonal events, such as flowering or egg-laying, have been occurring several days earlier each decade.72 Coral bleaching has become increasingly prevalent since the 1980s. Arctic and mountain ecosystems are acutely vulnerable – polar bears, caribou and white spruce have all experienced recent declines.73 Climate change has already contributed to the extinction of over 1% of the world’s amphibian species from tropical mountains. Ecosystems will be highly sensitive to climate change (Table 3.4). For many species, the rate of warming will be too rapid to withstand. Many species will have to migrate across fragmented landscapes to stay within their “climate envelope” (at rates that many will not be able to achieve). Migration becomes more difficult with faster rates of warming. In some cases, the “climate envelope” of a species may move beyond reach, for example moving above the tops of mountains or beyond coastlines. Conservation reserves may find their local climates becoming less amenable to the native species. Other pressures from human activities, including land-use change, harvesting/hunting, pollution and transport of alien species around the world, have already had a dramatic effect on species and will make it even harder for species to cope with further warming. Since 1500, 245 extinctions have been recorded across most major species groups, including mammals, birds, reptiles, amphibians, and trees. A further 800 known species in these groups are threatened with extinction.75 A warming world will accelerate species extinctions and has the potential to lead to the irreversible loss of many species around the world, with most kinds of animals and plants affected (see below). Rising levels of carbon dioxide have some direct impacts on ecosystems and biodiversity,76 but increases in temperature and changes in rainfall will have even more profound effects. Vulnerable ecosystems are likely to disappear almost completely at even quite moderate levels of warming.77 The Arctic will be particularly hard hit, since many of its species, including polar bears and seals, will be very sensitive to the rapid warming predicted and substantial loss of sea ice (more detail in Chapter 5).78 • 1°C warming. At least 10% of land species could be facing extinction, according to one study.79 Coral reef bleaching will become much more frequent, with slow recovery, particularly in the southern Indian Ocean, Great Barrier Reef and the Caribbean.80 Tropical mountain habitats are very species rich and are likely to lose many species as suitable habitat disappears. • 2°C warming. Around 15 – 40% of land species could be facing extinction, with most major species groups affected, including 25 – 60% of mammals in South Africa and 15 – 25% of butterflies in Australia. Coral reefs are expected to bleach annually in many areas, with most never recovering, affecting tens of millions of people that rely on coral reefs for their livelihood or food supply.81 This level of warming is expected to lead to the loss of vast areas of tundra and forest – almost half the low tundra and about one-quarter of the cool conifer forest according to one study.82 • 3°C warming. Around 20 – 50% of land species could be facing extinction. Thousands of species may be lost in biodiversity hotspots around the world, e.g. over 40% of endemic species in some biodiversity hotspots such as African national parks and Queensland rain forest.83 Large areas of coastal wetlands will be permanently lost because of sea level rise (up to one-quarter according to some estimates), with acute risks in the Mediterranean, the USA and South East Asia. Mangroves and coral reefs are at particular risk from rapid sea level rise (more than 5 mm per year) and their loss would remove natural coastal defences in many regions. Strong drying over the Amazon, according to some climate models, would result in dieback of forest with the highest biodiversity on the planet.
Climate change kills biodiversity which threatens beneficial medical science

Ahlstrom, Dick (Science editor of The Irish Times. “Disappearing biodiversity a huge threat to medical science” http://www.lexisnexis.com.turing.library.northwestern.edu/us/lnacademic/results/docview/docview.do?docLinkInd=true&risb=21_T4162653354&format=GNBFI&sort=BOOLEAN&startDocNo=76&resultsUrlKey=29_T4162653349&cisb=22_T4162710017&treeMax=true&treeWidth=0&csi=142626&docNo=83) 4/24/2008
CLIMATE CHANGE is driving many species of plants, amphibians and other creatures to extinction, and there will be consequences for all of us. Plants and animals are a proven source for substances that could deliver novel drugs and treatments for human diseases. The resultant disappearance of biodiversity will cause "huge" losses to medical science, according to the authors of a new book, Sustaining Life. Published by Oxford University Press and launched this morning by the United Nations Environment Programme, its authors highlight the true significance behind the loss, for example, of frogs and other amphibians. Nearly one-third of all the 6,000 known species of frogs, toads, newts and salamanders are threatened with extinction, the authors indicate. These animals produce a wide range of substances that may be important for human medicine. The Panamanian poison frog, for example, produces pumiliotoxins that strengthen heart contractions and could lead to new heart drugs. Ecuadorian poison frogs produce chemicals that have potential as powerful pain killers and antibacterial compounds have been identified in compounds produced in the skin of a number of frog species including the Mexican leaf frog. Substances with medicinal potential don't just come from amphibians, the authors state. Novel substances have been recovered from species as varied as bears, cone snails, pine trees, sharks and horseshoe crabs. While not all these species currently face extinction, any loss of biodiversity could represent an incalculable loss to humanity, the authors argue. Our warming climate has been identified as a driver of species loss, as highlighted in Sustaining Life but also in new research published nearly every week.
Warming destroys biodiversity- harms biodiversity hotspots and ecosystems

IPCC, a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP), 2007, Climate Change 2007:Synthesis Report, Summary for Policymakers, An Assessment of the Intergovernmental Panel on Climate Change, http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf
Risks to unique and threatened systems. There is new and stronger evidence of observed impacts of climate change on unique and vulnerable systems (such as polar and high mountain communities and ecosystems), with increasing levels of adverse impacts as temperatures increase further. An increasing risk of species extinction and coral reef damage is projected with higher confidence than in the TAR as warming proceeds. There is medium confidence that approximately 20 to 30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5°C over 1980-1999 levels. Confidence has increased that a 1 to 2°C increase in global mean temperature above 1990 levels (about 1.5 to 2.5°C above preindustrial) poses significant risks to many unique and threatened systems including many biodiversity hotspots. Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1 to 3°C are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatisation by corals. Increasing vulnerability of indigenous communities in the Arctic and small island communities to warming is projected.
Warming causes widespread species loss

IPCC, a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP), 2007, Climate Change 2007:Synthesis Report, Summary for Policymakers

An Assessment of the Intergovernmental Panel on Climate Change, http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf

Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change. {3.4} Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded. {3.4} Climate change is likely to lead to some irreversible impacts. There is medium confidence that approximately 20 to 30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5 to 2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40 to 70% of species assessed) around the globe. {3.4}
Warming destroys wetlands, which are biodiversity hotspots

John Houghton, cochair of the IPCC, Professor in atmospheric physics at the University of Oxford, former Chief Executive at the Met Office and founder of the Hadley Centre 4 May 2005 “Global warming” INSTITUTE OF PHYSICS PUBLISHING REPORTS ON PROGRESS IN PHYSICS 1343–1403

It is not only in places where there is dense population that there will be adverse effects. The world’s wetlands and mangrove swamps currently occupy an area of about a million square kilometres (the figure is not known very precisely), equal approximately to twice the area of France. They contain much biodiversity and their biological productivity equals or exceeds that of any other natural or agricultural system. Over two-thirds of the fish caught for human consumption, as well as many birds and animals, depend on coastal marshes and swamps for part of their life cycles, so they are vital to the total world ecology. These areas could not adjust to the rapid rate of sea-level rise that is likely and in many cases would be unable to extend inland. Net loss of wetland area will therefore occur [97]
Higher carbon dioxide levels will destroy biodiversity-models and fossil records prove.

Ward, professor of geological sciences at University of Washington, 2008 [Peter, Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Tell Us About Our Future, p. 134-138]
The best of the methods is a computer program developed by the great Robert Berner of Yale University. His program depends on inputs ranging from estimates of the rate of sediment burial to direct measurement of carbon isotope values from carbonate rocks. Known as GEOCARB, the model shows the major trends in carbon dioxide through time, while a second such model known as GEOCARBSULF allows estimates of ancient oxygen levels through time. Combined, these results have given us a new, and in many ways largely unexpected, view of how much these two gases have varied through time. That levels of atmospheric carbon dioxide must have varied through time became evident after geologists discovered times in Earth's history when much of Earth was tropical, and other times when there were glaciations on larger scale than the recent Pleistocene epoch glacial events. Although there were several possible causes, such as variation in solar heating over time or changes in heating from the interior of Earth, detailed research into both eventually ruled them out, leaving greenhouse gases as the major suspect for having caused climate shifts. The study of ice cores from glaciers formed in the Pleistocene epoch finally demonstrated that carbon dioxide values can and did vary, and not just in the long term but over astonishingly short time intervals, some as short as a decade. Although none of the various models such as GEOCARB attempting to calculate carbon dioxide and oxygen lev­els over the last 500 million years has such precision, they can discern longer-term (greater than a million years) changes (Figure 6.1). The carbon dioxide curve is striking. Compared with today, it was high for much of the Paleozoic era, but as oxygen began its climb some 375 million years ago, the levels of carbon dioxide plummeted and only rose again sometime into the Mesozoic era; the gas was plentiful through much of the era, culminating in a maximum in the late Jurassic period, of about 150 million years ago, and then declin­ing throughout the Cenozoic era, coming to a minimum level" today. But as we shall see, even the last 200 years have produced an upswing of carbon dioxide that is of too short a duration to be visible on this long-term graph. The long-term decline in carbon dioxide over the past 100 mil­lion years is both interesting and misleading. The gradual reduction is due to the slow enlargement of the continents and to the increased amount of carbon locked up in vast mineral deposits, which erode and liberate carbon at a slower rate than others of their composition are formed. Ultimately, the long-term drop will spell doom for our Earth as a habitable planet, as Don Brownlee and I explained in our 2003 book, The Life and Death of Planet Earth. But that eventuality is far, far in the future, and the reduction in atmospheric carbon dioxide has halted and reversed with a vengeance over not only the past centuries of the Industrial Age of humans but also in fact dating back through the millennia that humans have engaged in agriculture. The carbon dioxide makes pretty clear that times of high car­bon dioxide-and especially times when carbon dioxide levels rap­idly rose-coincided with the mass extinctions. Here is the driver of extinction. Here is the cause of the changes in the ancient conveyer belts-short-term warming caused by increases in greenhouse gases. The flood basalts that also correspond with those extinctions is the source of the greenhouse gases. Lest the models used to support this argument seem unsatisfac­tory, the other method for ascertaining past carbon dioxide levels pro­vides independent corroboration of my hypothesis. Paleobotanists have done some very clever work on fossil leaves that resulted in an important breakthrough in the quest to find a relative measure of an­cient carbon dioxide levels. Their method enables a paleobotanist to say whether carbon dioxide levels were rising, falling, or constant dur­ing million-year intervals, and furthermore, the method enables an investigator to estimate how many times higher or lower the carbon dioxide levels were than some base-level observation. The measure turns out to be both clever and simple, as is so often the case with wonderful breakthroughs. Botanists looking at modern plant leaves had done experiments whereby they grew plant species in closed systems where the amount of carbon dioxide could be raised or lowered relative to the level found in our atmosphere (about 360 parts per million when these experiments were first conducted). Plants, it turns out, are highly sensitive to carbon dioxide levels, because the carbon dioxide in the atmosphere serves as their source for carbon the major building block of life. They acquire this mainly through tiny portals in their leaves called stomata; the stomata allow carbon diox­ide in and water out. When grown in high levels of carbon dioxide, the plants produced a small number of stomata, as just a few sufficed with the gas plentiful; when grown in low levels, the opposite was true. Such a clear result delighted the experimenters, which included a colleague of Berner's named David Beerling, now teaching at the Uni­versity of Sheffield in England. Leaf stomata are readily observable on most well-preserved fossil leaves, and when the investigators turned to the fossil record, the results confirmed Berner's model results. LET US BRING THIS ALL TOGETHER. IT IS HERE PROPOSED THAT EACH OF the greenhouse extinctions had a similar cause, and here we can sum­marize the sequential steps. First, the world warms over short intervals of time because of a sudden increase of carbon dioxide and methane, caused initially by the formation of vast volcanic provinces called flood basalts. The warmer world affects the ocean circulation systems and disrupts the position of the conveyer currents. Bottom waters begin to have warm, low-oxygen water dumped into them. Warming continues, and the decrease of equator-to-pole temperature differences reduces ocean winds and surface currents to a near standstill. Mixing of oxygen­ated surface waters with the deeper, and volumetrically increasing, low-oxygen bottom waters decreases, causing ever-shallower water to change from oxygenated to anoxic. Finally, the bottom water is at depths where light can penetrate, and the combination of low oxygen and light allows green sulfur bacteria to expand in numbers and fill the low-oxygen shallows. They live amid other bacteria that produce toxic amounts of hydrogen sulfide, and the flux of this gas into the at­mosphere is as much as 2,000 times what it is today. The gas rises into, the high atmosphere, where it breaks down the ozone layer and the subsequent increase in ultraviolet radiation from the sun kills much of the photosynthetic green plant phytoplankton. On its way up into the sky, the hydrogen sulfide also kills some plant and animal life, and the combination of high heat and hydrogen sulfide creates a mass extinc­tion on land. These are the greenhouse extinctions. The sequence of events outlined above can be considered a com­bined hypothesis for the cause of greenhouse extinctions and can be named the conveyer disruption hypothesis. There was obviously variability in each extinction, but if the extinctions are examined in a fashion similar to how taxonomists classify living organisms as a spe­cies, it seems quite clear that the mass extinctions considered here as greenhouse extinctions are a different beast than the K- T, our now sole known impact extinction.

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