Geography, asked by vinay1393, 11 months ago

Which is a threat to environment 1) increase in carbon dioxide 2) increases in trees 3) increases in ponds 4) increases in crops ​

Answers

Answered by shraddhashree119
0

Answer:

increase in carbon dioxide is a threat to environment

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Answered by harshtiwari72003
1

Answer:

The impact of CO2. The global rise in the levels of CO2 is good for trees, bad for grasses and terrible for corals

This year's Nobel Peace Prize for former US Vice President Al Gore and the Intergovernmental Panel on Climate Change (Geneva, Switzerland) again highlighted the importance and possible threat of anthropogenic climate change by rising levels of carbon dioxide (CO2) in the atmosphere. Worse still—and often ignored—are the effects of rising levels of CO2 in their own right, regardless of climate change. However, research focusing on the carbon dimension is now giving a more accurate picture of how land plants and marine organisms in particular will respond to progressively higher concentrations of CO2 in both the atmosphere and the sea.

…coral reefs could start to dissipate once the level of CaCO3 falls below 3.25 times oversaturation or as soon as atmospheric levels of CO2 reach 550 ppm

The impact of elevated levels of atmospheric CO2 on land and in water will be very different but both already have scientists worried, particularly with regard to the fate of calciferous marine organisms such as corals. “On the ocean side, the effects of CO2 rise are much more pernicious,” said Ken Caldeira of the Department of Global Ecology at the Carnegie Institution of Washington, DC, USA. “For land plants, CO2 can be thought of as an essential nutrient. There is a constant struggle [for land plants] to let in more CO2 and let out as little water as possible. But ocean organisms are almost never limited by the availability of CO2. They are more constrained by light or availability of nutrients.”

The crucial point for marine organisms is that rising levels of CO2 will lower the pH of their environment, which will challenge their biochemistry—particularly organisms such as corals, coccolithophores (single-celled algae), crustaceans and molluscs, all of which use calcium carbonate (CaCO3) to produce external skeletons or shell coverings. Seawater is slightly alkaline, with a pH now in the range of 7.9 to 8.2 in the open ocean. This value has decreased by an average of approximately 0.1 since the beginning of the industrial era as a result of the anthropomorphic release of CO2 into the atmosphere, which, in turn, has increased the concentration of CO2 in the oceans. CO2 lowers the oceanic pH by increasing the concentration of hydrogen ions (H+) in the water. It also reacts with water to form several ionic and non-ionic species including bicarbonate ions (HCO3−), which are less alkaline than carbonate ions (CO32−). The net effect is a decrease in alkalinity and a lower concentration of carbonates in the water.

The decreasing amounts of calcium carbonates threaten a wide variety of calcifying marine organisms. The timing of their potential extinction will depend largely on the type of CaCO3 that they require. Corals, for example, use aragonite to build their exoskeleton, whereas many plankton organisms use calcite for protective coverings. Aragonite dissolves more easily than calcite, so there is a more immediate threat to corals and their associated reefs, including the Great Barrier Reef off the coast of Queensland, Australia, which spans an area of 344,400 square km. According to Caldeira, coral reefs could start to dissipate once the level of CaCO3 falls below 3.25 times over-saturation, or as soon as atmospheric levels of CO2 reach 550 ppm. “At current emission levels, this will happen by mid-century, perhaps even 2040,” he said.

The outlook is less bleak for other calciferous organisms such as many plankton. However, even they will not be able to survive the higher levels of CO2 that are likely if humans continue to burn significant amounts of fossil fuel; Caldeira believes that 750 ppm in the atmosphere is the upper limit in which they could survive. “In any case, as CO2 concentrations increase […] it becomes harder for organisms with shells to build, and they need to put more energy in, leaving less for reproduction, finding food and avoiding predators,” he said. Some organisms might therefore start to become extinct even before concentrations of CaCO3 reach the critical point, as they will be unfit to compete against non-calciferous rivals.

While primitive animals are bearing the brunt of the CO2 onslaught in the oceans, it will be plants that are mostly affected on land

At least one organism, the pteropod, also known as the sea snail or sea butterfly—which inhabits cold waters in which CO2 dissolves more readily—is already losing shell mass. “With respect to calcifiers, areas which already exhibit a low CaCO3 saturation state will be affected first,” commented Jean-Pierre Gattuso, Senior Research Scientist at the Laboratoire d'Océanographie in Villefranche-sur-mer, France. “These are high-latitude regions and deep waters.”

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