Archive for the 'Environment' Category

11
Jan
10

Old Hay and Alpine Ibex Horns Reveal How Grasslands Respond to Climate Change..

 

Inner Mongolia, the grasslands are turning to sand

How do plant ecosystems react to rising concentrations of the greenhouse gas CO2 in the atmosphere over the long term? This fundamental question is becoming increasingly pressing in light of global climate change. Researchers from the Chair of Grassland Science at the Technische Universitaet Muenchen (TUM) have now — for the first time worldwide — taken up this issue for grasslands. The scientists found their answers in two unlikely places: in horns of Alpine ibex from Switzerland and in 150-year-old hay from England.

 

 

Young ibex (Bouquetin). Ibex store isotopic information in their horns that reflects the water use of the vegetation they consume.

Researchers studying the reactions of trees to rising CO2 concentration in the atmosphere have it easy. Since trees store the carbon they absorb in wood, all they need to do is take core samples from tree trunks. A centenarian oak will reveal how it coped with the incipient climate change over a period of a hundred years in its annual rings. “However, the grassland vegetation we work with is grazed or dies off in a matter of months and decomposes,” explains Prof. Hans Schnyder, who is doing research in the field of grasslands at the Center for Life and Food Sciences Weihenstephan at the TUM. The Swiss scientist nonetheless wanted to establish out how economically grasslands deal with water when temperatures rise and the carbon dioxide concentration in the air increases.

Important in this context is that all plants absorb CO2 from the atmosphere. At the same time they transpire water vapor to cool their sunlit leaves. Both processes run via the stomata, tiny pores in the leaves, the opening size of which plants can regulate. During longer periods of drought plants close the stomata to curb water loss, albeit at the expense of CO2 absorption. Laboratory experiments show that, for a given stoma aperture, an artificial increase of ambient CO2 leads to a temporary increase in the absorption capacity for the gas. However, to ascertain the actual change of water use efficiency in grassland vegetation over the course of the last century, Prof. Schnyder had to find grassland time series comparable in length to those of trees.

 

Alpine Ibex

This is where the team turned their sights to the Alpine ibex horn collection at the Museum of Natural History in Bern. Ibex store isotopic information in their horns that reflects the water use of the vegetation they consume. The TUM researchers went at the museum collection, which covers the years 1938 to 2006, with a carving knife, to remove tiny samples from the horns. Since ibex horns also have annual rings, the grassland researchers were able to use the samples to draw conclusions about temporal changes in the grassland vegetation of the Bernese Alps where the ibex had grazed.

A unique specimen archive at the research station Rothamsted in England eventually enabled a comparison with a second grassland region. The “Park Grass Experiment” — the longest running ecological grassland experiment worldwide — was initiated in Rothamsted over 150 years ago. Since 1857 specimens have been archived there to allow future generations of scientists to gain long-term insights into the local ecosystem using modern research methods. And indeed, the TUM scientists were able to benefit from the hay specimens dating as far back as 150 years. Once again analyzing the isotope signature, they could infer how the English grassland vegetation had utilized the water over the years.

The Weihenstephan researchers thus determined the individual isotope composition of the grassland vegetation in both the Bernese Alps and in the British lowlands over extended periods of time: more than 69 years based on the horns, and as far back as 150 years using the hay specimens. In a second step this data was lined up with climate data, e.g. air temperature and aridity, of the respective region.

The result:

In both locations the intrinsic water-use efficiency of the grassland vegetation rose over the years. This implies that the plants improved their water storage potential as temperatures rose and the level of CO2 in the atmosphere increased. Based on these results the TUM scientists have now, for the first time ever, managed to demonstrate the long-term effects of anthropogenic climate change on the water-use efficiency of grasslands.

 

Alpine Meadows

There were, however, also differences between the two locations. In Switzerland the effective water-use efficiency of the Alpine meadows remained unchanged in spite of the increased intrinsic water-use efficiency of the grassland. This was because, overall, the air had become drier and warmer as a result of the climate change. In England the scientists found evidence for this effect only during the fall. In the spring though — which in Rothamsted is no drier today than it was 150 years ago — the water storage potential of grassland vegetation had a real effect. This insight will help to further improve climate simulations. In the past, complex simulation models that included vegetation had to rely on estimates where grassland was concerned. The scientists at the TU Muenchen have now succeeded in prying open this climate research black box.

Source: ScienceDaily (Jan. 10, 2010)

11
Jan
10

Coral Can Recover from Climate Change Damage…!!

New research suggests that coral reefs located in marine reserves can recover from the impacts of global warming. (Credit: iStockphoto/Edwin Van Wier)

A study by the University of Exeter provides the first evidence that coral reefs can recover from the devastating effects of climate change. Published Jan. 11, 2010 in the journal PLoS ONE, the research shows for the first time that coral reefs located in marine reserves can recover from the impacts of global warming.

Scientists and environmentalists have warned that coral reefs may not be able to recover from the damage caused by climate change and that these unique environments could soon be lost forever. Now, this research adds weight to the argument that reducing levels of fishing is a viable way of protecting the world’s most delicate aquatic ecosystems.

Increases in ocean surface water temperatures subject coral reefs to stresses that lead quickly to mass bleaching. The problem is intensified by ocean acidification, which is also caused by increased CO2. This decreases the ability of corals to produce calcium carbonate (chalk), which is the material that reefs are made of.

Coral bleaching — in which corals expel their symbiotic algal partners and turn pale or white — is one of the most visible impacts of climate change on marine ecosystems. Typically caused by higher-than-normal ocean temperatures, it can lead to widespread death of corals and is a major contributor to the rapid decline of coral reef ecosystems worldwide.

Approximately 2% of the world’s coral reefs are located within marine reserves, areas of the sea that are protected against potentially-damaging human activity, like dredging and fishing.

The researchers conducted surveys of ten sites inside and outside marine reserves of the Bahamas over 2.5 years. These reefs have been severely damaged by bleaching and then by hurricane Frances in the summer of 2004. At the beginning of the study, the reefs had an average of 7% coral cover. By the end of the project, coral cover in marine protected areas had increased by an average of 19%, while reefs in non-reserve sites showed no recovery.

Professor Peter Mumby of the University of Exeter said: “Coral reefs are the largest living structures on Earth and are home to the highest biodiversity on the planet. As a result of climate change, the environment that has enabled coral reefs to thrive for hundreds of thousands of years is changing too quickly for reefs to adapt.

“In order to protect reefs in the long-term we need radical action to reduce CO2 emissions. However, our research shows that local action to reduce the effects of fishing can contribute meaningfully to the fate of reefs. The reserve allowed the number of parrotfishes to increase and because parrotfish eat seaweeds, the corals could grow freely without being swamped by weeds.

Scientists sampled DNA from coral reefs in the Indiana Ocean and found that individual corals located in the same group of reefs are more closely related than previously thought.

As a result, reefs inside the park were showing recovery whereas those with more seaweed were not. This sort of evidence may help persuade governments to reduce the fishing of key herbivores like parrotfishes and help reefs cope with the inevitable threats posed by climate change.”

Professor Mumby’s research was funded by National Environment Research Council (NERC) and the Khaled bin Sultan Living Oceans Foundation.

Reef facts

  • A coral reef is made up of thin layers of calcium carbonate (limestone) secreted over thousands of years by billions of tiny soft bodied animals called coral polyps.
  • Coral reefs are the world’s most diverse marine ecosystems and are home to twenty-five percent of known marine species, including 4,000 species of fish, 700 species of coral and thousands of other plants and animals.
  • Coral reefs have been on the planet for over 400 million years.
  • The largest coral reef is the Great Barrier Reef, which stretches along the northeast coast of Australia, from the northern tip of Queensland, to just north of Bundaberg. At 2,300km long, it is the largest natural feature on Earth.
  • Coral reefs occupy less than one quarter of one percent of the Earth’s marine environment, yet they are home to more than a quarter of all known fish species.
  • As well as supporting huge tourist industries, coral reefs protect shorelines from erosion and storm damage.

High quality reef videos by Professor Peter Mumby can be viewed at: www.reefvid.org

The main funding for the research came from Khaled bin Sultan Living Oceans Foundation and the Natural Environment Research Council.

Source: Science Daily (Jan. 10, 2010)




Categories

Bangla Medi@’s Calender

August 2017
M T W T F S S
« Jan    
 123456
78910111213
14151617181920
21222324252627
28293031  

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 2 other followers

Blog Stats

  • 4,377 hits

Pages