Parts of an Ecosystem: Climate

This video does a pretty good job simplifying and summarizing what we covered in class today.

Here is a video that views the scientific debate over global climate change…

Followed by a National Geographic Video on Global Warming…

Kudzu Vines Spreading North from US Southeast With Warming Climate

Kudzu, the plant scourge of the U.S. Southeast. The long tendrils of this woody vine, or liana, are on the move north with a warming climate.

But kudzu may be no match for the lianas of the tropics, scientists have found. Data from sites in eight studies show that lianas are overgrowing trees in every instance.

If the trend continues, these “stranglers-of-the-tropics” may suffocate equatorial forest ecosystems.

Tropical forests contain more than half of Earth’s terrestrial species, and contribute more than a third of global terrestrial carbon and a third of terrestrial net primary productivity, says ecologist Stefan Schnitzer of the University of Wisconsin-Milwaukee.

Schnitzer is co-author with Frans Bongers of Wageningen University in the Netherlands of a paper on lianas in the current issue of the journal Ecology Letters.

“Any alteration of tropical forests has important ramifications for species diversity, productivity–and ultimately the global carbon cycle,” says Schnitzer.

Tropical forests are indeed experiencing large-scale structural changes, the most obvious of which may be the increase in lianas, according to Robert Sanford, program director in the National Science Foundation’s (NSF) Division of Environmental Biology, which funded the research.

Lianas are found in most tropical lowland forests. The woody vines are “non-self-supporting structural parasites that use the architecture of trees to ascend to the forest canopy,” says Schnitzer.

In tropical forests, lianas can make up some 40 percent of the woody stems and more than 25 percent of the overall woody species.

Lianas usually have a high canopy-to-stem ratio, says Schnitzer, “which allows them to deploy a large canopy of leaves above those of the host tree, competing aggressively with their hosts for sunlight, water and nutrients.”

Intense competition from lianas for above- and below-ground resources limits tropical tree growth and survival.

Increasing liana abundance and biomass may have far-reaching consequences for tropical forest community composition, says Sanford.

For example, in a tropical moist forest on Barro Colorado Island, Panama, researchers found that the proportion of liana infestation in the crowns of trees changed from 32 percent in 1967-68 to 47 percent in 1979, to nearly 75 percent in 2007.

The number of trees with severe liana infestation (more than 75 percent of a tree’s canopy covered by lianas) increased by 65 percent between 1996 and 2007.

In this forest, liana leaf litter and flower production, compared with that of host trees, increased substantially from 1986 to 2002, says Schnitzer.

Lianas have also overgrown other tropical forests.

In an old-growth forest surrounding the Nouragues Biological Research Station in French Guiana, scientists found that over the decade from 1992 to 2002, the number of lianas shot up while that of trees fell.

In a forest in the central Amazon, biologists discovered that over the six-year-period from 1993 to 1999, new liana seedlings were 500 percent higher than estimates from previous periods whereas tree seedling recruitment decreased.

But a tree need not live in the tropics to fall victim to lianas.

More than 80 non-native liana species have invaded North America.

Kudzu is joined by English ivy, Japanese honeysuckle and oriental bittersweet, to name a few. Oriental bittersweet is expanding in North American forests, where it has reduced native tree survival.

After hurricane damage in a Florida forest, invasive lianas rapidly colonized the damaged trees and persisted for many years afterward, reducing numbers of native trees, shrubs and herbs.

In 50-year-old forests in the Piedmont region of New Jersey, lianas are now abundant.

“A major factor limiting liana abundance in temperate forests is freezing temperatures,” says Schnitzer. “Both native and invasive lianas are likely to increase most rapidly in forests that don’t have long, cold winters.”

For snow-birds–both avian and human–who escape to tropical climes each winter, a strangler-free paradise may be in the woods they left behind.

Drought triggered Mayan demise

By Helen Sewell
BBC News Online science staff

Climate change was largely to blame for the collapse of the Mayan civilisation in Central America more than 1,000 years ago, research suggests.
By the middle of the 8th Century there were up to 13 million people in the Mayan population but within 200 years their cities lay abandoned.

The Mayans built complex systems of canals and reservoirs to collect rainwater for drinking in the hot, dry summers.

Despite this there has long been speculation that the whole population was wiped out by drought, but there has not been enough evidence to support this theory.

Now research published in the journal Science suggests that climate change was indeed a major factor.

Coloured bands

To investigate the Mayan decline, scientists studied the ancient build-up of sediment on the sea floor just off the northern coast of Venezuela.

They discovered layers of deposits in bands of alternating dark and light colours each about a millimetre deep. The light bands consisted of algae and tiny fossils, while the dark bands were due to sediments of the metal titanium.

The scientists say titanium was washed into the sea by rivers during the rainy seasons. Shallower dark bands, which indicate lower levels of the metal, show the rivers were flowing more weakly. The researchers say this was because there was less rain.

They have worked out that in the 9th and 10th Centuries, probably just before the Mayan civilisation collapsed, there was a long period of dry weather and three intense droughts.

Modern implications

Archaeological evidence suggests that one reason for the Mayans’ initial success over other societies was that they controlled the artificial reservoirs.

If this is true, the scientists say the drought could easily have pushed the whole civilisation to the verge of collapse.

The German scientist who led the research, Gerald Haug, said this had serious implications for climate change today.

“A three-to-nine-year drought, which could be a failure of the monsoon systems in Africa or in India, and in particular the change in the background state of climate… is a very severe threat to modern humanity,” he told BBC News Online.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/2848977.stm

Published: 2003/03/14 04:20:31 GMT

Roman rise and fall ‘recorded in trees’

14 January 2011 Last updated at 12:19 ET

By Mark Kinver

The study offers a link between changes to the climate and the rise and fall of human societies

An extensive study of tree growth rings says there could be a link between the rise and fall of past civilisations and sudden shifts in Europe’s climate.

A team of researchers based their findings on data from 9,000 wooden artifacts from the past 2,500 years.

They found that periods of warm, wet summers coincided with prosperity, while political turmoil occurred during times of climate instability.

The findings have been published online by the journal Science.

“Looking back on 2,500 years, there are examples where climate change impacted human history,” co-author Ulf Buntgen, a paleoclimatologist at the Swiss Federal Research Institute for Forest, Snow and Landscape, told the Science website.

Ring record

The team capitalised on a system used to date material unearthed during excavations.

“Distinct drying in the 3rd Century paralleled a period of serious crisis in the western Roman empire” – Ulf Buntgen

“Archaeologists have developed oak ring width chronologies from Central Europe that cover nearly the entire Holocene and have used them for the purpose of dating artefacts, historical buildings, antique artwork and furniture,” they wrote.

“Chronologies of living and relict oaks may reflect distinct patterns of summer precipitation and drought.”

The team looked at how weather over the past couple of centuries affected living trees’ growth rings.

During good growing seasons, when water and nutrients are in plentiful supply, trees form broad rings, with their boundaries relatively far apart.

But in unfavourable conditions, such as drought, the rings grow in much tighter formation.

The researchers then used this data to reconstruct annual weather patterns from the growth rings preserved in the artefacts.

Once they had developed a chronology stretching back over the past 2,500 years, they identified a link with prosperity levels in past societies, such as the Roman Empire.

“Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from 250-600 AD coincided with the demise of the western Roman empire and the turmoil of the migration period,” the team reported.

“Distinct drying in the 3rd Century paralleled a period of serious crisis in the western Roman empire marked by barbarian invasion, political turmoil and economic dislocation in several provinces of Gaul.”

Dr Buntgen explained: “We were aware of these super-big data sets, and we brought them together and analyzed them in a new way to get the climate signal.

“If you have enough wood, the dating is secure. You just need a lot of material and a lot of rings.”

If an island state vanishes, is it still a nation?

By CHARLES J. HANLEY, AP Special Correspondent Charles J. Hanley, Ap Special Correspondent
Mon Dec 6, 2:27 pm ET

CANCUN, Mexico – Encroaching seas in the far Pacific are raising the salt level in the wells of the Marshall Islands. Waves threaten to cut one sliver of an island in two. “It’s getting worse,” says Kaminaga Kaminaga, the tiny nation’s climate change coordinator.

The rising ocean raises questions, too: What happens if the 61,000 Marshallese must abandon their low-lying atolls? Would they still be a nation? With a U.N. seat? With control of their old fisheries and their undersea minerals? Where would they live, and how would they make a living? Who, precisely, would they and their children become?

For years global negotiations to act on climate change have dragged on, with little to show. Parties to the 193-nation U.N. climate treaty are meeting again in this Caribbean resort, but no one expects decisive action to roll back the industrial, agricultural and transport emissions blamed for global warming — and consequently for swelling seas.

From 7,000 miles (11,000 kilometers) away, the people of the Marshalls — and of Kiribati, Tuvalu and other atoll nations beyond — can only wonder how many more years they’ll be able to cope.

“People who built their homes close to shore, all they can do is get more rocks to rebuild the seawall in front day by day,” said Kaminaga, who is in Cancun with the Marshallese delegation to the U.N. talks.

The Marshallese government is looking beyond today, however, to those ultimate questions of nationhood, displacement and rights.

“We’re facing a set of issues unique in the history of the system of nation-states,” Dean Bialek, a New York-based adviser to the Republic of the Marshall Islands who is also in Cancun, told The Associated Press. “We’re confronting existential issues associated with climate impacts that are not adequately addressed in the international legal framework.”

The Marshallese government took a first step to confront these issues by asking for advice from the Center for Climate Change Law at New York’s Columbia University. The center’s director, Michael B. Gerrard, in turn has asked legal scholars worldwide to assemble at Columbia next May to begin to piece together answers.

Nations have faded into history through secession — recently with the breakup of the former Yugoslavia, for example — or through conquest or ceding their territory to other countries.

But “no country has ever physically disappeared, and it’s a real void in the law,” Gerrard said during an interview in New York.

The U.N. network of climate scientists projects that seas, expanding from heat and from the runoff of melting land ice, may rise by up to 1.94 feet (0.59 meters) by 2100, swamping much of the scarce land of coral atolls.

But the islands may become uninhabitable long before waves wash over them, because of the saline contamination of water supplies and ruining of crops, and because warming is expected to produce more threatening tropical storms.

“If a country like Tuvalu or Kiribati were to become uninhabitable, would the people be stateless? What’s their position in international law?” asked Australian legal scholar Jane McAdam. “The short answer is, it depends. It’s complicated.”

McAdam, of the University of New South Wales, has traveled in the atoll nations and studied the legal history.

As far as islanders keeping their citizenship and sovereignty if they abandon their homelands, she said by telephone from Sydney, “it’s unclear when a state would end because of climate change. It would come down to what the international community was prepared to tolerate” — that is, whether the U.N. General Assembly would move to take a seat away from a displaced people.

The 1951 global treaty on refugees, mandating that nations shelter those fleeing because of persecution, does not cover the looming situation of those displaced by climate change. Some advocate negotiating a new international pact obliging similar treatment for environmental refugees.

In the case of the Marshallese, the picture is murkier. Under a compact with Washington, citizens of the former U.S. trusteeship territory have the right to freely enter the U.S. for study or work, but their right to permanent residency must be clarified, government advisers say.

The islanders worry, too, about their long-term economic rights. The wide scattering of the Marshalls’ 29 atolls, 2,300 miles (3,700 kilometers) southwest of Hawaii, give them an exclusive economic zone of 800,000 square miles (2 million square kilometers) of ocean, an area the size of Mexico.

The tuna coursing through those waters are the Marshalls’ chief resource, exploited by selling licenses to foreign fishing fleets. “If their islands go underwater, what becomes of their fishing rights?” Gerrard asked. Potentially just as important: revenues from magnesium and other sea-floor minerals that geologists have been exploring in recent years.

While lawyers at next May’s New York conference begin to sort out the puzzle of disappeared nations, the Marshallese will grapple with the growing problems.

The “top priority,” Kaminaga said, is to save the isthmus linking the Marshalls’ Jaluit island to its airport, a link now swept by high tides.

Meantime, a lingering drought this year led islanders to tap deeper into their wells, finding salty water requiring them to deploy emergency desalination units. And “parts of the islands are eroding away,” Kaminaga said, as undermined lines of coconut palms topple into the sea.

This week in Cancun and in the months to come, the Marshalls’ representatives will seek international aid for climate adaptation. They envision such projects as a Jaluit causeway, replanting of protective vegetation on shorelines, and a 3-mile-long (5-kilometer-long) seawall protecting their capital, Majuro, from the Pacific’s rising tides.

Islanders’ hopes are fading, however, for quick, decisive action to slash global emissions and save their remote spits of land for the next century.

“If all these financial and diplomatic tools don’t work, I think some countries are looking at some kind of legal measures,” said Dessima Williams, Grenada’s U.N. ambassador and chair of a group of small island-nations. Those measures might include appeals to the International Court of Justice or other forums for compensation, a difficult route at best.

In the end, islanders wonder, too, what will happen to their culture, their history, their identity with a homeland — even to their ancestors — if they must leave.

“Cemeteries along the coastline are being eroded. Gravesites are falling into the sea,” Kaminaga said. “Even in death we’re affected.”