A trickle of water might save estuary

Sonoran Institute

About 90% of the delta’s wetlands and natural habitat dried up over the past half-century, as water was diverted from the Colorado River, which is Southern California’s biggest urban water supplier.

Conservationists believe a small but immediate step could renew the Colorado River Delta.

By Frank Clifford, Special to The Times
September 17, 2007

The Colorado River Delta was once a watery labyrinth of willow thickets, mesquite and cottonwood, bigger than the state of Rhode Island and teeming with bird and animal life. Today it is a barren expanse of salt-stained mudflats where the river used to meet the sea south of Yuma.

About 90% of the delta’s wetlands and natural habitat dried up over the last half century, as water from the Colorado was captured in reservoirs and diverted to farms and cities from Las Vegas to Mexicali.

For more than a decade, conservation groups in the U.S. and Mexico have tried unsuccessfully to restore North America’s largest desert estuary. Now the Sonoran Institute is warning that unless restoration is undertaken before a prolonged dry spell, which many scientists are predicting, it could be too late.

In its forthcoming analysis of the delta, the nonprofit Arizona institute paints a dire picture of the once-vibrant ecosystem. But it also puts forth a proposal for replenishing much of the area by replacing a tiny fraction of the river water that once flowed through the delta, saying it would be enough to restore much of the area’s natural wealth.

Under the institute’s plan, the delta would get about three-tenths of a percent of the river’s historic annual flow, making it one of the more modest claims on a river that serves 30 million people. But even that amount could be a hard sell.

Eight years of drought in the Colorado watershed have raised the likelihood of shortages in the near future, and as officials in the U.S. and Mexico look for creative ways of limiting future cutbacks, every drop will count.

The river’s annual flow has fallen as low as 25% of normal since 2000, and some scientists have predicted that with the growing influence of climate change, flows will average 50% to 60% of normal over the next 50 years.

Later this year, Interior Secretary Dirk Kempthorne is expected to announce the first-ever guidelines for managing reduced water deliveries from the Colorado in the event of shortages. Officials say a shortage will be declared when the water level at Lake Mead drops 36 feet below its current level, a change that is expected within the next few years.

As the government draws up plans for dealing with a reduced water supply, environmentalists believe restoration must be made a priority or the delta will be doomed.

“If we fail right now, we might really fail, as the shortage becomes a reality and discussions about saving water for conservation become a lot harder,” said Jennifer Pitt, a policy analyst with the group Environmental Defense, which works closely with the Sonoran Institute.

Advocates for the delta have little legal leverage.

Neither the 1944 treaty that allocates Colorado River water to Mexico nor any environmental law in that country mandates water for the delta. Late last year, in support of efforts by California to reclaim water that has been seeping across the border and nourishing crops and wetlands in the delta, Congress passed legislation barring the use of U.S. environmental laws to protect Mexico’s interests.

But the Sonoran Institute contends that there is still nearly enough unclaimed water in the river to revive the delta without impinging on any existing rights on either side of the border.

“What we are talking about is the slop, leakage and waste discharges, ” said Peter Culp, a lawyer who represents the institute. It’s the water that slips past Mexico’s Morelos Dam after a storm or that trickles back to the river from irrigated fields.

For 30 years, the crown jewel of the delta’s remaining wetlands, the 40,000-acre Cienega de Santa Clara in Sonora, Mexico, has relied entirely on brackish discharges from a nearby irrigation district.

The problem with such releases, however, is that they can’t be counted on forever and don’t always occur when nature needs them. To ensure timely flows, the institute has proposed amending the 1944 treaty to allow Mexico to bank water in the U.S. and participate in a bi-national water market.

“There are significant human benefits to the proposal,” said Mark Lellouch, one of its authors. About 200,000 people live in scattered communities in the delta, Lellouch said, and restoration would provide more sustenance and more jobs.

Even now, nature tourism is a going concern. Visitors from the U.S. and Mexico are drawn to the Cienega de Santa Clara and other destinations by the estimated 350,000 birds that still nest and feed in the delta.

“There are a number of stakeholders in Mexico interested in that environment,” said Steve Smullen, principal engineer for the International Boundary and Water Commission, the agency that administers water-rights treaties between the United States and Mexico. But he said the institute’s plan “works against agricultural interest, conservative interest and the interests of large communities” vying for the water.

“If there’s enough will, you can make anything happen,” he said. “But it’s an uphill battle.”

From: Los Angeles Times.

Climate change will harm life on the deep ocean floor, study finds

By Steve Connor, Science Editor

Published: 10 September 2007

 

A study of the most remote forms of life on Earth has found that their splendid isolation on the deep seabed will not protect them from environmental catastrophes on the surface.

Scientists used to believe that a global disaster that wiped out most of the life on Earth would not touch the unusual organisms that live around the mineral-rich vents on the sea floor. But research by a team of British scientists has found that even these deep-sea creatures which live in total darkness and survive on the chemical energy oozing from mineral vents on the seabed are not immune from the seasonal changes above.

“The marine ecosystem may be even more interconnected than we previously realised and in fact there may be nowhere for life to hide from global catastrophes,” said Jon Copley of Southampton University.

“I used to think that life on the deep ocean-floor environment is pretty much quarantined from what happens in the sunlit world up here thanks to their chemical energy supply,” Dr Copley will tell the British Association’s Science Festival today.

A study of a species of tiny shrimp living around deep-sea vents has found that they produce microscopic larvae as part of their lifecycle and that when these larvae migrate they have to rely on food coming down from the sunlit waters above. So the animals living on the deep seabed have to time the hatching of their eggs to coincide with spring blooms of microscopic plant life growing at the surface – a link that has been overlooked.

Dr Copley and his colleagues studied deep-sea shrimps and mussels and found they have a reproductive cycle that is seasonal – just like surface creatures – even though they are totally isolated from the changes in the seasons. They have to do this to ensure their larvae survive.

“So if an asteroid slams into the Earth and blocks out the Sun, these environments won’t be perfect air-raid shelters,” he said. “Similarly if climate change were to alter the pattern of life on the surface waters, I would suggest that potentially such changes could be communicated even to these remote corners on the ocean floor.

“Finding seasonality down there shows life beneath the waves is more connected than we realised.”

Source: The Independent

When bivalves ruled the world

Paleobiologist studies how elevated

C02 affected ancient marine life

 

Before the worst mass extinction of life in Earth’s history – 252 million years ago – ocean life was diverse and clam-like organisms called brachiopods dominated. After the calamity, when little else existed, a different kind of clam-like organism, called a bivalve, took over.

What can the separate fates of these two invertebrates tell scientists about surviving an extinction event”

A lot, says UWM paleoecologist Margaret Fraiser. Her research into this particular issue not only answers the question; it also supports a relatively new theory for the cause of the massive extinctions that occurred as the Permian period ended and the Triassic period began: toxic oceans created by too much atmospheric carbon dioxide (C02).

The theory is important because it could help scientists predict what would happen in the oceans during a modern “C02 event.” And it could give them an idea of what recovery time would be.

Studying the recovering ecology is equally significant, says Fraiser. The evolution of surviving species in the aftermath of the mass extinction set the stage for dinosaurs to evolve later in the Triassic.

From air to water Fossil records suggest that trauma in the oceans actually began in the air.

“Estimates of the C02 in the atmosphere then were between six and 10 times greater than they are today,” says Fraiser, an assistant professor of geosciences. It makes sense, she says. The largest continuous volcanic eruption on Earth – known as the “Siberian Traps” – had been pumping out C02 for about a million years prior to the Permian-Triassic mass extinction.

The time scale shows the expanse of time between the Permian-Triassic mass extinction and the less severe mass extinction that wiped out the dinosaurs. Click here for more information.

The Permian-Triassic extinction wiped out 70 percent of life on land and close to 95 percent in the ocean – nearly everything except for bivalves and a fewer number of gastropods (snails).

C02 is a greenhouse gas that influences global temperatures. But, says Fraiser, according to the fossil record, high levels of C02 and the correspondingly low levels of oxygen do much more than that.

The hypothesis unfolds like this: High C02 levels would have increased temperatures, resulting in global warming on a large scale. With no cold water at the poles, ocean circulation would have stagnated. The oceans would have become low in oxygen, killing off life in deeper waters where there was no opportunity for water to mix with the little oxygen in the atmosphere.

More carbon dioxide would have been created as life forms died and microbes broke them down, which also would have created poisonous hydrogen sulfide. The oceans would have become an inhabitable chemical cocktail.

Follow the CO2 In fact, there have been many CO2 events in geologic time, and they’ve literally left their mark.

“You can see where the rock turned dark,” says Fraiser, pointing out different-colored layers in a fossil samples from the period. “That is an indicator of low oxygen at the time. These are from sites that were underwater at the beginning of the Triassic period.”

Fraiser, who has just finished her first year at UWM, is one of several new faculty in geosciences and its emerging paleobiology program.

She has collected fossil samples of the marine survivors from the period in what today are China, Japan, Italy and the western United States. The similarities of the fossils from all these locations have been surprising.

“It is unexpected to see that,” says Fraiser. “It appears that these bivalves and gastropods were the only survivors worldwide.”

They had all the right characteristics to tolerate the lack of oxygen, she says. They were tiny, shallow-water dwellers, with a high metabolism and flat shape that allowed them to spread out to extract more of the limited oxygen when feeding.

Toxic conditions also inhibited marine life from producing a shell. Size suddenly mattered for mollusks, and only the very small survived, eroding the balance of the marine food chain.

Ultra-slow rebound As she sorts through the rock record from just after the Permian-Triassic extinction, Fraiser also has unearthed evidence that explains why it took so long for life to recover. The answer appears to be more of the same: C02 levels remained high long after the initial die-off.

“After other extinction events on Earth, life bounced back within 100,000 to a million years,” she says. “But with the Permian-Triassic extinction, we don’t see a recovery for 5 million years. There is very low ecological complexity and diversity for all of that time.”

Another intriguing aspect of this interval in Earth’s history, says Fraiser, is that, according to the rock record from the Triassic, it was bounded by two C02 events.

The first was the disappearance of coral reefs. “That gap sounded the alarm,” she says. “That’s what indicated that C02 levels were elevated.”

On the back end, large communities of bivalves prevailed in such large numbers that they formed their own reefs.

Fraiser’s charting of the C02 “domino effect” on Early Triassic marine life is valuable as scientists study climate change today, says UWM Geology Professor John Isbell.

“The Earth’s system doesn’t care where the C02 comes from,” Isbell says. “It’s going to respond the same way.”

From Site: http://www.eurekalert.org/