Just right' plant growth may make river deltas resilient

A press release from Indiana University: Research by Indiana University geologists suggests that an intermediate amount of vegetation -- not too little and not too much -- is most effective at stabilizing freshwater river deltas. The study, "Optimum vegetation height and density for inorganic sedimentation in deltaic marshes," was published online Aug. 24 by Nature Geoscience. The findings may help guide restoration of river deltas, such as those near the mouth of the Mississippi River, which are under threat as sea levels rise.

Authors are William Nardin, a postdoctoral fellow in the Department of Geological Sciences in the IU Bloomington College of Arts and Sciences; and Douglas A. Edmonds, who holds the Robert R. Shrock Professorship in Sedimentary Geology and is an assistant professor of geological sciences.

Vegetation on marsh surfaces in river deltas can slow the flow of water and cause more sediment to be deposited, helping prevent sea-level rise from drowning sensitive marshlands. But the study finds that, if the vegetation is too tall or dense, it diverts water into the river channel, resulting in less sediment being deposited on the marsh.

“In river deltas the effect of vegetation on sedimentation seems to follow the Goldilocks principle,” Edmonds said. “You want the amount of vegetation that is just right -- not too much, but also not too little.”

The world’s river deltas are rich and productive and are home to about 10 percent of the world’s population. But they are threatened by an array of forces, including population growth, pollution, development and erosion, as well as sea-level rise associated with climate change.

...In tidal saltwater marshes, research has shown that vegetation enhances sedimentation. But scientists know less about how vegetation affects sedimentation in freshwater marshes that are common in river deltas. Nardin and Edmonds used sophisticated computer modeling to study how marsh vegetation influences the transport and deposition of sediment in river deltas. They conducted 75 simulations involving varying scenarios of vegetation height and density and rates of water flow.

They found that vegetation of intermediate height and density results in the greatest deposition of sand and mud. However, if the plants are too tall or densely packed, sediment tends to remain in the river channel, bypassing marshes and being carried directly to the sea....

From the IU website: This image shows freshwater marsh vegetation in Wax Lake Delta, La. Aquatic vegetation on low-elevation marshes is pictured in the foreground, while woody vegetation occupies a levee on the left. The open water in the distance is a deltaic distributary channel. Photo by Elizabeth Olliver

Surviving and thriving under climate change in the world’s deltas

A press release from the University of Exeter: Researchers from the University of Exeter are investigating the effect of climate change on deltas in South Asia and Africa to understand how people will respond and adapt.

Deltas are economic and environmental hotspots, with many large deltas in South, South-East and East Asia and Africa. The new $13 million project examines four deltas that are home to almost 200 million people, many of whom are farmers who provide food for a large proportion of the population.

The project will work with scientists, demographers and social scientists in the Nile delta in Egypt, the Ganges-Brahmaputra in Bangladesh and India, the Mahanadi in India and the Volta in Ghana.

This week the latest report by the Intergovernmental Panel on Climate Change (IPCC) highlighted that people and assets exposed to coastal risks will increase significantly in the coming decades due to population growth, economic development and the growth of cities. This study will focus on how people move within deltas and how cities will cope over the next half century.

Robert Nicholls, Professor of Coastal Engineering at the University of Southampton who is leading the project, said: “Deltas are vulnerable areas and we need to act quickly to make more informed choices about how best to live with and thrive in conditions of climate stress. We are working with the Governments and people of these regions to understand the challenges and identify with a wide range of stakeholders the implications of different adaptation options to those challenges.”...

In southern Ethiopia, the Omo River delta and Lake Turkana, shot by NASA

Netherlands to upgrade flood defenses to cope with climate change

Sophie Yeo in Responding to Climate Change: A national effort is underway in the Netherlands to upgrade the thousands of miles of dykes and dams responsible for keeping the country dry.  As the planet warms, experts say the Netherlands’ network of flood defences will no longer be able to hold up against rising sea levels, and this autumn, the government will explain how it plans to hold the sea back for another century.

In 2007, an investigation was launched into whether the the famously low-lying country could survive at all should projections of almost a metre of sea level rise by the end of the century come to pass. A committee concluded that life could go on in the Netherlands, but work must begin immediately to upgrade the country’s 3,700km of dykes, dunes and dams, which hold back the water in the country’s most vulnerable coastal areas.

On the committee’s advice, a Delta Programme was set up, which began work on a new policy framework for the country that will be put before Parliament this September, including five “Delta Decisions” that will form the basis of the country’s new water strategy.

These five decisions lay out concrete ideas on how the Netherlands can deal with some of the biggest challenges posed by their troublesome geography. The proposals will renew the government’s strategy on water safety and flood risk management, the future scarcity of freshwater supplies, and spatial planning of new buildings and infrastructure.

They also propose specific plans for the most vulnerable regions of the Netherlands, the IJsselmeer region and the Rhine-Meuse Delta....

The Rhine-Meuse-Scheldt delta, shot by NLR and ESA, Wikimedia Commons. The copyright holder of this work allows anyone to use it for any purpose including unrestricted redistribution, commercial use, and modification. 

A call for new attention to restoring sedimentology of river deltas

Indiana University News Room: Rapid advances in the new and developing field of restoration sedimentology will be needed to protect the world's river deltas from an array of threats, Indiana University Bloomington geologist Douglas A. Edmonds writes in the journal Nature Geoscience.

The commentary, published this week in the November issue, addresses the fact that land is disappearing from river deltas at alarming rates. And deltas are extraordinarily important: They are ecologically rich and productive, and they are home to about 10 percent of the world's population. "There's a lot of talk about ecological restoration of the coast," Edmonds said. "But with delta environments, before ecological restoration can happen you have to stabilize the coastline."

Under naturally occurring processes, coastal land is both created and destroyed at river deltas. River sediment is deposited at the delta, building land. Erosion takes some of the land away. The rate of land growth or loss depends on the balance between "sources" and "sinks," which is influenced by the complex interaction of floods, ocean waves and tides, vegetative decay and wind.

But sea-level rise and coastal subsidence have tilted the scales toward land loss, and dams and levees built for flood control have interfered with the delivery of sediment. In the Mississippi River delta, the chief focus of the article, an expanse of land the size of a football field disappears every hour....

A floating house in the Mekong Delta, shot by Étienne André, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 2.5 Generic license

A Mississippi River diversion helped build Louisiana wetlands

Terra Daily via SPX: The extensive system of levees along the Mississippi River has done much to prevent devastating floods in riverside communities. But the levees have also contributed to the loss of Louisiana's wetlands. By holding in floodwaters, they prevent sediment from flowing into the watershed and rebuilding marshes, which are compacting under their own weight and losing ground to sea-level rise. Reporting in Nature Geoscience, a team of University of Pennsylvania geologists and others used the Mississippi River flood of the spring of 2011 to observe how floodwaters deposited sediment in the Mississippi Delta.

Their findings offer insight into how new diversions in the Mississippi River's levees may help restore Louisiana's wetlands. While scientists and engineers have previously proposed ways of altering the levee system to restore some of the natural wetland-building ability of the Mississippi, this is among the only large-scale experiments to demonstrate how these modifications might function.

The 2011 floods broke records across several states, damaged homes and crops and took several lives. The destruction was reduced, however, because the Army Corps of Engineers opened the Morganza Spillway, a river-control structure, for the first time since 1973 to divert water off of the Mississippi into the Atchafalaya River Basin. This action involved the deliberate flooding of more than 12,000 square kilometers and alleviated pressures on downstream levees and spared Baton Rouge and New Orleans from the worst of the flood.

For the Penn researchers, the opening of the Morganza Spillway provided a rare look into how floods along the Mississippi may have occurred before engineered structures were put in place to control the river's flow. "While this was catastrophic to the people living in the Atchafalaya Basin, it was also simulating - accidentally - the sort of natural flood that used to happen all the time," Jerolmack said....

A scene in the Atchafalaya Basin in Louisiana, USA. Photo by the US Army Corps of Engineers, public domain

‘Study coastal areas' vulnerability to sea rise’

Bennett Oghifo in This Day (Nigeria):  It is imperative to map the vulnerability of sea level rise on coastal areas, Director of the Climate Change Adaptation Unit of the Federal Ministry of Environment, Dr. Samuel Adejuwon has said.

He stated this at the Climate Change and Coastal States Dialogue. A two-day Workshop organised by the UNDP in collaboration with Lagos State Government at the weekend in Lagos. The theme was ‘Challenges of Sea Level Rise Induced Flooding in Nigeria; Coastal States in Focus. States in attendance were; Lagos, Delta, Akwa Ibom, Rivers, Cross River, Ondo and Ogun.

The first paper; Potential Consequences and Response Strategies to Sea Level Rise in Nigeria’ was presented by Prof. Emmanuel Oladipo; the second paper was; ‘Industrial Pollution and Water Quality in Coastal States in Nigeria’ by Prof. Labode Popoola and the third paper, ‘Climate Change and Coastal Environment: A Case Study of Lagos State’ was delivered by Prof. Jide Alo, who was represented.

Adejuwon while commenting on the presentations said different coastal states have separate characteristics and that it would be good to map individual state’s vulnerability. “We have not been able to really do this. We need to do the mapping to see the adaptation measures we can put in place in order to combat the effect of climate change.”

He also agreed with the Cross River State Commissioner for Environment who said there were other factors that cause flooding that should not be ignored, stating that there was need to do research to unearth these factors. “All these factors are being [ex]acerbated by climate change.”...

The Third Mainland Bridge in Nigeria, one of three bridges from Lagos Island to the mainland, shot by Zouzou Wizman, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Migration from Mekong Delta to rise on climate change

VietnamNetBridge: The migration from the Mekong Delta to other areas will increase in the future as the Mekong Delta is one of the three areas most vulnerable to the global climate change, an expert told a seminar ending in Can Tho City on Tuesday.

Florian Forster, Chief of Mission of the International Organization for Migration (IOM) in Vietnam, told the seminar on the climate change adaptation in the Mekong Delta’s city that if the sea level rises by one meter, one third of the Mekong Delta will be flooded.

Le Anh Tuan from Research Institute for Climate Change under Can Tho University said that the weather in the delta has changed much with prolonged dry season, sudden floods, increasing saltwater intrusion, drought and landslides along the sea.

...According to Le Thanh Sang, deputy director of the Southern Institute of Sustainable Development, the Mekong Delta is the area having the highest number of migrants. Most migrants come from rural areas and three fourths of them come to work in industrial parks in southeast provinces. However, this issue has yet to receive full awareness and suitable policies....

Niger river dams could displace 1.5 million

Fred Pearce in New Scientist: Seen from space, it is a vast green and blue smudge on the edge of the Sahara desert. Close up, it is a watery wilderness of lakes and flooded forests and grasslands, home to 1.5 million fishers, cattle grazers and farmers, and millions of birds wintering from Europe.

But the inner Niger delta in northern Mali, one of the world's largest wetlands, could soon run almost completely dry every fourth year. Massive engineering works on the Niger river, West Africa's largest river, are set to turn the delta into a desiccated sump. The result would be a "human catastrophe as vicious and shameful as the drainage of the Aral Sea" in central Asia by Soviet engineers, warns Jane Madgwick, head of Wetlands International.

The first threat comes from the Malian government itself. It has sanctioned a series of schemes to extract water from the Niger river just upstream of the delta to irrigate thirsty crops such as rice, cotton and sugar. The two largest projects, due to be completed by 2015, will provide water for the South African sugar giant Illovo and a Chinese state enterprise. They could take the entire river flow during the dry season, says hydrologist Leo Zwarts of the Dutch consultancy Altenburg & Wymenga...

The MODIS on NASA's Terra satellite took this picture of the Inland Niger Delta on November 11, 2007 shortly after the end of the rainy season when the landscape remained lush and green. This inland delta is a complex combination of river channels, lakes, swamps, and occasional areas of higher elevation. One such area of higher elevation is obvious in this image, and it forms a branching shape, like a tan tree pushing up toward the north. This wet oasis in the African Sahel provides habitat both for migrating birds and West African manatees. The fertile floodplains also provide much needed resources for the local people, who use the area for fishing, grazing livestock, and cultivating rice.

California flood plan calls for up to $17 billion in repairs

Gosia Wozniacka in the Associated Press: California water officials recommended a historic investment in the state's aging flood control system Friday, saying more than half of the state's levees do not meet standards and the system needs up to $17 billion in repairs and investment.

The Department of Water Resources' release of the first statewide flood plan follows a call by Gov. Jerry Brown to refocus state efforts on preparing for the effects of a warming climate as floods from a faster-melting snowpack already place increased strain on the state's aging levees.
Officials and experts say the state's flood control system — a piece-meal collection of 14,000 levees and other infrastructure built along the Sacramento and San Joaquin rivers by farmers and local governments over the last 150 years — is no longer adequate.

Once a mostly agricultural region that was lightly populated, the Central Valley where the rivers meet has experienced rapid development and population growth. "The system is based on antiquated technologies, so you have to upgrade it and keep in mind changing societal demands," said Jeffrey Mount, professor and founding director of Center for Watershed Sciences at UC Davis.

Central Valley's flood risk ranks among the nation's highest. About 1 million Californians now live in floodplains and levees protect an estimated $69 billion in assets, including the state's water supply, major freeways, agricultural land and the valley's remaining wetland and riparian habitat, said Mike Mierzwa, senior engineer in the Central Valley Flood Protection Office.

The Sacramento-San Joaquin River Delta is a freshwater source for two-thirds of California's population and irrigates millions of acres of farmland throughout the state. While officials have long known the flood control system was in disrepair, it's the first time they have studied it as a whole, come up with long-term solutions and a priority for investments....

The Suisun Marsh Salinity Control Gates (foreground) span the Montezuma Slough at the Roaring River intake (background). They operate like a heart valve, allowing flow in only one direction. In this picture, the three gates are open to allow the freshwater ebb tide from the Sacramento-San Joaquin Delta to push the more saline Grizzly Bay water out of the slough. US Army Corps of Engineers photo

Mekong Delta told it must improve flood forecasting systems

Vietnam News: Weather forecasting must improve in the Cuu Long (Mekong) Delta so the region can better cope wth floods and high tides, experts have said. Flood forecasting must be accurate and timely, especially in the context of climate change, they said.

...Effective flood-forecasting can help reduce 30 per cent of losses caused by floods, according to the National Centre for Hydro-Meteorological Forecasting. Many serious floods have occurred in the Mekong Delta this year, with the volume and level becoming more and more serious than in previous years, especially since the 2000-02 period.

Flood forecasting activities must be modified, and long-term plans for coping with floods needed to be carried out, the centre said.

According to the Southern Hydro-Meteorology Centre, most serious floods this year have been caused by an extremely large volume of rainfall in the middle of Laos and in lower Laos areas and the Central Highlands region. Thus, flood forecasting work must be focused on these areas....

A floating market in Can Tho, Vietnam, shot by Doron, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Bangladeshi women on the brink

Naimul Haq in IPS: Char Nongolia village is a basket case when it comes to climate change impacts such as increasing salinity, frequent cyclones, tidal surges, erratic rainfall and extended droughts. Yet, the 40,000 people of this village, sitting on a delta that drains the sub-continent’s major river systems, have endured the creeping devastation of their homeland in southeastern Bangaldesh with no help from anywhere.

There is no drinking water supply, no land to grow food crops on, no healthcare facility, no roads, no jobs and absolutely no sign of any security or authority. Any natural protection afforded by forests has long ago been stripped away.

...Several other women, victims of climate change, told stories of lost livelihoods to a mock jury at Char Nongolia organised by a local non-government organisation, Noakhali Rural Development Society and the People’s Forum on the Millennium Development Goals with support from the Global Call for Action Against Poverty.

...Once known for its rich forests, Char Nongolia is now barren and surrounded by similar islands of accumulated silt. Farming is now rare, although riverbeds and embankments are known to be naturally fertile. For centuries, the people in this area coped with cyclones, floods and droughts but the adaptation to increase in frequency and intensity of adverse climatic events has reached the limit....

Climate change effect on San Francisco Bay and Delta detailed in new study

Mike Taugher in the San Jose Mercury News via the Contra Costa Times: California's water problems and the ecological pressure on the West Coast's largest estuary will intensify in a warming world, according to a first-of-its-kind scientific study.

San Francisco Bay and the Delta will get warmer, saltier and clearer if global warming continues over the next several decades. That will increase the risk of extinction for some kinds of fish and could help unwanted species, including a toxic algae, flourish Flooding is likely to be more common upstream and along the coast, and water supplies will be stretched due to a shrinking snowpack, the researchers found.

In the Delta, already seeing a broad ecological decline, the probability of further ecological surprises will increase. "We're going to enter a new era of environmental conditions," said James Cloern, the study's lead author and a phytoplankton ecologist at the U.S. Geological Survey in Menlo Park.

Cloern said the seven-year study was the most complex research project he's undertaken in 36 years at the USGS. The researchers said their paper appears to be the first multifaceted assessment of how the estuary could respond to climate change.

...The researchers took two climate change scenarios they considered reasonably likely and projected what would happen to the estuary given the way it is managed now for wildlife and water supplies. In the first scenario, greenhouse gas emissions would be curbed in the coming decades, and the climate would turn out to be only moderately sensitive to the gases. In the second, bleaker, scenario, greenhouse gas emissions would continue to increase, and climate would react strongly to them....

NASA image of San Francisco Bay

Drought and poachers take Botswana's natural wonder to brink of catastrophe

David Smith in the Guardian (UK): The Okavango delta in Botswana has suffered "catastrophic" species loss over the past 15 years, researchers have announced , in the latest sign of a growing crisis for wildlife in Africa. Some wild animal populations in the delta, one of the wonders of the natural world, have shrunk by up to 90% and are facing local extinction, according to the most comprehensive aerial survey yet undertaken there.

The findings come after a study this month showed dramatic declines in animal numbers in the Masai Mara wildlife reserve, south-west Kenya, raising anxiety about the effectiveness of conservation across the continent.

The delta, in north Botswana, has about 50,000 islands among a series of channels, lagoons and swamps, whose waters reach the Kalahari desert. Travellers pay premium rates to stay in upmarket safari lodges, many accessible only by air, and for the chance to explore the pristine 16,000 sq km oasis.

Botswana has been careful to restrict visitor numbers and preserve the fecundity of this watery wilderness. But that strategy has suffered a blow from research which shows that some of the delta's most precious assets will be jeopardised unless urgent action is taken.

"The results were unexpected," said Mike Chase, founder of Elephants without Borders, which did the aerial survey of the region. "There has been a cosy pretence that wildlife is thriving and doing well in the Okavango delta. Our survey provides the first scientific evidence that wildlife is declining, and pretty sharply too. That cosy pretence has been blown out of the water."…

Giraffes in the Okavango Delta in Botswana, shot by Cojharries, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Letting Mississippi run its natural course could save New Orleans from hurricanes

William Sargent in the Christian Science Monitor analyzes the stark long-term choices faced by everyone living in and near the Mississipi Delta: During the next few days the Army Corps of Engineers must continue making their Hobbesian choice between the ultimate disaster for New Orleans and an $18 billion bet that they can beat Mother Nature. To keep flood waters from breaking the levees and charging into the city, the Corps is making an $18 billion gamble that they can divert a fourth of the Mississippi’s flow down the Atchafalaya River without losing control of the situation.

The choice may seem obvious, but the Corps’ gamble also holds potentially devastating consequences for New Orleans. If it loses control of the diversion, the entire flow of the Mississippi could suddenly come thundering down the Atchafalaya – the course nature wants it to follow – never to be diverted back. Farms, towns, and oil refineries would be drowned, and the key port cities of New Orleans and Baton Rouge would be left without their river.

As the Corps begins the partial diversion of the Mississippi down the Atchafalaya, coastal scientists should seize on the opportunity to consider longer-term shifts in the river’s course. It’s possible that this crisis could lead to a less costly and more sustainable way of dealing with the problems of coastal Louisiana.

Although such a shift in the river’s path would deal a devastating economic blow to the region, allowing the Mississippi to flow west down the Atchafalaya would ultimately be in the best long-term ecological interest of the area because it would build up the southern Louisiana coast as a buffer against future hurricanes.

… For thousands of years, the Mississippi River has naturally writhed back and forth like a water hose, spewing muddy sediment loads first one place then another along several hundred miles of coast. These movements built up a number of major deltas along the southern Louisiana coast.

This shifting geography has gradually reoriented the course of the river. Now the river is running about as far east as it can possibly go, and it wants to writhe back west, away from New Orleans and down the Atchafalaya River Basin instead.

But in the late 1950’s, Congress passed a bill to save the port of New Orleans by making it illegal for more than a third of the Mississippi to flow down the Atchafalaya River basin. This is akin to passing a bill to hold back the tide….

Water is flowing through bays at the Morganza floodway, May 14, 2011. (U.S. Army Corps of Engineers photo)

Waters still rising in uneasy Mississippi Delta

CBS News: Officials in a small town are trying to assure its 500 residents they are doing what they can to shore up the levee to protect them from the swollen Mississippi River. ..The uneasiness is being felt all along the poverty-stricken Delta as oozing floodwaters from the Mississippi River and its tributaries spilled across farm fields, cut off churches, washed over roads and forced people from their homes Wednesday.

Some used boats to navigate flooded streets as the crest rolled slowly downstream, bringing misery to low-lying communities. About 600 homes have been flooded in the Delta in the past several days as the water rose toward some of the highest levels on record.

Mississippi Gov. Haley Barbour urged people to get out if they think there is even a chance their homes will flood. He said there is no reason to believe a levee on the Yazoo River would fail, but if it did, 107 feet of water would flow over small towns. "More than anything else, save your life and don't put at risk other people who might have to come in and save your lives," he said.

CBS News correspondent Mark Strassmann reports that there are about 300 homes in tiny Tunica Cutoff, an hour south of Memphis, and they have all been flooded, CBS News correspondent Mark Strassmann reports.

Other swamped communities may rebuild, but Tunica Cutoff may not. New housing codes mandate raising new homes above the 100-year flood plain. Most victims in Tunica had no flood insurance, and couldn't afford raising their homes. So here's their worry: Tunica Cutoff could be gone for good, flooded into history…

The Great Mississippi Flood of 1927. Frontispiece - beginning of crevasse breaching levee at Mounds Landing, Mississippi. From: "The Floods of 1927 in the Mississippi Basin", Frankenfeld, H.C., 1927 Monthly Weather Review Supplement No. 29

Flexibility key to tackling climate change in the Mekong Delta

Ngoc Le in Vietnam News: Long-term vision and short-term planning should be the twin planks on which the Cuu Long (Mekong) Delta should base its adaptation to climate change, Dutch experts said at a workshop yesterday. It would be unwise to make big investments in impact mitigating projects like dykes when the actual phenomena could not be predicted with high accuracy, they said.

The two-day workshop, titled "Towards a Mekong Delta Plan", brought together policy-makers and hundreds of experts from the two countries in the presence of Dutch Crown Prince Williem-Alexander, who has been on an official visit to the country.

Workshop participants discussed different options to optimise plans for the Delta relating to many areas including the predicted rise in sea levels, salinity intrusion, drought, insufficient supply of fresh water, agricultural and aquaculture production as well as urban development.

Various scenarios and solutions were discussed based on a "design table" application developed by the Dutch. The design table presented three-dimensional images of the Delta that changed in response to different input data. The design table session was an interactive spatial planning exercise that sought to help key Vietnamese decision makers "map out scenarios for the future of the Mekong Delta in relation to climate change adaptation," organisers said.

The Dutch side gave a design table to their Vietnamese counterparts at the workshop as a present. "In the long term, many things will remain unclear," said Prof L. O. Fresco of the University of Amsterdam. "We do not know by how much the sea levels will rise and water discharge will increase," she told Viet Nam News. "Sometimes we cannot change things back," she added.

Speaking to Viet Nam News on the sidelines of the workshop, deputy minister of Agriculture and Rural Development Dao Xuan Hoc said the step-by-step approach was a good idea. It would allow authorities to have updated statistics on hand to develop the most accurate and appropriate plans, he added. "We should have a vision for the next 50 years, then we get back to where we are now to develop strategies for every five years," he said….

Flood in the streets of Can Tho, shot by Atsaigon, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

San Joaquin River delta's biggest enemy hard to pinpoint

Alex Breitler in Recordnet.com (Stockton, California): There are more than 40 potential causes for the [San Joaquin River] Delta's decline, scientists said Friday, but ranking them in order is just too difficult "We're not in a position now - we may be in a position later - to say it's these three stressors that are causing 90 percent of the problem, or one stressor causing 45 percent of the problem," said Richard Norgaard, chair of the Delta Independent Science Board, a panel of 10 experts established by California's sweeping water reform in 2009.

"At the present state of knowledge, we just think there's a lot of interacting stressors," Norgaard told the Delta Stewardship Council on Friday. Scientists say many causes may be contributing to the decline of the Delta:

Global causes: Climate change (sea level rise, changes in water flows, higher temperatures and changes in ocean conditions); earthquakes; population growth; state economy.

Historic causes: Habitat loss; mercury from the Gold Rush accumulating in fish; toxic selenium runoff from farms; sinking Delta islands; artificial levees that may break, causing flooding; upstream dams that cut off breeding areas for salmon; agricultural subsidies; development, zoning and building codes; invasive species.

Current causes: Water withdrawals upstream of the Delta, in the Delta and outside of the Delta; fish sucked into export pumps; nutrients from farm runoff and city wastewater treatment plants; pesticides; metals that enter the water from farms, cities and industry; channel dredging; illegal harvest of threatened species; hatcheries that alter the genetic makeup of fish.

Anticipated causes: Landscape changes; urban expansion; land use along streams feeding the Delta; people's lifestyle decisions on where and how they live….

The San Francisco Bay Area, home to the San Joaquin River Delta, via NASA

Climate change threatens Sierra, delta

Kelly Zito in the San Francisco Chronicle: Two of California's most treasured natural settings are also among the most imperiled landscapes on Earth, as disruptive changes in climate patterns promise to melt glaciers, dry out rivers and set forests ablaze in coming generations, says a coalition of conservation, sporting and community groups.

Unless people significantly alter the way they manage water supplies and fuel their cars and homes, the Sierra Nevada and Sacramento-San Joaquin River Delta will become increasingly hostile to already-dwindling wildlife and fish species, the Endangered Species Coalition said in a report released Wednesday. Likewise for the Hawaiian Islands, Southwest deserts, Arctic sea ice and shallow-water coral reefs around the globe.

"Climate change is no longer a distant threat on the horizon," said Leda Huta, executive director of the Washington group. "It has arrived and is threatening ecosystems that we all depend upon, and our endangered species are particularly vulnerable."

In the report, "It's Getting Hot Out There," the coalition ranks the top 10 "hot spots" for vulnerable species, mostly within the United States with a few beyond. No. 1 on the list: the Arctic ice sheets where polar bears, seals, walruses and sea ducks make their home. Tropical coral reefs were second. The delta is No. 5 and the Sierra Nevada No. 6 on the list….

East of Ward Mountain, LeConte Divide, John Muir Wilderness, shot by Tom Hilton, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Deltas at the front line

Olivia Boyd in China Dialogue: This year, officials in Jakarta realised they had a serious problem: rain – and more rain. Indonesia’s wet months are famously soggy and rainstorms nothing new for the capital. But this time around the downpours continued long after they were meant to have passed. “We have noticed there is no more dry season,” said Fauzi Bowo, the governor of Jakarta. “We use the dry season to repair and prepare our infrastructure for the rainy season. Now we have no chance. It rains every day.”

Jakarta, at the mouth of the Ciliwung River, is just one of many major global cities situated in low-lying, coastal deltas and already grappling with the effects of climate change. Deltas are areas of land formed from sediment where a river flows into the sea or another body of water. They are home to more than half the world’s population and many of its most valuable assets.

…It was in this context that Bowo, speaking at an international conference on the impacts of climate change on deltas earlier this year, made his remarks. The gathering in the Dutch port city of Rotterdam brought together scientists and policymakers from delta regions across the world, from Vietnam to northern Italy, to share knowledge and ideas on adaptation and mitigation. It also acted as a launch pad for the Delta Alliance, a new network of cities and provinces working towards solutions to their common climate-related problems.

And the problems are significant. In 2001, the Intergovernmental Panel on Climate Change (IPCC) singled out deltas as some of the most vulnerable systems in the world. As Martin Parry, climate scientist at London’s Imperial College and former co-chair of IPCC working group II, said in Rotterdam: “Deltas already have high vulnerability – high flood risk, weather extremes. With climate change, these get worse.”…

Pinisi ships dock at the Sunda Kelapa Harbor, Jakarta. Shot by Danumurthi Mahendra from Indonesia, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Dead zone in gulf linked to ethanol production

Carolyn Lochhead in the San Francisco Chronicle: While the BP oil spill has been labeled the worst environmental catastrophe in recent U.S. history, a biofuel is contributing to a Gulf of Mexico "dead zone" the size of New Jersey that scientists say could be every bit as harmful to the gulf. Each year, nitrogen used to fertilize corn, about a third of which is made into ethanol, leaches from Midwest croplands into the Mississippi River and out into the gulf, where the fertilizer feeds giant algae blooms. As the algae dies, it settles to the ocean floor and decays, consuming oxygen and suffocating marine life.

Known as hypoxia, the oxygen depletion kills shrimp, crabs, worms and anything else that cannot escape. The dead zone has doubled since the 1980s and is expected this year to grow as large as 8,500 square miles and hug the Gulf Coast from Alabama to Texas. As to which is worse, the oil spill or the hypoxia, "it's a really tough call," said Nathaniel Ostrom, a zoologist at Michigan State University. "There's no real answer to that question."

Some scientists fear the oil spill will worsen the dead zone, because when oil decomposes, it also consumes oxygen. New government estimates on Thursday indicated that the BP oil spill had gushed as much as 141 million gallons since an oil-rig explosion and well blowout on April 20 that killed 11 workers…..

Sunlight illuminated the oil slick off the Mississippi Delta on May 24, 2010. The Moderate-Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image the same day.