Climate change

.Asia’s disappearing lakes

Asian Correspondent,

2 December 2013

One of the worst environmental disasters in living memory is the near vanishing of the Aral Sea in Central Asia. What was once one of the world’s four largest lakes, containing some 1.5 thousand islands and covering 68,000 square kilometres (26,000 miles), by 2007 the Aral Sea was only 10% of its previous size and divided into four lakes.

What happened to Kazakhstan and Uzbekistan’s inland sea was not the result of normal changing weather patterns. The fate of the Aral Sea is a story of human intervention, contamination and local climate change.

From a 2010 ABC/AP report:

The shrunken sea has ruined the once-robust fishing economy and left fishing trawlers stranded in sandy wastelands, leaning over as if they dropped from the air. The sea’s evaporation has left layers of highly salted sand, which winds can carry as far away as Scandinavia and Japan, and which plague local people with health troubles.

The regional competition for water from the lake began in the 1940s with leaky irrigation canals and took a great leap forward in the early 1960s with the Soviet diversion of two major tributary rivers in order in order to promote desert agriculture. Most of the water went to waste. Salinity went up to around three times that of normal seawater, which – together with agricultural runoff, pesticides, industry and weapons testing waste – has resulted in the death of the local fishing industry, water shortages and health problems.

Over in China, the largest desert fresh water lake has also been steadily declining since the 1970s and rapidly disappearing (nearly by a third) in only the past four years.

From the Guardian:

Hongjiannao Lake, several hundred kilometres to the west of Beijing, has been disappearing since the 1970s, due to a combination of coal mining and climate change. But the speed at which it is losing area has increased rapidly since 2009, when it measured 46 square kilometres (sq km), down from 67 sq km in 1969.

The multi-pronged threat of decreasing rainfall, rising temperatures and a water-greedy large scale coal mine are reminders of how industrial development can exploit an extremely valuable natural area and ruin it in the process.

Another example is the picturesque Black Dragon Lake in the city of Lijiang, northwest Yunnan province. In this case hot weather and drought have caused the lake to disappear altogether. Furthermore, Yunnan’s hydroelectric projects are putting stresses on water resources across the region.

Dried up reservoir in China's Yunnan province, Pic: Remko Tanis

Lijiang is hardly alone. Similar situations are happening across other parts of Yunnan province, which usually has more rain than half of China’s regions. But it has experienced extremely low rainfall for the past three years.

In the first quarter of this year, Yunnan’s average rainfall dropped by 70 percent, indicating the start of the drought’s fourth consecutive year, according to the water resources department in the region.

–EE News

Future weather forecasts are grim and the replacement of natural forests with commercial timber is not helping. Many of Yunnan’s farmers are struggling to survive

Study warns of catastrophic wildlife population collapse in Sahara

U.S. and British wildlife experts say the world's largest tropical desert, the African Sahara, has suffered a catastrophic collapse of its wildlife populations.

UPI,

3 December 2013

A study led by the Wildlife Conservation Society and Zoological Society or London assessed 14 desert species and found half of them are regionally extinct or confined to 1 percent or less of their historical range, a WCS release said Tuesday.

The causes of the declines are difficult to determine because of a chronic lack of studies across the region, due to past and ongoing insecurity, the study author said, although overhunting is likely to have played a role.

"The Sahara serves as an example of a wider historical neglect of deserts and the human communities who depend on them," study lead author Sarah Durant said. "The scientific community can make an important contribution to conservation in deserts by establishing baseline information on biodiversity and developing new approaches to sustainable management of desert species and ecosystems."

Some governments have begun to make commitments to protect the Sahara, the researchers noted.

Niger just established the 37,451-square-mile Termit and Tin Toumma National Nature Reserve, home to most of the world's 200 or so remaining wild addax, a type of antelope, and one of a handful of surviving populations of dama gazelle and Saharan cheetah.

Dust, global warming portend dry future for the Colorado River 

Rocky Mountain snowpack melts six weeks earlier than in the 1800s

Desdemona Despair,

2 December 2013

14 November 2013 (CIRES) – Reducing the amount of desert dust swept onto snowy Rocky Mountain peaks could help Western water managers deal with the challenges of a warmer future, according to a new study led by researchers at NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.

With support from the CIRES Western Water Assessment (WWA) and NASA’s Interdisciplinary Science program, CIRES’ Jeffrey Deems and his colleagues examined the combined effects of regional warming and dust on the Colorado River, which is fed primarily by snowmelt.

During recent years, desert dust has been settling thick and dark on the snowpack in the northern Rocky Mountain headwaters of the Colorado River, and snowpack is melting out as many as six weeks earlier than it did in the 1800s, according to the new assessment, published last week in Hydrology and Earth System Sciences. Snow dusted with dark particles absorbs more of the Sun’s rays and melts faster than clean snow.

Add the regional warming expected in the future, and the situation seems likely to grow more dire for the 40 million people who depend on the Colorado River for water. The river’s flow falls by more than 20 percent by 2100 in some of the future climate scenarios Deems and his colleagues investigated. Moreover, warming could make dust problems worse, by increasing the risk of drought.

“But we may be able to do something about dust,” said Deems, who works with WWA and CIRES’ National Snow and Ice Data Center. “If the future normal is this extreme dust scenario and we can push that scenario back to lower dust levels with land restoration or management, we could keep the snow in the mountains longer, and maybe even get some of that water back.”

Since the mid-1800s, human land use activities have disturbed Southwestern desert soils and broken up the soil crust that curbs wind erosion, leading to increased dust. In previous research, Deems and his colleagues showed that increasing dustiness leads to accelerated snowpack melt.

That earlier work was based on the moderately dusty years of 2005­–2008, with about five times as much dust than in the 1800s. But during 2009, 2010 and 2013, unprecedented amounts of desert dust fell on Colorado snowpacks, about five times more than observed from 2005–2008. Moreover, other researchers have reported that climate change is likely to increase the frequency and intensity of drought in the Southwest, which could increase dust problems further by harming the grasses and shrubs that reduce surface wind speeds.

For the new work, the researchers used climate and hydrology models to investigate the effect of that “extreme dust” on the Colorado River’s flow now and in the future, as the Southwest continues to warm. Snowmelt in the extreme dust scenario shifted even earlier in the season, by another three weeks, pulling peak water levels in the Colorado River to earlier in the spring and leaving less water for later in the year.

“In the Upper Colorado River Basin, the snowpack is our most important reservoir,” said co-author Thomas Painter of NASA’s Jet Propulsion Laboratory. “With continued dusty years and greater warming, water managers will have to make their decisions very early in the season. No longer will they have the nice long snowmelt season, shortened as it already has been, to see how snowmelt runoff is going.”

The research team also found a subtle shift on the total water loss in the Colorado River, from a loss of 5 percent estimated during the moderate dust years of 2005–2008, to a total loss of about 6 percent lost during extremely dusty years. This relatively small change is due primarily to the fact that as snowmelt creeps earlier and earlier in the year, the Sun’s angle in the sky is shallower and provides less energy for evaporation than it does later in the spring.

“Our results suggest that if we can adopt dust-reducing land management strategies and rehabilitate major dust sources, we can keep our snow on the mountains longer, and perhaps offset some of the emerging climate impacts,” said co-author Brad Udall, director of the Getches-Wilkinson Center for Natural Resources, Energy and the Environment at CU-Boulder. “Dust reduction could be a very powerful strategy to help us adapt to the growing impacts of climate change on our precious water supplies in the American Southwest.” [more]