Through The Sandglass

Sand wars continue, unabated

It just doesn't stop, and the scale of the damage to communities and the environment is staggering.

NASA recently released the pair of images, above, showing changes to the sediment system of Poyang Lake and its rivers. The lake, these days much diminished in size, was once the largest freshwater lake in China, its water feeding into the Yangtze and providing an important haven for migrating birds. But when, in 2000, China shut down sand mining along the middle and lower Yangtze, the activity, legal and illegal, simply moved to Ponyang. The image on the left was acquired in 1995, the one on the right in 2013. The scale of devastation is obvious - try the "image comparison" feature for drama. 

The text accompanying the images describes the problem here (and elsewhere) in depressing detail:

When you see the vast expanses of sand in the Sahara and other major deserts, it is hard to comprehend how sand could ever be a resource in short supply. Yet for certain types, the supply of sand is indeed short.

For the construction industry, river and lake sand is more desirable than desert and ocean sand. To produce mortar for cement, concrete, and other building materials, the angular sand particles found in rivers and lakes are most useful. Making a strong mortar with the particles found in deserts—which are rounded by winds—is more challenging because the sand does not bind together as well. Likewise, ocean sand is mixed with salt, which can cause metals to corrode. Washing this marine sand can be time-consuming and expensive.

Over the past few decades, the global demand for construction sand has boomed, especially in Asia due to rapidurbanization. In China alone, the demand for cement has increased 438 percent over the past two decades,according to the United Nations Environmental Program.

In 2000, dredging and other sand mining become so intensive along the Yangtze River that Chinese authoritiesbanned the activity along the lower and middle reaches of the river. This drove many sand mining operators to Poyang Lake, a large body of water that flows into the Yangtze about 600 kilometers (400 miles) upstream ofShanghai.

This pair of false-color images captured by Landsat satellites shows the impact of sand mining on the northern reaches of Poyang Lake. The top image was acquired by the Thematic Mapper on Landsat 5 on December 7, 1995; the second image shows the same area as observed by Landsat 8’s Operational Land Imager on December 24, 2013. Water levels vary throughout the year at Poyang Lake, with the lowest levels occurring in winter.

By contrasting the two images, we can see dramatic changes in the outlet channel that connects Poyang Lake to the Yangtze river. Sand removal and dredging have deepened and widened the channel significantly. These activities also have left the remaining sandbars and shores with an irregular, serrated appearance. Turn on the comparison tool to see the changes.

As part of an effort to assess the scale of the sand mining and its environmental impacts, a group of researchers analyzed data collected by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor on NASA’s Terra satellite. Using infrared data collected by ASTER in 2005, the researchers found that the lake was producing up to 236 million cubic meters of sand per year—about 9 percent of the total produced by China. The researchers estimated that the volume of sand removed was probably enough to make Poyang Lake the largest sand mining operation in the world.

“Sand mining has compromised the ecological integrity of the lake by contributing to less predictable seasonal water fluctuations and to a series of recent low water events,” said James Burnham, an ecologist with the University of Wisconsin and the International Crane Foundation. Burnhan has conducted field research on wintering waterbirds at Poyang Lake. “This is a lake that hosts 98 percent of the endangered Siberian Cranes and Oriental White Storks, as well as a significant number of over a dozen other endangered waterbirds in the winter.”

Google "sand" and news and, among the entertaining images of sand sculptures and odd reports such as the discovery of hundreds of kilos of marijuana buried in the dunes of South Padre Island, Texas, you will find, every day, endless reports of the issues of sand mining around the world. A sampling:

Vietnam, Nepal, India (endless problems, mafias, crime), Cambodia, Singapore and Malaysia, the list goes on. The issues raised by the documentary, Sand Wars, have also been taken up by The Smithsonian, the United Nations, Wired, and Coastal Care. Numerous TV and radio programmes have covered the topic. And yet so few people are aware of it, and it just goes on and on.

 

Totally off-piste, but I have to say this

I spent twenty years of my life living and working in the US.

My wife is American. My kids were born in Detroit and Dallas (and my daughter currently works in non-profit health care in New York). My first visit was for a year when I was six years old – my father was one of the pioneers in developing American Studies programmes in British universities where, at the time, literature stopped in the nineteenth century. I first heard a Bob Dylan record sitting in a café in Berkeley in 1963. I spent a year at graduate school in the US during the turmoil of the late 1960s – US graduate programmes had more to offer than UK universities and, anyway, I loved the US. Later, I taught geology at two different US universities, working with (and learning from) terrific graduate students whose dedication led to their obtaining masters’ degrees while holding down jobs. I can only name a couple of states that I haven’t spent any time in. I have worked in five different US cities. To say that some of my best friends are American is correct, and this doesn’t include the countless people I admire and respect.

Whenever, in the early days, I returned to the UK, I found that I had to spend significant time defending the US against the knee-jerk Americophobia of the Brits – but I did so with sincerity and enthusiasm.

Today, however much I would want to, I just can’t do that anymore, and that saddens me – deeply. It’s no longer easy to recognise the country that, for decades and despite all its faults, I enjoyed and admired.

What the hell is happening to the US? Why do I find myself the victim of a masochistic obsession to constantly check the news, follow up on the latest outrageous events in the dominant half of the presidential campaign – and, more often than not, find myself shouting at my computer? In November 2008, there were, quite literally, tears in my eyes as I watched Obama’s victory speech. Today, there are again tears in my eyes – not, this time, of optimism, but rather of bewilderment, disbelief, and something close to horror.

When did the US become a country in which hatred dominates the news, and, of course, social media? When did the US become a country in which most of the so-called political debate, highjacked by the leaders of one deranged party, takes place in the gutter, with rhetoric and vocabulary at the level of a fourth-grader? When did the US become one of the world leaders in inequality? When did home eviction become big business? When did the US become a country that poisons the water of its citizens and yet no-one is accountable? When did the “land of the free,” whose greatness was founded on immigration and diversity, embrace the rhetoric of xenophobia?

Why do I see on social media posts of which Goebbels would have been proud?

When did a complete disregard for facts and evidence become a hallmark of so many American politicians? When did science - when the US has some of the world’s finest institutions - become something to denigrate? And when were humanity and engagement with the rest of the world dropped from the agenda of so many representatives of the home of democracy?

Now please don’t get me wrong. By my standards, the UK has little to be proud of when our government, declaring itself the home of “compassionate conservatism,” presides over rampant inequality, undermines our health system, callously penalises the disabled, spies on its citizens (sorry, “subjects”), attempts to muzzle our scientists through lobbying legislation, and refuses to take in desperate refugees. And yes, we have right-wing lunatics of our own.

No, I’m not claiming any moral high ground – indeed, I’m not sure where to find such a place. I simply can’t defend many of my country’s actions or the way in which our politics is evolving. But I find it impossible to explain or defend what’s going on the US today – and I am deeply saddened.

[I sincerely hope that I have not offended any of my American readers. I shall return to the arenaceous and the arid shortly.]

Sunbathing in the microscopic desert jungle

The desert has its own palette, distinctive and at the same time subtle yet dramatic. There are many factors at work creating the patterns and hues of arid lands - obviously the kind of sand, the kind of rock, the vegetation, minerals and salts, desert varnish - but there are also artists at work that we can't see and barely understand: microbial communities.

We can see the mosses and the lichens, but the vast ecosystem of bacteria and fungi operates essentially invisibly; we are only beginning to scratch the surface of the desert to reveal the ubiquity and importance of microbial life in environments we often describe as "lifeless." These are communities labelled "cryptic" by biologists, a useful term disguising the fact that they are something we really don't understand very well. I found this definition helpful, from a piece in Nature a few years ago titled "Body doubles" by Alberto G. Sáez and Encarnación Lozano:

Have you ever approached someone whom you thought you knew, talked to him with familiarity, only to find out later that he was a complete stranger, albeit remarkably similar in appearance to the person you had in mind, such as a twin brother? Well, taxonomists are similarly puzzled when they come across two or more groups of organisms that are morphologically indistinguishable from each other, yet found to belong to different evolutionary lineages. That is, when they discover a set of cryptic species.

The microscopic cryptic communities of arid lands form the well-known "desert" or "cryptobiotic" crusts that we now realise play key roles in the ecosystem, cycling carbon dioxide and nitrogen, providing resources for plant life, controlling drainage and the hydrologic behaviour of the soil, and reducing erosion - and hence, atmospheric dust. 

Among the leading researchers shedding light on these cryptic communities is Ferran Garcia-Pichel at Arizona State University's School of Life Sciences. For example, in 2013, togather with international colleagues, he published a paper titled "Temperature Drives the Continental-Scale Distribution of Key Microbes in Topsoil Communities." Science summarises the work as follows:

Soil microorganisms make up a substantial fraction of global biomass, turning over carbon and other key nutrients on a massive scale. Although the soil protects them somewhat from daily temperature fluxes, the distribution of these communities will likely respond to gradual climate change. ... [We] surveyed bacterial diversity across a range of North American desert soils, or biocrusts—ecosystems in which photosynthetic bacteria determine soil fertility and control physical soil properties such as erodability and water retention. Most of the sites were dominated by one of two cyanobacterial species, but their relative proportions were controlled largely by factors related to temperature. Laboratory enrichment cultures of the two species at different temperatures also showed temperature as a primary determining factor of bacterial diversity. It is unknown if temperature will affect the distribution of other soil microorganisms, but the marked shifts of these two keystone bacterial species suggest further change is in store for these delicate ecosystems.

The work, only available behind the Science paywall, was helpfully reported by Live Science. The two dominant "keystone" bacterial species are  Microcoleus vaginatus and M. steenstrupii, the former preferring cooler conditions whereas the latter likes things hot. As temperatures vary, things become competitive and warming conditions result in the mysterious steenstrupii taking over. Now, because these communities are microscopic and cryptic, we can only measure such effects - and detect which organisms are in the soil - through sophisticated DNA analysis. It is further results of this kind of painstaking and careful work that Garcia-Pichel and his colleagues have just published in Nature. With Estelle Couradeau, also at Arizona State, as the lead author, the paper describes - startlingly - how "Bacteria increase arid-land soil surface temperature through the production of sunscreens." Microcoleus vaginatus and M. steenstrupii are far from alone, and, amongst their companions are tribes of cyanobacteria such as the hundreds of species belonging to the genera Scytonema and Tolypothrix. These little critters dislike the sun and apply a biosynthetic sunscreen, scytonemin, an alkaloid pigment that strongly absorbs solar radiation and dissipates this energy as heat. This sunscreen can be seen as patches of darker colour covering areas of desert crust, as in this photo by Garcia-Pichel from the recent report on Science Daily.

This pigmentation may protect some members of the bacterial community, but it can locally warm up the surface by as much as 10 degrees C (18 degrees F). This has a dramatic effect on the health of the cool-loving Microcoleus vaginatus, but is welcomed by M. steenstrupii, who come to dominate as the sunscreen develops, at the expense of vaginatus. As Garcia-Pichel comments:

... we can show that the darkening of the crust brings about important modifications in the soil microbiome, the community of microorganisms in the soil, allowing warm-loving types to do better. This warming effect is likely to speed up soil chemical and biological reactions, and can make a big difference between being frozen or not when it gets cold... On the other hand, it may put local organisms at increased risk when it is already quite hot.

And this has to be happening on a global scale. As Estelle Coradeau suggests, "Because globally they cover some 20 percent of Earth's continents, biocrusts, their microbes and sunscreens must be important players in global heat budgets. We estimate that there must be some 15 million metric tons of this one microbial sunscreen compound...warming desert soils worldwide."

But because we have only a poor understanding of what exactly these desert crusts are and how they work, their roles in local ecology and global systems are impossible to define. It is only through the meticulous work of Ferran Garcia-Pichel and his team, together with others such as Jayne Belnap of the USGS in Moab, Utah, that we can begin to unravel the extraordinary nature and contributions of these long-ignored microbial desert communities. As Belnap has commented:

These are the only game in town to prevent dust storms and erosion, so they're really, really critical parts of this ecosystem. Yet we've never asked the question, 'who's really in there, and what's going to happen there as things shift?'

and, as reported in a piece on Belnap in High Country News, the palette and patterns of our arid lands owe much to an invisible living world: 

She also remains convinced that the dark shadows on the desert are the true — and fragile — foundation of the Colorado Plateau. "Whenever we pull on the thread of what makes the system tick," she says, "we end up with soil crusts on the other end."

[See also Belnap's USGS site at www.soilcrust.org. Crust photos credit: Linda and Dr. Dick Buscher, Live  Science "The Mysterious World of Cryptobiotic Soil."]