The Earth Story

Great Blue Hole sheds light on Maya collapse

Located off the coast of Belize in an idyllic coral reef, the blue hole is part of a karst limestone landscape that was flooded by sea level rise at the end of the last ice age (see http://on.fb.me/1KbMC2M). Made famous by one of Jacques Yves Cousteau's films (for our biopic see http://on.fb.me/1wcAeKd), it is a famous site in the diving world that he first made possible by inventing the aqualung.

The cave has already been used in research on Saharan dust transport across the Atlantic since its depths make an ideal sediment trap, and now new work has confirmed the inference from other sources that the Maya civilisation fell after a series of long droughts. They used a series of sediment samples from the epoch of their demise (around 800-1000 CE) and compared the changing ratios of aluminium and titanium, which reveal periods of heavy rainfall from tropical cyclones (the source of most of the water that kept the Mayans alive).

These indicated several long periods of drought at the time of their slow downfall that eked out over two centuries as the inter tropical convergence zone shifted north and south, taking the rain giving cyclones with it. The science is simple, in times of greater rain, more of the volcanic rocks in the area are weathered, and the water flows into the sea dumping its sediment and accompanying titanium with it. Analysing through the core allows the shifting rainfall densities to be tracked over time.

The new evidence joins other proxy data from stalagmites in caves, but the blue hole lies on the line of typical cyclone tracks and the Mayan capital of Tikal, sited in present day Guatemala, rendering its data more relevant. Despite their excellent water engineering in a resource poor karstic area (in which most of the water lies underground), the evidence (as outlined for example by Jared Diamond in his book Collapse: how societies choose to fail or survive) shows that a burst in population growth coincided with a long term decrease in rainfall, with several decades long droughts straining the culture beyond its capacities.

The civilisational collapse involved a population crash, the abandonment of the cities and a return to small scale subsistence agriculture, the entire culture nearly vanished from the record until its cities started to emerge from the jungles of Central America. The culture survived another century or so at Chichen Itza on the Yukatan peninsula, but the research shows that a second prolonged drought coincided with its abandonment.

The work also emphasises the link between ecology and climate. Some areas can take greater levels of strain and still keep going. The changes in European agriculture from the late medieval warm period, through the little ice age and intothe current warming reveals a certain integrity. The evidence revealing the Mayan demise implies that the area they lived in is much more sensitive to changing precipitation than some other areas of Earth.

The warning is clear, as the climate warms and rainfall patterns redistribute chaotically across the globe, some areas will take the strain better than others, but detailed ecological studies will be needed to quantify this (as much as we can) in order to help the most people survive the rough ride to the future (as James Lovelock's latest book puts it so well) that is already starting.

Loz

Image credit: USGS http://www.livescience.com/49255-drought-caused-maya-collapse.html http://www.theguardian.com/world/2015/jan/03/great-blue-hole-belize-clues-fall-mayan-civilisation http://io9.com/5886796/did-mild-weather-really-destroy-the-mayan-empire http://www.nature.com/srep/2014/140127/srep03876/full/srep03876.html#/results Papers, paywall access

http://www.sciencemag.org/content/338/6108/788 www.sciencemag.org/content/335/6071/956.abstract

Let’s talk gravity

The earth’s gravitational field isn’t quite constant. If you put a spacecraft around Earth in a perfectly circular orbit, over time, its orbit will experience small changes due to differing amounts of gravity in different areas.

Of mist and nuts...

California remains one of the main source of fruit, vegetables and nuts for both the US market (95%) and worldwide export. Much of this is grown in the Central Valley, watered by irrigation, pollinated by bees, and dependent on a particular kind of winter fog to convince these originally colder clime plants that a winter has occurred. New research suggests that these vital fogs are becoming rarer with climate change, endangering a substantial chunk of the state's economy.

The mists are known as Tule fogs after the grassy wetlands that once covered the valley. They form between November and April, and are caused by cold air sinking into the valley at night from the surrounding mountains, condensing the moisture in the warmer valley air (a process known as radiation fog). They can linger for days along the whole 650km length of the valley, since winds cannot budge the dense air and temperature inversions can often keep them confined in the valley.

These fogs are crucial for may fruit and nut trees, giving the plants the impression of a dank, dark and cool European winter. Some trees, such as cherries, almonds and peaches need a dormant period during the winter that needs prolonged coolth to trigger. The rest is vital to their ability to produce buds, flowers and fruit, and its absence results in drastically lowered yields. Recent research at the University of California at Berkeley has shown that these vital fogs have declined dramatically during the last 30 years.

The team used both NASA/NOAA satellite data and weather station records to chart the fogs over the last 32 winters, revealing a 46% drop in fog days during the crucial winter season. Variability between seasons is due to whether the year is wetter or drier, but the lowering trend is unmistakeable. Other work underlines this, showing a drop in several hundred hours of temperatures between 0 and 7 degrees Celsius since the 1950's. The current drought is also preventing their formation, exposing the fruit trees to a variety of mixed stresses.

Climate forecasts imply this situation will worsen, eventually threatening the entire current model for Californian agriculture. Fruit developers are trying to breed varieties that can do without a winter, but without much success for now. Only the future will tell exactly where and how the chips are going to fall, but the best educated guesses suggest that threats to crop yields worldwide from a changing climate are considerable, and may already be affecting world politics, such as the food riots in 2008-9 when a series of unfortunate climate events caused huge rises in the prices of a variety of staple grains. Maybe when climate change hits enough people in the wallet, they may finally awaken and take notice of what is going on around them, lets hope it won't be too late to seek viable solutions to these problems.

Loz

Image credit: CSERC.org

Original paper, paywall access: http://onlinelibrary.wiley.com/doi/10.1002/2014GL060018/abstract

Tree rings reveal historical megadroughts in US West

While some chunks of california are dying for rain, evidence has emerged that even the worst drought to strike the region, the Dust Bowl of the 1930's was a pipsqueak compared to some relatively recent events. A team from Brigham Young University in Utah used dendrochronology (the study of tree rings) to tease out records of droughts past from sensitive tree species. How it works is simple, if the tree is drought sensitive, it produces wide rings in years of plenty, and thin ones during dearth.

Their record now extends back to 1429, before the 'discovery' and settlement of America by Europeans. Some of the work involved trees by streams, allowing a gauge of past stream flows to be established. Focussing on the Weber river basin of Utah (though surrounding areas will have been experiencing similar conditions), they discovered several worrying multi-year events that imply much worse than currently experienced is possible. For example, in 1703, a 16 year drought started, that's a long time for even a resilient society like the modern USA to endure. The worst era was that of Columbus's lifetime, with 4 of the 5 worst recorded.

If climate change aggravates the situation further, we could start seeing events that go further than these already scary historic droughts. The work has revealed that the climate oscillates much more strongly in this area than we thought, since the 19th century, when the area was settled was wetter than the average. Water resource management workers will be using this research to help build the sort of resilience into the water use system that will take account of the newly revealed reality.

Our recent post on the current drought: https://www.facebook.com/TheEarthStory/posts/689930364401344 Loz

Image credit, galaxy above bristlecone pine: Rogelio Bernal Andreo (DeepSkyColors.com)

http://news.byu.edu/archive14-apr-dendrochronology.aspx

Rainbow falls

Although the drought of 2014 reduced the flow to a trickle, the Upper Yosemite Falls still found a way to put on a show here, with just enough water lofting into the air to create a rainbow. -JBB Image credit: Yosemite National Park/National Park Service

The current state of the Salton Sea system in California - already an ecological issue due to decades of pollution flowing into it, there is now such high demand for water that within a few years, the lake itself is expected to begin rapidly shrinking, which will expose the entire area to everything deposited on the bottom.

Dry Astronaut Alexander Gerst captured this photograph of Spain, Portugal, Morocco, and the Straits of Gibraltar from the International Space Station last Sunday. Much of Europe has been parched by the recent heat waves and as a consequence Spain and Portugal look as brown as the Sahara Desert to the right of the frame. You can see a couple dust plumes coming off of Portugal, in addition to a smoke cloud fed by fires burning in the Algarve region. -JBB Image credit: ESA/NASA/Alexander Gerst https://flic.kr/p/L8ue4n

Original caption:

21st Century Water Challenges

Some of us tend to take the availability of fresh, potable water for granted. We turn on a faucet and water comes out. Without thinking, we pull out garden hoses and water our lawns or fill our swimming pools.

However, many of us have become more aware of water issues, especially if we live in areas prone to droughts. Here in Austin, TX, we’ve been on Stage Two water restrictions since 2011, when we had more than 100 days of greater than 100°F (37.77°C) temperatures and Lake Travis, upon which many local businesses depend, dried up. Drought is not a new circumstance in Texas, but across the world, with global population increases, climate change, degradation of the environment, and large-scale urbanization, more and more people are coming to realize that our water is not an endless resource.

Although more than 70% of Earth’s surface is covered in water, only 2.5% of it is fresh water and much of that is trapped in glaciers and snowfields. Agriculture uses 70% of available freshwater for irrigation. Industry uses about 20%, for energy and manufacturing, leaving only 10% for domestic use. When all is said and done, a mere 0.007% of the planet’s water is available for 7.3 (and growing) billion people. Already, 2.1 billion people in our world lack access to safe drinking water.

In some places, like Miami, Florida, climate change is still a factor, even though rainfall is generally abundant. Early in the 20th century, before the importance of wetlands was truly appreciated, swamps near Miami were drained, allowing seawater to seep in and contaminate the Biscayne aquifer. Although attempts were made in the 1930’s to address the problem, increasing sea levels still allow saltwater to broach the underground barriers.

As bad as these things sound, there are cities in the world that are in more immediate crises. Cape Town, South Africa is expected to run out of potable water sometime this summer, leaving more than 4 million people in danger. As in Sao Paolo, Brazil, Jakarta, Mexico City, and many others, Cape Town’s infrastructure is insufficient to cope with such issues as heavy metal contamination, unsanitary conditions, and is unable to deal with the number of people it needs to supply. Mexico City already imports 40% of its drinking water, but has no acceptable way to deal with wastewater. Globally, 80% of wastewater generated by society is returned to the environment without treatment or reuse. In the Indonesian province of Jakarta, half of its 10 million citizens have no access to piped water. The digging of illegal wells has almost completely drained the aquifers and because of this practice, the World Bank estimates that about 40% of Jakarta has subsided and now lies below sea level. A quarter of the world’s fresh water reserves are in Russia, but regulatory officials admit that 35-60% of drinking water reserves are not sanitary, polluted by Soviet-era industry. The list goes on and on.

Today, March 22, 2018, marks the 25th anniversary of the United Nations’ World Water Day. This year’s theme for World Water Day is “Nature For Water”, which is focused on using nature-based solutions (NBS) to help solve the water crises being seen around the world. Nature-based solutions involve the management of soils, wetlands, rivers, lakes, and vegetation and create what is known as “green infrastructure”. Unbalanced by climate change, overpopulation, and environmental degradation, the water cycle can be improved by restoring the wetlands that act as water filters and natural storage. So-called “grey infrastructure”, or man-made solutions such as dams and reservoirs are not sustainable and are considerably less cost-effective. Planting new forests and grasslands and utilizing conservation agriculture can serve to reduce evaporation and decrease agricultural pollution and erosion. Caring for watersheds, and reconnecting rivers to floodplains would help with water purification, drought mitigation, erosion control, and overall water quality regulation. In China, 16 cities are piloting a “Sponge City” initiative to improve the quality of urban water supplies. Within the next two years, these 16 cities will implement innovative measures like permeable pavement, green walls and rooftops, and the construction of bioswales (filtration channels) that will capture water and divert it back to natural storage for use during droughts. Their objective is to be able to absorb and reuse 70% of rainwater.

NBS are not a cure for the critical water challenges that global populations are facing, but they’re a good start. Political leaders must be willing to address the issue of water shortages in pragmatic and tangible ways, but individuals and local groups can still make a difference.

CW

Image

http://n.pr/2FYkJxW

Sources

http://worldwaterday.org/

http://www.bbc.com/news/world-42982959

https://stateimpact.npr.org/texas/tag/drought/

http://bit.ly/2DWGMEi

http://on.natgeo.com/2ptNL2m

Day Zero

The city of Cape Town, South Africa, is fighting a hard fight to avoid becoming the first major, modern city on Earth to totally run out of water. Cape Town cycles between a rainy season and a dry season, and the reservoirs seen in this satellite photo store water to keep the city alive during the dry season. However, the area has been hit by three straight years of drought, during which time the reservoirs have been drawn down and nearly depleted. If the reservoirs drop below a certain level, the water pipes will be shut off and water supplies to the city will end. Rather than flowing water in pipes, water will only be available at select distribution sites around the city starting on that day. This day has been nicknamed “Day Zero”.

There are weather records for Cape Town going back nearly 100 years. With a weather record of that length, scientists can use statistics to project to how extreme this drought is under the assumption of stable weather and climate patterns. Under that assumption, the current 3-year drought would occur once every thousand years or so.

These type of “thousand year” events are the type that are hammering cities around the world; thousand year storms are triggering floods, while thousand year droughts are leaving reservoirs barren. The problem with these statistics is that they assume the climate recorded during the last century hasn't changed; cities are built with the assumption that weather patterns will remain constant but with enough change in the atmosphere, that may not be the case.

Cape Town is currently rushing to complete water diversion projects and desalination projects that could come online as early as 2019, but that doesn’t solve the problem of Zero Day. Massive conservation efforts are underway, with people and farmers dramatically cutting their water usage. So far this year, the inhabitants of Cape Town have successfully delayed the projected time of Zero Day from April to July, closing in on the time of the rainy season. At some point though, the city still needs rain to return and the drought to break. Furthermore, the costs are high; South Africa’s agricultural industry has basically been shut down by this drought and the country is heavily importing food to replace those supplies.

Cape Town is, right now, the closest we’ve seen to running out of water. As urban populations expand and droughts become more extreme, even if Cape Town does avoid Zero Day this year, this story will continue around the world.

-JBB

Image credit: NASA/EO https://earthobservatory.nasa.gov/IOTD/view.php?id=91649

References: http://www.csag.uct.ac.za/2017/08/28/how-severe-is-this-drought-really/ https://www.iol.co.za/capetimes/news/defeating-day-zero-is-in-sight-says-city-13380794 https://www.brookings.edu/blog/africa-in-focus/2018/02/23/day-zero-on-the-back-of-drought-in-southern-africa-lessons-for-the-future/

Lake Tahoe in April, this year deluged by meters of snow and last year in the middle of the drought.

Evidence of Middle Eastern megadroughts comes to light

A core drilled under the slowly drying Dead Sea (see http://bit.ly/2oeU6hH) contained salt layers between the more normal lake bottom mud, the thickest being 100 metres. These record past periods of dryness beyond any experienced in recorded history, some 120,000 and 10,000 years ago. Sitting some 300 metres below the surface the layers record extended periods when the rainfall was 20% of modern levels, a situation that would prove catastrophic in the modern world.

The causes back then were minor oscillations in the world system as atmospheric flows shifted, but scientists were surprised by their magnitude, since current models did not tease such events out of the data. In other words the region got drier in reality than was thought was possible in theory.

The first event records a drying out of the closed basin (fed by the Jordan drainage basin) during the last great interglacial period, at a time when temperatures were some 4 degrees Celsius hotter than last century's average, a scenario within the bounds of possibility for the coming century recorded by the IPCC. The team analysed layer by layer the changing chemistry of fluid inclusions within the salt crystals to deduce past rainfall and runoff patterns, revealing a 50-80 percent decline lasting for decades or centuries each time.

As the region is already suffering the worst drought in a millennium (average rainfall has fallen 10% since 1950, models predict a potential 20% more this century) and the world continues to warm from our modern atmospheric stimulation, the likelihood increases of such events returning in the future. Since the current dry period was recognised as a contributing factor in both the Arab Spring and the ongoing horrors/knock on effects of the Syrian civil war (see http://bit.ly/2o6rwPF), the possibly is preoccupying in an area already rent with tensions, tight water supplies (some 10% per capita of the world average), a fast growing frustrated and impoverished population and many layers of ongoing conflict.

The same climatological risks have been recognised in the western USA (see http://bit.ly/2nQZRib and http://bit.ly/2ommHlK), itself just recovering from a multi year drought.

Loz

Image credit: The Dead Sea; Vladimir Popov Uhaiun

http://bit.ly/2nShbog http://bit.ly/2mQ2KnM

Original video caption:

World Water Day

71% of the Earth is water, of which there is a finite amount, constantly moving between one form and another and from one place to another. About 96.5% of that water is saline, filling our oceans and seas. The remaining 2.5% is freshwater. That small percentage of freshwater is found in ice caps and glaciers, in atmospheric water vapor, in rivers, lakes, swamps, wetlands, and streams, in the soil, deep in the Earth in aquifers, and in living organisms. There seems to be so much water on the planet, but less than 1% of it is actually available to people for use.

In 1993, the General Assembly of the United Nations designated March 22nd as World Water Day, with each year given a designated theme. The 2017 theme for World Water Day is “Wastewater”, which is defined as any water that has been used in a home, business, industry, or agriculture. Today, at least 1.8 billion people across the world have drinking-water sources that are contaminated with fecal and other matter, which leaves them at risk of contracting water-borne diseases, such as polio, dysentery, cholera, and more. In lower socio-economic regions, water is also often contaminated with highly toxic chemicals and medical wastes from hospitals, small industry, and automobile garages. Much of this is disposed of in the nearest drain with little or no treatment.

663 million live without a source of safe drinking water near their homes, requiring them to walk many miles to the nearest source. 400 million of those people live in Central Africa.

Because of global population growth, the amount of wastewater produced and the pollutants it carries are increasing as well. One of the goals of this year’s World Water Day is to increase awareness of how wastewater can be considered as a sustainable source of water, energy, nutrients, and other materials that can be recoverable. In general, the potential of wastewater as a sustainable resource is being neglected as an offset to the growing water crisis. According to U.N. statistics, the global demand for potable (drinkable) water is expected to increase by 50% by 2030.

Some parts of the world are attempting to rectify this issue. In Emalahleni, South Africa, the Anglo-American mining company created a water treatment plant that converts water from the mine to drinking water, via desalination. It treats industrial water as well, so that it can be released safely into the environment and at the same time, extracts gypsum from the water, for use as a construction material. Kalundborg, Denmark uses, in a closed cycle, the by-products of one industrial process as a resource for other processes. The Asnæ Power Station receives water from Statoil (a petroleum refining industry), treats it, and uses it for water feeding into its boiler system. The power company uses an additional amount of treated wastewater from the refinery for cleaning. As a result, approximately 3 million cubic meters (more than 790 million gallons) of groundwater and 1 million cubic meters (264 million gallons) of surface water are saved per year. Treated wastewater can also be used for agricultural irrigation needs, as it is used in Israel, providing 50% of irrigation water.

Here in Texas, where we are in the midst of what authorities are calling a 20-year drought cycle, water conservation has become a priority with many. A number of areas are under mandated water restrictions. Experts with the Texas A&M University System have stated that the use of “gray water” (the soapy water that comes from washing machines, bathtubs, showers, and bathroom sinks, which in general does not contain serious contaminants) for watering grass, trees, and ornamental plants, could potentially reduce household water use for these purposes by 50%. Urban use is also being studied. Some gray water usage is currently in place in various cities,but only under strict state guidelines.

Liquid water, which, to our current knowledge, is required by every living thing, is a finite resource and is already scarce in many parts of the world. Conserving it, keeping it clean, treating it, and reusing it is in the best interests of us all. CW

Image

http://bit.ly/2ntrxhh

Sources

http://www.worldwaterday.org/

http://www.unwater.org/about/en/

http://www.who.int/mediacentre/factsheets/fs391/en/

https://water.usgs.gov/edu/earthhowmuch.html

http://today.agrilife.org/2012/12/07/gray-water-landscapes/

http://on.natgeo.com/2mNdjE9

The Morning Glory spillway at Lake Berryessa, California - the spillway is flowing for the first time in years this year, and is back to looking like someone divided by 0.