Geology for Global Development

Geology for Global Development

Saltwater intrusion: causes, impacts and mitigation

In many countries, access to clean and safe to drink water is often taken for granted: the simple act of turning a tap gives us access to a precious resource. In today’s post,Bárbara Zambelli Azevedo, discusses how over population of coastal areas and a changing climate is putting ready access to freshwater supplies under threat. 

Water is always moving downwards, finding its way until it gets to the sea. The same happens with groundwater. In coastal areas, where fresh groundwater from inland meets saline groundwater an interesting dynamic occurs. As salt water is slightly denser than freshwater, it intrudes into aquifers, forming a saline wedge below the freshwater. This boundary is not fixed, it shows seasonal variations and daily tidal fluctuations. It means that this interface of mixed salinity can shift inland during dry periods, when the freshwater supply decreases, or seaward during wetter months, when the contrary happens.

Freshwater and saltwater interaction. Credit: The National Environmental Education and Training Foundation (NEEF).

Once saline groundwater is found where fresh groundwater was previously, a process known as saltwater intrusion or saline intrusion happens. Even though it is a natural process, it can be influenced by human activities. Moreover, it can become an issue if saltwater gets far enough inland that it reaches freshwater resources, such as wells.

According to the UN report, about 40% of world’s population live within 100km from the coastline or in deltaic areas. A common source of drinking water for those coastal communities is pumped groundwater. If the demand for water is higher than its supply, as can often occur in densely populated coastal areas, the water pumped will have an increased salt content. As a result of overpumping, the groundwater source gets contaminated with too much saltwater, being improper for human consumption.

With climate change, according to the IPCC Assesment Reports, we can expect  sea-level to rise, more frequent extreme weather events, coastal erosion, changing precipitation patterns and warmer temperatures. All of these factors combined with the a increased demand for freshwater, as a result of global population growth, could boost the risk of saltwater intrusion.

Shanghai – an example of densely-populated coastal city. By Urashimataro (Own work) [CC BY-SA 3.0 ],via Wikimedia Commons.

Although small quantities of salt are important for regulating the fluid balance of the human body, WHO advises that consuming higher quantities of salt than recommended can be associated with adverse health effects, such as hypertension and stroke. In this manner, reducing salt consumption can have a positive effect in public health, helping to achieve SDG 3.

With the aim of preserving fresh groundwater resources for coastal communities at present and in the future, dealing with the threat of saline intrusion is becoming more and more important.

Therefore, to be able to mitigate the problem, first of all, it needs to be better understood. This can be done by characterising, modelling and monitoring aquifers, assessing the impact and then drawing solutions. Currently there are many mitigation strategies being designed worldwide. In Canada, for example, the adaptation options rely on monitoring and assessment, regulation and engineering. In the UK, on the other hand, the simpler solution adopted is reducing or rearranging the patterns of groundwater abstraction according to the season. In Lebanon, a fresh-keeper well was developed as an efficient, feasible, profitable and economically attractive way to provide localised solution for salination.

Every case should be analysed according to its own characteristics and key management strategies adopted to ensure that everyone has access to clean and safe water until 2030 – SDG6.

How deep-seated is bias against scientists in the Global South? Can we attribute individual disasters to climate change? Find out in Jesse Zondervan’s Dec 20  – Jan 24 2018 #GfGDpicks #SciComm

Each month, Jesse Zondervan picks his favourite posts from geoscience and development blogs/news which cover the geology for global development interest. Here’s a round-up of Jesse’s selections for the last four weeks:

If we want to solve the world’s problems, we need all the world’s scientists. Social Entrepreneur Nina Dudnik speaks out against prejudice towards scientists in the developing world. In her article, The Science Community’s “S**thole Countries” Problem, she will challenge many scientists’ own deep-seated bias.

Encouragingly, South African climate researcher Francois Engelbrecht got in the news recently. He developed a climate model, improving projections and supporting the vulnerable community in decision making.

One thing that I believed impossible, is attributing specific extreme weather events to climate change. Well, now it’s possible due to a breakthrough by climate scientist Myles Allen. Harevy reports on the rapidly expanding area of climate science.

Further in the news this month, is activity at the Mayon volcano in the Philippines, a 20-acre mega-landslide about to go in Washington State and the destruction caused by thawing permafrost in Alaska.

There’s a lot to read this month, so go ahead!

The Global South

The Science Community’s “S**thole Countries” Problem by Nina Dudnik at Scientific American

Homegrown African climate model predicts future rains – and risks by Munyaradzi Makoni at Thomson Reuters Foundation

Credit: Rhoda Baer (Public Domain)

 

Climate Change Adaptation

Scientists Can Now Blame Individual Natural Disasters on Climate Change by Chelsea Harvey at ClimateWire

Researchers explore psychological effects of climate change at ScienceDaily

Australia’s coastal living is at risk from sea level rise, but it’s happened before at The Conversation

Why Thawing Permafrost Matters by Renee Cho at State of the Planet

 

Activity at the Mayon Volcano & Other Volcanic Topics

Authorities waging war vs. fake volcanologists in social media by Aaron Recuenco at Manila Bulletin

Scientists monitor volcanic gases with digital cameras to forecast eruptions by Kimber Price at AGU’s GeoSpace blog

We’re volcano scientists – here are six volcanoes we’ll be watching out for in 2018 at The Comversation

Sustainable Cities

‘The bayou’s alive’: ignoring it could kill Houston by Tom Dart at The Guardian

‘Does Hull have a future?’ City built on a flood plain faces sea rise reckoning by Stephen Walsh at The Guardian

Education/Communication

From Natural Disasters to Other Threats, This Initiative Is Teaching Delhi Kids All About Safety by Rinchen Wangchuk at The Better India

Disaster Risk

Why the Swiss are experts at predicting avalanches by Simon Bradley at swissinfo

Tracing how disaster impacts escalate will improve emergency responses at UCL

Watching a Ridge Slide in Slow Motion, a Town Braces for Disaster by Kirk Johnson at The New York Times

The risk of landslides in Rohingya refugee camps in Bangladesh by Dave Petley at AGU’s The Landslide Blog

Deadly California mudslides show the need for maps and zoning that better reflect landslide risk by David Montgomery at The Conversation

Will Tehran be able to withstand ‘long overdue’ quake? By Zahra Alipour at Al-Monitor

Scientists to map quake-prone Asian region in hope of mitigating disaster by Michael Taylor at Thomson Reuters Foundation

How forests could limit earthquake damage to buildings by Edwin Cartlidge at IOP Physics World

Avalanches and floods, drawing by Johann Jakob Wick, 1586

 

External Opportunities

Get involved in knowledge in action

IRDR Young Scientists Programme: Call for application (3rd Batch)

Apply to join the Pressure Cooker event on Risk Communication at the 2018 Understanding Risk Forum

Vacancies: Two Research Positions on Climate & Development, The German Development Institute (DIE) Bonn

Call for applications for the Research School within the Mistra Geopolitics program

Australian Disaster Resilience Conference 2018

Check back next month for more picks!

Follow Jesse Zondervan @JesseZondervan. Follow us @Geo_Dev & Facebook.

The Case Against Fieldwork – How can we internalise the carbon cost of fieldwork, as scientists who investigate the earth system?

Contrails from a jetliner. Image courtesy Pixabay/diddi4

There are few, if any, fields of human study for which fieldwork is more fundamental than geology. For many geologists, the solid earth itself is their subject, and this means observations can be made at any given location on the planet. Moreover, the local quirks of different environments almost necessitate a diverse range of study sites for us to fully comprehend the differing processes that govern the world we see around us.

Beyond offering us the chance to make observations in a variety of different locations, fieldwork allows us to test our laboratory models, to interact with researchers from other institutions, and from a personal standpoint can broaden perspectives while exploring and experiencing new places. These positive consequences of exploration and observation are offset by the impact that researchers have on their chosen field sites. ‘Leave only footprints, take only photos’ is a fine motto, but much like Schrödinger’s cat of quantum physics, when we choose to observe the natural system, we have an impact on the subject of our observation.

The scale of that impact can vary widely. When I undertook fieldwork in New Zealand, in field areas culturally significant to the Maori people, we took great pains to limit any long lasting effect on the landscape (with help from the NZ Department of Conservation), taking only small quantities of water samples and keeping to specific areas. The vast majority of field scientists recognise that their own presence can be a source of systematic bias, and experimental or observational design to limit that bias is undoubtedly essential. There’s one big impact that we rarely consider, though; the carbon footprint of travel to and from far-flung locations. Even if the effect of emissions from a single trip is relatively minor, the cumulative effect of climate change systematically influences a great many geological processes.

The carbon footprint of an individual is not always an easy number to pin down. Given that nearly every action we take has some impact on emissions, there are a huge number of variables to constrain for any single person. With some caveats, it’s easier to use data for large populations and average to an individual level. The World Bank provides nation-level data for CO2 emissions per capita, which is highly informative. Unsurprisingly, emissions from Western Europe are higher than the so-called developing world (approx 6.4 tons of CO2 per person per year in W Europe, and 0.8 tons in sub-Saharan Africa for example), while the US values are higher still (16.5 tons).

How do these numbers compare with the emissions from flying? Again, it is difficult to nail down an exact value for airline pollution, with estimates complicated by a variety of aircraft of differing efficiencies in service, as well as non-linear emissions with respect to the length of a journey (taking off burns more fuel, meaning shorter flights have a higher proportional impact – read more here). Roughly, though, airliners emit between 100-260g of CO2 per passenger kilometre. Scaling up, this means a return trans-Atlantic flight puts around a ton of CO2 into the atmosphere per passenger; thus, fieldwork across the world could rapidly make a huge impact on the overall carbon output of an individual.

My own experience is illustrative. As a PhD student in Germany, I felt very fortunate to carry out fieldwork in both Taiwan (c. 9000km from Berlin) and New Zealand (c. 18000km from Berlin); the high rates of erosion in the mountains in those settings made them the ideal location to study landslides and related chemical weathering. However, comparing my emissions from flying over the course of a 4-year PhD purely for fieldwork (probably at least 10-12 tons) with the average emissions per person in Germany (around 8-10 tons of CO2 annually) makes for uncomfortable reading. Not only was this worth more than a whole years’ worth for the average German citizen, but it was far in excess of a level that would, if adopted by everyone, help mitigate dangerous climate change. While it is still under debate what the acceptable level of emissions per person would be, my personal emissions are certainly incompatible with any of the proposed levels, which are often cited as closer to 2 tons per year each.

This would even be true if I had made every other lifestyle change that is often discussed to reduce one’s own ecological impact; a vegan diet, using only public transport, and limiting purchases of new goods; these would not have sufficiently offset the emissions just from fieldwork.

More and more scientists are already reckoning with these moral questions in regards to conferences. A recent editorial about the amount of emissions from the American Geophysical Union’s Fall meeting highlighted that scientists gathered together from across the world have a non-negligible impact on CO2. Such large conferences also present a problem of ‘optics’ as the media might describe it; how are scientists supposed to advocate for a lower carbon economic system when their massed meeting could create such potential harm? Perhaps fieldwork has a less obvious optics problem, given that geologists are scattered around the world, but there remains potential for accusations of hypocrisy to be made.

I’m certainly not the first to be concerned about these issues. When I’ve discussed them before with friends and colleagues, a kind of compromise is often the solution that has been suggested to me: weigh up the costs and benefits of the fieldwork. Perhaps the work in question is directly relevant for carbon capture research, or modelling of the climatic system; in this case, the direct impact of the research resulting from the fieldwork might be more tangible, and in some cases even quantifiable.

For a great many geologists who don’t work on the climate system, these direct comparisons are not possible. In this case, we are forced to make subjective value judgements about how the positive outcomes of our research and findings should be compared with the incremental changes that result in the environmental system from our emissions. These judgements are certainly not unique to geologists, but are perhaps more stark than others given the potential for dramatic climate change to fundamentally alter many surface or marine environments that have been the subject of centuries of geological observation.

I certainly would not presume to make these value judgements for other scientists. We each have our own perspectives, and these may often be highly personal decisions. Moreover, I wouldn’t expect geologists to give up fieldwork lightly, or even at all; it’s so crucial to the science as we know it, and is often the highlight of many researchers calendars.

I would argue, though, that the time has come for us to seriously question whether we can do fieldwork in a more sustainable fashion. We’re often seeking the prime location to test our hypotheses, which may be half way around the world, but instead of forgoing these field sites, we should perhaps ask ourselves: could local researchers take the samples we require on our behalf? There’s an added bonus to this suggestion, too – it could encourage productive collaboration across borders, as well as helping development in economically deprived-but-geologically-interesting countries through the intersection of ideas.

Whether it’s seeking new collaborators in the ‘perfect setting’, or seeking a compromise field-site closer to home, or even to embrace a slower way of travelling (such as trains) there are ways to reduce flight for fieldwork. As earth scientists, we are among the most informed citizens about the potential for catastrophic climate change. It is up to each scientist to decide for themselves whether this knowledge carries with it an imperative to act, but given the global consequences of our actions such an imperative seems more urgent than ever.

Robert Emberson is a science writer, currently based in Vancouver, Canada. He can be contacted via Twitter (@RobertEmberson) or via his website (www.robertemberson.com).

Peat in the Tropics

As has been previously discussed in Robert’s blog, fertile soil is an incredibly important resource that is fast running out in many regions of the world. It is true that soil’s importance for agriculture (and sustainable development) cannot be understated, but I wish to focus on another aspect of soil in this week’s blog– its ability to store carbon.

One soil type in particular, peat, is an incredibly important form of carbon storage. Despite only covering 3% of the Earth’s land surface it contains a third of the carbon stored in soils, formed by the build-up of partially decomposed organic carbon, trapped in waterlogged and anoxic conditions. For this reason the preservation of peatland is of the upmost importance, and should be considered in sustainable development efforts in order to prevent the release of vast amounts of carbon into the atmosphere.

Figure 1- Distribution of mires around the world. Source: International Peat Society, Available www.peatsociety.fi

When you picture peat it is typically in a cool and damp climate, such as in the highlands of Scotland or expanses of tundra within the Arctic Circle. This is because the cooler climates further impede the decomposition of organic matter and facilitate the formation of peaty soils. Recently, however, it has been discovered that peat forms in other regions too, and in quantities far vaster than had ever been considered before. These tropical peat deposits form in the swamps commonly found in the river basins of warm and humid regions. Although warm and wet conditions typically aid the processes of rot and decay, the often stagnant water of swamps produces anoxic environments not dissimilar to those in the extensive peatlands found at higher latitudes. Conditions are exacerbated by poor drainage, high rainfall and overbank flooding by rivers, meaning that the land never truly gets the opportunity to dry out and peatlands are able to form, albeit in much smaller expanses than those in the North.

Despite the smaller size of tropical peat deposits they are disproportionately more significant to sustainable development, as they tend to be focussed in regions where development is occurring rapidly – central Africa, South East Asia and South America. Building on and draining these fragile ecosystems could result in mass release of carbon dioxide.

An example of a tropical peat deposit is the Cuvette Centrale depression in the Central Congo basin, where the peat is relatively shallow (with a median depth of 2m), but has a large aerial extent, making it the greatest ranging peatland in the tropics. Other extensive peat deposits can be found in the amazon rainforest and in tropical Asia (for example the island of Borneo) but land use changes in recent years have drastically reduced the amount of peatland in SE Asia, as much has been drained for agricultural use. It is predicted that SE Asian peatland will be lost completely by 2030, but thankfully the peatlands in other areas of the world are in a significantly more pristine condition, relatively unaffected by humans due to their relative inaccessibility.

Drainage of land for agricultural use is not the only threat to tropical peatlands. Climate change is acting to reduce the annual precipitation in many tropical regions, meaning carbon trapped in peat is oxidised more readily and able to decompose. Even though tropical peatlands are only a fraction of the size of their northern, cooler cousins, they still represent huge carbon stores that, if destroyed, could accelerate the release of carbon into the atmosphere and accelerate global warming further, entering into a feedback loop which will release tonnes of carbon into the atmosphere that has lain trapped underground for millennia. Carbon stocks of peat in the Cuvette Centrale alone are potentially equal to 20 years of current fossil fuel emissions from the USA, demonstrating the importance of protecting this seemingly insignificant soil type.

Figure 3 – SE Asian rainforest. It is in rainforests such as this that peatlands are quickly being drained for agricultural use. Source: https://imaggeo.egu.eu/view/4268/

A further concern is that swamplands are a refuge for many of the world’s remaining megafaunal populations, including lowland gorillas and forest elephants. It is clear that if Africa and South American peatlands are to avoid the fate of the SE Asian counterparts, they must become a conservation research priority.  Doing this would undoubtedly help to combat the rise of CO2 levels and simultaneously work towards the UN Sustainable Development Goal 13 – climate action.