A PhD amongst the paddy fields of south west China

Blog post by Sarah Buckerfield

Part 1: Some background, and a first trip to China (Zhōngguó – “Middle Kingdom”)

China is truly enormous, comparable in size to the entirety of Europe, and I had little appreciation of this before catching a 3 hour flight only half way across the country from bustling Beijing on the eastern seaboard, the second busiest airport in the world, to Guiyang in the mountainous south west. It is as diverse in landscape and culture as it is wide, with monasteries, mosques, shrines, and churches almost side by side in small mountain towns, food specialities from every province, county, and village, the most populous cities on the planet, and all rimmed with the world’s highest mountains where nomadic pastoralists still move their yak through the high passes. The area I was headed for – Puding county, southwest of Guiyang, the capital of Guizhou Province, is within the southwest China karst region, an enormous expanse of carbonate rock covering 20% of China’s land area.

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The location of Puding county in the south west of China

The region contains the largest known cave systems in the world and absolutely spectacular UNESCO listed limestone formations. However, a less desirable property of karstic limestone is its high vulnerability to soil erosion. Combined with heavy monsoonal rains and population pressure driving land-clearance for crops, this has resulted in widespread denudation of the limestone bedrock, in a process called ‘karst rocky desertification’. The net result is drastically diminished available crop area, the primary factor responsible for the high poverty rates in this region.

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An example of karst rocky desertification – corn is planted in the crevices

Another commonly found problem in limestone terrain across the world is high vulnerability to water contamination. This is due to the high solubility of limestone leading to an abundance of dissolution-formed underground rivers, connected directly with the surface water system by sinkholes and springs. Contaminants from the land’s surface can be flushed directly into underground rivers and re-emerge rapidly down catchment at springs, or drinking water bores, with little chance for the filtration and removal of contaminants that naturally occurs when water passes slowly through layers of soil and rock before reaching underground aquifers in non-karstic terrain. This lack of filtration in karstic limestone is the cause for countless disease outbreaks across the world, and there have been a large number of studies performed in America and Europe, aiming to identify the primary sources of contaminants, the mechanisms by which they end up in underground aquifers, and how long they survive there.

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Karst land that has not been eroded; phenomenally hard physical work goes into tending the crops in this steep terrain where tractors are not an option

Microbial contaminants from human and animal faecal matter are the most prevalent form of contamination, and the leading cause of waterborne disease worldwide, a burden felt most heavily in developing countries and rural areas lacking infrastructure. Little research has been done in the southwest China karst region, which is home to ~100 million people and China’s highest poverty rates. This leads to how I found myself there, taking a large number of water samples in aid of understanding controls on microbial water quality, and regretting not having learnt Mandarin earlier.

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A little girl helps her grandmother tilling the thick soils in the valley depressions, which are flatter, prime crop land

My first visit early on in my PhD was a whirlwind two weeks with two of my supervisors, David Oliver and Larissa Naylor, who are leading components of a large multi-disciplinary karst critical zone project within which my PhD is nested. As a whole, the project aims to understand processes controlling soil sources, formation, and erosion, and water quantity, distribution, and quality in the critical zone, in order to inform on urgently needed restoration and remediation of these critical resources. This is a joint funded program between NERC and the National Natural Science Foundation of China (NSFC), one of a series of UK-China collaborative projects. During this visit we surveyed 500 villagers in a typical mixed land-use catchment with the aid of a team of super helpful students from Guiyang. Questions targeted their water issues (shortages, disease, etc.) and day to day practices likely to contaminate the catchment water system – fertilisers, manure/sewage storage, etc. This allowed identification early in the project of potential sources and land-use practices relevant to faecal contamination, and also whether waterborne illness was significant. I was also able to grab a scoping round of samples from springs, streams, and reservoirs across the catchment, to gauge typical contamination levels and plan for the longer field seasons ahead.

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Villagers in the square coming to participate in the survey

The general conclusions were (i) there were moderate levels of contamination throughout the catchment, (ii) human and livestock waste from a range of sources including untreated septic systems, manure heaps, manure spread on crops, and grazing livestock were all likely sources of contamination, and (iii) that people did believe they became ill from their drinking water. You can read more about the outcomes of this, and priorities identified for further research in my review paper here.

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A farmer taking the buffalo home in the evening – no amount of hassling seems to make them walk faster up the road

The field station where we were based during this trip, and where I lived on subsequent trips, is north of Puding city, and surrounded by farming villages. The farmers and villagers were so incredibly friendly, wasting no opportunity to invite me in for tea, or dinner, to the extent I was constantly feeling bad for being too busy on sampling rounds to stop and drink tea all day. This, along with many other little day to day things, typified their generosity, and by the end of it all I was left feeling quite embarrassed and humbled about how little effort we typically go to in the countries I call home to look after foreign visitors. Students would think nothing of giving up days of their time to help me get a visa, and took great pride in including me in their traditions, or explaining the meanings behind all of their national holidays.

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Preparing a paddy field for planting – the spectrum of noises used to control the buffalo was amazing to listen to

On this and subsequent trips I slowly learnt Mandarin, aided by the students that frequent the field station, much to their great amusement. This trip was mercifully only hindered by one bout of gastro, which hit right before the flight home. I narrowly avoided having to explain to the insurance company that I’d missed my plane as I couldn’t get off the bathroom floor, after already re-booking due to a completely unannounced flight cancellation due to airline overbooking…. What joy.

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Photo of all the team members on my first trip during the dry, cold season