Planned Mega-Dam Threatens Fish Populations and Food Security in Cambodia
By Sabrina Gyorvary
Auntie Punleu has spent most of her life on Koh Dambang, an island set in the middle of the Mekong River in Cambodia. A small, grandmotherly woman, she paints an idyllic picture of life there.
"We catch fish as our main food every day. We eat fish nearly six days a week," she said. With her gentle strength and keen knowledge of community affairs, people on the island look to her as a natural leader. "My children and grandchildren have enough food to eat every day and they are healthy. We do not need to spend money to buy fish. We do not need to beg people for them. They come naturally from the river."
The Mekong River is threatened by a mega-dam project in the Sambor District, one of 11 large hydropower dams planned for the river's lower mainstream.International Rivers
A few kilometers away, Uncle Songom, a resident of the quiet riverside village of Svay Chek, echoed Punleu: "My family have enough food and my children are healthy because of the Mekong River."
Punleu's story is replicated up and down the riverbanks. The livelihoods and cultures of 60 million people in the lower Mekong Basin are intimately connected with the Mekong River's natural cycles. Boasting one of the world's most diverse and productive inland fisheries, the Mekong supplies people in the region with approximately 80 percent of their protein needs. For families living on the margin, the river is an invaluable source of both protein and income.
But this vital lifeline is now at risk, and families like those of Punleu and Songom face an uncertain future. Regional governments are pushing forward a series of large-scale hydropower dam projects that are threatening the Mekong's abundant fisheries, and consequently the food supply of millions.
This past September saw the inauguration of the Lower Sesan 2 Dam, a project that fisheries experts warn will block fish migrations on two of the major tributaries of the Mekong River, the Sesan and Srepok rivers, causing a 9.3 percent drop in fish biomass for the entire river basin. The dam is also expected to flood 36,000 hectares, displacing about 5,000 people. The plans for these large-scale projects are typically conceived and approved in secret, and the communities who stand to lose the most are never consulted.
Punleu's island is now facing inundation by one such project: the proposed Sambor Dam. The dam would be located on the Mekong River's mainstream at Sambor town, Kratie Province, Cambodia. This would be one of 11 large hydropower dams planned for the Mekong River's lower mainstream. (In total, some 200 dams are already built, under construction, or planned on the Mekong River system.)
The dams that clogged rivers in the American west in the twentieth century decimated salmon populations, blocking their access to traditional spawning grounds. Now it looks like the same sort of catastrophe is headed for the Mekong, but on an even larger scale. The Sambor Dam alone would block major fish migrations between Southern Laos and Cambodia's Tonle Sap Lake, destroy critical deep pool fish habitats, and interrupt the river's hydrological, sediment, and nutrient cycles, impacting the river's wider ecology.
Combined, the 11 dams on the lower Mekong would block the major fish migrations that are essential to the life cycle of around 70 percent of the Mekong River's commercial fish catch. This would result in a total estimated fishery loss of 26 to 42 percent, placing at risk the livelihoods and food security of millions of people.
This would be devastating to Cambodia food security. The country's per capita consumption of inland fish is among the highest in the world and its people depend on fish for nearly three-quarters of their protein intake. According to one estimate, Cambodian fishers pull between 289,000 to 431,000 tons from the Mekong every year.
And impacts would extend beyond those to fish. In addition to providing Cambodia's main source of protein, the Mekong supplies water for the cultivation of rice in an area where irrigated land is scarce. "We can grow rice even in the dry season by pumping water from the river to our rice paddies," Puleau explained. "The river is absolutely essential to us."
The Mekong River supplies water for the cultivation of rice, as well as for drinking and other household uses. International Rivers
The Mekong also serves as the community's only reliable source of water for drinking and household use. "The river is central to our daily lives," said Bunleap, a homemaker and mother of three on Pdau Island. "Not only do we bring water from the river to cultivate our rice fields and vegetable gardens, we also use it for cleaning, cooking and drinking."
Dams upstream are already changing the river, and the area's residents are no longer able to count on the Mekong to meet their needs.
Just five years ago, Punleu's son-in-law could earn 300,000 Riel (US $75) per fishing trip. He made two to three trips per week. This income provided a critical safety net, helping the family cope with unexpected shocks such as hospital bills. Now her son-in-law earns only 100,000 Riel (US $25) per trip—his income has declined by two-thirds.
When asked about the reason for this sharp decline, Punleu said, "I suspect upstream dams could be one of the reasons." So far, seven megadams have been built on the upper Mekong in China, and construction is well underway on the Xayaburi and Don Sahong dams in neighboring Lao PDR. Despite these projects' profound impacts on the food security of Cambodia, they have proceeded with no transboundary environmental impact assessments, and no consultation with affected communities downstream. "I need more information regarding these dams' impacts," said Punleu.
Bunleap's family is also finding it harder to catch fish. Five years ago, the fish they caught for sale provided a crucial source of income. "Now we usually only catch enough fish to eat within our family, and sometimes, we don't even catch enough to eat," she said. "I don't know why. Now we sometimes have to buy fish to cook. My husband has had to change his career from fishing to work as a logger."
Punleu, too, is seeing more family members go off to the forest to log trees. She's saddened by this turn of events, and well aware of the unsustainability of this new enterprise. "What career will we have in our village when there are no more forests to log?" she asked. "In the future, if this decrease in fish continues, making a living will become more and more difficult, and my children's nutrition will suffer. This could really harm my children's health."
Punleu's fears are well founded. A 2013 report financed by Danida, Oxfam, and the World Wildlife Fund shows that the combined impact of mainstream dams and population growth could reduce consumption of fish in Cambodia from 49 kilograms per person per year to as little as two kilograms by 2030. This would have a profound impact on child nutrition in a country where nearly 40 percent of children under five are chronically malnourished, more than 28 percent are underweight, and roughly 11 percent are acutely malnourished.
Songom shares Punleu's concern. "If the fishing gets any worse, I'm scared that I won't be able to feed my family," he said. "I am worried that my children and grandchildren won't have enough food to eat every day, and that they'll get sick."
Five years ago, many people in Bunleap and Songom's villages caught fish not only for their daily meals, but also to make supplemental foods like prohok (fermented fish) that can be stored long-term. For many poorer Cambodians, prohok is the only affordable source of complete protein available year-round, and it's crucial to the country's most vulnerable communities.
Fish and fish products like prohok are critical sources of iron. Already in Cambodia, an estimated 70 percent of pregnant women and 74 percent of children under the age of five suffer from iron deficiencies. Iron shortages rob people of energy, ultimately perpetuating the cycle of poverty.
A decline in fish could also result in weakened muscles and bones associated with calcium deficiency; body-wasting and memory-loss associated with zinc deficiency; decreased resistance to disease from insufficient Vitamin A; and mental retardation caused by too little iodine.
Food security is a foundation on which other important forms of development are built, and wild-capture fisheries are a vital source of nutrients to rural families throughout the Mekong region. As such, protection of wild-capture fisheries should be central to poverty-reduction efforts.
Cambodia still has time to pull back from this path. The Cambodian government could embrace the innovative renewable and decentralized electricity technologies like wind and solar, which are now available and cost-competitive, and could help Cambodia avoid these large-scale and destructive mega-dam projects. By adopting national energy policies that encourage investment in these new energy technologies, the Mekong governments could start growing sustainable, modern economies without losing the many benefits that healthy rivers bring. Punleu, for one, would thank them.
All names have been changed to protect people's identities.
Sabrina Gyorvary is the Mekong Program Coordinator for the global river protection group International Rivers.
Reposted with permission from our media associate Earth Island Journal.
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By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
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