Freshwater edible aquatic plants, SE Asia
The cultivation and consumption of edible cultivated freshwater
macrophytes and their impact on food security has long been
unrecognised and under-recorded in both the scientific and grey
literature. In a geographical context they have largely been
unrecognised outside South and Southeast Asia where for centuries
they have provided millions of often lower income communities with a
low cost, nutritious foodstuff for both themselves and also their
including cultured fish.
Freshwater macrophytes are often used to recycle “waste” nutrients
and also provide significant employment and incomes. It could quite
rightly be said that freshwater aquatic macrophytes (FAMs) are the
“most forgotten form of freshwater aquatic food production” as they
continually remain unrecorded in most government and (inter)
national agriculture and/or aquaculture statistics and planning
documents, despite their significant contribution to food production
and nutrient recycling. In terms of the global aquaculture
development community the range and scale of cultivated edible
aquatic plants production is little known or practised outside South
and Southeast Asia, and is rarely taught in the curricula or
addressed in the research agenda of the major academic aquaculture
and agriculture or international non-government research
Edwards (1980), estimated that there were more than 40 species of edible freshwater aquatic macrophytes (FAMs), of which around 25 % either are already being cultivated for food at a scalable level or have the potential to be developed into commercially viable cultivation species. In terms of their genetic improvement, and species selection for improvements in growth performance, productivity, phytoremediation of waste water and even disease resistance, despite the significant translocation of germplasm between countries or regions over the last 600 years, there is little either in the research literature or at the grass roots production level to indicate selective breeding programs, and/or selection or genetic modification towards improved strains occurring. However, owing to their scale and their importance particularly in Southeast Asia, FAMs can be considered a key tropical/sub-tropical cultivatable crop which can contribute sustainable food production in developing countries in the future in a financially viable and environmentally responsible way.
Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes. These plants require special adaptations for living submerged in water, or at the water’s surface. The following aquatic plants are the most common used as a substitute of food in Asia.
Water spinach or morning glory
Water spinach is a semiaquatic, tropical plant grown as a vegetable for its tender shoots and leaves. It is found throughout the tropical and subtropical regions of the world. This plant is known as river spinach, water morning glory, water convolvulus, Chinese spinach, Chinese Watercress, Chinese convolvulus, swamp cabbage or kangkong. Water spinach grows in water or on moist soil. Its stems are 2–3 metres or more long, rooting at the nodes and they are hollow and can float. The leaves are arrow head-shaped 5–15 cm long and 2–8 cm broad. Water Spinach is a common ingredient in Southeast Asian dishes. Stir-fried water spinach is a popular vegetable dish in Southeast Asia (source: text Ashwini R., photo Eric in SF /CC BY-SA 4.0 | Water Spinach). Morning glory was found to be by far the most common aquatic plants in the cities which were considered in this case.
Watercress is an aquatic plant species with the botanical name Nasturtium officinale. Watercress is a rapidly growing, aquatic or semi-aquatic, perennial plant native to Europe and Asia and one of the oldest known leaf vegetables consumed by humans. It is a rapidly growing, aquatic or semi-aquatic, perennial plant native to Europe and Asia and one of the oldest known leaf vegetables consumed by humans. The hollow stems of watercress are floating and the leaves are pinnately compound. Small, white and green flowers are produced in clusters. In some regions, watercress is regarded as a weed, in other regions as an aquatic vegetable or herb. Watercress has been grown in many locations around the world. Watercress contains significant amounts of iron, calcium, iodine, manganese and folic acid. Because it is relatively rich in vitamin C, watercress was suggested by English military surgeon John Woodall (1570–1643) as a remedy for scurvy. (source: text Ashwini R., photo Wendell Smith /CC BY 2.0 | Watercress With Flowers)
Lotus Lotus is native to tropical Asia and Queensland, Australia. It is commonly cultivated in water gardens. It is also the national flower of India and Vietnam. The roots of lotus are planted in the soil of the pond or river bottom, while the leaves float on top of the water surface or are held well above it. The flowers are usually found on thick stems rising several centimeters above the leaves. The plant normally grows up to a height of about 150 cm and a horizontal spread of up to 3 meters. An individual lotus can live for over a thousand years. The flowers, seeds, young leaves, and roots are all edible. In Asia, the petals are sometimes used for garnish, while the large leaves are used as a wrap for food. In South Indian states, the Lotus Stem is sliced, marinated with salt to dry and the dried slices are fried and used as a side dish (source: text Ashwini R., photo Loren Kerns /CC BY 2.0 | Lotus Root Slices).
Water caltrop is any of three extant species. The species are floating annual aquatic plants, growing in slow-moving water up to 5 meters deep, native to warm temperate parts of Eurasia and Africa. The plant is also called water chestnut, buffalo nut, bat nut, devil pod, ling nut and singhara. They bear ornately shaped fruits. Each fruit contains a single very large starchy seed. In India and Pakistan it is known as singhara or paniphal and is widely cultivated in fresh water lakes. The fruits are eaten raw or boiled. When the fruit has been dried, it is ground to a flour called singhare ka atta. Singhare ka atta is used in many religious rituals and can be consumed as a phalahar diet on the Hindu fasting days, the navratas. Water caltrop has been an important food for worship as prayer offerings since the Chinese Zhou Dynasty. The Chinese Herbal Medicine Summary indicates that water caltrop can help fever and drunkenness (source: text Ashwini R., photo TheDarkCurrent /CC BY-SA 3.0 | Water Caltrop Seeds).
The Water chestnut or Chinese water chestnut is a grass-like sedge native to Asia, Australia, tropical Africa and various islands of the Pacific and Indian Oceans. It is widely grown in many countries for its edible corms. The water chestnut is actually not a nut at all, but an aquatic vegetable that grows in marshes, underwater in the mud. It has tube-shaped, leafless green stems that grow to about 1.5 metres. The small, rounded corms have a crisp white flesh and can be eaten raw, slightly boiled or grilled, and are often pickled or tinned. They are a popular ingredient in Chinese dishes. In China, they are most often eaten raw, sometimes sweetened. Raw water chestnuts are slightly sweet and very crunchy. Boiled water chestnuts have a firm and slightly crunchy texture with a flavour that is very mild and slightly nutty. Water chestnuts are often combined with bamboo shoots, coriander, ginger, sesame oil and snow peas. They are often used in noodle or rice dishes (source: text Ashwini R., photo Joscha Feth /Public Domain | Water Chestnut Corm).
Aquatic food products are important in the diets of people of the SE Asian region and include a variety of vegetables, fish and other animals. The origins of farming aquatic animals in the Region are quite likely to be urban since until recently most rural areas of Asia where people value fish and edible aquatic plants as food had access to abundant natural stocks of both without the needs to cultivate. The graph below depicts an example in Thot Chrum, a community in Cambodia, about the role of aquatic plant production in livelihoods.
Urbanisation in SE Asia is occurring most rapidly in larger cities typically situated on the floodplains of large rivers. Limited drainage infrastructure and formal sanitation serving such cities, together with the extraction of fill from surrounding areas for construction and flood defences has frequently resulted in peri-urban wetlands that become both de facto waste treatment and food production systems. Such peri-urban wetlands have been important food production centres and appear to have enduring importance to the livelihoods of lower income poor people. By the same token these peri-urban lagoons, canals and ponds commonly provide the only accessible means of disposing of human excreta and therefore have much broader importance to urban communities. Although attention has been drawn to the benefits of such wetlands, generally their value is unmeasured and impacts of contamination from wastes, changing access and urbanisation unknown.
policy and management of peri-urban zones in Asia is handicapped by
a lack of informed and balanced debate regarding how stakeholders
value aquatic production systems in terms of public health risks,
food availability and livelihoods. The lack of information about
these systems contrasts with an extensive knowledge base on solid
waste and wastewater reuse in agriculture.
The dynamic nature of peri-urban areas require scientists, planners and policy makers to deal with rapid and often destructive changes to Periurban Aquatic Food Production Systems PAFPS whilst attempting to meet the challenge of meeting urban populations basic needs.
Freshwater edible aquatic plants or macrophyte production was found through the EC funded PAPUSSA project to be a significant food production sector employing thousands across the value chain, and supplying fresh food to millions of citizens in 4 SE Asian cities, this by primarily recycling and reusing nutrients from urban wastewater. The EC funded PAPUSSA (Production in Aquatic Peri Urban Systems in SE Asia) project (2003-2006) initially chose Hanoi and HCMC in Vietnam, Phnom Penh in Cambodia, and Bangkok, to study and evaluate the importance of periurban aquaculture production in these 4 SE Asian cities. It was found contrary to our original research hypotheses suggesting the importance of periurban fish production, rather it was the production, sale and consumption of four species of edible aquatic plants which predominated to the level of supplying millions of urban citizens with a fresh daily supply of nutritious food, as well as providing thousands of individuals, often at household level income earning activities across the value chain.
Mainly four edible freshwater aquatic plants are cultivated, sold, and consumed on a huge commercial scale in 4 SE Asian cities Asian cities, such as Hanoi, Ho Chi Minh City (HCMC), Phnom Penh and Bangkok, primarily recycling nutrients from urban waste water. Ipomea aquatica and Neptunia oleracea are cultivated 12 months per year in Bangkok, Phnom Penh and HCMC. Whilst in the more seasonal climate of Hanoi they are grown in summer months and then water cress and water dropwort rotated on same plots in their winters. Typically morning glory and water mimosa are grown in wastewater irrigated, 0.5-2.0 hectare former, periurban rice plots, and harvested every 25-30 days for 12 months of the year in HCMC. Whilst in Phnom Penh lower income families living on the edge of a large periurban wetland/lake fed by 80% of the city’s urban waste water cultivate significant volumes of water morning glory and water mimosa. Productivities range from 15-50 MT per hectare per year, most of which is washed and bundled up and then transported by motorbike to local urban markets early each morning to be sold to millions of urban consumers. These aquatic plants are rich in minerals especially iron, and form the basis for millions of urbans dwellers noodle and other soup dishes.