The rapid spread of waterlilies in Kuttanad’s paddy fields has created a tourism boom, boosting local incomes and infrastructure.
However, scientists warn of ecological risks, including biodiversity loss, water quality decline and increased greenhouse gas emissions.
Balancing tourism benefits with sustainable management is crucial to protect the wetland ecosystem and long-term agricultural viability.
Kerala’s Kuttanad region has a unique topography, with most of its 55,000 hectares situated 1-2 metres below sea level, becoming the lowest elevation in India. But there's an ugly side to this landscape's beauty that has been ignored.
Covering Alappuzha, Kottayam and Pathanamthitta, the region is part of the expansive Vembanad Kole Wetland Ecosystem Ramsar site and is a prominent tourism spot in India, especially backwater and farm tourism.
Its distinctive below-sea-level farming system, consisting of paddy field clusters, was acknowledged as a Globally Important Agricultural Heritage System by the United Nations Food and Agriculture Organization in 2013.
However, this unique wetland ecosystem is threatened by many factors, the most recent being the pink bloom caused by a Nymphaea species.
A surge of the hybrid waterlily (Nymphaea × omarana Bisset) in Kuttanad's paddy fields is sparking interest in waterlily tourism, similar to that in the Malarikkal region of Kottayam district.
A significant increase in the waterlily population was noted after the devastating flood in 2018. The pink-flowered waterlilies in Malarikkal are drawing visitors, leading to the rise of waterlily tourism, which began on a small scale in 2019 but has since expanded, attracting many tourists from June through October.
During these months, the area experiences a surge in tourism activities, with farmers and locals offering boat rides, food, refreshments and selling waterlily plants and flowers.
The Local Self Government Department is actively involved in promoting tourism, which is boosting the local economy and securing funds from agencies like the National Bank for Agricultural and Rural Development for road and other developmental projects in the region.
While this has strengthened the local economy, there ecological and socio-economic dimensions of the water lily invasion and spread, as well as their sustainable utilisation in Kuttanad's paddy fields, to be considered.
Although the 2018 flood damaged the standing paddy crop, the subsequent season saw a remarkable yield. Scientists attribute this increase to several factors, including the washing away of acidity and iron and aluminium toxicity in acid sulphate soils, pest and pathogen removal and the accumulation of nutrient-rich silt in the fields.
These factors may have also contributed to the waterlily's proliferation, an emergent weed that's classified as an introduced plant by the 2023 Global Register of Introduced and Invasive Species – India.
The annual exponential growth of waterlily-covered areas in paddy fields is further influenced by the recent absence of natural saline water inundation during summer. The prolonged closure of the Thanneermukkam barrier, beyond the usual three months, to protect late-sown paddy crops in polders has disrupted the balance of saline and fresh water in the ecosystem.
Our study, funded by the Kerala State Council for Science Technology and Environment (KSCSTE), found that water lily tourism significantly benefits the local community. From July to September, a farmer in the Malarikkal region can earn an additional Rs 1-2 lakhs, with an overall turnover of Rs 150-200 lakhs.
Another benefit is the substantial biomass of the aquatic plant that enhances the soil's physico-chemical and biological properties and nutrient dynamics, including phytoremediation effects that remove toxic heavy metals like iron and aluminium in acid sulphate soil. It was noted that promoting waterlily growth during the fallow period helps control noxious weeds such as weedy rice (Oryza sativa f. spontanea).
Switching from broad-spectrum herbicides to newer selective herbicides before rice planting brings ecological advantages. In the past, broad-spectrum herbicides like glyphosate were utilised to tackle mixed weed species, including grasses, sedges, and broadleaved plants. However, with waterlilies becoming more prevalent, a selective herbicide (Metsulfuron Methyl 10.1 per cent + Chlorimuron Ethyl 10.1 per cent WP) is now used, which is a modern combination herbicide that requires a smaller amount.
Despite these advantages, several disadvantages have been noted, especially by local farmers. After harvesting, many farmers initially relied on broad-spectrum herbicides to manage various weeds. This practice has become widespread and essential for most farmers to promote waterlily populations by suppressing competing weeds. As a result, the invasion of weeds has indirectly promoted the routine post-harvest use of broad-spectrum herbicides.
This is sometimes followed by dry ploughing before allowing water from nearby canals into the fields. Once the fields are flooded post-harvest, waterlily plants sprout from underground seeds in most areas. Farmers need to put in considerable effort to prepare the fields for the next cultivation cycle once waterlilies infest them.
Some farmers successfully incorporate waterlilies mechanically during land preparation, but this method can be more time-consuming and costly than the less labor-intensive herbicidal management option.
An additional herbicide application during the crop growth period, typically 12-14 days after sowing, is a common practice. All weeds, including waterlilies, are controlled until the 30-day critical weed-free period of the rice crop. If weeds like sedges are not controlled by the initial chemical application, another herbicide, 2,4-dichlorophenoxyacetic acid, selective for broadleaved weeds and sedges, is applied 18-20 days after sowing to prevent waterlily emergence. These herbicide applications destroy the vegetative parts of waterlilies, but the seeds remain intact in the underwater sediments.
Like other invasive aquatic plants, waterlilies in Kuttanad cause various issues, such as hindering navigation, reducing water quality, blocking sunlight due to their spreading leaves, and affecting the habitats of other macro and microorganisms. The decay of large biomass can produce significant amounts of methane, a greenhouse gas that may contribute to climate change.
Poor water quality can decrease fish populations in aquatic environments, impacting fish catches and the livelihoods of fishermen. Additionally, the increasing rodent population in the area may be linked to the availability of waterlily buds, flowers and seeds as alternative food sources during the lean season.
The extensive application of chemicals for rodent control, particularly by farmers along field boundaries, is causing unintended harm to other organisms, negatively impacting biodiversity. This invasion is benefiting turtles and wetland birds like the bronze-winged Jacana.
Some insect pests, such as moths, gall insects, and beetles, have been observed damaging waterlily plants, and there is a need to investigate their potential impact on future paddy crops. Notably, each flower is visited by at least five insects during blooming, which could eventually influence pollination patterns of land crops.
A few farmers have found success with eco-friendly waterlily management through mechanical methods during land preparation before sowing, and this practice could be promoted. Any additional costs incurred might be offset by revenue from tourism, benefiting all affected fields. However, the use of herbicides during the post-harvest and crop growth periods remains irreplaceable by other management strategies.
Significant damage to waterlily plants by a moth caterpillar has been observed, suggesting a potential avenue for future biological control of this invasive species. The inundation of saline water from March to May, coinciding with the opening and closing of the Thanneermukkam saltwater barrage, serves as a natural method for controlling waterlily growth. Therefore, timely operation of the barrage offers a natural solution for managing all aquatic invasive weeds in the ecosystem.
Paddy cultivation is currently facing challenges such as increasing labour costs, harvesting difficulties and packing expenses, which are reducing farmers’ profits.
Additionally, recent disputes with paddy procurement mills due to declining grain quality have dampened farmers’ enthusiasm, potentially leading them to abandon paddy cultivation.
The perennial nature of waterlily plants presents new opportunities for year-round tourism and revenue from paddy fields. However, if Kerala, which is striving for food security with its staple food, rice, replaces paddy cultivation with waterlily growth to promote year-round tourism, it could suffer losses.
Meanwhile, the impact of waterlily on the wetland ecosystem needs thorough analysis to assess the long-term threat posed by this aquatic macrophyte. Changes in biodiversity, nutrient dynamics, and other physical, chemical and biological soil properties, as well as effects on water quality, phytoremediation potential and subsequent crops, should be studied to understand the overall influence of waterlily invasion on the wetland. Any biodiversity changes in the wetland ecosystem due to invasion should be taken seriously, despite the monetary benefits it may bring to the local community.
The agro-ecosystems of Kuttanad are deteriorating rapidly, and paddy cultivation is becoming less profitable for various reasons. Apart from the initial financial benefits, we think that the invasion and establishment of waterlilies can contribute to further degradation of ecosystem functions and services. Thus, a management strategy needs to be developed for Nymphea omarana with focus on both tourism potential and ecosystem conservation.
It is the need of the hour to act and adopt proper management strategies with the involvement of all stakeholders (farmers, ecologists, agriculture scientists, local self government department) to come out with a management plan, otherwise the cost to be paid will be high in the long run, in terms of ecological and socio-economic aspects.
This article was developed on a context of a project funded by the Kerala State Council for Science Technology and Environment under the Ecology and Environment scheme.
Devi VS is the assistant professor of agronomy at the Regional Agricultural Research Station, Kumarakom, Kottayam, Kerala. Jayasooryan KK is Scientist B and head i/c, KSCSTE- Centre for Water Resources Development and Management, Kottayam Sub-Centre. KB Rameshkumar is principal scientist of phytochemistry and phytopharmacology at KSCSTE-Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Palode, Thiruvananthapuram, Kerala. Sona Sebastian is project fellow at Regional Agricultural Research Station, Kumarakom.
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth.