Impacts of Green Revolution on Agro-ecosystem in Sri Lanka

The green revolution started in the mid-20th century when Norman Borlaug developed an ultra-resilient strain of wheat in Mexico. He earned the title of “father of Green Revolution” and the Nobel Peace Prize for saving billions of the world’s population from starvation. During the Green Revolution high crop productivity was achieved by adapting measures including

• planting high-yielding varieties (HYV) seeds
• water-intensive farming
• increased usage of inorganic fertilizers and pesticides
• farm implements and machinery with high-technology
• double cropping and
• expansion of cultivated land.

The green revolution was started in India around 1960s led by M.S.Swaminathan and contributed to mitigate hunger and malnutrition in India to a large extent within a short time. There was a significant increase in the production of cereals (especially wheat and rice) in developing countries due to the introduction of HYV of cereals in the mid-20th century.

Sri Lanka is one of the earliest countries to embrace the technologies of the Green Revolution, by producing many new high-yielding varieties through hybridization. The country, which was facing severe food shortages in the 1970s, became food secure while becoming an exporter of tea, rubber, and cinnamon.

There was more research to improve the genetic components of traditional crops which includes selection for higher yield potential, short crop cycle, adaptation to diverse environments, resistance to biotic and abiotic stress, etc. Though the world cereal production was tripled with poverty reduction and lower food prices, some unintended but adverse effects of the green revolution were noticed. This article discusses the negative impacts of the Green Revolution on eco system and the environment and ways to mitigate those.

For the genetically improved HYVs timely application, correct quantity of nutrients was crucial for a good yield. Therefore, inorganic fertilizers like urea, muriate of potash, and triple super phosphate were developed. In order to encourage farmers to switch from traditional rice varieties to HYVs that are highly responsive to chemical fertilizers, the Sri Lankan government initiated the fertilizer subsidy in 1962. Though there was a significant increment in paddy and vegetable production with fertilizer subsidies, eventually farmers lost fertility in the croplands which further increased their dependency on external applications. This was mainly due to the myth that excess fertilizer would increase the yields of the crops. Excess urea application to paddy fields causes higher greenhouse gas emissions including Methane and Nitrous Oxide. Also, the intensive cropping systems resulted in the loss of soil organic matter. Since most of the high-yielding varieties are less resistant to plant diseases than traditional varieties, timely application of pesticides is of great importance.

According to the data of the Food and Agriculture Organization of the United Nations, agricultural pesticide use in Sri Lanka increased 43% from 1991 to 2018. From the conducted studies, it was reported that several pesticides were overapplied at rates 1.2–11 times the recommended application. Also, farmers in Welimada and Badulla areas in Sri Lanka had shown unsafe disposal of empty pesticide containers and washed their sprayers in common water bodies. Amphibians, fish, beetles, and insects are, facing a wide range of adverse outcomes due to pesticides like diazinon, captan, thiamethoxam, and chlorantraniliprole. The best example is the reduction of the earthworm population which is a beneficial animal in soil rejuvenation, in agricultural soil.

This has caused destruction in terrestrial and aquatic ecosystems, negatively affecting the food chains. The misuse of chemical weedicides also has the same effects as pesticides in the ecosystem. Over usage of inorganic chemicals also destroys the beneficial microbial population in soil, causing hindrance for nutrients circulating in soil. From a study conducted to assess the heavy metals and health risk in the vegetable market in Dambulla, it was revealed that Pb and Cd content in potato, brinjal, and bitter gourd has exceeded the maximum permissible levels. This can be due to excess accumulation of heavy metals; Cd, Pb, and as in soil from over-application of pesticides and fertilizers. The practice of monoculture has a negative impact on many soil properties, which include the movement of silt from the surface to subsurface layers and a decrease in soil organic carbon content. The use of a selected set of hybrid seeds and heavy use of weedicides has had deleterious effects on both flora and fauna. The heavy use of agricultural machinery and ploughs in tillage operations has It is a timely requirement to discuss and implement necessary measures to mitigate the adverse effects caused by the green revolution to ensure the sustainability of agricultural ecosystems to feed the increasing population.

The main factors that lead to pesticide and fertilizer overapplication include the lack of awareness among farmers about the importance of using fertilizer and pesticides according to recommendations, health and environmental risks associated with high pesticide and fertilizer use and the perception that increased pesticide and fertilizer improve yields. Awareness campaigns should be conducted to give knowledge to small and medium-scale farmers about correct pesticide and fertilizer usage and disposal. Farmers need to be encouraged to obtain a GAP(Good Agricultural Practice ) certificate for their produce following the given guidelines to ensure the quality and safety of the product.

Effective implementation of precision agriculture and integrated pest management also give realistic solutions for pest control in agroecosystems.

Instead of weedicides hand weeding and transplanting could be practiced if the plants are grown in rows by transplanting. Using multiple cropping systems along with legumes, cover cropping, mulching, addition of crop residues after harvesting and addition of composts are some very simple measures that farmers can adopt to ensure soil rejuvenation. Tillage practices such as zero tillage and minimum tillage are encouraged to protect the soil structure properties. Ensuring the sustainability of agroecosystems should be given top priority in order to feed the escalating population with the limited resources on land.