El Nino and La Nina: Understanding Their Impact on Agriculture

El Niño and La Niña, the climatic siblings whose dance dictates the ebb and flow of global weather patterns.

El Nino and La Nina: Understanding Their Impact on Agriculture
El Nino and La Nina: Understanding Their Impact on Agriculture
Hurmat Zehra
December 15, 2023
Blogs

Once upon a time, in the vast expanse of the Pacific Ocean, there existed two powerful siblings — El Nino and La Nina. They were not ordinary siblings; they were atmospheric forces that held the key to the delicate balance of weather patterns across the globe. El Nino, the older brother, was known for his warm and unpredictable nature. He could heat the waters of the Pacific, sending ripples of change throughout the atmosphere. People often called him the "little boy" or "Christ Child" because his arrival was around Christmas time.

On the other side was La Nina, the younger sister, with a cooler temperament. She had the power to bring about a chill in the Pacific waters, creating a contrasting impact on weather patterns. La Nina was often associated with strength and determination, and her arrival was seen as a force of nature, capable of shaping the climate for months on end.

Recent years show increased global warming and the catastrophe of the greenhouse effect owing to human activities, especially industrialization. The agricultural sector faces regular fluctuations in crop yields due to erratic weather conditions. Scientists are intrigued to study the short-term changes in weather patterns to assist in predicting the near future to mitigate future risks. Understanding the effects of these events is essential for farmers, policymakers, and researchers alike.  

In this blog post, we will delve into the harmonious coexistence story of the siblings, El Nino and La Nina, allowing for a natural ebb and flow in the climate. However, while there were times when the balance was disrupted, leading to unforeseen consequences for the underwater world exploring their mechanisms and uncovering how they impact agriculture, shaping the livelihoods of farming communities worldwide.

Under normal circumstances, permanent east-to-west winds known as trade winds blow westward along the equator in the Pacific Ocean, moving warm water from South America toward Asia. The sun’s rays afflict the equator’s surface directly and the area receives a constant 12 hours of direct sunlight a day. The wave action replaces warm water with nutrient-rich cold water rising from the deep ocean in a process known as upwelling. This burst of nutrients from the depth drives seaweed growth and supports vast blooms of phytoplankton — microscopic organisms — which are a crucial energy source for large animal populations creating a robust marine food chain.

However, due to disruptions in climate patterns, the rays hit directly on the equatorial belt for a longer time, the Central Pacific is heated more, and the sea surface temperature (SST) rises accordingly. The two opposite phenomena spring due to this action.

Difference between El Nino and La Nina

In the vast expanse of the Pacific Ocean, the two powerful siblings, El Nino and La Nina, held sway over the delicate balance of weather patterns. The graph below shows a historical overview of the occurrence of these events:

El Nino, the older brother with warm and unpredictable tendencies, possessed the ability to weaken the normal trade winds, redirecting warm water towards the western coastlines of the Americas. This disruption caused a diminishing upwelling of cold water, unsettling the natural ecosystem below. On the other side was La Niña, the younger sister with a cooler temperament. When La Nina took charge, the trade winds intensified, showcasing her determination. This resulted in a robust push of warm water towards Asia. Simultaneously, off the coast of the Americas, the upwelling of cold, nutrient-rich water increased.

What is El Nino?

El Nino is a Spanish word that means “the little boy or Christ-child”. The little boy brings a warm phase of the El Nino-Southern Oscillation (ENSO) cycle, characterized by the abnormal warming of sea surface temperatures (SST) in the central and eastern tropical Pacific Ocean. He occurs roughly every 3 to 7 years, disrupting atmospheric circulation patterns and leading to significant global climate anomalies that could persist for 9 to 12 months. According to the National Oceanic and Atmospheric Administration (NOAA), El Nino generally occurs more frequently than La Nina. The last sighting of Brother El Niño was in the winter of 2018-2019.

El Nino, the older brother with warm and unpredictable tendencies, could weaken or even reverse the normal trade winds. As he did so, sea temperatures in the tropical eastern Pacific rose 0.5 degrees Celsius above the long-term average, setting off a cascade of changes in oceanic and atmospheric conditions. This alteration triggered a causal nexus, a complex interplay that reverberated across the globe, influencing weather systems far and wide. The very heartbeat of the ocean seemed to synchronize with El Nino's whims, creating a symphony of climatic effects on a global scale.

What is La Nina

The word “La Nina” also originates from Spanish which means “the little girl”. She embraces the cold phase of ENSO. The ENSO cycle refers to the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West). La Nina brings normal east-to-west winds in the Pacific with a slightly higher tendency. The strong tread wind pushes warm seawater to Australia’s East coast and warm water begins to deplete near the Peru coast. This depletion is filled by cold seawater from the lower level of sea replacement. 

Effects on  Overall Global Climate

  1. Temperatures: Brother El Nino blows to warm the central and eastern equatorial Pacific Ocean during March and April 2023 creating a climatic spectacle. Resultingly surface temperatures soared several degrees above normal, forming a heated zone around the South American coast that extended hundreds of kilometers westward. The map below of sea surface temperature anomalies on April 4, 2023, painted a vivid picture of this warming phenomenon. According to data from the Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) project, offshore waters of Peru were approximately 6°C (10.8°F) warmer than usual on that date, illustrating the profound impact of El Nino's influence on the ocean's thermal tapestry in the figure below.

In contrast, the good sister  La Nina leads to a cooling of sea surface temperatures in the central and eastern equatorial Pacific. However, regions such as the western Pacific, Indian Ocean, and parts of the Americas may experience warmer-than-average temperatures. The collective action of both siblings is evident with the scale of anomalies in global temperatures shown below, it also shows that the equatorial areas are the most affected by their actions. 

  1. Changes in Atmospheric Circulation: The atmospheric circulation patterns are altered, leading to changes in the location and intensity of the jet stream. In the case of El Nino, the strongest parts of the jet tend to shift southward and extend farther eastward across the North Pacific Ocean, reaching closer to North America and steering storms across the southern third of North America.

On the other hand, La Nina usually leads to a jet that is shifted poleward and retracted to the west. La Nina's retracted jet is often associated with a negative Pacific-North American pattern, with higher pressure south of Alaska, lower pressure over western Canada, and higher pressure over the Southeast. This in turn can encourage drier conditions through the southern US.

  1. Shifts in Rainfall Patterns: The figure below shows the distribution of precipitation in various regions across the globe. For example, it often leads to drier-than-average conditions in parts of Australia, Indonesia, and India, while increasing precipitation in the central and eastern Pacific, parts of South America, and the southern United States. Record amounts of rain poured in semi-arid northern Peru on March 9, 2023. Pacasmayo received 13.7 centimeters of rain in 24 hours, and Chiclayo saw 8.7 centimeters. This change was attributed by Peru's National Meteorology and Hydrology Service (Senamhi) as a coastal El Niño.

La Niña tends to enhance the natural patterns of precipitation, leading to increased rainfall in some regions and droughts in others as evidenced by the graph below. Areas like the western Pacific, Southeast Asia, and Australia often experience above-average rainfall, leading to an increased risk of flooding. The Indian monsoon tends to be influenced by La Nina, with some years experiencing enhanced rainfall. Drier-than-normal conditions are observed along the west coast of tropical South America, the Gulf Coast of the United States, and the Pampas region of southern South America.

  1. Wildfire Risk: Drier conditions in certain areas during El Nino can elevate the risk of wildfires. On February 7, 2009, the Australian state of Victoria experienced as many as 400 individual bushfires. They attribute the “Black Saturday Bushfires” the worst natural calamity in Australia’s history to the coastal El Nino effect. In contrast, since La Nina has a cool temperament no such risk is observed.

  1. Hurricane Activity: El Nino tends to suppress the development of hurricanes in the Atlantic basin but can enhance tropical cyclone activity in the central and eastern Pacific. Evidence shows the 2023 Pacific hurricane season was an active and destructive Pacific hurricane season. In the eastern Pacific basin (east of 140°W), 17 named storms formed; 10 of those became hurricanes, of which 8 strengthened into major hurricanes – double the seasonal average. The figure below shows the season summary map where the first system formed on June 27, 2023, and the last system dissipated on November 26, 2023.

In contrast, La Nina is associated with an increased likelihood of more active tropical cyclone and hurricane seasons in the Atlantic and Pacific basins. The decreased wind shear increases tropical activity. As of September 2021, there have been 88 tropical cyclones in the off-season, with the most recent being Tropical Storm Ana in May 2021.

 In 2022, Hurricane Ian, which swiped Cuba and the south-eastern US in late September, became the third costliest hurricane record

Effects on Agriculture

It is evident irrigation is the most important component of agriculture, so any changes in the annual amount of rainfall, water table, etc directly affect the crop yield and quality. With recent changes in world temperatures, rain cycles have also been affected drastically. The impacts on agriculture can vary, with some regions benefiting from increased rainfall while others may face drought conditions.

El Nino is associated with reduced rainfall in the East Pacific region, leading to droughts, water scarcity, and decreased soil moisture. In Australia, agriculture and its closely related sectors earn $155 billion a year with a 12% share of the  GDP. Climate change has damaged farming productivity, reducing broadacre farm profits by an average of 22% since 2000. Additionally, bushfires in Australia are a widespread and regular occurrence in the region. The 2019–20 Australian bushfire season or Black Summer was one of the most intense and catastrophic fire seasons on record in Australia. It caused 33 deaths destroyed 3,094 houses; and burned over 17 million hectares (ha), including 210,606 ha of land on Kangaroo Island and 90,000 ha of national park in South Australia.

As the world temperature rises, reaching up to 50 degrees Celsius in hotter parts of the world, heat strokes, and desertification have become a common phenomenon. This not only affects crops but also livestock and animal husbandry, leading to lower milk and meat production due to reduced availability of fodder and water scarcity. Warmer temperatures and altered precipitation patterns can lead to increased pest populations. This poses additional challenges to farmers demanding additional pest control measures and disease management strategies and ultimately increasing the costs for poor farmers.

In Cambodia annual average rice production changes from the average of the previous three years, between 1995 and 2014 (left), and simulated changes in beans, maize, rice, and vegetable yields during El Niño and La Niña years compared to average years (right):

A photo in this story

It is visible from the graph that while El Nino reduced the rice production, the latter shows an increase and the trend is general across other crops as well. However beans show an opposite trend, the yield improved during the El Nino period and was adversely affected in the coastal areas during the La Nina period.

In Vietnam, during La Nina years, maize production increases are on par with maize production losses in North and Central Vietnam. In South Vietnam, maize production increases during La Nina are only about half the size of maize production losses during El Nino. Overall, ENSO phases cause land area damage, but particularly El Nino years cause much more damage (408,000 ha) than La Nina years (114,000 ha). Overall, these figures are equivalent to losing 6 percent of the total rice area during El Nino and 2 percent during La Niña. 

The figure below shows crop model estimated deviations in rice, maize, and tomato yields of Vietnam during "moderate" and "strong" El Nino and La Nina years. On average La Nina gives a positive yield of all three crops in all three geographical zones. However, tomato yield is adversely affected in the north by a negative 7% fall. On the other hand moderate and strong El Nino reduce yield as a whole. The highest dip of 15% was observed in the southern region for both rice and maize.

A photo in this story

Geographical Impact

El Nino has occurred eight times since 1980, with the most recent major event, from 2014 to 2016, being the most severe, causing billions of dollars in damage to the west Pacific region. Meanwhile, La Nina has occurred six times since 1980 and has had both positive and negative impacts on agriculture and food security. As climate change intensifies, the swings from extreme El Niño to extreme La Nina are projected to occur more frequently.

In Lao PDR, 71% of flood or drought disasters since 1966 coincided with ENSO events, causing USD 625 million in damages, with the most severe instance in 1992. Cambodia experienced a significant El Nino event from late 2014 to mid-2016, resulting in higher temperatures, reduced rainfall, and a severe drought in 2016, one of the driest years in the last 50 years. In Vietnam, the 2016 El Nino affected 52 provinces, leading to drought and saltwater intrusion, particularly impacting 18 provinces with a population of 2 million people in urgent need of humanitarian aid. The Philippines faced a severe El Nino in 1997–1998, causing a significant reduction in rainfall, drought in two-thirds of the country, and destructive forest fires. In Myanmar, the 2016 El Nino resulted in water shortages in 1,700 villages, affecting 15 million people, primarily farmers, with ENSO impacts exhibiting localized variations.

Mitigation and Adaptation Strategies

According to World Bank Reports policy interventions can mitigate the negative impacts of El Nino and maximize the benefits from La Nina. The study under the name Striking Balance surveyed Cambodia, LAO PDR, Myanmar, the Philippines, and Vietnam reflected regional governments making gains in preparing for climate events like floods and other natural disasters, but more could be done to prepare for El Nino and La Nina specifically. Investing in early warning systems, developing national action plans, and cooperating with other East Asia–Pacific countries could boost resilience. This also includes drought-tolerant crop varieties, expanding irrigation, restricting rice exports, storing and distributing grains, expanding social protection coverage, and introducing food import subsidies. Protectionist cash transfer policies for the welfare of the vulnerable population are also an efficient solution. 

Vietnam has been a regional leader in working toward ENSO preparedness. The government took action as the 2015–2016 El Nino progressed. The government mobilized NGOs, international organizations, and local and national government agencies to support the different ENSO response measures. The figure bellow shows the timeline of Veitnami government’s action to mitigate the drought onset.


Conclusion

In the grand narrative of El Nino and La Nina, the climatic siblings whose dance dictated the ebb and flow of global weather patterns, the conclusion unfolded with a call to action—a harmonious response to mitigate their impactful effects. Recognizing the dynamic nature of these atmospheric forces, communities worldwide united in resilience and adaptation.

In the face of El Nino's warm embrace, strategies emerged to address the disruption of normal weather patterns. Enhanced climate preparedness became a beacon, as nations fortified themselves against the potential consequences of extreme events—be it intense heat, droughts, or altered precipitation patterns. Early warning systems, bolstered by advancements in meteorological technology, stood as guardians, providing vital information to vulnerable regions and allowing for timely evacuation and resource allocation.

During La Nina's cool interlude, the focus shifted to harnessing abundant natural resources. With strengthened trade winds and increased upwelling of nutrient-rich waters, sustainable practices in agriculture and fisheries thrived. Communities adapted resilient agricultural techniques, leveraging the climatic conditions to foster growth and abundance.

Recognizing the interconnectedness of the world's climate systems, nations collaborated to pool resources for comprehensive climate mitigation and adaptation strategies as reflected in the Striking Balance Report. This financial synergy aimed to address the socio-economic impacts, fortify infrastructure, and support vulnerable communities in the wake of El Nino and La Nina events.

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