As we approach mid-2025, it may be easy to forget last year’s record global weather anomalies associated with global warming and the recent El Niño event. This cyclical phenomenon occurs in the Pacific Ocean and significantly affects weather patterns, affecting millions of people living along the eastern and western Pacific coasts, as well as in countries across the Indian Ocean. El Niño and other climate drivers also cause more frequent extreme weather events such as droughts and floods. These events may trigger disease outbreaks, crop failures, rising prices and food insecurity, potentially driving individuals and families towards economic hardship, displacement, or malnutrition. However, what evidence is available about the nature and extent of the damage to agriculture, trade, health, and broader ripple effects like migration and conflict? To explore this question, the UK Foreign, Commonwealth and Development Office commissioned 3ie to systematically review research papers on the socio-economic effects of El Niño in low- and middle-income countries across South Asia, South-East Asia and Oceania which may be more vulnerable to climate shocks1.
The evidence is recent and concentrated on few outcomes and countries
We found 88 studies exploring the association between El Niño and economic and health outcomes, but no studies exploring the effects on food security, migration or social conflict. The evidence on the economic effects of El Niño primarily focuses on agricultural output and productivity, with some studies also examining consumer and commodity prices. When it comes to health, the most commonly studied outcome is the incidence of vector-borne diseases such as dengue.
Most research on the socio-economic effects of El Niño has been undertaken over the last decade, with two-thirds of the included studies published after 2013. Most of the evidence comes from just a few countries: India (20% of all included studies), Indonesia (20%), Malaysia (11%), Philippines (11%), and Bangladesh (9%).
El Niño’s toll: declining agricultural yields at the Indo-Pacific level
We found that El Niño events are associated with reduced agricultural production and productivity in Indo-Pacific countries. This is no surprise given the overall reduction in rainfall and increased risk of drought which accompany El Niño events in the region. Effects varied by crop, geographical region, and other factors related to agricultural production such as irrigation systems and seasonality. The evidence also suggested that agricultural output and yield may recover after the initial contraction observed during the El Niño events.
We found no effect of El Niño events on consumer and commodity prices or the incidence of vector-borne diseases such as dengue. However, the evidence varied significantly. For example, we found contrasting results for the effects of El Niño on the incidence of vector-borne diseases even between studies from the same country. The evidence was insufficient for a quantitative analysis, preventing synthesis of results for other outcomes. We focused subsequent analyses on countries with the most data (India, Indonesia, Philippines, Malaysia, Bangladesh) and two key regions (Lower Mekong River and Oceania), using narrative synthesis to explore the varying cascading effects across individual studies.
High risk of bias undermines the quality of studies
Our review of the studies revealed a generally high risk of bias in estimating the socio-economic effects of El Niño. We rated seven out of ten studies as having issues with study design, data quality, and/or selective reporting. For example, many studies struggled to isolate the effect of the climate driver from other factors like recurring data patterns, temperature changes, precipitation, technological innovations, or shifts in population immunity, all of which could have influenced the outcomes. Future research should adopt robust methodologies, use mixed methods, and consider regional and local differences.
Strategies and research priorities to address El Niño
Addressing the varied effects of El Niño requires several key considerations. Firstly, adaptation strategies should be tailored to fit specific local and regional contexts. Secondly, policies need to be flexible and adaptable to changing circumstances. Thirdly, proactive and preventive strategies can help mitigate adverse effects.
Further research is required in the following areas to address gaps in our understanding of how El Niño affects societies and economies of low- and middle-income countries in the Indo-Pacific region:
- We found no evidence on how this climate driver influences food security, migration and social conflict.
- There is limited research on the differential effects by magnitude of the El Niño events.
- We found no studies exploring the combined effects of El Niño and the positive Indian Ocean Dipole (+IOD).
To our knowledge, our systematic review is the first to focus on climate drivers’ socio-economic effects at the Indo-Pacific level and can offer valuable insights for researchers (published article) and practitioners alike (policy brief).
1The review also explored the effects of the positive phase of the Indian Ocean Dipole (+IOD), another climate driver affecting the region of interest. However, +IOD has not been explored enough to have sufficient data for a meaningful quantitative synthesis.
