Wednesday, 18 September 2013

Climate Change Models Shift Boundaries of Agro-Ecological Zones in Sri Lanka

By Muththuwatta, L.P. and Liyanage, P.K.N.C.

Climate change models for Sri Lanka suggest that profound and complex changes in rainfall patterns are becoming a reality.. It’s never too early to consider what this means and how it could impact agriculture and therefore all of us. 

The news that climate change will affect Sri Lanka’s weather will surprise very few these days. However, a recent study1 projecting rainfall distribution patterns in Sri Lanka for 2050 warns that climatic zones could shift. It also suggests that the intensity of rainfall will vary more greatly than observed over recent times. The findings reported by Muththuwatta and Liyanage, have important implications for agriculture – from farmers to policymakers.

With global temperatures warming over the past century, Sri Lanka has already displayed its share of signs of climate change. The resulting extreme weather events have even now affected agricultural production. Concerns for water and food security for a projected global population of 9.6 billion in 2050 are high. In its 2007 assessment report, the Intergovernmental Panel on Climate Change (IPCC) stated that the nature of changes will vary across different geographical regions and development statuses. It added that the way regions respond and adapt will also affect climate change.

Using rainfall data from a baseline period of 1970 to 2000, the researchers analysed a climate model projection to 2050 and looked at how and where rainfall in the major agro-ecological zones may change. In Figure 1 they show climatic zone boundaries could be affected due to changes in rainfall in 2050. The changes of areas under major climate zones are shown in Table 1.

Figure 1: Changes in climatic zone boundaries by 2050 

Re-drawing boundaries and policies?

The key findings show that average rainfall in Sri Lanka in 2050 will increase by 155 mm or about 7%, compared to the period 1970-2000, with the highest proportional increase of rainfall predicted for southern and south-eastern parts of the country. It shows the Dry Zone of the island shrinking by 8.1%. But the biggest change appears to be in the Intermediate Zone where in 2050, it is predicted to expand by 21.8%.

The model also shows that of the 48 agro-ecological regions, 11 agro-ecological regions display decreasing rainfall patterns. The rest of the agro-ecological regions display an increasing trend of rainfall in the future, and of these, 11 show the greatest changes.

A silver lining

The model predicts that two of the regions now included in the Dry Zone could be re-classified as Intermediate, while three currently in the Intermediate Zone could be eligible to be Wet Zone regions by 2050. With intensity, duration and distribution of rainfall changing beyond current boundaries of climatic zones by 2050, it’s time to re-think long term agricultural policies.

Contrary to most gloomy climate change forecasts, these results are welcome news for Sri Lanka. But they come tempered with a prediction that although there will be more rain in a greater expanse of land, the variability of rainfall in 11 of the 48 agro-ecological regions exceeds data from the baseline period. What this means is that we can expect an increase in extreme rainfall too which will greatly affect food production.
Increased food demand

As Sri Lanka increases her per capita income, higher incomes and a larger population will result in increased food demand. Without adaptation and mitigation plans in place to offset climate change impacts, self-sufficiency in major crops and water and food security will be seriously compromised. This is a prospect that a developing economy can ill afford, especially an agricultural-based one such as Sri Lanka. Paddy cultivation is notoriously susceptible to variations of rainfall while other exports like tea, rubber, and coconut, also depend on rainfall during crucial growth periods.

The global trend is expected to continue and countries are gearing up to deal with it. For Sri Lanka, analysing the magnitude and areas of climate change and how water resources and agriculture will be impacted over time will be critical to being better prepared to face them.

Planning for the future

It is clear that forward planning is required to mitigate the impacts of climate change as well as to formulate adaptation strategies. The projected data for 2050 in this study suggests that the type of agro-ecological area could change in several regions. This implies that crops cultivated at present may be affected and may provide benefits to farmers and agriculturalists in areas hitherto disadvantaged by climate. Co-author Muththuwatta says, “This information is very valuable for those planning to expand crops into new, non-traditional areas as well as policy makers. All agriculture and livestock farming could be affected.”     
Approaches such as integrated water resources management, closer collaboration and knowledge sharing will be key to good management practices and governance. Research is vital to minimise the inherent errors in climate change modelling, and decreases risk and uncertainty. Studies of other climate variables such as temperature and evapotranspiration are necessary to estimate the water availability and requirement for different crops under future climate projections.  While the study brings hope that climate change may bring advantages as well as disasters, there is no better advantage we could have than good preparation.  


  1. Thank you for the informative post. could you please add a link to the full study (publication) where further details can be found? thank you very much

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