<p>Climate change is a global threat, projected to steadily worsen in its impact on the natural environment and anthropogenic activities" thus, becoming a compounding economic burden. Since weather and its associated climatic factors are the key determinants of crop production, the agricultural sector is considered to be the sector most vulnerable to climate change. Food security implies sustainable food production growth, sufficient to feed the demand of growing populations. Already, this fundamental human need is under threat due to irreversible climate fluctuations such as higher temperatures, changing precipitation patterns, and greater weather variability. This aspect of climate change has proven most serious for developing nations, particularly regions such as South Asia, where the agricultural sector plays an integral part of the economy. As a South Asian developing nation, the island of Sri Lanka and its agricultural sector has experienced the impacts of climate at a level above the global average. Hence, it is a matter of urgency to assess the projected future impacts of climate change on agricultural productivity and the overall economy and its welfare component, to develop potential adaptation policies and strategies.</p> <p>The objectives of this thesis were to analyse the vulnerability of the Sri Lankan agricultural sector to climate change, assess the economy-wide implications of the negative impacts in agricultural productivity, evaluate potential adaptation strategies to mitigate the negative impacts on the agricultural sector and examine the economic consequences of climate change for South Asian regional agriculture. Five research studies were conducted using three main methodologies to achieve these objectives. This entailed: (1) the development of four vulnerability indices, incorporating values based on environmental and socio-economic indicators, to assess the agricultural sector's vulnerability to climate change" (2) the construction by the author of, a singlecountry CGE model, known as ORANI-G-SL, to assess the economy-wide implications of the climate change impacts on the agricultural sector and to evaluate potential adaptation strategies" (3) the employment of the GTAP-E model, an energyenvironmental substitution modification of the GTAP global CGE model, to examine the economic consequences of climate change for South Asian regional agriculture.</p> <p>The overall results revealed that agricultural vulnerability to climate change in Sri Lanka remains at a moderate level, notwithstanding the increasing trend over the study period. Hence, inadequate adaptation strategies could increase the vulnerability in the future. The simulation results of the ORANI-G-SL modelling revealed economic contraction in both the short and long-run scenarios due to climate change-induced crop productivity changes in the agricultural sector. Compared to the baseline scenario, Sri Lanka's GDP and several macroeconomic variables including household consumption, government expenditure and investment, net exports, aggregate employment, and real wages were projected to decline in the future. The country will experience a decline in agricultural output leading to inflationary food prices which will threaten food security. These changes reflect the overall economic contraction and decline in household welfare. Improving agricultural productivity by greater investment in agricultural research and development and the expansion of agricultural land areas were both considered to be beneficial adaptation strategies, increasing GDP and the other major macroeconomic variables by increasing agricultural production and decreasing food prices. However, increasing investment in agricultural research and development was shown to be more beneficial for Sri Lanka than agricultural land expansion, due to limitations in the potential for extending farming lands. Furthermore, all South Asian economies will experience a contraction by 2050 due to the impacts of climate change on regional agricultural sectors, with Sri Lanka being one of the hardest hit countries in the region. All South Asian nations will experience a decline in GDP and other important macroeconomic variables by 2050. The GTAP model also projects a decline in agricultural production, causing an upsurge in the prices of most agricultural produce and a consequential rise in the cost of living by 2050. A simultaneous decline in the average real wage will reduce household income, resulting in a reduction in consumption and threatening future food security in the region. Most interestingly, the study revealed that the projected reduction in agricultural labour productivity due to heat stress will cause more severe economic losses in the region than the other two forms of climate change-induced losses (crop productivity loss and land productivity loss due to rising sea levels). It was also confirmed that the negative economic impacts faced by South Asian countries exceeded the projected global averages for their respective income groups.</p> <p>The study results reveal the importance of implementing adaptation strategies and the urgency with which this needs to occur. Thus, the study provides decision-makers with options for mitigating the impacts of climate change and adaptation strategies and suggests some vital policy implications to consider in addressing this issue. The development of the single-country ORANI-G-SL model offers a platform for other researchers and can be used in the context of other developing nations by incorporating local data.</p>