Key findings – Tonga
Tonga is ranked among the most disaster-prone nations globally due to its high exposure to natural disasters, rising sea levels, and limited adaptive capacity. It faces many challenges from climate change, particularly sea level rise, which is occurring at a rate exceeding the global average. The low elevation of many of Tonga’s islands amplifies their vulnerability to inundation and storm surges, infrastructure damage, groundwater salinization, and population displacement.
By 2051, routine flooding in the capital city of Nuku’alofa is projected under moderate sea level rise, with chronic flooding expected by 2059. Rainfall projections for Tonga are highly uncertain due to disagreement among climate models, but in a dry future scenario, dry season rainfall could decrease by up to 15% in the mid-term, severely impacting water availability in already drought-prone islands. With most of Tonga’s islands lacking surface water resources, water supply is highly dependent on rainwater harvesting and groundwater from freshwater lenses. The heavy dependence on rainfall makes communities particularly vulnerable to droughts and unpredictable climate patterns. Agriculture, a cornerstone of Tonga’s economy, is primarily subsistence and semi-subsistence based, making it especially vulnerable to climate impacts.
To enable sustainable access to high-quality water while protecting ecosystems critical to the nation’s resilience and livelihoods, recommended interventions include:
- Expanding rainwater harvesting infrastructure to meet future water demand, and combining residential rainwater harvesting with improved business water systems to increase water security during dry periods.
- Establishing and maintaining comprehensive groundwater monitoring
- Developing models and frameworks to predict the impacts of droughts on freshwater lenses and disseminating information to residents
- Providing advice on suitable crops for seasons, ensuring resilient crops for dry conditions, and investigating the expansion of irrigation systems to address increased rainfall variability and dry season rainfall shortages.
- Protecting mangrove ecosystems to maximise coastal protection against storm surges and sea level rise
- Improving water quality monitoring of freshwater lenses to identify sources of pollution and maintain protection zones.
- Establishing and maintaining water quality monitoring systems for rainwater harvesting systems.
