Despite less frequent disasters as compared to other Pacific Island Countries, Tonga experiences a high degree of economic and social shock during disaster years: over 40 percent of the population of Tonga is affected during a typical disaster year and Tonga’s economic losses are equivalent to 14 percent of gross domestic product (GDP). The probability and likelihood of natural disasters increasing under future climate events would bring more serious and greater economic losses. In the capital city of Tonga, a cyclone with a 100-year return period, or with a 50% chance of occurring within the current generation, could likely inflict damage equivalent to 60 percent of GDP. Tonga is at risk to tropical cyclones and storms, tsunamis, volcanic activity, and drought.
This section provides a summary of key natural hazards and their associated socioeconomic impacts in a given country. It allows for a quick assessment of most vulnerable areas through the spatial comparison of natural hazard data with development data, thereby identifying exposed livelihoods and natural systems.
The charts provide overview of the most frequent natural disaster in a given country and understand the impacts of those disasters on human populations.
Climate change is now recognized to have a significant impact on disaster management efforts and pose a significant threat to the efforts to meet the growing needs of the most vulnerable populations. The demands of disaster risk management are such that concise, clear, and reliable information is crucial. The information presented here offers insight into the frequency, impact and occurrence of natural hazards. Source (PDF)
Understanding natural hazard occurrence as well as historical climate conditions, in relation to development contexts, is critical to understanding a country’s historical vulnerability. This tool allows the visualization of different natural hazards or historical climate conditions with socio-economic and development datasets. Select the Development Context and either a Natural Hazard or Climate Condition and overlay horizontally by sliding the toggle left or right to gain a broader sense of historically vulnerable areas.
Data presented under Historical Climate Conditions are reanalysis products derived from ERA5-Land data. ERA5-Land is a global land-surface dataset at 9 km resolution, consistent with atmospheric data from the ERA5 reanalysis from 1950 onward. Climate reanalyses combine past observations with models to generate consistent time series of multiple climate variables. They provide a comprehensive description of the observed climate as it has evolved during recent decades, on 3D grids at sub-daily intervals.
This data has been collected, aggregated and processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative.
- Cyclones in Tonga commonly occur between November and April, on average 1.3 times per year. Cyclones causing serious damage occur approximately once every 10 years.
- Tonga’s southwestern location bordering the Pacific ”Ring of Fire” increases its risk to tsunamis. This area of high tectonic activity has had 115 tsunamis since 1900. Tonga’s volcanic activity has been recorded since 1839, including submarine eruptions and emerging and disappearing islands. In terms of impact on human settlement, there is an active volcano on the island of Niuafo’ou.
- The last three major droughts that have occurred in Tonga in 1983, 1998, and 2006 have been directly linked to the May 1982–June 1983, May 1997–April 1998, and September 2006–January 2007 El Niño events. Since the mid-1970s, there has been a tendency for more frequent El Niño episodes, and without significant intervening La Niña events, points to more prolonged drought periods in the Pacific under future climate trends.
More information on natural hazards can be found at ThinkHazard.
- A current lack of effective or efficient water storage infrastructure endangers agricultural production and water quality and quantity for human consumption in Tonga. The likelihood of increased sedimentation and salt water intrusion under future sea level rise and extended drought conditions could cripple existing water infrastructure.
- Hurricane-strength cyclones, or those with winds stronger than 63 knots or 117 km/hr, have increased systematically in the southwest Pacific and the region now experiences on average four hurricane-strength cyclones a year. Increased cyclone intensity under possibly future climate change remains a matter of debate among the climate science community, however likely trends of drier and warmer climate and an increase in sea surface temperatures these disasters are likely to increase.
- A general increase in tropical cyclone intensity (lower central pressures, stronger winds and higher peak and mean precipitation intensities) appears likely, as does an eastward extension in the area of formation. Early Warning Systems need to be expanded and improved and better climate modeling available to prepare for impending storms and their correlative effects.
- Future climate is expected to become more El-Nino like, resulting in more droughts in the southern Pacific and more rain and consequent floods in the equatorial Pacific and Cyclones are expected to increase in intensity by about 5–20 percent. Risk management of natural hazards (RMNH) such as Planting mangroves to stabilize land against erosion and managing.
- Expected sea level rise may completely inundate the villages of Villages of Kanokupolu-Ha’akili-‘Ahau, Nukuleka-Talafo’ou-Navutoka-Manuka and all the areas East of Sopu and Siesia at Nukunukumotu Island and Atata Island. A long lasting and effective foreshore protection seawall similar to the present Nuku’alofa foreshore protection would minimize and flooding in these and other low-lying areas.