The Kingdom of Tonga is located in the Western Pacific ocean and is made up of 171 islands, 36 of which are inhabited (Mimura, 1997). The impacts of changing climate are arguable most prevalent in the small island nation states of the South Pacific Ocean. Tonga is no exception, given the nations reliance on coastal agriculture and coral reef ecosystems for survival and economic productivity (Barnett, 2011). Tonga's culture centers around family and community connectivity using food as a centerpiece in their cultural practice, both in daily life and special ceremonies (Bennardo, 2017). Agriculture is integrated into every aspect of life in Tonga.
Climate Change Hazards
Sea Level Rise
Global sea levels have been increasing at an average rate of 3.2 mm (+/- 0.4 mm) per year (IPCC, 2014). South Pacific islands often face a greater average sea level rise than cooler areas due to their proximity to the relatively warm equator and thermal expansion (IPCC, 2014). Tonga faces an average annual sea level rise of about 6 mm, almost twice the value of the global average (Englart, 2011; Australia, 2011). Projections for Tonga show the possibility of a 5 cm-15 cm sea level rise by 2030 and a 20 cm-60 cm rise by 2090 (Englart, 2011).
Sea level rise in the Pacific Ocean fluctuates with El Niño and La Niña oscillation patterns (IPCC, 2014). During La Niña events, the trade winds increase, pushing a large warm water mass across to the Western Pacific (IPCC, 2014). La Niña exposes small islands to further thermal expansion from the warm mass of water and sea levels rise (IPCC, 2014). These climate events cause (+/-) 20 cm-30 cm fluctuations in sea levels putting small islands in the Pacific at much greater risk (IPCC, 2014).
The impact of a warming global climate has shown to decrease the frequency of storms, however the number of extreme weather events is increasing (IPCC, 2014). In Tonga, the normal frequency of category five cyclones is every five to ten years (Parliament of Tonga, 2015). However between 2013 and 2015, Tonga experienced two category five cyclones (Parliament of Tonga, 2015). Tropical storm Ian, a category five cyclone hit Tonga in 2015, displacing 70% of Ha’apai residents (Woonton, 2015). The destruction of homes and loss of resources in the region was valued at forty-eight million US dollars, forcing the region to declare a state of emergency for relief efforts (Woonton, 2015).
Exposure and Vunerability
Sea Level Rise Threatens Agriculture
Salt water intrusion especially during weather events with substantial storm surge, affects agriculture in the South Pacific (Australia, 2011). When sea levels rise and inundate fertile crop land, the crops are often destroyed along with the productivity of the soil (IPCC, 2014). As the soil becomes infertile, crops are planted further inland to find soil that is adequate for productivity (Barnett, 2011). The small islands provide a finite amount of space and resources in terms of finding new suitable cropland (Mimura, 1997; Barnett, 2011). Stresses on agricultural land produce similar impacts on the economy; in order to preserve food security Tonga must increase its imports to accommodate for the loss of agricultural productivity (Mimura, 1997; IPCC, 2014).
Fresh Water Aquifers At Risk
Water security is a threat in Tonga stemming from sea level rise and a changing climate (Englart, 2011; Parliament of Tonga, 2015). Along with ocean temperatures, mean annual air temperatures are rising, and the number of days of extreme heat are increasing (Australia, 2011; IPCC, 2014). Furthermore, overall rainfall in the islands is decreasing (Australia, 2011). The freshwater aquifers on Tonga rely almost exclusively on rainwater for replenishment (Parliament of Tonga, 2015).
Water security problems also threaten the livelihood of communities in Tonga due to their economic dynamics. Tonga relies heavily on imports and exports for economic productivity and resource acquisition (IPCC, 2014). Freshwater insecurity on Tonga increases the need for freshwater imports, further stressing Tonga’s, already fairly weak economy (Englart, 2011; IPCC, 2014). The need for imports of freshwater are also amplified by growing demand due to population growth, land use change, and urbanization (IPCC, 2014).
Impacts of Coral Bleaching
Rising ocean temperatures also have negative effects on coral reef ecosystems (Barnett, 2011). Ocean acidification is increasing along with ocean temperature as the seas absorb carbon dioxide, mostly from anthropogenic emissions (IPCC, 2014). As oceans become warmer and more acidic, coral bleaching occurs from the acidity and thermal stress of the aquatic environment (Brandt, 2009; Barnett, 2011; IPCC, 2014). The coral reefs are a diverse aquatic ecosystem and are very productive for offshore fishing (Brandt, 2009; IPCC, 2014). Coral reefs also act as a buffer for ocean waves, and coral reef mortality is linked to increased coastal erosion (Brandt, 2009; Barnett, 2011). Coral bleaching and mortality is also linked to disease in coral and mortality of reef building coral organisms (Brandt, 2009). These multifaceted feedbacks accelerate the destruction of coral reefs and undermine Tongan resilience (Brandt, 2009).
Coastal Mangrove Erosion
The increase in coastal erosion from coral bleaching and mortality also negatively affects coastal mangrove ecosystems, which act as another natural buffer to ocean waves (Gillman, 2008). When saltwater inundation reaches coastal mangroves it deposits a dense layer of sediment over the root structure, disrupting the natural uptake of nutrients into the mangrove (Gillman, 2008). The saline intrusion can weaken or kill much of the vegetation in the mangrove (Gillman, 2008). In events of greater sea level rise or storm surge, ocean waves can erode sediment around the root structures, destroying trees in the mangroves (Gillman, 2008).
Trees in the mangrove adapt by migrating inland further to survive, however, they face competition from previously established terrestrial plants, that is if the hydrology further inland can properly support mangroves (Gillman, 2008). The overall effect is often a decline in mangroves, or disappearance of the ecosystem all together, undermining the natural coastal buffer (Gillman, 2008).
Adaptation and Resilience
Tonga's reliance on agriculture for economic and human welfare is one of their highest priorities when facing climate change. Some adaptation strategies that would increase their resilience are:
- On improving agricultural practices further inland to substantially reduce the threat of rising seas
- On diversifying Tonga's economic trade to be more economically resilient, especially relating to affording relief imports as necessary
- On the dynamics of climate threats in Tonga and how to contribute to adaptation at the local level
- Improvements to withstand the impacts of extreme weather events more effectively
- Investing in renewable energy infrastructure to reduce Tonga's reliance on fuel imports, further reducing stress on their economic structure
- Installing underwater structures to imitate the wave buffering action of coral reefs, which lost their full functionality due to coral bleaching, as well as permanent seawall structures to protect against flooding and storm surge
These adaptation efforts may help Tonga preserve their civilization and their culture in the face of the accelerating impacts of global climate change.
About the author
My name is Jesse Lowell I am from Gray, Maine. I made this web page in the spring of 2017 as part of a research project for my Adaptation to Climate Change course at St. Lawrence University. In the summer of 2017 I traveled to Shaktoolik, Savoonga, and Gamble, Alaska to continue researching climate impacts, specifically impacting these indigenous communities. Everyone depends on and deserves a livable climate.
IPCC, 2014: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 688 pp.
Englart, J. (2011, December 10). Tonga and climate change: Sione Taulo Fulivai "Our people are on the line, our cultures are going to disappear."
Australia. (2011, November). Current and Future Climate of Tonga.
Parliament of Tonga. (2015, September 14). Parliament's soft closing ceremony marks end 2016/2017 sessions.
Woonton, N. (2015, March 16). Secretariat of the Pacific Regional Environment Programme.
Mimura, N., & Pelesikoti, N. (1997). VULNERABILITY OF TONGA TO FUTURE SEA-LEVEL RISE. Journal of Coastal Research, 117-132.
Barnett, J., 2011: Dangerous climate change in the Pacific Islands: food production and food security. Regional Environmental Change, 11(1), 229-237.
Brandt, M.E. and J.W. McManus, 2009: Disease incidence is related to bleaching extent in reef-building corals. Ecology, 90(10), 2859-2867.
Bennardo , G. (2017). Tonga.
Gilman, E.L., J. Ellison, N.C. Duke, and C. Field, 2008: Threats to mangroves from climate change and adaptation options: a review. Aquatic Botany, 89(2), 237- 250.
European Space Agency
Weather Channel Online
Jamland; Blogspot Online
Encyclopedia Britannica Inc.