Climate Change

Small islands, whether located in the tropics or higher latitudes, have characteristics which make them especially vulnerable to the effects of climate change, sea-level rise, and extreme events (very high confidence) ♦  Sea-level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening vital infrastructure, settlements and facilities that support the livelihood of island communities (very high confidence). ♦  There is strong evidence that under most climate change scenarios, water resources in small islands are likely to be seriously compromised (very high confidence). ♦  It is very likely that subsistence and commercial agriculture on small islands will be adversely affected by climate change (high confidence). IPCC 4th Assessment Report, 2007

Tonga Pilot Site
Wednesday, 09 June 2010 17:07

Pilot Site 1: ‘EUA ISLAND

'Eua national forest park, Tonga‘Eua is one of the oldest islands of the Pacific and the oldest in the Tongan archipelago. It lies at the southern end of the Tonga group of islands, south east of Tongatapu. The island is the third largest in the group measuring 19 km long and up to 7.5 km wide with an area of about 8500Ha. It has two administrative districts with a total of 14 villages and a population of just over 5,200 inhabitants (2006 Census).

Although most of its surface is covered by limestone, 'Eua is unique among Tonga's limestone islands in that its core consists of volcanic rocks, and these form exposed outcrops along the eastern ridge and eastern cliffs (Hoffmeister 1932; Bryan et al. 1972).

‘Eua serves as an important supplier of agricultural produce to Nuku’alofa, and increasingly (because the island has the only significant stands of native forest in Tonga), firewood and natural forest products such as medicines and custom material used in crafts, decoration, and personal adornment (‘Eua State of Environment report).

The Pilot Site

'Eua indigenous forestThe forest area of ‘Eua makes up the pilot site for the SPC/GTZ Programme on Adaptation to Climate Change in the Pacific Island Region. However, project activities will not be confined to the forest area as abandoned and degraded croplands will also be targeted for rehabilitation and sustainable agriculture development.

The indigenous forest of ‘Eua hosts at least eight flowering plant species found only on the island and these species are considered threatened. There are at least 16 other threatened species that can be found elsewhere in the Pacific. These threatened species require undisturbed forest for their continued survival.  Most of the ferns in Tonga are found only in ‘Eua, including one species unique to the island.

Current situation

The need to sustainably manage ‘Eua’s forest has been an issue raised by scientists for more than two decades. These concerns came from different sectors in regards to water quality, biodiversity, and cultural values.

‘Eua’s forest is currently under threat from agriculture conversion. Farmers are increasingly entering the state-owned forest to cultivate mainly kava and taro.  Most cultivation is on a semi to full commercial scale and a recent survey of the illegal farmers reveal varying socio-economic backgrounds. The normal clearance practice is to indiscriminately burn trees at the base, leaving it to die and rot. A recent comparative assessment showed clearance of indigenous forest to have accelerated since 2005. This pressure on the forest is expected to increase with growing population and economical pressure.

Alu vines, 'Eua, Tonga

kato alu, 'Eua, TongaConsultation workshops with the ‘Eua community reveal a growing concern towards the forest clearance, that is carried out by a handful of farmers. Concerns from the community were based largely on cultural reasons and for the protection of their water source. The forest provides material for local handicrafts, medicine, and food. The traditional ‘Eua basket, kato alu, is special in Tonga as it is made from vines (Epipremnum pinnatum, Araceae, aerial roots) now found only in the ‘Eua forest. Certain medicinal plants and trees can only be sourced from the Eua forest and is sought after by other islands.

The maintenance of ‘Eua’s forest is essential for ensuring a clean water supply for the island. Increased forest clearance for agriculture, removal of ground litter and vegetation, and roaming livestock has been blamed for the contamination of water sources.

A survey of the island reveals many abandoned croplands. Many of these abandoned sites are former squash fields and now taken over by guinea grass. With the increasing population and growing socio-economic demands, such idle land should be regarded with potential and soil amelioration and land management regimes explored.


Climate Change Impacts

A projected increase in temperature and rainfall show ‘Eua having the highest soil productivity and soil erosion risk level compared to the other islands. The risk of soil erosion is high for ‘Eua and Vava’u due to its rugged terrace formation. Predictions of increased frequency of extreme events such as increased rainfall and higher temperatures will make the forest of ‘Eua more vulnerable as most of the forest grows on highly erodable soils. The increasing pressure of farming sloping lands from the increasing population and export will undoubtedly exacerbate the impacts of the increasing temperature and rainfall (Manu, 2009).

Table 2    Range of increased mean temperature and increased annual rainfall (mm/year) for the island of ‘Eua projected by the SimCLIM Global Climate Model CSIRO 30 with the upper and lower boundary from the Global Projection IPPC SRES A1F1and B2.


Normalised Mean Temperature Change Pattern  (oC/oC)

Normalised Precipitation Change Pattern  (%/oC)

0.5 - 0.6

-12.8 to -11.0

Projected Year

Generated range of Increased Mean Temperature (oC)

Generated Range of Increased Annual Rainfall (mm/year)


23.78 - 23.85

1739 - 1794


23.86 - 24.03

1754 - 1832


24.14 - 24.97

1813 - 2067


24.56 - 27.11

1876 - 2596

(adapted from V. Manu, 2009)


Forest clearance in Eua National Park

The impacts of current land use practices in the ‘Eua forests will be aggravated in the face of climate change. Preliminary assessments in the field already show soil degradation in cultivated areas and the smothering of regenerating indigenous species by weeds in the cleared sites.  The impact of climate change on the forest ecosystem and biodiversity is yet to be determined but continuing forest clearance will be sure to amplify the impacts.

The vulnerability assessment of the agriculture sector in Tonga places ‘Eua as one of the more vulnerable islands. This is largely due to its high soil erosion risk factor and the scale and type of agriculture practised on the island.

The ‘Eua water supply heavily relies on rainfall patterns and distribution (‘Eua State of the Environment Report). Increased sedimentation and turbidity is often reported during periods of high rainfall when eroding soils and contaminants, such as chemicals used in nearby croplands, drain into the water catchments. During the drier season, organic waste sometimes settles in the pipelines causing blockages, which in turn contributes to the already low water pressure, further restricting water supply to the upper part of the island. According to figures from the Tonga Water Board, water usage has significantly increased in the island and this demand puts more pressure on the water supply (‘Eua State of the Environment Report). Previous studies recommend that it would be more economical to look after the watershed than maintaining expensive equipment such as water filters and purifiers to remove the contaminants.

SPC/GTZ Regional Programme on Adaptation to Climate Change focus

The focus of the project in ‘Eua is the development of a land use plan to:Forest clearance in 'Eua National Park for agriculture

1) reduce the vulnerability of ‘Eua’s forests and its island the community

2) promote sustainable agriculture practices and sustainable land management technologies to ease the pressure off forest areas and to cope with changing climate

Most of the agriculture clearance is for growing kava and efforts will be made to promote a cropping system where farmers will be encouraged to cultivate in already established croplands instead of targeting forest areas. Agroforestry and mixed cropping systems will be the focus of this programme and appropriate climate resilient crop varieties will be identified to ensure food security.

The project will also:

1) assess the vulnerability and adaptation capacity of the ‘Eua forest

2) support the establishment of forest monitoring plots and subsequent monitoring to record forest dynamics, carbon/biomass, and biodiversity

3) increase awareness and understanding of the ‘Eua community on climate change impacts and adaptation measures such as sustainable land management


Institutional set-up for implementation

All project activities are guided by the national project steering committee, chaired by the Director of the Ministry of Environment and Climate Change. Members include the Forestry Division, Agriculture Division, Lands Department, Civil Society Organisation, Meteorology Department, Tonga Water Board, Women’s Association and GTZ as secretariat.

A multi-disciplinary technical team is implementing the project in ‘Eua.  The team comprises of technical officers from the Ministry of Environment and Climate Change, the Forestry Division, the Agriculture Division, the Lands Department, the Tonga Water Board, and representatives from the ‘Eua community. The Ministry of Agriculture, Food, Forests, and Fisheries (MAFFF) is the assigned lead agency for implementation in ‘Eua.

A local taskforce has been set up to assist in local coordination, consultations and implementation. Most members of this team are decision-makers in their villages and districts. The taskforce members were nominated by the ‘Eua community during the ‘Eua planning workshop held in May 2010. Almost fifty participants representing various sectors and community organisations, including women and youth groups, developed a workplan for project activities at this May workshop.




Nakolo Pilot site, TongatapuThe village of Nakolo is in the district of Tatakamotonga, South East of Tongatapu with a population of around 450 (2006 Census). Nakolo is identified to be highly vulnerable to climate change as it sits on one of the most vulnerable soils in Tonga, the Lapaha soil series.

Tongatapu have the major share of the low level soil productivity risk area compared to other islands. High risk land areas in Tongatapu are villages and farmland within the Lapaha soil series. Lapaha soils series have none to very thin layer of the younger volcanic ash soils, with imperfect drainage, deficient in soil nutrients and sloping limitations (Manu V. 2009). Agriculture production is affected by the poor Lapaha soils. In some areas soils have been further degraded with intensive squash cultivation and high chemical fertiliser inputs.

Aside from the Lapaha soils, the location and elevation of Nakolo farmlands makes it more vulnerable to soil degradation. Nakolo sits on the most elevated position of the island at 65m and is directly exposed to the south-east trade winds. The main influences on Tonga’s weather are the south-east trades, the permanent belt of high pressure over the South Pacific, and the SouthPacific Convergence Zone (SPCZ). The south-east trades cause more erosion and brings with it sprays of salt water.

Farmlands facing the south are currently under utilised or abandoned. Areas that were once under production (mainly from mono-cropping) are now covered with hardy guinea grass and reeds. The project site encompasses 3 tax allotments facing south. From inland the allotments rundown a slope towards the coastline. With projections of increased rainfall and temperature, the productivity of the farmlands of Nakolo will worsen.

The focus of the project in Nakolo is:

1)     The establishment of sustainable land management technologies to reduce the vulnerability of the site

2)     The identification and implementation of suitable technologies to restore the productivity of the farmland soils

3)     The identification of appropriate adaptation technologies, such as drought resilient tree and crop species, and systems to ensure food security