Tonga

Resources

Geography

Geographic description

The Kingdom of Tonga is located 173º W longitude 22º S latitude, south of the equator and slightly above Tropic of Capricorn. Tonga consists of 170 islands spread over approximately 360 000 km² of the Pacific Ocean. They are divided into three main groups–Tongatapu, Ha'apai and Vava'u. About 37 of the islands are inhabited. Total land area is 747 km².

Tongatapu is the largest island. The eastern islands, including Tongatapu, are of coral, while islands of volcanic origin lie to the west. The highest point in Tonga is Mount Kao (1 030 m), a volcano forming Kao Island in the Ha'apai group. Several islands have active volcanoes. Volcanic ash creates fertile soil, even on the limestone islands, and the islands are well vegetated.

The climate is oceanic tropical with high humidity and an average daily temperature range of 16° to 29° C. Precipitation averages from 1 800 mm a year on Tongatapu to 2 500 mm on some of the northern islands. The rainiest months are from December to April. Cyclones occur every few years during the rainy season and can be quite destructive.

Forest cover

Description of the natural woody vegetation

The Kingdom of Tonga is comprised of 170 islands that vary in size from Tongatapu (over a third of the total land area of Tonga at 257 km²) to rocks and reef islets. The main island groups are composed of raised coral limestone buried in deep layers of fine ash derived from the string of active and dormant volcanic islands located to the west. Large tracts of land are cultivated or fallow. Forested areas include mangrove and coastal swamps; coastal and littoral, tropical lowland and upland rain forests (especially on ‘Eua), and tropical lowland and secondary disturbed forests. The following description of vegetation types is derived from Susan K. Wiser, Larry E. Burrow, William S. Sykes, Donald R. Drake and Terry J. Savage (1999), Mueller-Dombois and Fosberg (1998), Drake et al. (1996) and Whistler (1992).

Natural forests

Closed broadleaved forests

Mangrove Swamp

Sheltered onshore mudflats, mainly on Tongatapu and in Vava‘u, support a depauperate mangrove swamp community dominated by the mangroves Bruguiera gymnorrhiza, Rhizophora samoensis and/or R. stylosa. Farther inland, where the water changes from saline to brackish or fresh, occur buttressed trees such as Excoecaria agallocha, Inocarpus fagifer and Xylocarpus granatum. Paspalum vaginatum often forms a dominant grass cover on the inland margin of the swamp.

Littoral Forest

This forest type grows inland from the harsh beach vegetation zone. On the sheltered western and northern sides of the islands these forests are typically dominated by Barringtonia asiatica, Hernandia nymphaeifolia, Hibiscus tiliaceus, Neisosperma oppositifolia, Terminalia catappa and Thespesia populnea. On exposed windward coastal sites the strand scrub zone is often backed by dense thickets of Pandanus, and further inland by a taller forest of Barringtonia asiatica, Calophyllum inophyllum, Casuarina equisetifolia, Guettarda speciosa, Tournefortia argentea and other widespread littoral trees and shrubs. The following two subtypes occur on ‘Eua:

• Excoecaria-Tournefortia Forest: Occurring on raised limestone substrates lacking sand or soil, this species-poor community forms narrow bands along the coast. Excoecaria agallocha and Tournefortia argentea dominate the canopy (up to 12 m high). Hibiscus tiliaceus forms a lower middle story, often along with Morinda citrifolia, Neisosperma and Schleinitzia insularum. The shrub layer consists of scattered individuals of Bikkia tetrandra, Clerodendrum inerme, Scaevola taccada and Wollastonia biflora. This littoral forest type is widespread in the Pacific except for the dominance of Excoecaria.

• Hernandia-Terminalia Forest: This forest type occurs on sand substrates and is more species-rich than the previous community. The upper canopy is dominated by Hernandia nymphaefolia and/or Terminalia catappa, with the subcanopy largely composed of Neisosperma oppositifolia. Other canopy trees include Guettarda speciosa, Hibiscus tiliaceus, Myristica hypargyraea, Pisonia grandis, Planchonella grayana, Schleinitzia and Terminalia litoralis. Microsorium scolopendria is a common terrestrial herb.

On the dormant Late volcano, on a substrate of cinder and lava rock, the main forest type up to 300 m is dominated by Casuarina equisetifolia, often with smaller trees of Alphitonia, Elattostachys, and Rhus, along with a variety of shrubs and lianas.

Tropical Lowland Rain Forest

Once the most common forest type in Tonga, but now largely displaced by agricultural practices, only remnant patches of lowland rain forest can still be found on Tongatapu but are still common on ‘Eua and the upper slopes of Vava‘u. These dense forests have a canopy 20 to 30 m high, a variety of lianas and epiphytes, and a sparse understory. The main tree species include Aleurites moluccana, Alphitonia zizyphoides, Calophyllum neo-ebudicum, Dysoxylum spp., Elaeocarpus tonganus, Elattostachys falcata, Ficus spp., Garcinia myrtifolia, Grewia crenata, Myristica hypargyraea, Rhus taitensis, Santalum yasi, Syzygium clusiifolium, Tarenna sambucina, Vavaea amicorum and Xylosma simulans. A few subtypes have been described for ‘Eua:

• Maniltoa-Pleiogynium Forest: Restricted to the northwestern part of ‘Eua above the littoral forest on volcanic soils overlying limestone, the canopy is dominated by Maniltoa grandiflora and Pleiogynium timoriense. Myristica hypargyraea and Neisosperma oppositifolia are conspicuous by their absence in this forest type. Other large trees include Aleurites moluccana and Sapindus vitiensis. Lianas comprise 29% of the species in this forest and include Alyxia stellata, Entada phaseoloides, Gynochtodes epiphytica, Jasminum spp. and Malaisia scandens.

• Myristica Forest: This forest type dominates the ecological zone above the littoral forest up to 110 m elevation, except for the previously described forest. It is heavily dominated by Myristica hypargyraea, which grows up to 25 m tall and is present in all size classes. Scattered trees include Calophyllum neo-ebudicum, Canarium harveyi, Diospyros samoensis, Guettarda speciosa, Maniltoa grandiflora, Planchonella grayana, and Pleiogynium timorense. The subcanopy includes Neisosperma oppositifolia and Xylosma simulans. Herbaceous ground covers are uncommon. Lianas comprise 25% of the species and include Alyxia bracteolosa, Entada phaseoloides, Epipremnum pinnatum, Gynochtodes epiphytica, Faradaya amicorum and Jasminum spp. Some areas are co-dominated by Dendrocnide harveyi, an apparent artefact of past disturbances.

• Calophyllum-Mixed Species Forest: Occurring on volcanic soils overlying limestone, this forest type appears mostly at elevations of 100 to 180 m. No tree species is dominant in this forest; Calophyllum neo-ebudicum is the most consistently abundant and reaches a height of 35 m, while Dysoxylum tongense is the most common co-dominant. Other canopy trees include Alphitonia zizyphoides, Canarium harveyi, Dysoxylum mollissimum ssp. molle, Elattostachys falcata, Litsea mellifera, Maniltoa grandiflora, Myristica hypargyraea, Neonauclea forsteri and Semecarpus vitiensis. Citronella samoensis, Cryptocarya hornei, Diospyros samoensis and Garcinia myrtifolia dominate the subcanopy. Macropiper puberulum is an abundant shrub, and the herb and liana layers are well developed. Some areas are dominated in the upper story by Dendrocnide harveyi and Bischofia javanica, or by Rhus taitensis alone, an apparent artefact of past disturbance as these species are absent from the smaller size classes.

• Calophyllum-Garcinia Forest: Occupying the highest elevations on ‘Eua at 190 to 300 m, again on volcanic soils overlying limestone, this forest type is best developed on steep slopes near the summit of the eastern ridge of ‘Eua. Here Calophyllum neo-ebudicum more clearly dominates the canopy and Garcinia myrtifolia the undercanopy. Other common canopy trees include Canarium harveyi, Dysoxylum tongense, Elaeocarpus graeffei, Hernandia moerenhoutiana, Homalium whitmeeanum, Myristica hypargyraea, Neonauclea forsteri, Podocarpus pallidus and Rhus taitensis. The herb and liana layers are well developed. Apparently disturbed sites are dominated by trees of Alphitonia zizyphoides and Elattostachys falcata.

On dormant Late, with its substrate of cinder and lava rock, an immature lowland rain forest dominated by Elattostachys falcata, and Rhus taitensis is developing. Casuarina equisetifolia, dominant in earlier stages of succession, occurs as 30 m tall emergent trees.

Secondary Forest

Now the dominant forest type in Tonga, secondary forest is a mixture of many native and introduced plant species, an artefact of land clearing. Shade-intolerant trees that replace secondary scrub dominate this high forest. The dominant overstory tree species are Alphitonia zizyphoides, Elattostachys falcata and Rhus taitensis, however these species are rare in the understory , indicating that they will eventually be replaced by other secondary and primary forest species. Other common secondary forest species include Adenanthera pavonina, Bischofia javanica, Cananga odorata, Dendrocnide harveyi, Dysoxylum spp., Hibiscus tiliaceus, Kleinhovia hospita and Neonauclea forsteri.

Open broadleaved forests

Coastal Swamp Forest

This open to semi-closed forest type is found in coastal areas occasionally inundated by fresh or brackish water from heavy rains or high tides, such as on the north coast of Tongatapu. The tree layer includes species of mangrove, along with Ficus prolixa, Hibiscus tiliaceus, Inocarpus fagifer, Pandanus tectorius and Thespesia populnea. In semi-open areas, the ground layer includes the grasses Ischaemum murinum and Paspalum conjugatum, the sedges Eleocharis dulcis and Cyperus javanicus, the fern Acrostichum aureum, low shrubs and vines, and weedy exotics such as Indigofera suffruticosa, Lantana camara, Psidium guajava and Stachytarpheta urticifolia.

On steep cliffs, at low elevations exposed to salt spray on ‘Eua, the open-canopied vegetation is dominated by Pandanus tectorius or Pritchardia pacifica. Where it is less steep, a low forest of Cycas seemannii, Hibiscus tiliaceus, Myristica hypargyraea, Neisosperma oppositifolia, Pandanus tectorius, Schleinitzia insularum and Terminalia catappa can be seen.

Other wooded land

Shrubs

Littoral Scrub

On ‘Eua, this coastal scrub zone varies with substrate. On bare limestone, the vegetation is dominated by the shrubs Bikkia tetrandra, Clerodendrum inerme, Scaevola taccada and Wollastonia biflora, with a ground layer of Pemphis acidula and Sesuvium portulacastrum. On sand, trees include scattered Acacia simplex, Cocos nucifera, Sophora tomentosa and Tournefortia argentea, with a shrub layer of Scaevola taccada and Wollastonia biflora.

Cliff Vegetation

On ‘Eua there are windswept zones of vegetation 3–5 m high on the upper cliffs that include Badusa corymbifera, Citronella samoensis, Diospyros elliptica, Maesa tongensis, and Maytenus vitiensis.

References

Drake, D. R., W. A. Whistler, T. J. Motley and C. T. Imada 1996. Rain forest vegetation of ‘Eua Island, Kingdom of Tonga. New Zealand J. Bot. 34:65–77.

Mueller-Dombois, D. and F. R. Fosberg 1998. Vegetation of the tropical Pacific islands. Springer-Verlag, New York. 733 pp.

Whistler, W. A. 1992. Vegetation of Samoa and Tonga. Pac. Sci. 46:159-178.

Information on forest assessments

Area of forest cover

Table 1 - Bibliographic references

Country	Tonga
Title	A Natural Forestry Inventory of Tongatapu and Nearby Island
Author	Susan K. Wiser, Larry E. Burrows, William S. Sykes, Donald R. Drake, Terry E. Savage.
Year	1999
Source	Aerial photograph (AUSLIG)1990, ground survey
Date of consult.	December 1998.
Location (of publication)	Landcare Research New Zealand

Description of source

(Including type of source, overall quality assessment and utility for FRA 2000)

Aerial photograph (AUSLIG) 1990, ground survey

Information content (check one or more topics as appropriate)

Natural Forest			Protected areas
Plantations			Biodiversity
Other wooded land			Forest ownership
Forest area change			Wood supply potential
Total volume			Non-wood forest products
Total biomass			Trees outside forest
Commercial volume			Forest fires

Name of reviewer: Sione Kaufusi

Table 2 - Description of forest inventories/surveys

Country

Tonga

Reference year

1999

Title of inventory

A Natural Forest of Tongatapu and Nearby Islands

Type of inventory

Field

Field / aerial photos / satellite images / ...

Brief summary of methodologies used

Before land survey was conducted land cover was analyzed based on aerial photograph by the Australian Surveying and Land Information Group (AUSLIG) 1900. Land cover types were then mapped and classed into 11 categories. Forest sampling plots were located in stands where the land-cover had been classed and to sample the range of variation in mapped soil types and degrees of coastal influence. Sample plots were 600 m2 (typically 20 m x 30 m). Within each plot all vascular plant species were recorded. Diameter at breast height (1.4m) was measured for all tree stems having diameter greater then 5 cm. A range of environmental and site characteristic were determined to aid in the interpretation of influences on vegetation types, species distribution and regeneration potential. Soil was sampled and analyzed for productivity, pH, and available phosphorous and total nitrogen. Plot locations were marked on 1:10,000 topographic maps, locations were described and illustrated to aid plot relocation in the future.

Reporting level	National	Country coverage	partial
	National / sub-national		Complete / partial
Map output	Yes	Scale of the map	1:50,000
	yes / no (also indicate format: analogue / digital)

Vegetation types included	yes/no		Additional information included	yes/no
Natural forests	Yes		Area by forest formation	Yes
Plantations	Yes		Volume	No
All forests	Yes		Biomass	No
Other wooded land	Yes		Forest naturalness	Yes
			Forest biodiversity	Yes
			Forest ownership	No
			Wood supply potential	No

Remarks

The information for this part of the report is based on “A Natural Forest Inventory of Tongatapu and Nearby Islands, 1999”.

Reliability class

high

1=high 2=medium 3=low

Table 3 - Area of woody vegetation according to national classification

Reference year: 1999 Geographic Unit: Tongatapu and nearby islands

Forest and other woody vegetation types (country classification)	Area (000 ha)
1. Natural Forest	0.8
2. Other natural cover types	1.4
3. Regeneration forest or fallow	2.1
4. Actively farmed land	19.4
5. Towns, villages settlements	3.1
Subtotal of country classes corresponding with FRA 2000 forest and other wooded land
Subtotal other land
Total land area

Definitions:

Comments:

Plantations

Gross estimated area 525 ha Annual planting 30 ha

Species group	Gross estimated area		Purpose	(%)	Ownership (%)
	ha	%			Public	Private	Others
Other Broadleaved spp.			Industrial		100
	195	37.0	Non-Industrial	100
Pinus spp.			Industrial		100
	330	63.0	Non-Industrial	100

Other Broadleaved spp. Agathis robusta, Toona australis and etc.

Pinus spp. P. caribaea

Non-forest Species	Age	Gross estimated area	Ownership (%)
		(ha)	Public	Private	Others
Coconut, tall	1-29
	30-59
	60+
	Total	35 900
Coconut, hybrid
Oil palm
Rattan*

Explanatory note on 2000 estimates Oliver (1999) gives plantation area by species in 1999 as 495 ha and annual planting as 20-40 ha. Taking an average annual planting rate and applying this to the total area in 1999 as a base, the area as of 2000 is estimated to be 525 ha. Species composition is assumed to be valid up to the year 2000. Oliver (1999) says that all land is the property of the government. Oliver (1992) suggests that the purpose is to produce timber. Regarding non-forest plantations, Oliver (1999) mentions there are coconut and oil palm plantations. Killman (1999) says that coconut plantations have been estimated at about 35 600 ha. A reference year is not mentioned but as no data except this is available about coconut plantations, it is assumed that this is still valid in 2000. There are no data about any oil palm plantations.

References

Killman, W. 1999. Coconut Wood Sawmilling and Utilisation in Tonga

Oliver, W. 1992: Plantation forestry in the South Pacific: A compilation and assessment of practices: Project RAS/86/036: UNDP-FAO. 121 pp.

Oliver, W. 1999. An Update of Plantation Forestry in the South Pacific, RAS/97/330 Working Paper No. 7, Pacific Islands Forests & Trees Support Programme

Volume and biomass

Table 6 - Volume data (of natural forests)

Reference year:

Part 1 : Forest Inventory Description

Name of the Inventory:

National Forest Inventory (Yes or No): No

Geographic location: Tongatapu and Nearby Island.

Total inventoried area (000 ha):

Sketch map attached (Yes or No): Yes

Part 2: Inventory methodology

Stratification criteria: tree and subcanopy (>3(5)m), shrub (1-3(-5)m), ground(<1.0), and epiphytes and liana

Sampling design: rectangular plot 600m2 (20 m x 3 m)

Sampling intensity (%): Cover all land cover classed

Species coverage: Forest trees, coconut plantation, woody crops, mangrove, marsh, non-woody vegetation, towns, non vegetated.

Minimum diameter: 5 cm

Type of volume measured:

(including or excluding branches, under bark or over bark, etc.)

Part 3: Inventory results (by reporting unit)

Reporting Unit name: Landcare Research New Zealand Ltd

Area (ha):

Average volume per hectare (m3/ha):

Sampling error for average volume per hectare at 95% probability (%):

Stand and stock tables attached (Yes or No): No

Comments:

Table 6A - Volume of woody vegetation according to national classification

Reference year: Geographic Unit:

Forest and other woody vegetation types (country classification)	Volume (1 000 m3)	Biomass (1 000 m3)
1. Natural forest	0.8
2. Other natural cover type	1.3
3. Regeneration forest or fallow	2.1
4. Actively farmed land	19.4
5. Town, villages settlements	3.0
Subtotal of country classes corresponding with FRA 2000 forest and other wooded land

Definitions:

Comments:

Change in volume and biomass

No information.

Mangroves

Area

Ha	Year	Source	Remarks
	2000
1,000	1995	Ellison, J.C. (1995) Status report on Pacific Island Mangroves. In: Marine and Coastal Biodiversity in the Tropical Island Pacific Region. Volume 1: Population Development and Conservation Priorities. Maragos, J. E., Peterson, M. N. A., Eldredge, L. G., Bardach, J. E. and Takeuchi, H. F. (Eds.). East-West Center, Honolulu, USA.
330*	1972	Spalding, M. D., Blasco, F. and Field, C. D. (Eds.) (1997) World Mangrove Atlas. The international Society for Mangrove Ecosystems, Okinawa, Japan. 178 pp.	* Tongatapu only. Map estimate based on DOS 1971 (aerial photos dated 1968 and field checked in 1972)

Description

Sheltered onshore mudflats, mainly on Tongatapu and in Vava‘u, support a depauperate mangrove swamp community dominated by the mangroves Bruguiera gymnorrhiza, Rhizophora samoensis and/or R. stylosa. Farther inland, where the water changes from saline to brackish or fresh, occur buttressed trees such as Excoecaria agallocha, Inocarpus fagifer and Xylocarpus granatum. Paspalum vaginatum often forms a dominant grass cover on the inland margin of the swamp.

References:

Ellison, Joanna C. 1998. Report on Development of a Mangrove Environmental Management Plan for Tongatapu.

Drake, D. R., W. A. Whistler, T. J. Motley and C. T. Imada 1996. Rain forest vegetation of ‘Eua Island, Kingdom of Tonga. New Zealand J. Bot. 34: 65–77.

Mueller-Dombois, D. and F. R. Fosberg 1998. Vegetation of the tropical Pacific islands. Springer-Verlag, New York. 733 pp.

Whistler, W. A. 1992. Vegetation of Samoa and Tonga. Pac. Sci. 46:159-178.

Forest management

“Limited indigenous forest remains in Tonga. Logging exhausted nearly all of the available and accessible forest some years ago. About 4 000 hectares of the natural hardwood forest remains, mainly on uninhabited islands, in very steep or inaccessible areas, in coastal littoral areas and swamps and in mangrove areas. Most of the remaining forest is on Eua Island in an area that has been proposed as a national park.”

Brown, C. 1997. Regional study – the South Pacific. Asia-pacific Forestry Sector Outlook Study, Working Paper No. APFSOS/WP/01. FAO, Rome.

Forest legislation and policy

“Tonga does not have a formal forestry policy. National forestry objectives are set out in government's five-year development plan; to promote balanced land use considering the importance of trees for soil and water conservation, wood production and shelter, to promote optimal use of senile coconut timber resources; to encourage private sector investment in reforestation, and to encourage woodlot planting for industrial and fuelwood purposes.”

Brown, C. 1997. Regional study – the South Pacific. Asia-pacific Forestry Sector Outlook Study, Working Paper No. APFSOS/WP/01. FAO, Rome.

Status and trends in forest management

“Tonga's major timber resource is currently coconut palms. A 1982 survey estimated Tonga's coconut population at almost 5 million trees of which 12 percent were senile. Production of coconut timber presently totals around 1500 m³ per annum. This is 80 percent of Tonga's sawn timber production. Most of the production comes from the Government-owned Mataliku Sawmilling Centre. The remainder is produced by small portable sawmills.

“Tonga is moving to establish a commercially viable and sustainable plantation estate. Currently Tonga's objective is to establish 1500-2000 hectares of plantation forest. Large scale planting began in 1984 and by 1992, 579 hectares had been planted. Most of the plantings are Caribbean Pine (Pinus Caribaea). Presently the target is to plant 80 hectares per year. Projections show this would be adequate to sustainably meet 80 percent of Tonga's sawn timber needs. Tonga will continue to import its requirements for other wood and paper products.

“In 1992 the plantation estate totalled 579 ha. Most of the plantings are Pinus caribaea on 'Eua Island. Annual planting is targeted at between 80 and 120 hectares per annum, which will yield an estate of around 2000 hectares by 2010

“Agroforestry remains an important land use with Government particularly keen to promote planting of species for timber and fuelwood, planting improved varieties of fruit trees and nitrogen-fixing trees, coconut rehabilitation and replanting, and commercial intercropping. Eucalyptus saligna has been the most popular agroforestry species in recent years.”

Brown, C. 1997. Regional study – the South Pacific. Asia-pacific Forestry Sector Outlook Study, Working Paper No. APFSOS/WP/01. FAO, Rome.

Land ownership

No information.

Protected areas

Area Name	Subclass	Type of area	IUCN Cat.	Size (ha)
Malinoa Island Park and Reef	NATIONAL	Reserve	IV	73
Ha'atafu Beach	NATIONAL	Reserve	IV	8
Monuafe Island Park and Reef	NATIONAL	Reserve	IV	33
Pangaimotu Reef	NATIONAL	Reserve	IV	49
Mui hopo hoponga Coastal Reserve	NATIONAL	Reserve	V	0
Fanga'uta and Fanga Kakau Lagoons	NATIONAL	Marine Reserve	VI	2835
'Eua National Park	NATIONAL	National Park	II	450

Forest products production, trade and consumption

Contribution of the forestry sector to the country’s economy

Products

Trade (1998)

		Import		Export		Production	Consumption
	Units	Quantity	$US (x1000)	Quantity	$US (x1000)	Quantity	Quantity
Sawnwood	Cum	4586	874	10	8	1489	6065
Sawnwood (C)	Cum	4561	864	0	0	609	5170
Sawnwood (NC)	Cum	25	10	10	8	880	895
Wood-Based Panels	Cum	897	378	0	0	0	897
Veneer Sheets	Cum	36	18	0	0	0	36
Plywood	Cum	639	282	0	0	0	639
Particle Board	Cum	4	1	0	0	0	4
Fibreboard	Cum	218	77	0	0	0	218
Paper+Paperboard	Mt	67	96	0	0	0	67
Newsprint	Mt	4	3	0	0	0	4
Printing+Writing Paper	Mt	45	64	0	0	0	45
Other Paper+Paperboard	Mt	18	29	0	0	0	18
Roundwood	Cum	649	30	116	12	4600	5133
Industrial Roundwood	Cum	36	4	116	12	4600	4520
Sawlogs+Veneer Logs	Cum	0	0	0	0	4600	4600
Wood Fuel	Cum	613	26	0	0	0	613
Wood Residues	Cum	43	2	0	0	0	43
Recovered Paper	Mt	282	8	0	0	0	282