Plants
of Tonga
by T.G. Yuncker (1959)
The
electronic Flora of Tonga is planned for development.
It will present in one published reference source, information on the uses, names,
taxonomic relationships, distributions, and morphological characteristics of plants
found in Tonga. Bishop Museum Bulletin 220 will be digitally
reproduced.
The
Tongan archipelago is a group of 150 or more islands and islets of volcanic and
coral formation. Of these, only a relatively small number are sufficiently large
or topographically suitable for plantations adequate to support populations of
any size. Most of the islands are arranged in three main, roughly circumscribed,
areas situated in the southern, central, and northern parts of the archipelago
known as the Tongatapu, Ha'apai, and Vava'u groups respectively. The islands of
these three groups are arranged in two roughly parallel lines from slightly southwest
to northeast in the south Pacific Ocean between 15° and 23° south latitude
and 173° and 177° west longitude. To the north, and somewhat remote from
the northern Vava'u group, lie the volcanic islands of Niuafo'ou, Tafahi, and
Niuatoputapu (Keppel). The islands of the eastern line are the more numerous and
are of coral origin. For the most part, they are low, flat, and topographically
uninteresting. The western line, extending from the extreme southern, and at present
uninhabited island of 'Ata to Niuafo'ou on the north, is of volcanic origin. It
includes the island of Kao in the Ha'apai group which rises to a height of about
1,000 meters, the highest of the Tongan islands. Some of the islands—for
example, Tofua, Fonualei, and Niuafo'ou— are still volcanically active. Tongatapu,
the largest of the coral islands, with an area of nearly 100 square miles, is
very flat and reaches an altitude of scarcely 90 meters at its highest point.
On it is located Nuku'alofa, which is the largest town in Tonga and the seat of
government (fig. 1, a ).
A
few miles to the east of Tongatapu lies the island of 'Eua, about 35 square miles
in area and composed of a volcanic base overlaid for the most part with limestone.
It has been built up to a height of approximately 300 meters at its highest point.
An elevated ridge runs along the eastern side of the island, rendering that coast
rugged and very picturesque (fig. 1, b). The seaward face of this ridge is precipitous
in places, and some parts are reached only with great difficulty. A much lower
ridge, with a maximum height of about 100 meters, lies toward the western side.
The ridges and slopes, especially those on the eastern side, are well covered
with native vegetation. Here, one finds some of the largest trees and densest
forests in all Tonga. Specimens of Laportea harveyi, Rhus taitensis, Alphitonia
zisyphoides, Dysoxylum spp., and other trees may reach considerable size. Tongatapu
and 'Eua are the only permanently inhabited islands of the Tongatapu group.
The
central, or Ha'apai, group is about 90 miles from Tongatapu. It includes the main
islands of Lifuka, the former capital and site of the Chief's Palace; Nomuka;
Kao; Tofua; and a large number of smaller islands, many of which now support no
permanent inhabitants.
Vava'u,
the largest and principal island of the Vava'u group, has an area of approximately
35 square miles and reaches an altitude of about 150 meters along the precipitous
northern coast. Its surface is uneven and the southern, very irregularly and deeply
indented coastline provides a beautiful and completely land-locked harbor, where
the principal town of Neiafu is situated. At the northwestern part of the island
is a lake of brackish water and nearby is a rather large swamp of marshy area
unique in the islands. Another, a large central lake connected at one point with
the sea during high water, is found on the island of Nomuka in the Ha'apai group.
Large crater lakes also occur on Tofua and on Niuafo'ou. Ocean-going steamers
are able to dock at Neiafu in Vava'u and at Nuku'alofa on Tongatapu. Cutters and
interisland boats can reach a jetty at the village of Pangai on Lifuka Island
in the Ha'apai group, and it is possible for very small boats to make a landing
at a makeshift dock on 'Eua. And it is usually possible, in moderate seas, to
get ashore from canoes or other small boats on the other low coral islands. It
is much more difficult, however, to land on the volcanic islands of Tofua, Kao,
Late, Niuafo'ou, or Tafahi where most of the coast is steep and abrupt and where
protecting reefs are lacking or do not break the often strong wave action. These
islands can be reached only by canoe or small boat and under most favorable weather
conditions, or by swimming from larger boats which must stand well off shore for
safety.
The
population of Tonga is nearly 50,000. It is heavily concentrated on the islands
of 'Eua, Tongatapu, Nomuka, Lifuka, and Vava'u and some of the smaller adjacent
islands. The volcanic islands of 'Ata, Tofua, Kao, Late, and Niuafo'ou have few
or no permanent inhabitants at the present time. The former population of about
1,300 on Niuafo'ou was evacuated after the disastrous volcanic eruption in 1946,
and at present makes up a large part of the population on 'Eua. (See figure 2.)
The more heavily populated islands show a high percentage of land utilization,
the indigenous plant species surviving only in occasional uncultivatable areas,
usually near the sea. Everywhere grows a number of species of greater or lesser
usefulness presumably brought to the islands by the aborigines as they arrived
in Tonga from other islands. These species predominantly show Asiatic, African,
or Malaysian origin. A possible exception is the sweet potato, and there is considerable
question as to how it reached Polynesia. In this group one may include that most
useful of all plants for island peoples, the coconut.
Presumably,
the unintentional introduction of certain weedy species occurred at the same time,
A good many cultivated species, together with many weeds, owe their presence to
the visits of European ships, starting early in the seventeenth century and continuing
with increasing frequency to the present time. Some of these alien species find
optimum conditions for growth and multiplication, and have undoubtedly played
a part in limiting or even exterminating some endemics or indigenous species through
aggressiveness. A high percentage of the usual strand and weed species includes
those frequently found on other Pacific islands and elsewhere in tropical countries.
