atoll research bulletin no. 392 the flora of - Smithsonian Institution ...

Species entering the succession early and remaining dominants in the 40- to 80-
year-old sites include: the trees, Calophyllum inophyllum, Dodonea viscosa, Ficus
prolixa, Guettarda speciosa, Morinda citrifolia and Premna serratifolia; the shrubs,
Phyllanthus societatis and Scaevola taccada; the grasses and sedges, Lepturus repens,
Fimbristylis cymosa and Qperus javanicus; the parasite, Cassytha filiformis; and the
diminutive fern, Ophioglossum petiolatum, All are indigenous. Larger exotics found in
the later stages of succession in more open habitats include Lantana camara, Psidium
guajava and Stachytalpheta urticifolia.
The study suggests that the potential natural disclimax vegetation of the open-cast
mined plateau will probably be dominated by Calophyllum inophyllum and Guettarda
speciosa, with the epiphytic Ficus prolixa dominating the more ecologically severe
pinnacle habitats. Morinda citrifolia, Premna serratifolia and the exotics, Lantana
camara and Psidium guajava, could become important components of the subcanopy. The
exotics, Casuarina equisetifolia (which is native to limestone habitats on other Pacific
islands) and Muntingia calabura, both now locally abundant in some mined areas, could
enter into the succession as well.
As argued by Manner et al. (1985), given no deliberate human intervention, the
succession to a disclimax vegetation association capable of sustaining human life will
probably take "many thousands of years". It is stressed that it is ironic that Nauru's
central plateau, from which Nauruans formerly obtained some of the necessities of life,
will be a "topographic jungle" stripped of its natural vegetation, before the next century,
in order to provide the phosphate needed to revive phosphate-poor soils to fuel the
development of Australia and New Zealand.
THE FLORA
Like the extremely limited, degraded and displaced vegetation types, the indigenous
terrestrial flora of Nauru exhibits extreme poverty and current numerical domination
by exotics. Of a total of 493 species or hybrid cultivars reported to have been present on
Nauru, only 59 (12%) are possibly indigenous (Tables 1 and 2). There are no reported
endemics, reflecting the lack of habitat diversity and the predominance of ubiquitous,
easily-dispersed pantropical or paleotropical coastal species. Two species (Achyranthes
canescens and Tarenna sambucina are presumably now extinct, Aidia cochinchinensis
possibly now extinct, and half (28) of the remaining 56 species are severely restricted in
distribution, endangered or possibly extinct, due to removal and severe habitat modification
or limitation (Table 2). The high number of recent introductions in Nauru reflects its
increasing contact with the outside world via its national airline, Air Nauru, increasing
urbanization and the total absence of quarantine regulations.
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