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Habitat Zoning

Habitat Zoning on the Land

The diagram shown here simplifies the natural habitat zoning on Niue, both above and under water. It shows a cross-section from roughly SE to NW such that the hurricane side is on the left side and the trade wind side on right. From left to right the following habitat zones can be distinguished:

Alofi underwater barrens

occasional tropical cyclones destroy coral life, resulting in a barren seascape to 70m depth, which is kept barren by incessant grazing of sea urchins, surgeonfish and parrotfish.

Alofi reef flats

coralline reef flats just above low tide level, heavily exploited by the practice of reef gleaning and collecting. During high tide this area is heavily grazed by surgeonfish.

Alofi terrace wind-struck rain forest

hurricane winds cause a heavy toll on the natural rain forest. This habitat has also been modified for living.

Mutalau ridge rain forest

a remnant of the original rain forest, not suitable for cultivation.

Fern lands

clearfelled rainforest and soils cultivated for food, resulting in fern lands.

Huvalu rain forest

a central lagoon remnant of the original rain forest. The remaining area of Huvalu high forest is estimated at 6000 acres (2400ha) with a tapu area of 40 acres (16ha) within, now protected for four generations.

Mutalau ridge rain forest

as above but this side adjoins to the unmodified saltspray vegetation, a haven for the coconut crab.

Saltspray karrenfeld and vegetation

because the rainforest never stood here, soils are poorly developed leaving an inaccessible terrain of sharp coral pinnacles and sink holes (karrenfeld) with low vegetation, dominated by salt-tolerant shrubs such as Pandanus mangrove trees.

High pools

as the trade wind swell bursts skyward, it deposits water on ever growing deep rock pools, the mysterious high pools with their own miniature ecosystems.

Trade wind barrens

the trade swell is not powerful enough to create deep barrens but only a short ledge and step. This shore shape breaks the swell by bursting it skyward and bouncing it back to sea.

The tradewind coral slope

a gradual slope of healthy corals with rapid water movement down to 20m. Although corals thrive, fish dislike the continuous water movement.

This map shows the actual location of Niue’s vegetation types. It distinguishes two zones, the coastal zone and the inland area. The coastal zone covers the salt spray zone, the coastal forest and coastal fernlands. The inland area covers regenerating forests and fernlands and the high rain forest. As one can see, the amount of original vegetation is not large but relatively larger than that in New Zealand. The Huvalu Forest Park covers both regenerating and original forest and may take several centuries to regenerate fully.
Click here for a larger version of this map: niue11m.gif.