Biodiversity of Niue

Dr J Floor Anthoni,  2005
The biodiversity of Niue was for many millennia influenced by natural forces but more recently also by humans. In this chapter we'll examine all these influences and how they have shaped Niue's current biodiversity.
  • principles: biodiversity is caused by the processes of evolution, whether natural or human-made. It is important to recognise the many factors involved.
  • habitat zoning on land: habitat zoning in the past and present.
  • more reading: there are other important chapters on the Seafriends web site
      • biodiversity: principles of biodiversity, evolution, extinction, ecosystem services, marine biodiversity
      • conservation: principles of conservation and restoration
      • marine conservation: problems and what does and does not work for saving the sea.
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-- seafriends home -- Niue index -- sitemap -- Rev 20050926,

Biodiversity is the long-term result of evolutionary forces which can be natural or originating from the way people interact with nature. On a small island like Niue, both have had important consequences. The way organisms change or adapt by evolution works like people breeding better plants, flowers or livestock, simply by selecting the ones to survive. In the case of breeding, people do the selection and in the case of evolution it is done by nature. Both result in the survival of the fittest, meaning the types with the required ('better') characteristics. To better understand the principles of biodiversity, visit the important biodiversity chapter on this site.

Niue is a very small island in the large southern Pacific Ocean. Ocean surface currents flow mostly with the trade winds in a north-westerly direction, arriving from a cooler area of the Pacific without neighbouring islands. But occasionally a reversal happens. During such instances, larvae or mature animals from neighbouring islands to the north may arrive at Niue. The gene pool in Niue is thus periodically updated, preventing unique endemic species to evolve here. Thus Niue is not likely to play a role in the world's biodiversity and it is unlikely to find species here that are found nowhere else in the world.

When species arrive in Niue's coastal seas, they are subjected to the following deselecting influences:

the slush hypothesis
In 2005 we discovered a new method to measure decomposer activity and biodensity in sea water. The Dark Decay Assay (DDA) has been treated extensively in its own section. With it we proved that the degradation in the sea is mainly caused by an imbalance between the nurturing and the bacterial side of the plankton. We also discovered that natural decomposition cannot complete because the energy locked up in biomolecules is insufficient to decompose them. What remains is a group of organic molecules we call slush as in incompletely molten snow. In July 2005 we measured the sea water around Niue and established that although it has almost ten times less phytoplankton than the sea around New Zealand, it has a large amount of slush, in fact equating to half the phytoplankton around NZ. Slush is neither food for plants nor animals, nor is it food for bacteria unless another form of energy is added to help them decompose it further. Such energy can be provided by plants alone when living in symbiosis with decomposing bacteria on their skins. Animals with plant cells and bacteria combined (mixotrophs) can decompose the abundant slush and become very productive, even though the water is so devoid of plant and animal plankton. It explains the success of corals and the algal slime covering the barrens of Alofi.
Please note that the slush hypothesis has not yet been confirmed by traditional science.

On land, nature has very similar influences. Sea birds for instance are too wasteful (energy-spending) to survive here because they depend on rich sea life in the sea around Niue. On land we can recognise the following selective factors:

In addition to natural influences, people have also made important changes to what lives on Niue:
habitat zoning on land
habitat zoning on NiueThe 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:

vegetation types on NiueThis 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.

habitat images
Below follow a number of images of the various habitats on and around Niue. It follows the habitat diagram from the hurricane side to the trade wind side.

Alofi underwater barrens
f044601: the Alofi underwater barrens are created by large storms and maintained by a large variety of grazers.
burrowed sea urchins waiting for the night
f044913: small black needle urchins inside their sockets waiting for the night to emerge when they graze their gardens.
the Alofi reef flats are wide
f220937: the coralline reef flats found mainly on the Alofi side of the island.

f223011: reef gleaning for sustenance is still widely practised. The coralline reef flats do not consist of corals but coralline algae, covered in a sum of brown-green slimy algae. Mysterious rock pools break the surface.

gleaning the reef flats for sustenance
Salt spray vegetation on the Alofi side
f222925: the Alofi terrace is frequently hit by hurricanes, low, salt-resistant shrubs survive.
wind-beaten coastal forest
0507008: on the hurricane side, tall trees are occasionally stripped, which selects for the most suitable types.
fallow land after cultivation
f221229: where good soils are found, people strip the vegetation for cultivating taro crops. Here the fields are left fallow to recover.
good taro crop
f220516: a prosperous taro crop.
Misa tours the Huvalu forest
0507450: the author and Misa by a tall forest tree with buttress root stabilising it against hurricane winds.
tall trees in Huvalu rain forest
0507451: tall forest trees are still found in the Huvalu rain forest.
the fou tree for making fire
0507470: the fou tree (Hibiscus ) was used for making fire.
coconut palms everywhere
0507140: coconut palms grow all over the island but are promoted near settlements and on soils unsuitable for farming.
coastal forest on the trade wind side
f223222: the coastal rain forest grows where jagged rocks prevent cultivation.
mangrove trees stand in the salt spray
f220816: pandanus mangrove trees are salt-resistant and thrive in the saltspray zone.
moon landscape
f220733: salt spray from incessant large swell has created a moon landscape of very sharp jagged rocks with salt resistant vegetation.
salt-resistant weeds
f223220: a salt-resistant perennial weed grows where no other can.
trade swell causes salt spray
f220503: the swell is thrown high skyward, causing copious amounts of salt spray (Anaana Point).
healthy corals on the tradewind side
f044715: underwater on the tradewind side extends a slope of healthy corals. The large giant clam seen here enjoys de-facto protection by the waves.