Nuku Hiva: The Physical Environment

Nuku Hiva is the largest of the twelve volcanic islands that make up the Marquesas Archipelago of French Polynesia[1]. The Marquesas are one of most isolated island chains in the world, located in the middle of the Pacific between 7° 53’ and 10° 35’S latitude and 138° 25’ and 141° 27’ W longitude[2]. These islands run northwest to southeast, with the youngest, Fatu Hiva, being approximately 1.3 million years old and the oldest, Eiao, being 6 million years old[3]. Nuku Hiva is estimated to be 3.1 to 4.8 million years old[4]. While plants and animals reached Nuku Hiva at earlier dates, humans first colonized the Marquesas between 1000 and 2000 years ago, with the population peaking around several hundred years ago at 80,000 inhabitants[5]. The geographic features of Nuku Hiva greatly impacted the rest of the natural environment of the island. Additionally, Polynesian and subsequent European colonization have played an integral role in shaping the environment of the island.

Arriving Hakaui

Nuku Hiva is a high island with an area of 130 square miles (thirty of which are over 2,000ft of elevation)[6]. It is roughly sixteen miles long and twelve miles wide with its highest peak reaching 4,000 feet[7]. Unlike most of the other islands in the Marquesas, Nuku Hiva does not have a central ridge[8]. Instead, it has a central plateau region[9]. High mountains to the North, West, and South surround this region, which has an average altitude of approximately 2,500 ft[10].

Stark rugged cliffs connected by sweeping valleys shape Nuku Hiva’s coastline. Five of these valleys are amphitheaters.With small low flats and gentle slopes that rise to the tips of mountains, they are shaped like giant arenas with the Pacific Ocean as a stage. Cutting into the surrounding mountains, large bays typically form when these valleys extend to the coastline[11]. The windward side of the island receives more rain and thus the valleys are more eroded and deep and the bays are larger[12]. The rest of the valleys are narrow and deep with eroded, flat floors[13]. Also, Nuku Hiva has essentially no coral reef development[14].

Arriving Hakaui

One notable feature of the Marquesas Islands is the high concentrations of Chlorophyll-a found in the leeward waters of the island group. This feature, also known as the island mass effect, results from the ways in which the currents interact with the islands. The Southern Equatorial Current is blocked and diverted by the islands, leading to eddies and upwelling downstream of them[15]. This upwelling brings nutrients to the surface, which helps to promote phytoplankton growth. Additionally, the Marquesas Islands provide a source of iron, which the currents help to disperse[16]. But still, iron availability is believed to limit phytoplankton growth in the Marquesas, because the water is comparatively nutrient-rich from the upwelling and iron-poor[17]. The combination of upwelling and the addition of iron leads to a phytoplankton bloom downstream of the Marquesas, the effect of which can be seen up the food chain. In addition, the plankton blooms in the Marquesas can be divided into three categories: seasonal, episodic, and La Niña related[18]. Thus the interaction of the sea with the islands leads to increased production downstream of the Marquesas, which is so profound that the Marquesas are easily identifiable on a global map of Chl-a levels.

The climate of Nuku Hiva is also shaped by its geography and geology. The temperature and rain patterns are largely affected by elevation and wind patterns. In general, the Marquesas experience a tropical climate and moderate warm weather with an average temperature of 29°C at sea level, decreasing with altitude to an average of 25° at higher elevations. The El Niño Southern Oscillation (ENSO) creates great variability in annual rainfall[19] While Nuku Hiva receives plenty or rain during La Niña years, El Niño causes a great decrease in annual rains and thus historically great famines[20]. In addition to ENSO, the height of the mountains also effects rain distribution with generally more precipitation at higher elevations[21]. Altitude, combined with consistent east-to-southeast trade winds, also effects rain distribution, creating very moist windward climates and a much drier rain shadow in leeward climates[22]. For example, Nuku Hiva’s central plateau, To’ovi, receives as much as 3000 millimeters of rain annually while the lower leeward side of the island receives an average of 700 millimeters[23].

Nuku Hiva’s geographic features make it an interesting case study for distribution of plants and animals. When Nuku Hiva first broke through the ocean surface it was just a small volcanic rock in the middle of the Pacific Ocean. Therefore, all of the plants and animals that now inhabit Nuku Hiva migrated there through overseas dispersal[24]. Over time a natural population of plants and animals established the endemic biology of the island. Out of the thousands of plant and animal species found in the Marquesas, forty-two percent of the plant species and many animal species are endemic, meaning they established populations on the island before the arrival of the first humans[25]. However, continued human influence since the time that the Polynesians first colonized the island two thousand years ago has had a profound impact on the local flora and fauna, particularly in the low-to-mid elevations[26]. This long history of human interaction with the environment has not only greatly reduced the number of native species but has also made it difficult at times to identify which species are native[27].

Arriving Hakaui

When the Polynesians arrived in the Marquesas, they brought with them plants and animals that altered the balance of habitats across the islands. Polynesians first brought food plants, pigs, fowls, and rats amongst other flora and fauna[28]. These introduced species, serving agricultural and ornamental purposes, aided humans in settling the island. In addition, they altered the natural landscape by quickly adapting and spreading over the environment. Introduced species such as the Hibiscus tiliaceus tree and Gleichena linearis staghorn fern, became extremely abundant and replaced much of native vegetation from sea level up to 2,500 feet[29].

Europeans later brought new species including disease, goats, sheep, cattle, pigs, horses, cats, and more invasive plants, which have had large and widespread impacts[30]. Worst of all, the Paspalum conjugatum now invades the rainforest. This tall grass kills trees in a short time, and has wiped out much of the native floras in its wake[31]. Furthermore, cattle, pigs, and other grazing animals play their share in disturbing the environment by deforesting the land[32].

Arriving Hakaui

In assessing the flora and fauna, there are several distinct microclimates on Nuku Hiva that can be defined by looking at two main factors: elevation and windward-versus-leeward location on the island. Elevation is important because it is related to rainfall and temperature and additionally the windward side receives more rainfall than the leeward[33].

The high elevation cloud forest found between 2,000 to 3,000 feet in elevation, is the microclimate least disturbed by human influence[34]. These rainforest regions, usually located on the summits of the mountains, are very densely covered with shorter trees, shrubs, and ferns[35]. Species include Metrosideros collina, Weinmannia, Crossostyles biflora, and tree ferns, or Cyathea, with Freycinetia and a wide variety of ferns dominating the underbrush[36]. Trees also tend to be smaller in windier regions, such as ridges[37]. Additionally, the majority of the species in these high regions tend to be native and there are only a few introduced species[38]. This is most likely due to the fact that these regions are very high and rugged and thus difficult for humans to reach.

The next highest microclimate is the intermediate zone, which is found more on the wetter windward side of the island than on the dry leeward slopes[39]. The upper limits of this region are normally 2,000-2,500 ft and go down to 1,000 to 1,500 feet[40]. However, the transition from the cloud forest to this zone is gradual and not easily marked[41]. This zone covers most of central Nuku Hiva[42]. The vegetation is marked by fewer ferns than the cloud forest and more herbaceous flowering plants and grasses[43]. The forested regions of this zone are often very dense, and open areas are grassy[44]. Some species found here include Hibiscus tiliaceus, Piper latifolium, Wickstroemia foetida, Freycinetia, Metrosideros, and Weinmannia[45]. Introduced plants have reached the intermediate zone, including guava and Paspalum conjagtum[46].

From sea level to 1,000-1,500 ft on the windward side and to 2,000-2,500 ft on the leeward side is the low level zone, the last of the microclimates[47]. This zone, which has been the most impacted by humans, contains a high number of introduced species including coconuts, breadfruit, and a variety of grasses[48]. Compared to the higher zones, ferns are relatively sparse[49]. Lining roadways and covering small valleys, wedelia, a plant with sprawling green leaves and small yellow flowers, is an invasive species that has taken over vast amounts of arable land throughout the low level zone. In areas such as the windward side of the island and valleys the undergrowth is very thick due to the high levels of rain[50], however on the leeward side, much of the low level zone is barren[51]. Human activity, especially agriculture, greatly shapes the flora that you find at low altitudes today. Starting just beyond the shoreline, there are a variety of cultivated food plants such as breadfruit, mango, lime, bananas, papaya, pomegranate, coconuts and star fruit. Also notable are a wide variety of hibiscus flowers, palm trees, and cotton trees. Dogs, cats, horses, and chickens run loose around the area. Mosquitoes and other biting insects are prevalent as well.

The introduction of plant and animal species, along with continued human manipulation of the environment, has led to a massive decline of endemic species found across the Marquesas[52]. Introduced animals such as the alien black rat (Rattus rattus) and the great horned owl (Bubo virginianus) have contributed to the endangerment of many endemic bird species including the ultramarine lorry (Vini ultramarina). Also, hunting has led to the endangerment of the endemic Nuku Hiva imperial pigeon (Ducula galeata). These are only two of many examples of introduced species greatly affecting native species.

People can thus be said to have greatly disturbed the “natural” environment of the island. While many might look at the loss of endemic species and introduction of invasive species as a negative effect of human manipulation of the environment, others might accept these changes as the ecological outcome of competitive exclusion and survival of the fittest. To what degree human manipulation will continue to be sustainable is the real question that needs to be addressed throughout the Marquesas and throughout the world.

Jackie Conese, Boston University
Tristan Feldman, Vassar College
2011

 

NOTES

[1]  Jacques Florence and David H Lorence, “Introduction to the Flora and Vegetation of the Marquesas Islands,” Allertonia 7.4 (1998): 226-237.

[2]  Melinda S. Allen, John Flenley, Kevin Butler, and Mark Horrocks, Preliminary Report on Pollen and Sedimentary Records from Nuku Hiva, Marquesas Islands, East Polynesia, Rep, Print.

[3]  W. L. Wagner and D. H. Lorence, "Flora of the Marquesas Islands," Smithsonian National Museum of National History, 2002, Web, 10 Jan. 2011, <http://botany.si.edu/pacificislandbiodiversity/marquesasflora/index.htm>.

[4]  Florence and Lorence, 1998.

[5]  World Wildlife Fund et al, "Marquesas tropical moist forests," Encyclopedia of Earth, 5 Dec. 2006, World Wildlife Fund, 10 Jan. 2011, <http://www.eoearth.org/article/Marquesas_tropical_moist_forests>.

[6]  A.M. Adamson, “Marquesan Insects: Environment,” Bernice P. Bishop Museum Bulletin 139.9 (1936): 1-78.

[7]  Adamson, 1936, 57.

[8]  Wagner and Lorence, 2002.

[9]  Florence and Lorence, 1998.

[10]  A. M. Adamson, 1936.

[11]  Ibid.

[12]  Ibid.

[13]  Ibid.

[14]  Wagner and Lorence, 2002.

[15]  Sergio R. Signorini, Charles R. McClain, and Yves Dandonneau, "Mixing and Phytoplankton Bloom in the Wake of the Marquesas Islands," Geophysical Research Letters 26.20 (1999): 3121-124.

[16]  Ibid.

[17]  Ibid.

[18]  Elodie Martinez and Keitapu Maamaatuaiahutapu, "Island Mass Effect in the Marquesas Islands: Time Variation," Geophysical Research Letters 31 (2004).

[19]  Florence and Lorence, 228.

[20]  Ibid.

[21]  A.M. Adamson 1936, p.18

[22]  World Wildlife Fund, 2006.

[23]  ORSTOM 1993, Cauchard and Inchauspe, 1978).

[24]  Adamson, 1939, p. 6.

[25]  Allen et al, 2009.

[26]  Florence and Lorence, 1998.

[27]  Melinda S. Allen, John Flenley, Kevin Butler, and Mark Horrocks, “Preliminary Reporton Pollen and Sedimentary Records from Nuku Hiva, Marquesas Islands, East Polynesia,” Rep., Print.

[28]  A.M. Adamson, 1939, p. 26

[29]  Ibid.

[30]  Ibid.

[31]  Ibid.

[32]  Adamson, 1936, p. 39.

[33]  Adamson, 1936.

[34]  Adamson, 1936, p. 12.

[35]  A.M. Adamson, “Review of the Fauna of the Marquesas Islands and Discussion of Its Origin,” Bernice P. Bishop Museum Bulletin 159.10 (1939): 1-92.

[36]  Adamson, 1936.

[37]  Ibid.

[38]  Ibid.

[39]  Ibid.

[40]  Adamson, 1936.

[41]  Adamson, 1939.

[42]  Adamson, 1936.

[43]  Ibid.

[44]  Ibid.

[45]  Ibid.

[46]  Ibid.

[47]  Adamson, 1939.

[48]  Adamson, 1936.

[49]  Ibid.

[50]  Ibid.

[51]  Ibid.

[52]  World Wildlife Fund, 2006.

Works Cited

Adamson, A.M. “Marquesan Insects: Environment.” Bernice P. Bishop Museum Bulletin 139.9 (1936): 1-73. Web. 16 Jan. 2011.

Adamson, A.M. “A Review of the Fauna of the Marquesas Islands and Discussion of its Origin” Bernice P. Bishop Museum Bulletin 159.10 (1939): 1-93. Web. 20 Jan 2011.

Allen, Melinda S., John Flenley, Kevin Butler, and Mark Horrocks. “Preliminary Report on Pollen and Sedimentary Records from Nuku Hiva, Marquesas Islands, East Polynesia.” Rep. Print.

Florence, Jacques and Lorence, David H. “Introduction to the Flora and Vegetation of the Marquesas Islands.” Allertonia 7.4 (1998): 226-237.

Martinez, Elodie, and Keitapu Maamaatuaiahutapu. "Island Mass Effect in the Marquesas Islands: Time Variation." Geophysical Research Letters 31.1 (2004). Print.

Millerstrom, Sidsel, and James H. Coil. "Pre-Contact Arboriculture and Vegetation in the Marquesas Islands, French Polynesia: Charcoal Identification and Radiocarbon Dates from Hatiheu Valley, Nuku Hiva." Asian Perspectives 47.2 (2008): 330-51. Print.

"Nuku Hiva." Encyclopedia Britannica. Encyclopedia Britannica Online. Encyclopedia Britannica, 2011. Web. 09 Jan. 2011. <http://www.britannica.com/EBchecked /topic/422212/Nuku-Hiva>.

Signorini, Sergio R., Charles R. McClain, and Yves Dandonneau. "Mixing and Phytoplankton Bloom in the Wake of the Marquesas Islands." Geophysical Research Letters 26.20 (1999): 3121-124. Print.

Wagner, W. L., and D. H. Lorence. "Flora of the Marquesas Islands." Smithsonian National Museum of National History, 2002. Web. 10 Jan. 2011. <http://botany.si.edu/pacificislandbiodiversity/marquesasflora/index.htm>.

World Wildlife Fund, David Richards et al. "Marquesas tropical moist forests." Encyclopedia of Earth. 2006. http://www.eoearth.org/article/Marquesas_tropical_ moist_forests10 Jan. 2011.