Wetlands of Rapa Nui affected by Climate Change

Wetlands of Rapa Nui affected by Climate Change

Wetlands of Rapa Nui affected by Climate Change

by Tahira Edmunds (Consultora Independiente – Independent Consultant),

Cristóbal Cox (GP Consultores – GP Consultores), Rachel Gauci & David Véliz (ESMOI)

Climate change is affecting a great part of our planet, with the increase in sea level being one of the most important issues. Another effect that clearly can be charged to climate change is unbalancing the patterns of rainfall. On Rapa Nui, a decrease in the volume of the water in the three local wetlands has been observed. Wetlands are a combination of terrestrial and aquatic environments and on Rapa Nui are found in shallow lagoons covered by vegetation in the craters of the Rano Aroi, Rano Raraku and Rano Kau volcanoes. These lagoons serve as reservoirs of biodiversity, as well as touristic and cultural sites that are very important for the Island community. Unfortunately, two of them have registered a notable loss in the volume of water, Rano Aroi and Rano Raraku at the famous quarry of the moai (statues).
[bsa_pro_ad_space id=3]
To study the present conditions of the waters on site, we gathered professionals from CONAF (Chilean National Forestry Service), from Nucleus for Ecology and Sustainable Management of Oceanic Islands (www.esmoi.cl) and from GP Consultores (www.gpconsultores.cl), obtaining data – biological, chemical and physical – on the wetlands. For the biological samples, we concentrated on obtaining information on the organisms that live permanently in the waters of the wetlands. We were able to observe a large quantity of gambusia fish (Gambusia holbrooki), introduced into these wetlands to control the larvae of mosquitoes.  With fine nets, we were able to catch microscopic organisms and collect different types of micro-algae, with the main ones being green algae and cyanobacteria. This biological information indicates to us that the common organisms of the wetlands are present and have not been significantly affected.
The first abnormal sign observed was during the measurement of the salinity of the water, through the use of a conductivity meter.  This tool showed relatively high levels of electrical conductivity (3,88 mS/cm), much higher than observed in the past (values below 1 mS/cm).  Electrical conductivity gives us information on the chemical components of the water and can range from ice melt-water with values of conductivity near to zero to sea water with values up to 50 mS/cm.  This evidence indicates that it is very possible that the chemical elements are becoming concentrated in the wetlands due to a negative balance of water, that is to say, a lower level of rain water entering the wetlands than water leaving the wetlands through evaporation. Historical data of precipitation taken from the Mataveri Airport on Rapa Nui, although not directly measured at the wetlands, offers valuable information on the changes in the volume of rainfall on the Island.  From the graph obtained, data from 1961 to 2017 shows that the year 2017 was the driest year on record and that the last five years have been the driest group for which we have information.
Another change that has been noted in the wetlands of Rano Raraku is the increase of sedge, or bulrush, reeds (Schoenoplectus californicus). The sedge are indispensable for the survival of the wetlands during times of drought as they retain humidity, avoid evaporation of the water and maintain a spongy layer underneath them, which also retains water.  The sedge reproduces through rhizomes as well as by seeding.  As the level of water has dropped completely in the summer months, the seeds have been able to fall into the under-layer and the rhizomes have multiplied, causing the sedge to increase considerably around and in the interior of the wetlands.  Under normal conditions of volume of water, the sedge remain on the edges without invading the deeper areas of the  wetlands.

 

[bsa_pro_ad_space id=2]
Another change observed is the increase of a species of thistle (Cirsium vulgare), an invasive plant called “cardo” or “kaiore” in the local language. This species has colonized several spots around the wetlands, and now even into the interior of the lagoon, which leads it to compete for space with the sedge. We know that diversity can be naturally reestablished, but it needs less negative human intervention for that. Measurements over a longer period to time and with more detail are necessary to corroborate and quantify  these effects, including in the famous wetlands of Rano Kau and Rano Aroi. With this, it would be possible to orient the Community in the best ways to adapt to our new reality.
[bsa_pro_ad_space id=1]

Featured Reports:

PURE The Endangered Sea Snail

PURE The Endangered Sea Snail

PUREThe Endangered Sea Snailby Ernesto Díaz CabreraEstudiante Doctorado en Ciencias, mención Ecología y Biología Evolutiva de la Universidad de ChileDoctoral candidate in Science of Ecology and Evolutionary Biology, University of ChilePure is a sea snail which has...

Magnetism on Rapa Nui

Magnetism on Rapa Nui

Magnetism on Rapa NuiAmong the sites most visited for their supposed magnetism are the large oval rock called Te Pito Kura and a section of the road to Anakena, about half a kilometer from the beach. Illusion or reality? What do the scientists say?by Cristian Moreno...

About The Author

Leave a reply

Your email address will not be published. Required fields are marked *