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Today the saga that is Easter Island's past is well known. There is a strict sequence of events following an indiscriminate harvesting of forests: (1) removal of vegetation, (2) soil erosion, and (3) desertification and loss of land fertility, as experienced in Easter Island. Recent studies suggest that Easter Island's rates of soil erosion are still extremely high, mostly due to illegal burns and overgrazing, as well as a lack of forests. On the other hand, wherever land is not overgrazed, the presence of an invasive grass makes land productivity impossible for the local tribes. However, by implementing some basic rainwater harvesting techniques and erosion control practices, land productivity could be restored on Easter Island.
The focus of this demonstration project is, for instance, to show how feasible is to bring back that productivity, after several centuries of land degradation. Land productivity could be restored on the island if two factors were met: (1) maximization of rain water infiltrating into the soil profile, and (2) minimization of soil water evaporation due to sunshine and wind. The study site was a north-east facing hillslope, about 35º steepness, with deep volcanic soils and completely covered by the invasive grass mentioned earlier. The tropical climate of the island is ideal to grow some agroforestry species, such as avocados and bananas, among others, which already grow within Rapa Nui’s residences. Due to their simplicity for replication and low labor demands, soil water infiltration was be maximized by the implementation of a system of infiltration trenches. Next, trees were be established on each trench. Evaporation was be minimized by covering the trenches and the plantation wholes with thick layers of organic material. Spacing between rows and trees, as well as the dimensions of wholes and channels was determined based on a 25-year return period design, using the Gumbel approach and the SCS Curve Number method. The trees will be monitored on a monthly base.
With this experience, the local tribes will be able to reclaim their ancestral land and produce/export avocados, bananas, and other products into the continent, by strategic alliances with supermarket chains. The relevance of this project is of epic proportions, since there is an important lesson that the whole humanity could learn by this experience.
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The views, opinions, advice or other content expressed by the author(s) or speaker(s) are their own and do not represent those of the Water Resources Research Center.