Restoration on Rapa Nui

Rapa Nui, better known by most of the world as Easter Island and to its native residents as Te Pito o Te Henua (The Naval of the World) and famous for its monumental moai, was once covered by subtropical forest but is now denuded of its native vegetation. Being only 166 square kilometers, this small and fragile island was unable to recover from the historical ecological devastation, whatever the cause might have been (Mann et al. 2008). Dave Egan (2005) gives a good synopsis of the history of Rapa Nui and presents the case for its ecological restoration.

As botanists and restoration practitioners, we were intrigued by the ecological problems on Easter Island. In January of 2007, we had the opportunity to join an Explorer's Club expedition to Rapa Nui, led by John Loret, an archaeologist who was part of Thor Heyerdahl's 1955 expedition and who has led many subsequent expeditions since 1996 (Loret 2003). This gave us a first-hand look at restoration efforts on an island so thoroughly deforested and a chance to learn how restoration practitioners are handling the issues. This expedition had two objectives: to help preserve several archaeological sites and to assist with reforestation efforts. While our contribution was tiny compared to what needs to be done, what we learned in the process is worth sharing.

Along with Patrick Franklin, arborist for Bartlett Tree Experts in South Carolina, we led the expedition's plant projects. The expedition included ten people, and we worked with the Corporación Nacional Forestal (CONAF), the Chilean agency in charge of managing Rapa Nui National Park, which encompasses almost half the island. Led by Ignacio Espina Igor of CONAF, we planted trees in two restoration projects.

Easter Island is located in the Pacific Ocean (27°S 110°W), 3,700 km from the coast of Chile and 2,250 km from Pitcairn Island, making it the most remote inhabited island in the world. It has a subtropical climate with mean annual temperature of 21°C and mean annual precipitation of 1,350 mm. When one arrives in Hanga Roa, the capital and only town, one is initially unaware of the deforestation, since there are many beautiful trees lining the streets. These, however, were planted only in the past 50 years. Once one leaves town, the change is stark; vast areas are covered in nothing but grasses, sedges, and other low-growing vegetation. As one looks more closely, severe erosion becomes evident. Large areas along the sides of the volcanoes and cliffs are washing away. At the quarry at Ranu Raraku, towering statues that once stood over 10 meters tall are buried up to their necks in erosion.

By the 1700s, this island was completely deforested; most of the native plants have been extirpated, and many endemic plants are now extinct. There are approximately 435 plant species on the island, and of those, only 48 are native (I. Espina, CONAF, pers. comm.). Plants have been introduced to this island for many reasons. Attempts at reforestation have introduced a number of tree species, including eucalyptus (Eucalyptus globulus) and Australian pine (Casuarina equisetifolia), known as aito in Rapa Nui, the language of the local population, most of whom are descended from the original Polynesian settlers. Introductions for agriculture include plants such as guava (Psidium guajava; tuova), papaya (Carica papaya), corn (Zea mays; tarake), mango (Mangifera indica; tumu ivi), and breadfruit (Artocarpus altilis). Some species were brought in as cattle fodder, such as molasses grass (Melinis minutiflora; mauku piru), which has since become a problem. Plants are continually introduced as ornamentals, for example, blood-flower (Asclepias curassavica). The list goes on. This island has lost its original plant community, and the question is how will all these introductions affect reforestation?

Ignacio spoke with us at length regarding the challenges to reforestation efforts on Rapa Nui. Erosion is worst on the slopes and cliffs that make up the natural topography of the island. The soil is volcanic in origin and therefore would be very fertile, were it not for erosion's leaching out nutrients. Also lost are the...