Tree islands more effective way to replant the world's forests

10 January 2014

Worldwide, large swaths of land lay barren in the wake of agricultural expansion, and as global forest cover continues to decline, carbon and water cycles, biodiversity, and human health are impacted. But efforts to restore abandoned pastures and agricultural plots back into functioning forest ecosystems are often hindered by high costs and time requirements. Fortunately, scientists have developed a new method for a more cost effective solution to forest restoration, the establishment of "tree islands."

Typically, forest restoration involves planting rows of trees, plantation style, which cover the entire restoration site. However, a team of researchers led by Rakan A. Zahawi of Las Cruces Biological Station in Costa Rica and Karen Holl of UC Santa Cruz recently tested an innovative method known as applied nucleation or the "tree island method" to facilitate forest recovery. In the tree island method, clusters of trees are spread out across the site instead of covering the whole deforested area. For this study, the researchers tested three different treatments on abandoned pasture plots in Costa Rica: planting tree islands, plantation style planting, and no planting or what is known as "passive restoration."

"We were surprised," Karen Holl told, "that the applied nucleation strategy was as effective in facilitating the natural establishment of forest tree seedlings as planting the entire area with trees, even though we only planted 27% of the trees in the applied nucleation treatment."

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