To restore the watersheds: Early twentieth-century tree planting in Hawai'i

The forest reserves of Hawai'i were established in the early 1900s in response to concerns about supplies of freshwater in the islands and the degraded condition of the native forests protecting the watersheds. Tree-planting was a coordinated effort involving both Harold Lyon and the Hawaiian Sugar Planters' Association and Territorial Forestry under the direction of R. S. Hosmer. The early foresters planted many types of trees on an experimental basis, but concluded that native species were of limited utility and turned largely to introduced species for large-scale reforestation efforts. The number of trees planted rose to many millions by the 1930s, when Depression-era labor was available for planting. Lyon envisioned the plantations as a buffer zone that would be established between the remaining native forests and the lower-elevation agricultural lands to protect the native forests and perform the functions (maintaining input of water to aquifers) that native forest no longer could. This large-scale attempt to engineer nature was probably the largest environmental project ever carried out in the islands. Forestry introductions have been a significant contributor to Hawaii's alien-species crisis, with many of these tree species now problem invasives.