Forestry in the Hawaiian Islands began in the mid-19th century when King Kamehameha III declared that "forests and timber growing therein shall be considered government property, and under the special care of the Minister of Interior...." In the next half-century, various private and governmental efforts were made to encourage reforestation. All this was in response to the general decline of native forests due to uncontrolled grazing, fires, cutting for firewood, clearing for farming, and the invasion of introduced insects, plants, and diseases. The Hawaii Sugar Planters' Association (HSPA) was a leading proponent of good forest management once it recognized the impact poor management had on the water supply. Sugarcane requires vast amounts of water for irrigation, and most of this water came from mountain streams. The decline of forests was associated with a sharp drop in the quality and quantity of water downstream. It was during this period that the importance of forests as watershed reserves became apparent. Watershed are areas that drain to a particular body of water. Rainforests act like sponges. Tall trees capture drifting rain and clouds in their leaves and branches. The water drips down to the lower forest layers where some is evaporated and some drains into the soil. Some of this water will be absorbed by roots and transpired through leaves, some will percolate through the soil and seep into the water table below, and some will drain into streams. The floor of a rainforest is covered with decaying organic material, ferns and mosses. It is so spongy that even hours after a rain, it is still very wet. Water absorbed by this spongy layer during heavy rains is available to streams during times of drought. This guarantees a constant , pure water supply for stream plants and animals. Hoofed animals like cattle, sheep, goats, deer, or pigs can significantly damage the forest floor by removing vegetation through grazing or rooting and by compacting the soil. They also pollute the water supply with their wastes. Without the forest cover, heavy rains result in soil erosion and flash floods. The eroded soil is carried downstream to the ocean where it can smother reefs. Where there's no rain, streams may run completely dry. In the 1930's, a massive reforestation effort was begun by the Civilian Conservation Corps (CCC). Thousands of trees were planted on barren hills and eroded slopes throughout the state, as a watershed protection measure. When reforesting the watersheds, foresters tried to use introduced species that were not valuable for timber so that later generations would not be tempted to cut the trees. They also experimentally planted many species from other parts of Asia and the Pacific. As a result, native forests are now found only in the most remote mountain areas. Two of the most widely planted trees, Cook pine and eucalyptus, are now common throughout the lower reaches of the forest. Unfortunately, there tends to be no understory (the lowest layer of plant life in the forest) associated with these trees. While there trees are a major improvement over bare soil, they don't provide adequate habitat for native plants and animals, and they may be less satisfactory than native forests in the watershed protection.
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