Hawai'i's forest resources | Forest inventory and analysis, 2010-2015

"Long-term forest monitoring is vital to understand how Hawaiian forests change over time and to manage and conserve natural resources. Forest inventories are assessed about every 10 years in Hawaiʻi by the U.S. Department of Agriculture, Forest Service, Forest Inventory and Analysis (FIA) program, in collaboration with state and federal partners. This report summarizes key findings from 246 forested plots in Hawai'i, inventoried from 2010 to 2015. Estimates were provided for forest area, tree species composition, size distribution, volume, biomass, carbon, understory vegetation, damage to trees, damaging agents, and invasive plant species across all management or owner groups (federal, state and county, and private). Forested FIA plots were located on five of the eight major Hawaiian Islands: Hawai'i, Maui, Lānaʻi, O'ahu, and Kaua'i. An estimated 1.5 million ac of forested lands were present statewide, containing many high-value resources, such as clean water, wood products, and carbon sequestration, and delivering a range of cultural ecosystem services. Hawai'i's forest inventory consisted of an estimated 1.8 billion live trees and 112 distinct tree species, including species that were native (indigenous), introduced (either by early Polynesians or more recently via European and Asian contact with Hawai'i), and invasive (those that cause economic, environmental, or ecological harm). Montane rainforests were the most common forest community type, accounting for 30 percent of Hawai'i's forested lands. ʻŌhiʻa lehua (Metrosideros polymorpha Gaudich.), an endemic, keystone tree species, was the most common and dominant tree species ≥5 inches diameter at breast height (d.b.h.) within Hawai'i's forests, followed by hāpuʻu ʻiʻi (Cibotium menziesii Hook.), hāpuʻu pulu (Cibotium glaucum (Sm.) Hook. & Arn.), and koa (Acacia koa A. Gray). Strawberry guava (Psidium cattleianum Sabine) was the most abundant tree species ≥1 inch d.b.h., followed by ʻōhiʻa lehua, invasive haole koa (Leucaena leucocephala (Lam.) de Wit), and Christmas berry (Schinus terebinthifolius Raddi). Strawberry guava is invasive and degrades Hawai'i's native forests, adversely affecting ecosystem composition, structure, function, and ecosystem services. Hawai'i's live trees represented 51 million U.S. tons of dry mass (46.3 Tg) carbon. A total of 47 percent of Hawai'i's forests were located on reserved land, primarily ceded lands managed by Hawai'i's state and county governments. This report also serves as a baseline for assessing the extent and health of ʻōhiʻa prior to the manifestation of rapid 'ōhi'a death, a disease that began causing widespread mortality of ʻōhiʻa lehua trees in 2014. This is the first FIA report for Hawai'i using the nationally standardized plot design developed by FIA, and it provides the baseline for future forest assessments and estimates of change in forest composition, structure, and health. Detailed tables and graphical highlights are included to inform resource managers, policymakers, and the public about the status and trends of their local forest ecosystems and resources."