Hawaiian Islands Dry Forest

Abstract

We present a status assessment of the Hawaiian islands dry forests, including the current status, stressors, and future viability. Dry forests generally have relatively low rainfall and are found on the leeward sides of the islands in lowland or in montane-subalpine zones. Historically, dry forests were located on all of the main Hawaiian islands and currently they are still found there. However, the quality of these forests is largely composed of a mix of native/nonnative vegetation. In addition to the native lowland and montane-subalpine dry forests that characterized dry forests historically, introduced dry forests and tree plantations are now classified as dry forests. Our assessment of dry forest viability, defined as the likelihood of persistence over the long term, is based on the conservation biology concepts of representation, redundancy, and resiliency. The main stressors to dry forests are invasive ungulates, plants, other herbivores, wildfires; drought; and agriculture and human development. Ongoing conservation efforts help to protect remnant patches of dry forests but this depends largely on combined efforts of various stakeholders. We developed four plausible future scenarios, each differing in levels of natural resource management, to evaluate the status of dry forests into the foreseeable future. Two of the scenarios, which are based on no change in conservation actions (Scenario One; status quo) and a slight increase in conservation actions (Scenario Two) have the highest likelihood of occurring in the foreseeable future while the other two, which are based on a slight to moderate decrease in conservation actions (Scenario Three) and a moderate to large increase in conservation actions (Scenario Four) do not. Scenario Three would severely degrade and fragment native dry forest and result in reduced resiliency, redundancy, and representation. In Scenario Four, the substantial improvements in restoration of native dry forests would result in increased resiliency, redundancy, and representation.