Drought

Average temperature changes for the USVI are projected to increase by 1.5 °F to 4 °F by 2050 (Bowden et al., 2020). Under a high emission scenario, more than 50 days per year are expected with unprecedented increases in maximum temperatures above the historical period (1986-2005), with some years having more than 200 days of extremely hot days (Bowden et al., 2020).

Drought is a complex phenomenon that is a challenge to define and quantify, but broadly results when there is a mismatch between moisture supply and demand. Drought can last for weeks or even decades in some cases and can develop slowly over months or come on rapidly. Meteorological drought happens when there is a severe or ongoing lack of precipitation. Hydrological drought results from deficits in surface runoff and subsurface moisture supply. Little change in total annual precipitation is projected over this century for the Southeast region (Hoffman et al., 2023). However, any increases in temperature will cause more rapid loss of soil moisture during consecutive dry days, increasing the intensity of naturally occurring droughts in the future for USVI (Runkel et al. 2022). 

In the USVI, repeated and lengthy meteorological droughts combined with increased hydrological drought have resulted in periodic drying of wetlands and ghuts. During these droughts, many of the salt ponds dry up and become salt flats, ghuts do not run for months at a time, and freshwater ponds will dry. If the drought is long enough, the wetlands can be filled in and taken over by terrestrial vegetation, oftentimes pioneer invasive species such as guinea grass and tan-tan. These drying events have direct consequences for all species that rely on these habitats. Although some species are able to adapt, either through using shoreline habitats or migrating to other locations, the more vulnerable or those that have more specific ecological needs cannot. Further, intense droughts, especially during the hottest times of year stress forest habitats, oftentimes resulting in drying and dropping of the leaves that make up the canopy, exposing the understory to heat and light conditions that they are not adapted to. This has allowed invasive species such as sweet lime to thrive and disrupt the native ecosystems. 

The SGCN that are affected by drought are many and include nearly every species that relies on wetlands and forests.