United States
Environmental Protection
November 2016
EPA 430-F-16-065
What Climate Change
Means for the y.s. Virgin Islands
The climate of the U.S. Virgin Islands is changing. The air
and ocean are warming, heavy rainstorms are becoming
more severe, sea level is rising, and the ocean is becoming
more acidic. In the coming decades, these environmental
changes are likely to increase threats to life and property
from severe storms, reduce the availability of fresh water
during the dry season, harm or destroy much of the
islands' coral reef ecosystems, and make air temperatures
uncomfortably hot more often.
Our climate is changing because the earth is warming.
People have increased the amount of carbon dioxide in the
air by 40 percent since the late 1700s. Other heat-trapping
greenhouse gases are also increasing. These gases have
warmed the surface and lower atmosphere of our planet
about one degree during the last 50 years. Evaporation
increases as the atmosphere warms, which increases
humidity, average rainfall, and the frequency of heavy
rainstorms—but also contributes to drought.
Greenhouse gases are also changing the world's oceans
and ice cover. Carbon dioxide reacts with water to form
carbonic acid, so the oceans are becoming more acidic.
Worldwide, the surface of the ocean has warmed about
one degree during the last 80 years. Warming is causing
mountain glaciers to retreat, and even the great ice sheets
on Greenland and Antarctica are shrinking. Thus the sea is
rising at an increasing rate.
Atlantic Ocean
Gulf of Mexico \ ) ^
U.S. Virgin Islands
Caribbean Sea
Change in sea surface temperature (°F)
0 0.5 1 1.5 2 2.5
Rising sea surface temperatures since 1901. The waters around
the U. S. Virgin Islands have warmed by nearly two degrees.
Source: EPA, Climate Change Indicators in the United States,
Ocean Warming and Sea Level Rise
The waters around the U.S. Virgin Islands have warmed by nearly two degrees
since 1901, and sea level has been rising by about an inch every ten years. As
the oceans and atmosphere continue to warm, sea level is likely to rise one to
three feet in the next century. Rising sea level submerges marshes, mangroves,
and dry land; erodes beaches; and exacerbates coastal flooding. Although most
of the territory is well above sea level, the waterfront blocks of Charlotte Amalie
are generally within three or four feet of sea level.
Eroding shoreline at Cinnamon Bay on St. John. Credit: Elizabeth Pendleton,
U.S. Geological Survey.
Coral Reefs and Ocean Acidification
In the next several decades, warming waters are likely to harm most coral reefs,
and widespread loss of coral is likely due to warming and increasing acidity of
coastal waters. Rising water temperatures can harm the algae that live inside
corals and provide food for them. This loss of algae weakens corals and can
eventually kill them. This process is commonly known as "coral bleaching"
because the loss of algae also causes corals to turn white.
Increasing acidity can also damage corals. Ocean acidity has increased by about
25 percent in the past three centuries, and it is likely to increase another
40 to 50 percent by 2100. As the ocean becomes more acidic, corals are less
able to remove minerals from the water to build their skeletons. Shellfish and
other organisms also depend on these minerals, and acidity interferes with their
ability to build protective skeletons and shells.
Warming and acidification could harm the U.S. Virgin Islands' marine ecosystems
and economic activities that depend on them. Coral reefs provide critical habitat
for a diverse range of species, while shellfish and small shell-producing plankton
are an important source of food for larger animals. Healthy reefs and fish
populations support fisheries and tourism.

Storms, Homes, and Infrastructure
Tropical storms and hurricanes have become more intense during the
past 20 years. Although warming oceans provide these storms with more
potential energy, scientists are not sure whether the recent intensification
reflects a long-term trend. Nevertheless, hurricane wind speeds and
rainfall rates are likely to increase as the climate continues to warm.
Towns, roads, and ports in the U.S. Virgin Islands are vulnerable to the
impacts of both winds and water during storms. Greater wind speeds
and the resulting damages can make insurance for wind damage more
expensive or difficult to obtain. Coastal homes and infrastructure are
likely to flood more often as sea level rises because storm surges will
become higher as well. As a result, rising sea level is likely to increase
flood insurance premiums for people living along the coast.
The changing climate is also likely to increase inland flooding. Rainfall
during heavy storms has increased by 33 percent in neighboring Puerto
Rico since 1958, and similar trends have been seen throughout the
Caribbean. The trend toward increasingly heavy rainstorms is likely to
continue. More intense rainstorms can increase flooding as dry guts
resemble rivers more frequently, and more water accumulates in low-
lying areas that drain slowly. In 2010, for example, flash flooding washed
out sections of roadway in Frederiksted.
*r Ik.

— | RjjH |
Flooding in Frederiksted on St. Croix in November 2010. © StCroixSource.com,
used by permission.
Water Resources
Although heavy rainstorms have become more common, shifting weather
patterns have caused total rainfall to decrease in the Caribbean region.
Total rainfall is likely to continue to decrease, especially during spring and
summer. Warmer temperatures also reduce the amount of water available
because they increase the rate at which water evaporates (or transpires)
into the air from soils, plants, and surface waters. With less rain and
drier soils, the U.S. Virgin Islands may face an increased risk of drought,
which in turn can affect water supplies, agriculture, and the economy. For
example, during the 2015 drought, farmers lost crops and livestock, and
some residents could no longer depend on rainwater collection or ground
water, and had to instead rely on water from desalination plants, delivered
by truck.
Warmer temperatures and changes in rainfall could expand, shrink, or
shift the ranges of forest plants and animals, depending on the conditions
that each species requires. For example, as summer rainfall decreases,
plant species that prefer drier conditions could move into areas once
dominated by wet forest species. Many tropical plants and animals live in
places where the temperature range is fairly steady year-round, so they
cannot necessarily tolerate significant changes in temperature.
Higher temperatures are likely to interfere with agricultural productivity
in the U.S. Virgin Islands. Hot temperatures threaten animals' health and
cause them to eat less and grow more slowly. Reduced water availability
during the dry season could stress crops, while warmer temperatures
could also reduce yields of certain crops. Studies in other tropical coun-
tries indicate that climate change may reduce plantain and banana yields.
If storms become more severe, sugar cane crops in neighboring countries
may be harmed more often, which could affect the availability of imported
molasses for the rum industry.
Human Health
Hot days can be unhealthy—even dangerous. Certain people are
especially vulnerable, including children, the elderly, the sick, and
the poor. Rising temperatures will increase the frequency of hot days
and warm nights. High air temperatures can cause heat stroke and
dehydration and affect people's cardiovascular and nervous systems.
Warm nights are especially dangerous because they prevent the
human body from cooling after a hot day. Although reliable long-term
temperature records for the U.S. Virgin Islands are unavailable, the
frequency of warm nights in nearby Puerto Rico has increased by about
50 percent since 1950.
The U.S. Virgin Islands' climate is suitable for mosquito species that
carry diseases such as malaria, yellow fever, and dengue fever. While
the transmission of disease depends on a variety of conditions, higher air
temperatures are likely to accelerate the mosquito life cycle and the rate
at which viruses replicate in mosquitoes.
The warm marine environment of the Virgin Islands helps promote
some water-reiated illnesses: Vibriosis is a bacterial infection that can
come from direct contact with contaminated water or eating infected
shellfish. Ciguatera poisoning comes from eating fish that contain a toxic
substance produced by a type of algae found in this area. Higher water
temperatures can increase the growth of these bacteria and algae, which
may increase the risk of these associated illnesses.
The sources of information about climate ana the impacts of climate change in this pubiication are: the national climate assessments by the U.S. Global Change Research
Program, synthesis and assessment products by the U.S. Climate Change Science Program, assessment reports by the Intergovernmental Panel on Climate Change, and EPA's
Climate Change Indicators in the United States. Mention of a particular season, location, species, or any other aspect of an impact does not imply anything about the likelihood or
importance of aspects that are not mentioned. For more information about climate change science, impacts, responses, and what you can do, visit EPA's Climate Change website
at www.eDa.aov/ciimatechanae.