United States
Environmental Protection
£%	United States
Environmental Protection
What Climate Change
Means for puert0 RjC0
August 2016
EPA 430-F-16-063
Puerto Rico's climate is changing. The Commonwealth
has warmed by more than one degree (F) since the mid-
20th century, and the surrounding waters have warmed by
nearly two degrees since 1901. The sea is rising about an
inch every 15 years, and heavy rainstorms are becoming
more severe. In the coming decades, rising temperatures
are likely to increase storm damages, significantly harm
coral reefs, and increase the frequency of unpleasantly hot
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 in many places—but contributes to drought in
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.
Puerto Rico
I *1
Change in sea surface temperature (°F)
Rising sea surface temperatures since 1901. The waters around
Puerto Rico have warmed by nearly two degrees. Source: EPA,
Climate Change Indicators in the United States.
Rising Seas and Retreating Shores
Sea level has risen by about four inches relative to Puerto Rico's shoreline
since 1960. As the oceans and atmosphere continue to warm, sea level around
Puerto Rico is likely to rise one to three feet in the next century. Rising sea levei
submerges marshes, mangroves, and dry land; erodes beaches; and exacerbates
coastal flooding.
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.
Cities, roads, and ports in Puerto Rico 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. Since 1958,
rainfall during heavy storms has increased by 33 percent in Puerto Rico, and the
trend toward increasingly heavy rainstorms is likely to continue. More intense
rainstorms can increase flooding as inland rivers overtop their banks more
frequently, and more water accumulates in low-lying areas that drain slowly.

Storm surge in San Juan. Credit: Jorge Rodriguez/Creative Commons.

Water Resources
Although heavy rainstorms may become more common, total rainfall is
likely to decrease in the Caribbean region, 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, Puerto Rico may face an increased risk of drought, which in
turn can affect public water supplies, agriculture, and the economy. For
example, during the 2015 drought—one of the worst in Puerto Rico's
history—hundreds of thousands of people faced water restrictions, and
some people's water was turned off for one or two days at a time.
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 iikely due to warming and increas-
ing 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.
Bleached corals off the coast of Puerto Rico. © Hector Ruiz; used by permission.
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
Warming and acidification could harm Puerto Rico's 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.
Warmer temperatures and changes in rainfall could expand, shrink, or
shift the ranges of various plants and animals in Puerto Rico's forests,
depending on the conditions that each species requires. For example, as
summer rainfall decreases, tree species that prefer drier conditions could
move into areas once dominated by wet forest species. Other species
might shift to higher altitudes. 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. Coqui
frogs, bromeliads, mosses, and lichens are potentially vulnerable.
Freshwater ecosystems also face risks due to climate change. Rivers,
streams, and lakes hold less dissolved oxygen as they get warmer, which
can make conditions less hospitable for fish and other animals.
Higher temperatures are likely to interfere with agricultural productivity
in Puerto Rico. Hot temperatures threaten cows' health and cause them
to eat less, grow more slowly, and produce less milk. Reduced water
availability during the dry season could stress crops, while warmer
temperatures could also reduce yields of certain crops. Studies in other
tropical countries indicate that climate change may reduce plantain,
banana, and coffee yields.
Human Health
Hot days can be unhealthy—even dangerous. Certain people are espe-
cially 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
off after a hot day. Since 1950, the frequency of warm nights in Puerto
Rico has increased by about 50 percent. Currently in San Juan, the
overnight low is above 77 degrees about 10 percent of the time.
Puerto Rico's 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
will likely accelerate the mosquito life cycle and the rate at which viruses
replicate in mosquitoes.
Certain types of water-related illnesses already occur in Puerto Rico,
supported by its warm marine environment. These include vibriosis, a
bacterial infection that can come from direct contact with water or eating
infected shellfish, and ciguatera poisoning, which comes from eating fish
that contain a toxic substance produced by a type of algae. Higher ocean
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.