A	United States
Environmental Protection
LI M % Agency
What Climate Change
Means ^Louisiana
August 2016
EPA 430-F-16-020
In the coming decades, Louisiana will become warmer, and both
floods and droughts may become more severe. Unlike most of the
nation, Louisiana did not become warmer during the last century.
But soils have become drier, annual rainfall has increased, more
rain arrives in heavy downpours, and sea level is rising. Our
changing climate is likely to increase damages from floods,
reduce crop yields and harm fisheries, increase the number of
unpleasantly hot days, and increase the risk of heat stroke and
other heat-related illnesses.
The climate is changing because our planet 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 the earth about one degree (F) 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 others. While most of the earth warmed, natural
cycles and sulfates in the air cooled Louisiana. Sulfates are air
pollutants that reflect sunlight back into space. Now sulfate
emissions are declining, and the factors that once prevented the
state from warming are unlikely to persist.
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. The surface of the ocean
has warmed about one degree during the last 80 years. Warming
is causing snow to melt earlier in spring, and mountain glaciers
are retreating. Even the great ice sheets on Greenland and Ant-
arctica are shrinking. Thus the sea is rising at an increasing rate.
Rising Seas and Retreating Shores
Rising sea level is likely to accelerate coastal erosion
caused today by sinking land and human activities. The
sediment washing down the Mississippi River created the
river delta that comprises most of coastal Louisiana. These
sediments gradually compact, so the land sinks about
one inch every three years. Historically, the river would
occasionally overflow its banks and deposit enough new
sediment to allow the land surface to keep pace with rising
sea level and the delta's tendency to sink. But today, river
levees, navigation channels, and other human activities
thwart this natural land-building process, so coastal lands
are being submerged. Louisiana has been losing about
25 square miles of land per year in recent decades.
If temperatures continue to warm, sea level is likely to rise
one to three feet during the next century. Rising sea level
has the same effect as sinking land, so changing climate is
likely to accelerate coastal erosion and land loss. Federal,
state, and local governments have ongoing projects to slow
land loss in Louisiana, but if the sea rises more rapidly in
the future, these efforts will become increasingly difficult.
Tropical Storms
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
Temperature change (°F):
Rising temperatures in the last century. Louisiana has warmed less than Most of New Orleans was flooded when rising water overtopped
most of the United States, and part of the state has cooled. Source: EPA, levees and floodwalls during Hunicane Katrina in 2005.
Climate Change Indicators in the United States.	Credit: LtCdr Mark Moran, NOAA Corps

Increased Flooding
Whether or not tropical storms become more frequent, rising
sea level makes low-lying areas more prone to flooding. Many
coastal roads, railways, airports, and oil and gas facilities are
vulnerable to the impacts of storms and sea level rise. Louisiana
is especially vulnerable, because much of New Orleans and
other populated areas are below sea level, protected by levees
and pumping systems that remove rainwater, which cannot drain
naturally. With a higher sea level, these levees may be over-
topped more readily during storms. Severe flooding can disrupt
the economy of a city by inducing people to move away, which
occurred after Hurricane Katrina in New Orleans. The greater
flood risk is also likely to increase flood insurance rates.
Changing climate is also likely to increase the risk of inland
flooding. Since 1958, the amount of precipitation falling during
heavy rainstorms has increased by 27 percent in the Southeast,
and the trend toward increasingly heavy rainstorms is likely to
continue. Moreover, the amount of rainfall in the Midwest is also
likely to increase, which could worsen flooding in Louisiana,
because most of the Midwest drains into the Mississippi River.
The Port of New Orleans is vulnerable to river floods that shut
down traffic on the Mississippi River, as well as coastal storms
that can flood port facilities. In 2011, high water levels on the
Mississippi River led the U.S. Army Corps of Engineers to divert
water through the Morganza Spillway to the Atchafalaya River to
prevent serious flooding of Baton Rouge and New Orleans. The
resulting high water on the Atchafalaya flooded small towns and
about 1,000 square miles of agricultural land, and required tem-
porary levees to protect Morgan City. Although major flooding on
the Mississippi River was avoided, high water levels still caused
a barge collision that led the Corps to close the river near Baton
Rouge for four days.
Heavy rains flooded Frankiinton in March 2016. Credit: Sgt. Cody
Westmoreland, Louisiana Army National Guard.
Agriculture, Forests, and Fisheries
Changing climate will have both harmful and beneficial effects
on farming. Seventy years from now, Louisiana is likely to have
35 to 70 days with temperatures above 95°F, compared with
about 15 days today. Even during the next few decades, hotter
summers are likely to reduce yields of corn and rice. But higher
concentrations of atmospheric carbon dioxide increase crop
yields, and that fertilizing effect is likely to offset the harmful ef-
fects of heat on soybeans and cotton—if adequate water is
available. On farms without irrigation, however, increasingly
severe droughts could cause more crop failures. Higher
temperatures are also likely to reduce livestock productivity,
because heat stress disrupts the animals' metabolism.
Higher temperatures and changes in rainfall are unlikely to
substantially reduce forest cover in Louisiana, although the
composition of trees in the forests may change. More droughts
would reduce forest productivity, and climate change is also
likely to increase the damage from insects and disease. But
longer growing seasons and increased concentrations of carbon
dioxide could more than offset the losses from those factors.
Forests cover about half of the state, with loblolly-shortleaf pine
forests most common outside of wetland areas. Changing
climate may cause the loblolly and shortleaf pine trees to give
way to oak-pine forests.
Rising sea level and higher temperatures threaten Louisiana's
fisheries. Coastal wetlands account for most of the land that the
state has been losing. Those wetlands support shrimp, oyster,
crab, crawfish, menhaden, and other fisheries-about 75 percent
of the state's total commercial fisheries. Rising temperatures
may also harm fish by reducing levels of dissolved oxygen in the
water, promoting harmful algal blooms, bacteria, and other
factors that contribute to diseases in coastal waters.
Human Health
Hot days can be unhealthy, even dangerous. Certain people are
especially vulnerable, including children, the elderly, the sick,
and the poor. High air temperatures can cause heat stroke and
dehydration and affect people's cardiovascular and nervous
systems. Warmer air can also increase the formation of ground-
level ozone, a key component of smog. Ozone has a variety of
health effects, aggravates lung diseases such as asthma, and
increases the risk of premature death from heart or lung
disease. EPA and the Louisiana Department of Environmental
Quality have been working to reduce ozone concentrations. As
the climate changes, continued progress toward clean air will
become more difficult.
The sources of information about ciimate and the impacts of climate change in this publication 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.epa.aov/climatechanae.