46

he Southeast "sunbelt" is a rapidly growing region with population increasing by more than 30% between 1970 and 1990. Much of this growth

occurred in coastal counties,which are projected to grow another 40%

between 2000 and 2025. The number of farms in the region decreased 80%

between 1930 and 1997,but the Southeast still produces roughly one quarter

of US agricultural crops. The Southeast has become America’s "woodbasket,"

producing about half of America’s timber supplies. The region also produces a large portion of the nation’s fish,poultry, tobacco,oil,coal,and natural gas. Prior to European settlement,the landscape was primarily forests,

grasslands,and wetlands,but most of the native forests were converted to managed forests and agricultural lands by 1920. Roughly half of the remaining wetlands in the lower 48 states are located in the Southeast,and more than threequarters of the Nation’s annual wetland losses over the past 50 years occurred

in this region. Although much of the landscape has been altered,a wide range

of ecosystem types exists and overall species diversity is high.

Observed Climate Trends

emperature trends in the Southeast vary between decades,with a warm

period during the 1920s-1940s followed by a cooling trend through the

1960s. Since the 1970s,temperatures have been increasing,with the 1990’s

temperatures as warm as the peaks in the 1920s and 30s. Annual rainfall trends

show very strong increases of 20-30% or more over the past 100 years across

Mississippi,Arkansas,South Carolina,Tennessee,Alabama,and parts of Louisiana,

with mixed changes across most of the remaining area. There has been a

strong tendency for more wet spells in the Gulf Coast states,and a moderate

tendency in most other areas. The percentage of the Southeast landscape experiencing severe wetness increased approximately 10% between 1910 and 1997.

There are strong El Niño and La Niña effects in the Southeast that can result in

dramatic seasonal and year-to-year variations in temperature and precipitation.

El Niño events also tend to create atmospheric conditions that inhibit Atlantic

tropical storm development,resulting in fewer hurricanes. La Niña events have

the opposite effect,resulting in more hurricanes.

Ghost Forests

Vast stands of coastal forest are dying

along the Gulf of Mexico shoreline. Sealevel rise resulting in saltwater intrusion is

the suspected cause, and the sun-bleached

remnants of dead stems have given rise to

the common term "ghost forest" in parts of

South Florida and Louisiana. Over the past

30 years, hundreds of acres of southern

baldcypress trees have died in Louisiana

coastal parishes, with losses most acute in

areas where subsidence and navigation

channels have accelerated the rate of saltwater encroachment due to rising sea level.

Baldcypress and live oak mortality have

occurred as far as 30 miles inland. In

SOUTHEAST

T

T

KEY ISSUES

• Weather-related

Stresses on Human

Populations 

• Agricultural Crop Yields

and Economic Impacts

• Forest Productivity

Shifts

• Water Quality Stresses

• Threats to Coastal Areas
47

Florida, chronic saltwater contamination of

forest soils occurs nearer the shoreline.

Since 1991 landowners and public land

managers in Florida have observed massive die-offs of sabal palm along a 40-mile

stretch of coast between Cedar Key and

Homosassa Springs. Ed Barnard, a forest

pathologist with Florida's Forestry Division,

compares what he has seen with the aftermath of Hurricane Hugo in South Carolina,

and he attributes the Florida problem to

saltwater.

Analyses also attribute the forest decline to

salt water intrusion associated with sealevel rise. Since 1852, when the first topographic charts of this region were prepared,

Scenarios of Future Climate 

limate model projections exhibit a wide range of

plausible scenarios for both temperature and precipitation over the next century. Both of the principal

climate models used in the National Assessment project

warming in the Southeast by the 2090s,but at different

rates. The Canadian model scenario shows the

Southeast experiencing a high degree of warming,

which translates into lower soil moisture as higher temperatures increase evaporation. The Hadley model scenario simulates less warming and a significant increase

in precipitation (about 20%). Some climate models suggest that rainfall associated with El Niño and the intensity of droughts during La Niña phases will be intensified

as atmospheric CO2increases.

C

high tidal flood elevations have increased

approximately 12 inches. Coastal forest

losses will be even more severe if sea-level

rise accelerates as is expected as a result

of global warming.

Louisiana’s Coastal Land loss 

Between 1956 and 1990 (Shown in Red)

Rising sea level is one of several factors that have caused the loss of about

one million acres of Louisiana wetland since 1900. Natural and humaninduced processes contributing to these losses include subsidence due to

groundwater withdrawal and natural sediment compaction, wetland

drainage, and levee construction. The white line designates the coastal

zone and red designates land that has been converted to open water. 

Temperature Change - 20th & 21st Centuries

Precipitation Change - 20th & 21st Centuries

Observed 20th Canadian Model 21st

The Canadian model scenario for the 21st century

indicates near neutral

trends or modest increases,

while the Hadley model projects increases of near 25%

for the region. 

Observed precipitation

changes during the last

century are a

patchwork of

moderate

increases and

decreases. 

100%

75%

50%

25%

0

-25%

-50%

-75%

-100%

100%

80%

60%

40%

20%

0

-20%

-40%

-60%

-80%

-100%

Hadley Model 21st

Observed 20th Canadian Model 21st

Model scenarios project relatively uniform increases in

annually averaged temperatures. However, the

Canadian model projects

increases that are twice as

large as the Hadley model.

The largest

warming during

the last century

has occurred

along the

coastal region

(as much as

4oF), with some

inland cooling.

Hadley Model 21st

+15oF

+10oF

+5oF

0o

-5oF

+15oF

+10oF

+5oF

0o

-5oF
Weather-related Stresses on

Human Populations 

he Southeast is prone to frequent natural weather disasters

that affect human life and property.

Over half of the nation's costliest

weather-related disasters of the past

20 years have occurred in the

Southeast,costing the region over

$85 billion in damages,mostly associated with floods and hurricanes.

Across the region,intense precipitation has increased over the past 100

years,and this trend is projected to

continue.

The southern heat wave and drought

of 1998 resulted in damages in excess

of $6 billion and at least 200 deaths.

Human health concerns arise from

the projected increases in maximum

temperatures and heat index in the

region. These concerns are particularly great for lower income households that lack sufficient resources to

improve insulation and install and

operate air conditioning systems. Air

quality degradation in urban areas is

also a concern associated with elevated air temperatures and increased

emissions from power generation,

which can increase ground-level

ozone. Increased flooding in lowlying coastal counties from the

Carolinas to Texas is also likely to

adversely impact human health;

floods are the leading cause of death

from natural disasters in the region

and nationwide.

Adaptations: Traditional approaches

such as flood levees,elevated structures,and building codes are no

longer adequate by themselves,particularly in the coastal zone,as sealevel rise alone continues to increase

the propensity for storm-surge flooding in virtually all southeastern

coastal areas. Improvements in risk

assessment,coastal and floodplain

management,linking insurance to

policies for mitigating flood damage,

and local mitigation planning are

strategies that are likely to decrease

potential costs. Changes in climate

and sea-level rise should be an integral consideration as coastal communities develop strategies for hazard

preparedness and mitigation.

48

SOUTHEAST KEY ISSUES

T

Flooded community along Bayou Lafourche

in South Louisiana after landfall of Hurricane

Juan in 1985.

July Heat Index Change - 21st Century

Summer Soil Moisture Change - 20th & 21st Centuries

Observed 20th Canadian Model 21st

The Hadley model projects

soil moisture will increase

substantially in most of the

region. In contrast, the

Canadian model, with larger

projected warming and little

change in rainfall, suggests

large decreases in soil

moisture.

The observed

record of soil

moisture

illustrates

mixed

changes

across the

region. 

100%

75%

50%

25%

0

-25%

-50%

-75%

-100%

100%

75%

50%

25%

0

-25%

-50%

-75%

-100%

Hadley Model 21st

Canadian Model Hadley Model

+25oF

+20oF

+15oF

+10o

+5oF

0o

+25oF

+20oF

+15oF

+10o

+5oF

0o

The changes in the simulated

heat index for the Southeast are

the most dramatic in the nation

with the Hadley model suggesting increases of 8 to 15oF for the

southern-most states, while the

Canadian model projects increases above 20oF for much of the

region.
Agricultural Crop Yields and

Economic Impacts

rop yield and economic impact

estimates vary by climate scenario,area,and crop. The Hadley scenario simulates decreases in the yield

of most dryland (non-irrigated) crops

in the Gulf Coast area but increases

elsewhere in the region through both

the 2030s and 2090s. Average yields

of irrigated soybean,wheat,and rice

increase under the Hadley scenario

by 10% in 2030 and by more than

20% in 2090. Under the hotter and

drier Canadian climate scenario,dryland soybean yields decrease 10-30%

in some key locations by 2030 and

decrease by 80% by 2090. Economic

impact simulations follow patterns

similar to the yield maps below.

Of the major crop growing areas of

the Southeast,the lower Mississippi

Valley and Gulf Coast areas are likely

to be more negatively affected,while

the northern Atlantic Coastal Plain is

likely to be more positively affected.

Adaptations:Expected impacts on

agricultural productivity and profitability will very likely stimulate

adjustments in management strategies. Producers can switch crops or

vary planting dates,patterns of water

usage,crop rotations,and the

amounts,timing,and application

methods for fertilizers and pesticides.

Analyses indicate that farmers, except

those in the southern Mississippi

Delta and Gulf Coast areas,will likely

be able to mitigate most of the negative effects and possibly benefit from

changes in CO2and moisture that

enhance crop growth. Improvements

in understanding climate and forecasting weather would enhance the

ability of agricultural resource managers to deal effectively with future

changes. In addition,plant breeders

could respond by developing new

and improved varieties to accommodate the changed climate conditions.

49

C

Changes in Yields of Rainfed Crops 

30 year Average

Projected changes in 30-year average rainfed yields of four major crops in the

Southeast by the years 2030 and 2090 using the Hadley model scenario.

Hadley Model 2030 Hadley Model 2090

The southern heat wave and

drought of 1998 resulted in

damages in excess of $6 billion and at least 200 deaths.

Human health concerns

arise from the projected

increases in maximum temperatures and heat index in

the region. 

Improvements in risk assessment, coastal and floodplain

management, linking insurance to policies for mitigating

flood damage, and local mitigation planning are strategies

that are likely to decrease

potential costs.

% Yield Changes

>-20

>-20 to -10

>-10 to 0

0 to 10

10 to 20

20 to 50

>50

Peanuts

Sorghum Soybean

Corn

% Yield Changes

>-20

>-20 to -10

>-10 to 0

0 to 10

10 to 20

20 to 50

>50

Peanuts

Sorghum Soybean

Corn
Forest Productivity Shifts

forest process model (PnET-II)

was used to evaluate the impact

of the Hadley climate scenario and

increasing atmospheric CO2on

southeastern forest productivity. The

model simulates an increase in the

productivity of southern loblolly pine

plantations of approximately 11% by

2040 and 8% by 2100;the productivity of hardwood and mixed pine hardwood forest (which represent 64% of

the total forest area) would increase

22% by 2040 and 25% by 2100,compared to 1990. The model indicates

that the greatest increases in productivity of both pines and hardwoods

would occur in the northern half of

the region.

Other VEMAP ecosystem models used

with the Hadley Scenario also project

increases in productivity across

southern forests by 2100. However,

when these models are run with the

Canadian climate scenario,they simulate decreases in productivity in parts

of the Southeast. Furthermore,several models that are designed to project

changes in vegetation distribution as

a consequence of climate change simulate a breakup of the pine-dominated forests in parts of the Southeast by

the end of the 21st century under the

Canadian scenario. These simulations

suggest that part of the forest will

possibly be replaced by savannas and

grasslands due to decreased soil moisture and fire (see Ecosystems).

Adaptations: As the northern parts of

the region become relatively more

productive as a result of climate

change and the southern parts are

more negatively affected,timber harvesting could be shifted northward.

Other adaptation strategies include

the use of more drought-hardy strains

of pine and other silvicultural and

genetic improvements that could

increase water use efficiency or

water availability. Improved knowledge of the role of hurricanes,

droughts, fire,El Niño-related changes

in seasonal weather patterns,and

other natural disturbances will be

important in developing forest management regimes and increases in

productivity that are sustainable over

the long term. Under a hotter, drier

climate,an aggressive fire management strategy could prove to be very

important in this region.

Water Quality Stresses

urface water resources in the

Southeast are intensively managed with dams and channels,and

almost all are affected by human

activities. In some streams and lakes,

water quality is either below recommended levels or nearly so. Stresses

on water quality are associated with

intensive agricultural practices,urban

development,coastal processes,and

mining activities. The impacts of

these stresses are likely to be exacerbated by climate change. For example,higher temperatures reduce dis50

SOUTHEAST KEY ISSUES

A

S

Hadley Model Southern Pines 2000 Hadley Model Southern Pines 2100

(10 year average)

Potential Southern Pines and Hardwoods Net Primary Productivity (NPP)

300 - 800

800 - 1200

1200 - 1500

1500 - 1800

1800 - 2100

2100 - 2500

grams/meter square/year

300 - 800

800 - 1200

1200 - 1500

1500 - 1800

1800 - 2100

2100 - 2500

grams/meter square/year
solved oxygen levels in water. The

1999 flooding of eastern North

Carolina offers a graphic example of

how water quality can also be affected by extreme precipitation events,

the frequency of which are likely to

continue to increase; flood waters

fouled with sewage,rotting farm animal carcasses,fuel,and chemicals

swamped water treatment plants and

contaminated public water supplies.

Threats to Coastal Areas

ea-level rise is one of the more

certain consequences of climate

change. It has already had significant

impacts on coastal areas and these

impacts are very likely to increase.

Between 1985 and 1995,southeastern states lost more than 32,000

acres of coastal salt marsh due to a

combination of human development

activities,sea-level rise,natural subsidence,and erosion. About 35 square

miles of coastal land were lost each

year in Louisiana alone from 1978 to

1990. Flood and erosion damage

stemming from sea-level rise coupled

with storm surges are very likely to

increase in coastal communities.

Coastal ecosystems and the services

they provide to human society are

likely to be negatively affected.

Projected impacts are likely to

include the loss of barrier islands and

wetlands that protect coastal communities and ecosystems from storm

surges,reduced fisheries productivity

as coastal marshes and submerged

grass beds are displaced or eliminated,and saltwater intrusion into surface and ground water supplies. The

extent of the ecological impacts of

sea-level rise is largely dependent

upon the rate of rise and the development that has occurred along the

shoreline. Other threats to these

ecosystems come from changes in

rainfall in coastal watersheds which

are likely to alter fresh water inflows

into estuaries,altering salinity patterns that determine the type and distribution of coastal plant and animal

communities. There are few practical options for protecting natural

ecosystems as a whole from increasing temperature, changes in precipitation,or rapidly rising sea level.

As noted for other coastal regions,

one possibility is the acquisition of

lands contiguous to coastal wetlands

to allow for their inland migration as

sea level rises.

51

S

Hadley Model Southern Hardwoods 2000

Timberland Acreage Shifts

Hadley Model Southern Hardwoods 2100

(10 year average)

Simulations of Net Primary Productivity (the net amount of carbon fixed by green plants over

the course of a year) of southern pines and hardwoods as projected by one ecological model,

PnET, using the Hadley model scenario. By 2100, PnET projects that southern hardwoods will

be much more productive than pines under the climate projected by the Hadley model.

The change in

forest productivity under the

Hadley-based

scenario is

expected to

cause slightly

higher softwood

timber prices

and lower hardwood prices

than would be

the case without

climate change.

Harvests and

inventory would

also shift northward, reflecting

the northward

productivity

shifts.

5% - 25% Decline

<5% Change

5% - 25% Increase

>25% Decline

5% - 25% Decline

<5% Change

5% - 25% Increase

1993 - 2040 Without Climate Change 

2040 Hadley Model Change

300 - 800

800 - 1200

1200 - 1500

1500 - 1800

1800 - 2100

2100 - 2500

grams/meter square/year

300 - 800

800 - 1200

1200 - 1500

1500 - 1800

1800 - 2100

2100 - 2500

grams/meter square/year