58

hile farming and ranching are still the primary land uses of the Great

Plains,urban areas provide housing and jobs for two-thirds of the

region's people. Native ecosystems and agricultural fields intermingle with small

rural communities and the expanding metropolitan centers. The region produces much of the nation’s grain,meat,and fiber, including over 60% of the

wheat,87% of the sorghum,and 36% of the cotton. The region is home to over

60% of the nation’s livestock,including both grazing and grain-fed-cattle operations. Recreation,wildlife habitat,and water resources are also found on the

landscapes of the Great Plains. The Prairie Pothole region provides important

habitat for migratory waterfowl. Surface water in rivers,streams,and lakes,and

groundwater in aquifers provide water for urban,industrial,and agricultural uses,

as well as riparian and aquatic ecosystems. Soil organic matter is a major

resource of the Great Plains as it provides improved soil water retention,soil fertility, and long-term storage of carbon.

Climate determines many aspects of life on the Plains. For agriculture, weather

determines the planting and harvesting dates for crops,livestock grazing and

breeding seasons, and water availability. The high natural variability of climate is

a characterizing feature of the region. Farmers and ranchers have survived by

being adaptive and incorporating new technologies to buffer their production

against the variable climate. For urban centers,the availability of water often

constrains urban and industrial development. Dams,diversions, channels,and

groundwater pumping have influenced nearly all freshwater ecosystems in the

region. Ongoing social and economic changes in the Great Plains will continue

to increase demands on the region's land and water resources and challenge its

physical and social infrastructure. Climate change will present additional challenges to long-term planning for new infrastructure and the sustainable use of

land and water.

Observed Climate Trends

cross the Northern and Central Great Plains,temperatures have risen more

than 2oF (1oC) in the past century, with increases up to 5.5oF (3oC) in parts

of Montana,North Dakota,and South Dakota. In the southern Great Plains,the

20th century temperature record shows no trend. Over the last 100 years,annual precipitation has decreased by 10% in eastern Montana,North Dakota,eastern

Wyoming,and Colorado. In the eastern portion of the Great Plains,precipitation

has increased by more than 10%. Texas has experienced significantly more high

intensity rainfall. The snow season ends earlier in the spring,reflecting the

greater seasonal warming in winter and spring.

Increasing Soil Carbon Helps

Buffer Against Climate

Change Impacts

Martin Kleinschmit, a farmer and rancher in

Bow Valley, Nebraska, says that farmers

have a lot at risk as global climate heats up,

but they also have a lot to gain by participating in the solution to climate change. By

conserving soil organic matter, farmers can

improve soil health and productivity as well

as capture and store (sequester) carbon in

the extensive crop and rangelands of the

Great Plains. The higher temperatures and

greater numbers of droughts and floods

projected for the region could threaten

crops, raise production expenses, and

increase the risk of failure. To protect our

food supply, healthy soils able to withstand

erratic weather patterns are needed. 

Increasing the carbon content of the soil will

help to mitigate global warming by keeping

carbon dioxide out of the atmosphere, but it

will do even more to buffer the soil against

the threats of climate change. Presently,

most US farmland has only half or less of

its historical level of organic matter. Soil

scientists have established that a 6-inch (15

cm) block of soil with 1 to 2% organic matter can hold only about one inch (2.5 cm)

of rain before it runs out the bottom. With 4

A

GREAT PLAINS

W

KEY ISSUES

• Alteration in Timing and

Amount of Water

• Changes in Climate

Extremes

• Invasive Species Effects

on Economy and Ecology

• Stress on Human

Communities

• Conservation of Soil

Organic Matter 
Temperature Change - 20th & 21st Centuries

59

to 5% organic matter, that same soil can

hold 4-6 inches (10 to 15 cm) of rain before

it leaves the root zone and takes with it the

water-soluble nutrients. Increasing soil

organic matter also reduces the risks of

flooding and erosion, and retains moisture

longer so plants have access to it during

periods of dry weather. Soil organic matter

lessens the need for (and expense of) irrigation, reduces ground water pollution, and

reduces the amount of run-off, lessening

Precipitation Change - 20th & 21st Centuries

Observed 20th Canadian Model

The Canadian model projects

decreases in precipitation in

the southern Plains and

increases in the north. The

Hadley model projects

increases over almost the

entire region, but some

decreases are also evident

east of the Rockies.

Precipitation averages over the 20th

century indicate a

decrease in precipitation to the east of

the Rockies.

Several areas, most

notably Texas, had

precipitation

increases.

100%

75%

50%

25%

0

-25%

-50%

-75%

-100%

100%

80%

60%

40%

20%

0

-20%

-40%

-60%

-80%

-100%

Hadley Model

Observed 20th Canadian Model

The model scenarios indicate additional 5oF (Hadley

model) to 12oF (Canadian

model) increases over the

21st century for much of the

Plains.

The observed

changes in air temperature for the

Great Plains over

the 20th century

indicate a greater

warming in the

north than in the

south on average.

Hadley Model

Scenarios of Future Climate 

limate model scenarios project that temperatures will continue to rise

throughout the region,with the largest increases in the western parts of

the Plains. The Canadian model projects greater increases throughout the

region than the Hadley model. The climate model projections,as well as other

tools utilized in analyzing impacts,include a greater number of heat events –

three days in a row above 90oF – a major cause of heat stress for people and

livestock. Seasonally, more warming is expected in winter and spring than in

summer and fall. Precipitation generally increases in the region in the Hadley

model,and in the northern parts in the Canadian model. Precipitation decreases in the lee of the Rocky Mountains in both models.This is accentuated in the

Canadian model,with decreases of up to 25% in an area centered on the

Oklahoma panhandle and covering northern Texas,eastern Colorado,and western Kansas. Smaller decreases are seen in the Hadley model in a band from

northern Texas through Montana. Although precipitation increases are projected for parts of the Great Plains,increased evaporation due to rising air temperatures are projected to surpass these increases,resulting in net soil moisture

declines for large parts of the region.

C

+15oF

+10oF

+5oF

0o

-5oF

+15oF

+10oF

+5oF

0o

-5oF

the threat of stream pollution. It also lowers

the cost of fertilization since nutrients not

lost to erosion and leaching need not be

replaced. Agricultural incentives that

encourage net carbon sequestration in soil

provide an opportunity to promote food

security in a changing climate and reduce

the threat of climate change at the same

time.

Seasonally, more

warming is expected in

winter and spring than

in summer and fall.

Precipitation generally

increases in the region

in the Hadley model,

and in the northern

parts in the Canadian

model. Precipitation

decreases in the lee of

the Rocky Mountains

in both models.
Alteration in Timing and Amount of Water

ater supply, demand,allocation,storage,and quality are all climate-sensitive issues affecting the regional economy. Farming and ranching use

over 50% of the region’s water resources. Ground-water pumping for irrigation

has depleted aquifers in portions of the Great Plains by withdrawing water

much faster than it can be recharged.Under today's irrigation demands, water

table levels are thus dropping in parts of the southern Great Plains. The projected climate-induced changes in water resources are likely to exacerbate the

current competition for water among the agricultural sector, natural ecosystems,and urban,industrial,and recreational users.

Adaptations: It is possible that current strategies to deal with drought, water

shortages, extreme weather, and variability could help the region cope with

future climate change impacts. These strategies include switching to crops that

use less water, retiring marginal lands,adopting conservation tillage,and

enhanced watershed storage capacity and groundwater recharge activities.

Water availability for crops could possibly be improved using new and existing

technologies for crop residue management,wind breaks, mulches,soil carbon

management,tillage practices,precision agriculture,and more efficient methods

of water application. While these strategies would improve water use efficiency, adaptive strategies would also need to include maintaining water quality.

Flexible policies and institutions would help to adapt to unanticipated hydrologic changes.

60

GREAT PLAINS KEY ISSUES

Historical CCC

HAD

0

10

20

30

40

50

60

corn

inches 10 Year Average, 1981-1990

Historical CCC

HAD

0

5

10

15

20

25

30

35

40

inches

Consumptive Water Use Irrigation Water 

Requirements

Lack of soil moisture can greatly reduce yield of crops and

forage. Under both climate scenarios, the consumptive

demand for water on grass pasture increases more than 50%

while the water needs for irrigated corn change little.

Perennial crops such as alfalfa experience an increase in

consumptive demand for water; the size of the increase

depends on the climate scenario.

Water supplies for agriculture have been decreasing in many

parts of the Great Plains, partly due to increases in urban

uses. Irrigation water needs for grass and alfalfa are projected to increase under both climate scenarios while those for

corn rise slightly. The changes in irrigation needs reflect the

seasonal shift in precipitation that favors corn more than

perennial crops such as grass, hay, and alfalfa.

Weld County, Colorado

Historical (1981-1990 average)

Canadian (2090-2100 average)

Hadley (2090-2100 average)

Weld County, Colorado

Grass Alfalfa Corn

W

The projected climateinduced changes in water

resources are likely to

exacerbate the current

competition for water

among the agricultural sector, natural ecosystems,

and urban, industrial, and

recreational users.

Canadian

Historical

Hadley Canadian

Historical

Hadley
Changes in Climate Extremes

xtreme climate and weather events have major effects on urban and rural

lives. The April 1997 flood put approximately 90% of Grand Forks,North

Dakota under water and caused over $1 billion in damages. A short-term heat

wave in July 1995 caused the deaths of over 4,000 feedlot cattle in Missouri.

The severe drought from Fall 1995 through Summer 1996 in the agricultural

regions of the southern Great Plains resulted in about $5 billion in damages.

There is some chance that the projected increase in drought tendency in the

Sand Hills of the Great Plains will result in expansion or shifting of sand dunes

if vegetation cover is not maintained. The potential for new patterns in climate

extremes raises questions about the ability of current coping strategies to deal

with future impacts.

Adaptations: Better access to more accurate and timely information about nearterm weather including extreme events,and longer-term forecasts could help

reduce risk and uncertainty in decision making. For example,heat stress events

are projected to occur more often in the central and southern Great Plains in

the future. This information can help intensive-livestock operators weigh strategic decisions about investments in cooling systems. Real-time weather information can prepare them to implement an immediate response to cool their animals.

61

E

The potential for new patterns

in climate extremes raises

questions about the ability of

current coping strategies to

deal with future impacts.

Both models project substantial

increases in the July heat index

(which combines heat and humidity)

over the 21st century. These maps

show the projected increase in average daily July heat index relative to

the present. The largest increases

are in southern areas, where the

Canadian model projects increases

of more than 25 ̊F. 

Canadian Model

Hadley Model

July Heat Index Change

21st Century

+25oF

+20oF

+15oF

+10oF

+5oF

0oF

+25oF

+20oF

+15oF

+10oF

+5oF

0oF

The Palmer Drought Severity Index (PDSI) is a commonly used measure of drought severity taking into account differences in temperature, precipitation, and capacity of soils to hold water. These maps

show projected changes in the PDSI over the 21st century, based on

the Canadian and Hadley climate scenarios. A PDSI of –4 indicates

extreme drought conditions. The most intense droughts are in the –6

to –10 range, similar to the major droughts of the 1930s. By the end

of the century, the Canadian scenario projects that extreme drought

will be a common occurrence over much of the Great Plains, while

the Hadley model projects much more moderate drought conditions.

Canadian Model Hadley Model

Palmer Drought Severity Index Change

21st Century

>10

8

6

4

2

0

-2

-4

-6

-8

-10
62

GREAT PLAINS KEY ISSUES

Invasive Species Effects on Economy and Ecology

he native grasslands,shrublands, forests,and riparian ecosystems of the

Great Plains are home to a variety of plants and animals. Nearly 60% of

the bird species that breed in the US do so in the Great Plains. Agriculture and

urban development have disrupted these native ecosystems,and invasive

species are currently a serious challenge in both native ecosystems and agricultural systems. For example,leafy spurge currently reduces grazing capacity on

grasslands. Field bindweed lowers crop production in Kansas by $40 million a

year. Projected climate change is likely to alter the current biodiversity. A possible migration of invasive species across the Great Plains is a concern to stakeholders because the rapid rate of climate change is likely to be disadvantageous

to native species. The exact social costs will depend upon the particular invasive species or type of change in biodiversity.

Adaptations: Effective coping strategies would help provide plants and animals

with habitats for adaptation such as maintaining a diversity of vegetation types

and connectivity between the types. Preserving intact riparian areas, wetlands,

and natural areas is likely to slow or reduce future invasions and is beneficial

even in the absence of climate change.

Stress on Human Communities

ural communities,already stressed by their declining populations and

shrinking economic base,are dependent on the competitive advantage of

their agricultural products in domestic and foreign markets. Large corporate

enterprises,the result of agribusiness modernization and consolidation,have

greater resources and technology with which to buffer themselves against both

economic and climatic variability. Thus,a changing climate is an additional

stress that disproportionately impacts family farmers and ranchers. In urban

Spotted knapweed has

infested over 5 million

acres in Montana and is a

threat to pristine natural

areas such as the Grand

Teton National Park in

Wyoming. 

Leafy spurge currently

reduces grazing capacity,

plant diversity, and wildlife

habitat on grasslands.

Yellow starthistle, an annual herb up to 3 feet tall,

currently infests over 9

million acres of rangeland

in the western US, with

nearly 8 million acres in

California alone. This invasive species spreads as a

contaminant in agricultural

seeds.

Leafy spurge, a federallydesignated noxious weed,

currently can be found in 8

of the 10 Great Plains states.

First recorded in 1827, leafy

spurge spread from

Massachusetts to North

Dakota in 80 years. This

deep rooted, perennial plant

forms dense stands that

aggressively crowd out

most other vegetation, causing a loss of plant diversity,

reduction of forage, and

loss of wildlife habitat.

Leafy spurge can spread

rapidly through seed dispersal as well as being carried

by birds and other animals.

It can expel its seeds to distances of 15 feet.

T

Distribution of Leafy Spurge in the Western US

By County - 1996

A possible migration of

invasive species across

the Great Plains is a concern to stakeholders

because the rapid rate of

climate change is likely

to be disadvantageous to

native species. R

Leafy Spurge

No Data
The productivity of the Great Plains increases from west to east and from north to south, following the precipitation and the temperature gradients. Land uses are strongly influenced by productivity. Both climate scenarios increase the moisture stress in the

central parts of the Great Plains and productivity declines in this region.

Net Primary Productivity (NPP)

1961 - 1990

0-100

100-200

200-300

300-400

400-500

500-600

600-700

700-800

800-900

900-1000

>1000

No Data

NPP (g/sq m)

<-100

-100- -40

-40- -20

-20- -0

0-20

20-40

40-60

60-80

80-100

100-150

>150

No Data

Difference 

(g/sq m)

Canadian Model 

Difference from 1961-90 by 2100 

Hadley Model 

Difference from 1961-90 by 2100 

Soil Carbon 

800-1600

1600-2400

2400-3200

3200-4000

4000-4800

4800-5600

5600-6400

6400-7200

7200-8000

8000-8800

8800-9600

No Data

Soil C (g/sq m)

<-1500

-1500- -500

-500- -250

-250- -200

-200- -150

-150- -100

-100- -50

-50- 0

0-50

50-100

100-500

>500

No Data

Soil C (g/sq m)

Canadian Model 

1961 - 1990 Difference from 1961-90 by 2100 

Hadley Model 

Difference from 1961-90 by 2100 

Soil carbon is vital for retaining water and

nutrients. The amount of carbon stored in the

soil is strongly influenced by past and present

land management practices and weather patterns. Overall, soil carbon is projected to

decline in response to higher temperatures in

both climate scenarios. In some areas, climate changes reduce the decomposition of

soil organic matter, resulting in increased soil

carbon.

63

Higher air temperatures increase the rate of evaporation, removing moisture

from the soil faster than it can be added by increased precipitation, resulting in

net soil moisture declines for a large part of the Great Plains.

Canadian Model Hadley Model

Summer Soil Moisture Change - 21st Century

+100%

+75%

+50%

+25%

0

-25%

-50%

-75%

-100%

communities,the impacts of floods,

heat waves,and other climate events

is a crucial emerging issue with significant economic implications.

Many poorer people can not afford

air conditioning,insulation,substantial housing,and other means of coping with climate extremes.

Therefore,climate change impacts

will vary significantly by social and

economic status.

Adaptations:Diversification within

enterprises and rural communities

could help to reduce risk and cope

with the additional stress of climate

change. Community-level dialogue is

vital in identifying information needed by managers and in assessing policy options for climate change.