Changing Vegetation in the Savanna:

Supplementary Material to Lesson 4 of the “East Africa Climate Change Curriculum Unit”

Available at http://www.eaclipse.msu.edu/teaching_materials.html

Lesson 4 by Dwight Sieggreen & Barbara Naess. PowerPoint based on presentation by Jennifer M. Olson,

2008.

The Eaclipse Project is supported by

National Science Foundation Award No. BCS/CNH 0709671.

http://eaclipse.msu.edu

1© 2010 Michigan State University Board of Trustees

Lesson 4: Changing Vegetation in the SavannaSupplementary Material

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Rising Temperatures in East Africa

Inland Coast

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Arusha 1961-2005 (+1.1°C)Arusha mean annual temperature time series (1961 -2005)

y = 0.0248x - 29.127

R2 = 0.5132

18.5

19.0

19.5

20.0

20.5

21.0

21.5

1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

Years

Tem

pera

ture

(C)

Annual Linear Trend

Zanzibar 1961-2005 (+1.9°C)Zanzibar annual mean temperature time series (1961 - 2005)

y = 0.0423x - 57.902

R2 = 0.5755

23.0

23.5

24.0

24.5

25.0

25.5

26.0

26.5

27.0

27.5

28.0

1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

Years

Tem

pera

ture

(C)

Annual mean Linear Trend

Source: Tanzania Meteorological Agency

Variable Rainfall in East Africa

Inland Coast

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Arusha 1961-2005Arusha annual rainfall time series (1961 -2005) y = -6.2175x + 13146

R2 = 0.0799

0

200

400

600

800

1000

1200

1400

1600

1800

1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

Years

Rain

fall

(mm

)

Annual rainfall Linear Trend

Zanzibar 1961-2005Zanzibar annual rainfall time series (1961 -2005)

y = -0.792x + 3251.6

R2 = 0.0007

0

500

1000

1500

2000

2500

3000

1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

Years

Rai

nfal

l (m

m)

Annual rainfall Linear Trend

Source: Tanzania Meteorological Agency

While climate change is affecting all of East Africa, the savanna is the most vulnerable ecosystem in East Africa

Savanna vegetation is highly vulnerable to changes in temperature and moisture availability

These changes affect people’s ability to grow crops and keep livestock in the savanna (livelihood)

The EACLIPSE Project focuses on the savanna in order to have the greatest possible impact 5

Changing Vegetation

In this lesson, you will

• look at how changes in temperature and water availability affect savanna vegetation and

• make predictions as to how these changes might affect people’s choices of livelihoods and land use

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The savanna is a biome defined as a tropical grassland with scattered shrubs and trees.

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Temperature vs. Precipitation Biome Graph

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Source: The Wild Classroom. http://www.thewildclassroom.com/biomes/precipitationgraph.html

Ecological Zones in East Africa• Rainfall and evaporation determine moisture availability

• High temperatures speed up evaporation and evapotranspiration, decreasing moisture availability

• In East Africa, seven ecological zones have been described based on moisture availability and temperatures.

• Three of these zones (IV, V, and VI) include the savanna 9

Source: Kenya Ministry of Agriculture 1980: Agro-climatic zone map of Kenya 1980

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Table based on: Kenya Ministry of Agriculture 1980: Agro-climatic zone map of Kenya 1980

Source: Pratt, Greenway and Gwynne, 1966. A Classification of East African Rangeland. Journal of Applied Ecology, 3, 2: 369-382.

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Zone IV: Dry Woodland and Bushland

Higher moisture availability

Taller trees

More ground cover

Better growing conditions

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Zone V: Bushland

Lower moisture availability

Scattered shrubs

Medium ground cover

Poor growing conditions

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Zone VI: Bushland and Scrubland

Low moisture availability

Infrequent shrubs or scrub

Less ground cover

Very poor growing conditions

Changes in Savanna Vegetation

Moisture availability will impact:• crops• livestock• wildlife habitats

…affecting people’s livelihood options and land use

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Impact on Crops

• Timing of planting and harvest• Length of growing season• What crops can be planted, where• Whether some areas will be suitable for

farming• Lower crop yields (productivity)• Greater risk of crop failure

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Impact on LivestockWhen there are higher temperatures and less moisture

availability:• vegetation dries out faster• water becomes scarce• ground cover decreases (less forage for livestock)• forage grows less quickly (lower productivity)• forage species are of lower quality (palatability)• droughts are more often

and more severe• livestock diseases

are more frequent

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Impact on Wildlife Habitats• Many wildlife are sensitive to changes in temperature

and to water availability• Plants needed by some species may not grow• Wildlife migration patterns may change

The EACLIPSE project is collecting data on changes in climate and ecosystems in East Africa.

The data collected include:

•temperature and rainfall

•plant species, and

•plant density (ground cover)

This information will help researchers predict the effects of climate change and anticipate what kinds of livelihoods and land use might be viable under different conditions.

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Discussion Questions1. How does climate change affect vegetation in the

savanna?

2. What factors affect moisture availability?

3. What happens to savanna vegetation as moisture availability decreases?

4. What would happen if there were not enough moisture available for bushland and scrubland vegetation? 

5. How does the changing vegetation affect people’s livelihood/land use options?

6. How does changing vegetation fit into the human-

land-climate system loop?19

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