Water and Agroforestry

ICRISAT Center, Patancheru, India, 1985

Chin Ong, 29 June 2007

ICRAF’s research on water,1991-2007

• Past, present and future issues• Machakos (‘Mecca’ for land recovery & agroforestry)• Challenges of more trees & climate change

Upper Mbeere

Machakos

Thika

Source: Anyango, 2005

Thika

20001986

More people, less erosionTiffin & Gichuki,1997

Machakos, 1991

Machakos, 2006

More people, more trees

Embu, 1997

Majjia Valley,Niger, 1975-2002

Source: C. ReijMore rain or more soil conservation?

• More adoption of water harvesting

• Increase in dry season cultivation

• Higher incomes• Improved nutrition• More firewood• More fodder • Less time fetching water

Impacts of land recovery in Niger & Machakos

Quickbird image of Lare, Nakuru District, 2006Malesu et al. 2006

Machakos, 1991-2000

Hypothesis: Trees can capture and use resources more efficiently than crops

Machakos Research, 1985-1992

Strong focus on alley cropping and erosion

However, large plots indicate little or no improvement in crop yields.

Controls plots invaded by tree roots.

(Ayeampong et al. 1995)

1991 1991

Microclimate improvements

Hypothesis: Improvements in microclimate lower soil evaporation & promote hydraulic lift.

Maturity delayed by 2 weeks due to lower temp (-4C). Soil water benefit is not as important.

Climate change benefits?

Ong et al. 2000. Agric. Ecosyst. Environ. 80: 121-145

1993 1995

Shade benefit on coffee?

Which tree species?

Shade benefit on tea?

Which tree species?

Complementarity in water uptake

Focus attention on Grevillea robusta-maize in different arrangements

Hypothesis: Deep roots of grevillea is highly compatible with maize.

Howard et al. 1997. Agrofor Sys. 35: 15-29

1992 1995

Fast-growing trees & competition

RAC: Root studies of fast-growing trees

Is the answer below-ground?

Ong et al, 2002. Agr. Water Manag. 53: 171-186

1997 1997

Fractal index & root studies

Fractal index = ratio of lateral vs vertical roots

Index determined for a range of species. How useful?

Ong et al.1999. Agrofor.Syst.44: 87-103

1994 1996

Water balance

Total transpiration by sole maize was only 50% rainfall

85% by agroforestry systems, including 25 % during the dry season

Lott et al . 2003. For. Ecol. Mange 180: 45-59

1996 1996

Long-term consequences of different resource capture strategies?

Cautious spender: deciduous & lateral rooting

Big spender: evergreen & deep rooting

Grevillea, 15 yr

Melia volkensii, 13 yr

July 2006

Machakos, July 2006

Comparison of deciduous & evergreen trees

Melia volkensii, Machakos, 1997 Paulownia fortunei, Naro Moro, 2001

Land use change & stream flow

Sondu-Miriu hydropower plant

Loss of watershed functionof the Mau Complex

Evidence?

Mau Forest Change 1973 - 2005Key areas of deforestation include:

Eastern Mau

Western Mau

Masai Mau

Lowery, 2005

Stream flow of Nyando River

Nyando, 1968-1991

0

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400

600

800

1000

1200

1400

1600

0 5000 10000 15000 20000 25000 30000 35000 40000

Cumulative rainfall (mm)

Cum

ulat

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stre

amflo

w (m

m)

Long term river flow is 4% of annual rainfall ( Sang, 2007)

More erosive rain is predicted for Lake Victoria Basin!

Quickbird, Katuk Odeyo, 2004Katuk Odeyo, 1998

Source : Meshak

Green-blue water globally

Source: SEI

Green and blue water fluxes in Kenya

Source: SEI

Eucalyptus: an ecological time-bomb?• Millions of eucalyptus were planted in

Mau & Central Kenya.

• What will be the ecological impacts?

• Promoted by Forest Department & for Carbon Trade by TIST.

• 250m3 of water for one ton of carbon!

1 year old eucalyptus uses 30 litres of water per day! Juja 2007

Sap flow equipment for water uptake

grevillea

Map of Eucalyptus Impact on Streamflow in South Africa

Source: Mark Gush,2005

More trees with less water?

Naro Moro: Muthuri et al. 2004

Lessons & challenges for ICRAF

• Predicted changes in land use & climate will have serious impacts on water supply & erosion

• Strong tradeoffs with carbon credits: which profitable trees to plant without loss of ecosystem services?

• Machakos lessons: long-term evidence is needed, reserve water for ecosystem functions.

• Make science more meaningful to policy makers e.g. eucalyptus, bioenergy & water

• Connecting upstream & downstream, combining land management across scales e.g. Green blue water initiative with Stockholm Environment Institute on Lake Victoria Basin

• Where are the future Machakos?

De Wit 2006

Acknowledgements

Contributions & dedication of countless students & technicians.

Partners: Nottingham, Bangor, Dundee,JKUAT, IH, UWA, Sokoine, Cornell, Florida

Donors: DFID, Sida, ACU, DAAD, BMZ

ICRAF: Peter Huxley, Tony YoungMeka Rao, Ahmed Khan

RELMA team

The future is bamboo

For zero carbon footprints!

Economy class Club class