International Thematic School ‘Water and society’

Oléron , 11-17 May 2014

Pastoralism and water resources in the Sahel region

Pierre Hiernaux agronomist, ecologist, retired CNRS scientist

pierre.hiernaux@wanadoo.fr

Intervention outline

The water needs of livestock

(individual animal/day-year)

Sahel desertification/greening

(local-continental/year-decades)

Water provision to pastoral systems

(Herd-populations/seasons-years)

Grazing impact on water cycling Northern Sahel rangelands (Gourma, Mali)

Southern Sahel agro-pastoral system (Fakara, Niger)

(local-district scale/seasons-years)

Water needs of livestock Water losses

Pulmonary

evaporation (<10%)

Evaporative cooling: sweating & panting

(≈ 80%) Urine (1200-3500 mOsm/kg) Feces (> 45-60 % water) Lactation (milk

85-88% water)

Water intake

Drinking (variable)

Ingested in

feed (5-85%) Metabolic

water (intracellular respiration) a few %

Respiratory (≈ 10%) intake cutaneous

exchanges (insignificant)

Water 60-70% (Δ <20%) Livestock bodies

Water needs of livestock

In average for cattle, sheep and goats:

20-50 l/day/ TLU

(i.e. 250 kg LW)

Ref.: King J., Liverstock water needs in pastoral Africa …, 1983

Unlike feed dry matter intake that is a function of the animal metabolic weight , the daily water intake by livestock drinking is quite variable with: • water ingested in feed • air temperature and relative humidity

(sweat, pant, pulmonary exchanges…) • livestock physical activity (distance

walked, draft…) • pregnancy and lactation (3L water/ L milk) • difference between species and

breeds (body size, urine concentration, feces water content, panting/sweating, cutaneous exchanges…)

Water needs of livestock

The drinking frequency do also vary with: • Species and breeds (daily for goats,

up to every 3 days for cattle and sheep, up to every 15 days for camels in Sahel breeds)

• water ingested in feed • air temperature and relative

humidity • livestock physical activity The drinking frequency determine

the maximum possible grazing distance from the water point (the radius of the « piosphere »)

The drinking frequency modifies the ratio of fodder to water resource

access to water is thus a key of the access to fodder resources.

I. Touré, 2010

District of Tessékré, Sénégal

30 km

Watering

frequency

distribution herds % (dry season northern

Mali) distance water to pasture (km)

10-19 20-29 30-39 >40

goats 1-2 54 46 0 0

sheep 3 30 54 16 0

zebu 2-3 19 66 15 0

camel 5-6 23 23 39 13

source Swift 1979

Water provision to livestock

Depending on seasons, geology, geomorphology and investment in infrastructure drinking water is provided to pastoral families and to livestock through a range of possible sources:

• Surface water: springs, streams, lakes, ponds of variable size and seasonality. No need of device to fetch water. Most of surface water points are open access.

• Shallow wells, wells, boreholes from which water is fetched either manually, or using animal draft, or with pumps (exceptionally artesian boreholes). Some are open access, other are communal access and a few private.

• Mobile water tanks filled either from surface water or from deep water. They allow to extend the radius at relatively high labour cost, mostly for small ruminants and young animals

Water provision to livestock Pastoral systems are breeding systems in which

animal nutrition is almost exclusively achieved by grazing rangelands, fallows, stubbles…

In Sahel, pastoral system adapt to the large temporal and spatial variations in fodder availability by different form of livestock mobility:

– Daily (or few days ) grazing circuit

– Seasonal and regional transhumance

– Nomadism

In all cases the access to water points structure herd mobility, and the rights to graze

Water provision to livestock

In Sahel, in adaptation to the large seasonal and interannuals variations in grazing resources, pastoral systems are communal: access to rangeland and water points are open either within communities or public, opposite to ranching systems developped in other arid and semi-arid regions (Australia, US, Argentina, Brazil…) where the access to rangeland is privatised. There are dynamics between the two systems (Botswana, Inner Mongolia)

Pastoral development programs have

concentrated on providing networks of water points (web of boreholds in Ferlo in the 50’s, recent work funded by AFD in Chad rehabilitation and complementary infrastructures; involving communities).

Water provision in pastoral systems Concentrations of livestock at main water points

are spectacular, yet in numbers the volume of water drinked by livestock per unit area grazed is minimal: fodder is the limiting resource of pastoral systems

This is confirmed by the minimal impact of

livestock drinking in the drying up of surface water points during dry seasons example Agoufou Mali (Gardelle et al. 2010) and pounds in Fakara (Desconet et al. 1997 )

This does not contradict the very low

performance of livestock products in terms of water use (e.g. 15000l virtual water/kg meat; 1500l of drinking water). However the same figure could be interpreted as ingenious ways to tap water resources that are not available to grow crops and yet produce high quality feed to humanity and a living for pastoralist families.

y = -0,0058x + 234,06 R² = 0,9628

1,40

1,90

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3,90

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Evolution saisonnière de la hauteur de l'eau de la mare d'agoufou en 2010-2011

decrue= 0,58cm/j

Hauteur (m)

Drinking water (l/m²/yr) /Stocking rate (TLU/km²)

TLU/km² 5 10 20 40

L/m²/yr 0,09 0,18 0,36 0,73

Grasing impact on water cycling

In addition to the direct intake and offtake of water grazing livestock indirectly affect water cycling through: • The short term effect of

trampling on soil surface (crust, litter burying) and sub-surface (compaction)

• The short and long term effects of fodder intake on herbage cover, species composition…

• The long term effects of nutrient cycling (fodder uptake and excretion deposition) on soil biological activity and fertility that contribute to vegetation production and species composition

During the dry season

• At short term straws transfered to litter by trampling

• Crust and litter fragmented and litter buryed by trampling

All year round

• Fertilization by excretion feces (1/2 of intake) and urines, biological activation, rise soil pH

• Seed dispersion (particular species)

During the wet season

• At short term herbage growth altered by grazing-trampling (grass tillering, regrowth function of timing and intensity of grazing, at worth 50% loss in production

• Trampling remove crust on sandy soils, compact loamy soils..

• At longer term selective grazing, trampling, organic matter recycling lead to species changes

The processes of impact:

Multi ways impact, globaly mild, althoug could be determining at long term in sedentary grazing systems

Grazing Impact on water cycling

Seasonal states: herbaceous

vegetation cover, mass, woody plant

leaf mass driven by soil

moisture regime, rainfall, climate

27-08-2007

07-06-2008

28-05-2008

26-09-2007

13-09-2010

30-09-2008

15-09-2009

26-08-2011

Large year to year variations in

herbaceous cover, production,

species composition, mostly driven by

rainfall distribution: Largely reversible

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amj j aasond j fmamj j asond j fmamj j asond j fmamj j asond

Site 17, Agoufou, Avril 2007 - Sept 2010

den…

Kg/ha plant/m² %

0

20

40

60

80

aamj j asonnd j fmamj j j asond j fmmamj j asonnd j fmamj j j asond

Daily rains (mm) at Agoufou 2007-2010

270 mm 324,5

514,5 mm 329 mm

Large seasonal and interannual dynamics

Grazing Impact on water cycling

0

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1/5 31/5 30/6 30/7 29/8 28/9 28/10

Standing herbaceous mass, site 17 2004

2005

2006

2007

2008

2009

2010

2011

50 kg/ha/d

0

20

40

60

80

100

A L R S1 S2 S3

Mean (180 site x year) growth rates on vegetated patches during rapid growth by soil and grazing

pressure typekg/ha/d

In average 85% of the herbaceous growth is achieved in a ‘rapid growth’ period of 45 days, from grass tillering to heading.

• The timing is controlled by the rainfall pattern and the productivity by soil fertility.

• The short term effect of grazing on herbaceous production during wet season is moderate and local, because to the rapid speed of the growth, yet it differs with soil types.

Grazing Impact on water cycling

During the dry season, the losses of standing (straws) and lying (litter) herbaceous masses is a function of the grazing pressure:

Dry season decrease of herbaceous mass at Agoufou

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1/9 1/10 31/10 30/11 30/12 29/1 28/2 30/3 29/4 29/5 28/6 28/7

2004-05

2006-07

2007-08

2008-09

2009-10

2010-11

kg/ha

20 kg/ha/d

5 kg/ha/d

b

Dry season decrease of herbaceous mass at Louggéré Kilouki

0

600

1200

1800

2400

3000

3600

4200

4800

1/9 1/10 31/10 30/11 30/12 29/1 28/2 30/3 29/4 29/5 28/6 28/7

2004-05

2005-06

2006-07

2007-08

2008-09

2009-10

2010-11

kg/ha

20 kg/ha/d 5 kg/ha/d

a

0

200

400

600

800

1000

1200

1400

Sept Oct-Nov Nov-Mar Mar-Jun

Mean herbaceous mass at the end of the three periods

of the dry season on sandy soils depending on grazing

pressure (H=high, M=medium, L=light), ( means for 365 periods out of 101 site-year series )

Sand_L

Sand_M

Sand_H

kg MS/ha

0

10

20

30

40

50

S_PP S_MP S_TP R_PP L_MP A_TP

Month rate of degradation of herbaceous (%) by soil type (S= sandy, R= rocky,L=loamy, A= clayed) and grazing pressure ( PP

light, MP moderate, TP high grazing pressure) , ( means for 365 periods out of 101 site-year series )

%overall mean = 24,1 10,3

Grazing Impact on water cycling

Standing

Straw (7) Litter

(8)

Livestock

intake

Livestock

excretions Trampling

Insect &

rodent …

herbivory

Insect &

rodent …

excretions

Litter

fragmentation

and burrying

Microbial & fungal decomposition

humification

Minéralisation

Components and

processes of herbaceous

vegetation degradation

during the dry season

Trampling

1

1

1

2

3

4

5

6

1

SOM

Soil litter

1

1 decay

Grazing Impact on water cycling

0

200

400

600

800

1000

1200

1400

setp oct nov dec janv févr mars avr mai juin

masse de paille et litière

Bdi

Bli

Bdni

Blni

kg/ha

20%

4%

25%31%

6%

14%

Bilan de masse des pailles et litière en saison sèche

standing offtake

litter offtake

trampling

degraded

standing June

litter June

high grazing pressure

Grazing Impact on water cycling

60 km Shallow soils (≈ 30%) Sandy soils (≈ 65%) Clay soils (≈5%)

Run–off and soil texture drives large edaphic diversity in Sahel rangelands

Shallow soils (≈ 30%)

Grazing Impact on water cycling Gourma

09/2009

10/1988

09/1993

09/1985 Sandy soil 09/1985

10/1988

08/2005

09/2009

09/1986

09/1991

05/1993

09/2009

Clay soil Shallow soil

The response to extreme events: 1983-84 drought, is site (soil type) specific

Gourma

y = 5,3 x - 124 r² = 0,17

-300

-200

-100

0

100

200

300

198

4

198

5

198

6

198

7

198

8

198

9

199

0

199

1

199

2

199

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2000

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1

2002

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201

0

201

1

mm Anomalies des pluies annuelles à Hombori, 1984-2011

y = 18,8x + 710 r² = 0,19

0

500

1000

1500

2000

19

84

19

85

19

86

19

87

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kg/ha moyenne des masses sur pied maximales annuelles tous sites du Gourma

Gourma

Barg = 36,7 x + 1070 r² = 0,15

Bgla = 8,2 x + 215 r² = 0,15

Bsab = 22,5 x + 717 r² = 0,20

0

500

1000

1500

2000

2500

3000

3500

4000

kg DM/ha

argileux

glacis

sableux

m = 1565 kg; cv = 46% m = 326 kg; cv = 51%

m = 1021kg; cv = 38%

m = 964 kg; cv = 34%

From field monitoring: very fast recovery for sandy soils from the 1983-84 drought (high rain use efficiency)

different dynamics involved for shallow: erosion and run-off increase and clay soils depressions): more water in depressions and ponds

Gourma

O verall increase in woody plant density and cover since the 80’s drought except on shallow soils

Hiernaux et al 2009b; Trichon et al. 2009

Canopy cover of woody plant populations (%)

0

10

20

30

40

1985 1990 1995 2000 2005

Co

ver

% (

clay

)

0

2

4

6

8

Co

ver

% (

shal

low

, san

d)

Clay Shallow Sand

1985

2007

1986 2007

Gourma

Persisting decrease in numbers and cover of woody plant thickets of the ‘tiger bush’ on shallow soils slopes (Ortondé site)

- 61 % - 65 % - 7 % 1955 1985 1996 2007

Courtesy: V. Trichon, L. Roussel

Gourma Gourma

On shallow soils: vicous circle of vegetation decay, increased runoff,

gully extenting, deepening and interconnecting, soil erosion and alluvium deposition

2008 1954

Ramarohetra 2010

Gourma

Paradoxal area and capacity increase of the Agoufou pond in last 40 years. From aerial photographies, LANDSAT, SPOT and MODIS satellite images.

J. Gardelle et al. 2010

Gourma

1966

2007

Gourma

0

2500

5000

7500

10000

12500

15000

1975 2002 1975 2002 1975 2002

Turbid water

Clear water

North Centre South

Total flooded pond area (ha)

+ 168%

+ 233%

+ 125%

+ 370%

+ 13%

- 8%

+ 57%

+ 115%

+ 48%

1996

Large edaphic diversity due to soils, run-off/run-on, and also to agro-sylvo-pastoral management in southern Sahel (Fakara, Niger)

Acacière

Dunes

Rangeland

Cattle path

Old fallow

Young fallow Millet field, not manured Millete field, manured Rangeland

Banizoubou

Grazing Impact on water cycling Fakara

2009

2011

2012

2010

Supervised classification

SPOT 1986 (LTHE),

P. Hiernaux

Supervised classification

SPOT 2011 (HSM),

P. Hiernaux

Crop land expansion keep going at 3.3% per year from 1986 and 2011, to the detriment of fallow

area while rangeland (uncropable lands) remain stable so as overall woody plant cover.

Annual rates of changes over the period

(%)

Cropland Fallow Rangeland

50-

75

75-

94

50-

75

75-

94

50-

75

75-

94

7.7 3.3 5.8 0.0 - 3.6 - 4.5

0

10

20

30

40

50

60

1980 1985 1990 1995 2000 2005 2010 2015

Land use dynamics, Fakara

% champs % jachères % parcours % ligneux

%

Historical dynamics of land use in the district of Dantiandou

Grazing Impact on water cycling

Fakara

Total des pluies annuelles à Banizoumbou, 1994 à 2010

0,0

200,0

400,0

600,0

800,0

19

94

19

95

19

96

19

97

19

98

19

99

20

00

20

01

20

02

20

03

20

04

20

05

20

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20

07

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08

20

09

20

10

mm

Mean herb standing mass in fallow-rangelands 1994-2010

y = -326Ln(x) + 1465

R2 = 0,63

0

500

1000

1500

2000

2500

3000

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

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2010

kg MS/ha

interannual changes in mean millet and weeds yield

Dantiandou sites

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500

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4000

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

weeds

millet

Jachère pâturée le 20/09/2010

Champ de mil, le 20/09/2010

Fakara

Decreasing trend in ‘tiger bush’ density on the hard pan plateaus from 1950 to 1992

Cropland expension and gully densification on the sandy slope from 1950 to 1992

(Leblanc et al., 2008)

Fakara

Impact of the land use and vegetation changes :

• increased run-off especially from the hard pan plateau and other shallow soils

• Extending, deepening and interconnecting gullies on sandy slopes

• Increase in water collected in temporal ponds dowslopes

• Increase percolation in gullies and ponds sandy floors leading to the rise of the water table

Rising CT water table height from 1963 to 1997, in Western Niger

Favreau & Leduc 1998

Fakara

Desertification vulnerability of Africa Source : GLASOD/UNEP (United Nations Environment Program)- 1991

Desertification is defined by United Nations : “Desertification is the degradation of land in any dryland. It is caused by a variety of factors, such as climate change and human activities”

The desertification paradigm has a long

history in Sahel and was debated since the late 19een century. It mobilised scientists and colonial administration (Hubert and Chudeau in 1920-1921; Stebbing 1934-35; Jones 1937 and get re-inforced by colonial ideology (Aubreville 1949).

The paradigm was refuelled by the

catastrophic draught of 1973-74, and the international community institutionalised the action to stop desertification by creating UNEP

Sahel desertification/greening

NDVI AVHRR 1982-99 Ekhlund et al. 2003

NDVI, GIMMS AVHRR 1981-2003 Anyamba &Tucker 2005

Residual of best NDVI fit with GPCP rainfall estimates 1982-2004 Herrmann et al. 2005

Sahel desertification/greening Sahel greening a recent finding of the satellite remote sensing : regional increase in NDVI

Re-greening trends are observed over most parts of the Sahel, except for western Niger and center Soudan, where negative trends are observed. These trends are significant over the period 1981-2011. Gourma => re-greening trends Fakara => degradation trends

Gourma (Mali)

Dardel C. et al. RSE 2014

Fakara (Niger)

Trend of mean NDVI in growing season over the period 1981-2011

Sahel desertification/greening

NDVI3g - Fakara

Regreening trends in Gourma and degradation trends in Fakara are robust over time. Same recovery behaviour for Gourma and Fakara right after the drought, but stories differ after the 1990’s.

Sensitivity analysis to time period

Dardel C. et al. 2014

Sahel desertification/greening

NDVI3g - Gourma

Good agreement in both regions between satellite NDVI trend and herbaceous mass measured on the fields confirmation of the overall greening trend in Sahel with a few local exceptions with persisting degradation of the vegetation cover/production independant of rainfall trends

Dardel C. et al. 2014

Fakara

Gourma

Sahel desertification/greening

Conclusion: pastoral systems and water in Sahel

The livestock water needs constraint pastoral production. They vary with pastoral environment and breeds but are quantitatively modest.

The provision of drinking water is key to pastoral systems and to their development, diversity of sources and free access secure pastoral economy.

The main impact of livestock grazing on water cycle is indirect, multi-way and site specific (soil texture, topography, land use, livestock mobility…). Small and gentle in average the impact can be locally determinant on the long run affecting water cycling and ecosystem functioning.

Grazing by pastoral livestock is contributing to both ‘greening’ trends on sandy soils and low land fine textured soils, and to the persisting degradation of vegetation cover on shallow soils with its consequences on increasing run-off, surface water stocks in ponds and water tables recharge.

Thank you for listening !

• Herbaceous, mostly annuals dominated by C4 grasses. -> The interannual fluctuations in species composition may be locally spectacular -> no obvious trend in C3/C4 contributions -> some trends in particular species contribution at medium term in response to drought, or to grazing pressure status

0

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1984

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'Cenchrus biflorus'

'Aristida mutabilis'

'Zornia glochidiata'

Contribution

to cover %

Sandy soils

centre sahel

Sandy soils, centre-south Sahel

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17 18 19 31

Grass %

c

Contribution of C4 species by soil type and grazing pressure (1984-2006)

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clay-high silt-mid

rock-low sand-low

sand-mid sand-high

%

Gourma

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2500

3000

1 2 3 4 5 6 7 8 ≥ 9

weeds millet totalYield Kg DM ha-1

Crop field age (y) ∞

Strong domination by to crop weeds Mitracarpus scaber (C3, refusal) and Eragrostis tremula (C4) in the first years of fallowing, then slow diversification with other grasses and also the small legume Zornia glochidiata (C3) as the fallow gets older. Except in manured fields (> 7 ans) trend in reduction of millet yields with the length of the cropping cycle. Strong increase in millet yield over four years following livestock corralling on the field to apply 2 to 14t DM of manure (+ urine).

Non manured field

0

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20

30

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50

1 2 3 4-8 >8

Mitracarpus scaber

Eragrostis tremula

Jacquemontia tamnifolia

Schizachyrium exile

Cassia tora

Cenchrus biflorus

cover %

a

0

5

10

15

20

25

30

1 2 3 6 9

Mitracarpus scaber

Eragrostis tremula

Ctenium elegans

Schizachyrium exile

Aristida sieberiana

Indigofera strobilifera

Walteria indica

Cenchrus biflorus

Jacquemontia tamnifolia

Cassia mimosoides

Andropogon gayanus

Zornia glochidiata

cover %

fallow age (y)

Incremental millet grain yield

-500

0

500

1000

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2500

2 4 6 10 14

Manure applied in 1997 (t DM/ha)G

rain

in a

dditio

n t

o c

ontr

ol yie

ld (

kg/h

a)

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Fakara