Olron , 11-17 May 2014 Pastoralism and water resources in the Sahel - - PowerPoint PPT Presentation

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 sheep 3 30 54 16 zebu 2-3 19 66 15 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,

• pposite 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

• f 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 2,40 2,90 3,40 3,90 /6/09 4/7/09 /7/09 1/8/09 /8/09 /8/09 /9/09 /9/09 /10/09 /10/09 11/09 1/09 12/09 /12/09 2/1/10 /1/10 /1/10 /2/10 /2/10 /3/10

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

10 20 30 40 500 1000 1500 2000 2500 amj j aasond j fmamj j asond j fmamj j asond j fmamj j asond

Site 17, Agoufou, Avril 2007 - Sept 2010

d e n…

Kg/ha plant/m² % 20 40

60 80 aa mj j asonnd j fm a mj j jasond j fm m a mj j asonnd j fm a mj 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

500 1000 1500 2000 2500 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

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 type kg/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

• f the grazing pressure:

Dry season decrease of herbaceous mass at Agoufou

500 1000 1500 2000 2500 3000 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 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

200 400 600 800 1000 1200 1400 Sept Oct-Nov Nov-Mar Mar-Jun Mean herbaceous mass at the end of the three periods

• f 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 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 ) %

• verall 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

200 400 600 800 1000 1200 1400 setp

• ct

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

100 200 300 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 mm

Anomalies des pluies annuelles à Hombori, 1984-2011 y = 18,8x + 710 r² = 0,19 500 1000 1500 2000 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 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 = 0,20 500 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 (%) 10 20 30 40 1985 1990 1995 2000 2005 Cover % (clay) 2 4 6 8 Cover % (shallow, sand) Clay Shallow Sand

1985 2007

1986 2007

Gourma

Persisting decrease in numbers and cover of woody plant thickets

• f 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

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

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

mm

Mean herb standing mass in fallow-rangelands 1994-2010 y = -326Ln(x) + 1465 R2 = 0,63 500 1000 1500 2000 2500 3000 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 kg MS/ha

interannual changes in mean millet and weeds yield Dantiandou sites

500 1000 1500 2000 2500 3000 3500 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

• ver 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

• n 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

20 40 60 80

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1998 1999 2000 2001 2002 2003 2004 2005 2006

'Cenchrus biflorus' 'Aristida mutabilis' 'Zornia glochidiata' Contribution to cover % Sandy soils centre sahel

Sandy soils, centre-south Sahel 20 40 60 80 100 17 18 19 31 Grass %

c

Contribution of C4 species by soil type and grazing pressure (1984-2006) 20 40 60 80 100 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1998 1999 2000 2001 2002 2003 2004 2005 2006 clay-high silt-mid rock-low sand-low sand-mid sand-high %

Gourma

500 1000 1500 2000 2500 3000 1 2 3 4 5 6 7 8 ≥ 9

weeds millet total

Yield 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

10 20 30 40 50 1 2 3 4-8 >8

Mitracarpus scaber Eragrostis tremula Jacquemontia tamnifolia Schizachyrium exile Cassia tora Cenchrus biflorus cover % a

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

500 1000 1500 2000 2500 2 4 6 10 14 Manure applied in 1997 (t DM/ha) Grain in addition to control yield (kg/ha) 2001 2000 1999 1998 1997

Fakara