Triple Green–Finding ways to meet the dual challenge of enhancing food production and meeting new sustainability criteria

Louise Karlberg, SEIABSTRACT: Sub-Saharan Africa (SSA) has been identified as a future hotspot for food shortage due to current low agricultural yields andhigh population growth. Two important ways to improve yields are: A) Bridging dry-spells by implementing water harvesting forsupplemental irrigation which results in more efficient use of the available green water and augmentation of the green water resource. B)Implementing productive sanitation systems, i.e. the collection of and safe reuse of human urine and faeces as a fertiliser for increasedfood production. In SSA the total amount of nutrients in excreta is roughly equivalent to the amount of nutrients applied as chemicalfertilizers today. Productive sanitation systems can contribute to increasing the carbon content of the soil through increased plantproductivity and thus increased input of leaf and root litter to the soil; it therefore represents a mitigation strategy for climate change. Waterharvesting is a climate change adaptation strategy, since dry-spells are expected to become increasingly common under a future climate.

Within the triple green project, we investigate the opportunities and challenges to increased crop productivity and food security through theuse of productive sanitation in combination with water harvesting: producing higher yields (green) by adopting productive sanitationsystems and supplemental irrigation, using green water more efficiently, in a sustainable (green) way. One of the key questions is thuswhether the effect of combining these two management interventions is additive, multiplicative or perhaps only determined by the mostlimiting factor (water or nutrients). In addition, the following questions will be addressed within the project: (i) whether the use of a waterharvesting approach is socially acceptable, (ii) whether the use of urine as a fertilizer may have potentially negative effects on salinity inthe soil in arid climates, (iii) to what degree carbon sequestration takes place.

In the second phase of the project the intention is to also include conservation agriculture, as an additional way of improving soil waterholding capacity and soil carbon storage. If the results from combining these management interventions indicate significant long-termbenefits in terms of yield, carbon sequestration and the ability to bridge dry-spells, the next step would be to repeat this set-up on thefarmers’ field.

Human growth20/80 dilemma

Ecosystems60 % loss dilemma

Climate550/450/350

dilemma

Surprise99/1 dilemma

TThe Quadruple Squeeze

Dual challenge – environment and development

• Meeting food requirements – MDG’s

• Reducing atmospheric CO2 levels to 350 ppm

Climate Change

Ocean acidification

Ozone depletion

Global Freshwater

Use

Rate of Biodiversity

Loss

Biogeochemical loading: Global

N & P Cycles

Atmospheric Aerosol Loading

Land System Change

Chemical Pollution

Planetary Boundaries

Climate Change< 350 ppm CO2 < 1W m2

(350 – 500 ppm CO2 ; 1-1.5 W m2)

Ocean acidificationAragonite saturation

ratio > 80 % above pre-industrial levels

(> 80% - > 70 %)

Ozone depletion< 5 % of Pre-Industrial 290 DU

(5 - 10%)

Global Freshwater Use<4000 km3/yr

(4000 – 6000 km3/yr)

Rate of Biodiversity Loss

< 10 E/MSY(< 10 - < 1000

E/MSY)

Biogeochemical loading: Global

N & P CyclesLimit industrial

fixation of N2 to 35 Tg N yr-1(25 % of natural fixation)

(25%-35%)P < 10× natural

weathering inflow to Oceans

(10× – 100×)

Atmospheric Aerosol Loading

To be determined

Land System Change

≤15 % of land under crops

(15-20%)

Chemical Pollution Plastics, Endocrine Desruptors, Nuclear Waste Emitted globally

To be determined

Planetary Boundaries

Example - carbon sequestration in terrestrial ecosystems

• Carbon sequestration by reforrestation

• Carbon sequestration in agricultural soils

• Improved water productivity by C-fertilisation

What is the impact on water and food production?

Reforrestation

An annual C seq rate of 1.6 GtC/yr by 2050 (Hansen et al) results in:

• 1300 km3/yr increased consumptive water use by 2050 – reductions in runoff (trade-off)

• If reforrestarion on current agricultural land: competition with food production (trade-off)

C seq on agricultural lands –Preliminary estimates

An annual C seq rate of 0.4-1.2 GtC/yr by 2050 (Lal et al) results in:

• 4000 – 10000 km3/yr increased consumptive water use by 2050 – reductions in runoff (trade-off)

• NOT realistic – assumes same water productivity

• Results in concurrent yield improvements (synergies)

Key question:

Are the current agricultural techniques sufficient to meet this dual challenge?

The Triple Green project - NigerAgricultural management interventions for a new

green revolution, in a green (sustainable) way based on green water, in the tropics

Louise Karlberg, Linus Dagerskog, Elisabeth Kvarnström and Jens-Arne SubkeStockholm Environment Institute

ANDMoussa Baragé and Moustapha Adamou

Abdou Moumouni University, Niamey, Niger

Triple Green - Rationale

Small scale agriculture in SSA

• Low yields

• Erratic rainfall

• Nutrient deficiency

Possible to double or even triple yields

Triple Green - MethodsTwo important ways to improve yields are:

A)Bridging dry-spells by implementing water harvesting for supplemental irrigation

B) Implementing productive sanitation systems, i.e. the collection of and safe reuse of human urine and faeces as a fertiliser for increased food production.

What are the added benefits of combining the two?

Triple Green – nutrients + water

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50

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200

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Crop

yie

ld im

prov

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)

Non fertilised

Fertilised

CA WH WSD

Triple Green – climate change

Mitigation: Productive sanitation + water harvesting systems can contribute to increasing the carbon content of the soil through increased plant productivity and thus increased input of leaf and root litter to the soil

Adaptation: Water harvesting can help bridging dry-spells, which are expected to become increasingly common under a future climate.

Randomised block-trial on supplementary irrigated, urine fertilised millet

Expected results

Field data will be combined with a physically based ecosystems model to study:

• Carbon sequestration, water flows, yields and salt accumulation over time under different management regimes.

Moreover, the model will be used to study the impact of a changed climate on these variables

Scaling out

To answer this questions, we need:

• Assessments across scales

• Integrated assesments focussing on several sustainability criteria (e.g. nutrients, land-use, carbon and water)

• A multi-sectoral approach (e.g. food, feed, fuel, fibre)

• Assessments of ecosystem services, livelihoods, resilience, policies and institutions, etc.

If implemented on a larger scale – would we produce enough food and still remain sustainable?