Agricultural intensification and aquatic ecology: impacts and trade-offs

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Agricultural intensification and aquatic ecology: impacts and trade-offs

Cecchi P. (1), Soleri R. (2), Sanogo S. (3), Bamba D. (3), Diakité K. (4), Poussin J.C. (5), Spinelli S. (2), Kabré A. (3), Gonzalez

C. (2)

(1, 5) IRD UMR G-eau (2) LGEI, Alès, France (3) Univ. Bobo-Dioulasso(4) 2iE

[email protected]

mailto:[email protected]

Andes • Ganges • Limpopo • Mekong • Nile • Volta

Content 1. Main message2. Background and Purpose3. Methodology4. Findings5. Lessons 6. Recommendations to defined stakeholder

Agriculture Intensification and Aquatic Ecology: Impacts and trade-offs


In the Boura Lake, evidences of eutrophication (macrophyte proliferation) and of contamination (pesticides residues) have been documented. Both are consequences of agricultural intensification and threaten the sustainability of the agro-ecosystem.

Content1. Take home message






Ceratophyllum submersumProliferation since a couple of years 1/ Strong LOCAL preoccupation Sensitization Workshop in Boura (2011)

- Infrastructures- Fishery

2/ METABOLISM consequences- Quality & productivity

3/ SCIENTIFIC priority- causes & impacts

From an ecosystem perspective: advanced eutrophication


MACROPHYTES(clear)

PHYTOPLANKTON(turbid)

BEFORENOW

WHEN?

WHY?

Both states are RESILIENT

Shifts associated to DISTURBANCES

Alternative Stable States theory for Shallow Lakes,Scheffer et al. 1993.


Algae Turbidity

SedimentResuspension

Nutrients

Cerato

? Allelopathy

? Pesticides

? Hydrodynamics

? Land Use erosion

? Origins

Fish? Structure

1/ Diagnose: realized by V3 project2/ Remediation: support to local communities

Boura stakeholders:


Algae Turbidity

SedimentResuspension

Nutrients

Cerato

? Allelopathy

? Pesticides

? Hydrodynamics

? Land Use

? Origins

Fish? Structure

Implementation of a series of dedicated activities





METHODOLOGY (1)

1/ Comparative studies in three sites: Boura vs two references (pristine vs impacted)

2/ Passive samplers: POCIS & ChemCatchers (3 sites)

3/ Macroinvertebrates: European Directive protocols (3 sites)

4/ Surveys (in Boura to document agricultural practices)

5/ Allelopathy (lab analyzes using a Phytoplankton Analyzer)


METHODOLOGY (3 sites)

BALA: ‘pristine’ BAMA: ‘impacted’

BOURA: ? Contamination status ?


METHODOLOGY (passive samplers; 3 sites)

3 Floating devices

2 Pocis

2 Chemcatchers

13 days


METHODOLOGY (passive samplers)

22 Chemicals


METHODOLOGY (macroinvertebrate communities; 3 sites)

Standard protocols (sampling, observations,…)

Statistical analyzes

Identification keys (taxinomy)


METHODOLOGY (surveys in Boura)

Two upstream Inland Valleys - agricultural practices

- intensification pathways


METHODOLOGY (allelopathy)

C. Submersum (fresh leaves and powder)• Preparation of Aqueous & Methanolic extracts • Phytoplancton exposure (different concentrations, 24-72h)• Phyto PAM analyzes (photosynthesis efficiency)





FINDINGS (pesticides 1)

Among the 22 chemicals targeted:• 12 exhibited concentrations up to the detection limits;• All were all present in Boura (i.e. N > Bala & Bama).


FINDINGS (pesticides 2)

The 6 principal have been quantitatively assessed:• No pesticide residues in Bala (Pristine = OK);• Comparable concentrations in Boura and Bama;• Cocktail in Boura: 5 herbicides & 1 insecticide


FINDINGS (macroinvertebrates 1)

26,400 specimens belonging to 33 families:• 30 in Bala;• 25 in Bama;• 23 in Boura.

BALA

BOURA

BAMA

DISTANCE


FINDINGS (macroinvertebrates 2)

Within the Noteridae family (beetle):• 3 ubiquitous species;• 1 candidate as ‘sentinelle’ species.

BALABOURABAMA


FINDINGS (surveys 1)

100% of farmers used pesticides and fertilizers• quantities of fertilizers are proportional to the surfaces of

Inland valleys’ fields


FINDINGS (surveys 2)

100% of farmers used pesticides and fertilizers• quantities of pesticides are inversely proportional to the size of exploitation


FINDINGS (allelopathy)

Both aqueous & methanolic extracts are potent• in the range [0.05 – 50] mg/L (dw) of C. submersum

Photosynthetic efficiency after 24h (MeOH extract)





LESSONS (1)

1/ Pesticide residues in Boura Below Norm values

? impacts of chronic exposures to cocktail?Associated to present/past landuse on watershed

2/ Fertilizers and eutrophicationimpact of (upstream) inland valleys

3/ Macroinvertebratesredundancy & « sentinelle » species

4/ Allelopathy (natural herbicide)? cumulative effects in presence of chemicals residues?


LESSONS (2)

1/ Polyactivity of households in Boura => increased incomes

=> multiple uses of available water resource (direct / indirect)

2/ Management strategies (1)=> evaluation of externalities (economy-health-water quality)

3/ Footprints of ecological disturbances in Boura=> impacts on resilience?





RECOMMENDATIONS

1/ Farmers => to control the origin and quality of phytosanitary products

2/ Managers => to preserve the multiple uses vocation of Small Reservoirs(irrigation is marginal in terms of livelihood…)

3/ Researchers=> to quantify the impacts => to explore the trade-offs


CHALLENGING, ISN’IT ????

THANK YOU…

Technology

Agricultural intensification and aquatic ecology: impacts and trade-offs