Contribution of MODIS land cover product to the analysis of the agricultural domain between 2001 and 2011 in West Africa

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CONTRIBUTION OF MODIS

LAND COVER PRODUCT TO

THE ANALYSIS OF

THE AGRICULTURAL DOMAIN

BETWEEN 2001 AND 2011 IN

WEST AFRICA

Leroux L1_{., Jolivot A}1_{., Zoungrana B}2_{., Bégué A}1_{., Lo Seen D}1

1_{CIRAD, UMR TETIS, Montpellier, France} 2_{AGRHYMET, Niamey, Niger}

March 19-21,2014 Berlin, Germany

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Background of the study

Food security in West Africa

West Africa is characterized by: A strong climate variability in space and time

 Impacts on agricultural production and on food security

Challenge of West Africa : Enhance knowledge on crop production

dynamics both at regional and local scale

Boyd et al., 2013, NCC

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Background of the study

Crop production and crop area in West Africa

Production = Yield x Area

Remote sensing and the monitoring of crop areas

208,256,000 ha 38,764,012 ha (20%) Cultivable area Cultivated area FAO, 2005

•

Global land products: improve our understanding of the extent and distribution of major land cover types at a global scale

•

Maps locating the most important cropping areas

0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 9 10 1991 1993 1994 1995 1997 1998 1999 2000 2001 2002 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 C u m u la ti ve ( % ) F re q u e n c y Frequency Cumulative (%)

Number of papers on global land products (Web Of Science)

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Objectives of the study

Question addressed:

What is the reliability of Global Land Cover products for crop areas

characterisation and mapping in West Africa?

Case study of the MODIS Land Cover Product v5.1 (MCD12Q1.V51)

Outline:

Assessment of cultivated areas 1 Agricultural statistic databases Spatial distribution of cultivated areas At local scale 2

Crop areas classification from high resolution

images

Examine the spatial distribution of the precision at regional

scale 3

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To what extent the MODIS Land Cover Product is able to estimate cultivated areas?

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Assessment of the MODIS LCP reliability for crop area

estimations

Data

•

Agricultural Statistic databases

FAOSTAT - Agricultural Land (2001 – 2011)

 Regional & National scales

AGRHYMET - Surfaces harvested for major crops (2001 – 2011)

 Burkina Faso : Subnational L-1 & Subnational L-2 scales

•

MODIS Land Cover Product V51 – 500 m - Yearly (2001-2011) 2 Cropland classes (IGBP):

 Cropland (100%)

 Cropland/Natural Vegetation Mosaic (50%)

𝐶𝑟𝑜𝑝_{𝑎𝑟𝑒𝑎} = 𝑛𝑏𝑠_{𝑝𝑖𝑥𝑒𝑙𝑠} × 5002

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Regional Scale – FAOSTAT/MODIS

Average values between 2001 - 2011

16 %

80.4Mha

18%

92.6Mha

Cropland FAOSTAT _{Cropland MODIS}

Assessment of the MODIS LCP reliability for crop area

estimations

Dynamics between 2001 - 2011 60 65 70 75 80 85 90 95 100 105 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 C ro p la nd a re a ( M h a )

Cropland area FAOSTAT (pvalue=4x10^(-6)***) Cropland area MODIS (pvalue=0.002**)

1.3 MHa/year 1.5 MHa/year

Good estimation at regional scale

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Assessment of the MODIS LCP reliability for crop area

estimations

National Scale – FAOSTAT/MODIS

Average values between 2001 - 2011 Dynamics between 2001 - 2011

MODIS FAOSTAT

Niger

Overall good estimation at national scale

Some discrepancies in terms of dynamics

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Assessment of the MODIS LCP reliability for crop area

estimations

Subnational L-1 Scale (Region)– Burkina Faso – AGRHYMET/MODIS Average values between 2001 - 2011

East AGRHYMET Dynamics between 2001 - 2011 MODIS Moderate estimation at subnational scale Overestimations by MODIS LCP Some discrepancies in terms of dynamics - East

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Assessment of the MODIS LCP reliability for crop area

estimations

Subnational L-2 Scale (Province) – Burkina Faso – AGRHYMET/MODIS Average values between 2001 - 2011

Tapoa Gourma Yatenga Dynamics between 2001 - 2011 AGRHYMET MODIS Poor estimation at subnational

scale

Overestimations by MODIS LCP Opposite dynamics

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What about the MODIS Land Cover Product accuracy concerning the spatial distribution of crop areas?

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Data

•

MODIS Land Cover Product

 Cropland and mixte cropland classes for 2011

•

High resolution classifications of the crop domain

 4 classifications from SPOT (2.5m) - Supervised method 2007-Mali (Vintrou et al., 2012, RSE)

 30 classifications from Google Earth by photo-interpretation Square of 25km²

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Methods Pareto Boundary MODIS HRS Omission error Comission error and F-Scores Error Matrix

Low resolution cell Crop class in HS data

75%-100% 50%-75% <25%

25%-50%

% of crop class in each low resolution cell

Site size = 5km x 5km (100 MODIS Pixels)

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Methods Pareto Boundary MODIS HRS Omission error Comission error Confusion Matrix Commiss ion Er ror Omission Error 1 0 0 ₁ Low-resolution biais Performance of the classification algorithm Pareto Boundary

Boschetti et al., 2004 (RSE)

Site size = 5km x 5km (100 MODIS Pixels)

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Crop areas estimation – MODIS vs HRS

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5 9 16 15 19 4 29 27 25 18 8 28 2 13 24 3 30 17 20 10 14 31 23 21 6 26 1 7 22 % C ro p Site

% Crop HRS % Crop MODIS

MODIS Over-estimation MODIS Under-estimation

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Crop areas accuracy – MODIS vs HRS

Zone 1 : North Senegal % of crop class in each MODIS cell

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Zone 1 : North Senegal The Pareto Boundary

Low unreacheable region

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Zone 2 : Gambia % of crop class in each MODIS cell

Fragmented site Large patches of crop

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

The Pareto Boundary

Moderate unreachable region

Moderate performance of the MODIS classification

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

Zone 18 : South Nigeria % of crop class in each MODIS cell

Highly fragmented site Little patches of crop

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Assessment of the MODIS LCP accuracy for crop area spatial

distribution

The Pareto Boundary

Very High unreachable region

Moderate performance of the MODIS classification

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Can we map the crop areas MODIS LCP accuracy considering the landscape spatial heterogeneity?

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Map of the MODIS LCP uncertainties for crop areas

Methods

MODIS Indicators of Landscape fragmentation

at regional scale

(grid of 5km x 5km)

Matheron Compactness _{Crop area}

Crop perimeter Nbs of patches Mean Focal Diversity

Multiple Linear Regression

at the site scale

ActualAccuracy Indicators

at site scale

Estimated Accuracy Indicators

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Map of the MODIS LCP uncertainties for crop areas

Variables Selection and Model Fitting

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Map of the MODIS LCP uncertainties for crop areas

Map of the users accuracy estimate

Maximum user accuracy estimate : 70% Better accuracy estimate in the West

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Conclusion

Crop area estimations

Regional-National-SubNational-1-SubNational-2

 Definition of Fallows (Statistic)

 Definition of the Mosaic class (MODIS)

 Weakness of aggregated statistic data: lack of spatial representativeness

MODIS LCP accuracy for crop area spatial distribution

 Over-estimation for crop fraction below 40%

 Fragmented landscape = impact on the low resolution map accuracy  Notion of Mixel = Mixed Pixel

Map of the MODIS LCP uncertainties for crop areas

 Omission error = 𝐹 𝑀𝑎𝑡ℎ𝑒𝑟𝑜𝑛, 𝐶𝑟𝑜𝑝 𝑃𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟  Maximum user accuracy estimate = 70% for crop

 Increase the number of test sites to improve our results

 Analyse the spatial distribution of accuracy in accordance with agro-ecological climatic zonations and slopes.

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Conclusion

Key ideas

Original approach based on Remote Sensing data and statistic data to assess the reliability of the MODIS LCP for crop areas estimation and localisation in West Africa

An assessment of the Global Land Product accuracy allows to anticipate product limitations for users and leads to appropriate map use

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Thank you for listening…

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mo nt hl y ND VI

Cropping system with 1 cycle Cropping system with 2 cycles

Benin

Mali

Assessment of the MODIS LCP accuracy for crop area spatial

distribution

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