MONITORING LAND USE AND LAND USE CHANGES IN
FRENCH GUIANA BY OPTICAL REMOTE SENSING
Photo : Valéry Gond
Photo : Valéry Gond
Gaëlle VERGER – ONF, French National Forest Office – [email protected]
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Photo
: Gaëlle
VERGER
Photo
: Valéry
Gond
Photo
: Valéry
Gond
Summary
Context and objectives:
• Objectives and method of the project
Implementation :
• Data
• Stratification
• Photo-interpretation
• Statistical estimates
Results and discussion:
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Summary
Context and objectives:
• Objectives and method of the project
Implementation :
• Data
• Stratification
• Photo-interpretation
• Statistical estimates
Results and discussion:
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Ongoing project in French Guiana
• Objectives of the project
– In the Kyoto Protocol framework
– To complement existing inventories made for 1990, 2006 and 2008 time points
– Provide surface data for 2012 and feed the last French GHG inventory
• Methods
–
–
–
–
Based on the existing method (developed and approved by IPCC in 2006)
Statistical inventory ≠ wall to wall mapping
On the basis of stratified sample points
By visual photo-interpretation of satellite imagery
• GLCF Landsat Images for year 1990
• SPOT images for years 2006, 2008 & 2012
• To be combined with emission factors
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Summary
Context and objectives:
• Objectives and method of the project
Implementation :
• Data
• Stratification
• Photo-interpretation
• Statistical estimates
Results and discussion:
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Satellite Data
• 1990: 8 Landsat Imageries
• 2008: SPOT 2, SPOT 4 & SPOT 5
• 2012: SPOT 5 (about 270 imageries, thanks to SEAS)
• Selection of imageries per frame depending on the cloud coverage
SPOT 5
SPOT 4
SPOT 2
Cloud
25
Cloud cover
cover << 75
10 %
%
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Definition of the strata
•
•
•
•
24/11/2009
Based on several existing studies and on
experts knowledge (ONF and National
Park of Guyane)
Strata R (Reinforced sampling)
– ONF GIS analysis on existing
information
• Roads
• Agriculture
• Cities
1km
Buffer
• Human settlements
• Urban areas
• Gold mining
– Mangroves ecological area
Strata N (Normal sampling) : all area not in
Strata R
Strata P : 52 km circle surrounding Petit Saut reservoir
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Sampling design
• Systematic/random grid
– Square grid - 932 m between points
– Random origin and inclination
•
Sample definition
– Strata R : All Grid points
– Strata N : One point over 5
Strata
Total Area
(ha)
Strata
Nbr of points
Distance between 2
points (m)
Surface of sample
points (ha)
N
7 030 800
Normal
1 953
4 194
3 600
R
1 526 241
Reinforced
17 543
932
87
TOTAL
8 557 041
19 496
• Permanent sampling : same samples in 1990, 2008 and 2012
Good estimation of Land Use areas AND Land Use Changes
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Photo interpretation
Shifting
Cultivation
Gold mining
SPOT55TM
2006
– ©- CNES
Landsat
1990
GLCF
Landsat
SPOT55TM
2006
1990
– ©- CNES
GLCF
Petit Saut
Reservoir
Landsat
SPOT54TM
2006
1990
– ©- CNES
GLCF
24/11/2009
Agriculture
extension
Landsat
SPOT54TM
2006
1990
– ©- CNES
GLCF
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Photo interpretation
1990
2008
Land Use categories
Forest
Mangroves
Other forests
Settlements
Gold mining
other Settlements
Cropland
Grassland
Wetlands
Sea
Other lands
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Statistical estimates
• Land use area estimates from Land use proportion in each strata
Area estimate
Sij  Pij  S j
Variance
Pij  (1  Pij )
2
Vij  S j  
nj
Stand. dev.
 i  Vi 
j
j
V
ij
j
Standard error of the estimate
• Land use conversion areas estimated from Land use conversion
proportions in each strata : Same formulas
– Estimates + Precision of estimates
• Sample used = All points without clouds in 1990 And 2006 And
2008 = 16469 points out of 17667.
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Summary
Context and objectives:
• Objectives and method of the project
Implementation :
• Data
• Strata
• Photo-interpretation
• Statistical estimates
Results and discussion:
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Results: Land uses 1990 2006 2008
•
•
24/11/2009
Land use 1990 / 2006 (methodology development) / 2008
Ongoing interpretation for 2012
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Results: Forest cover changes
Land use changes
between forest and non forest (ha)
1990 - 2008
Strata N
Estimate
Stand. error
Forest > Forest
6 824 884
30 971
Forest > Non forest
8 067
8 063
Including Forest > Settlements
8 067
8 063
Including Forest > Gold mining
0
0
Including Forest > Other settlements
8 067
8 063
Including Forest > Cropland
0
0
Including Forest > Grassland
0
0
Including Forest > Wetlands
0
0
Including Mangroves > Wetlands
0
0
Including Forest > Other lands
0
0
Including Mangove > Sea
0
0
Including other Forest > Other lands
0
0
Non Forest > Non forest
112 941
29 938
Non Forest > forest
0
0
Including Cropland > Forest
0
0
Including other non forest > Mangrove
0
0
24/11/2009
Strata P
Strata R
TOTAL
Estimate
Estimate
Estimate
Stand. error Stand. error Stand. error
176 030
1 028 196
8 029 110
1 622
4 046
31 276
34 790
65 662
108 518
1 589
2 419
8 566
954
21 166
30 188
287
1 399
8 188
868
14 863
15 731
274
1 175
1 207
87
6 303
14 457
87
768
8 100
0
27 281
27 281
0
1 584
1 584
0
2 258
2 258
0
460
460
33 835
4 892
38 727
1 571
677
1 711
0
2 634
2 634
0
497
497
0
10 066
10 066
0
969
969
0
9 595
9 595
0
946
946
0
470
470
0
210
210
1 822
131 605
246 369
396
3 326
30 125
0
12 229
12 229
0
1 067
1 067
0
3 292
3 292
0
556
556
0
6 867
6 867
0
802
802
A large majority of the forest is
unchanged
> 98 %
A changed observed on 1 point of strata N
Large Influence on the estimates and the
standard error of the estimates
3 main causes of human deforestation in
French Guiana
Petit Saut Dam
Natural evolution ≠ deforestation (Kyoto)
Little Non forest to forest changes
Mainly in croplands (Shifting cultivation)
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Results : Annual deforestation
• Analysis annual deforestation during 1990/2006 and 2006/2008
– Without Petit Saut Dam (temporal event) and without Mangrove to sea
conversions (= Natural ≠ Deforestation)
Forest to other lands
Forest to settlements
Forest to wetlands
Forest to Grassland
Forest to cropland
1990-2006 period
2006-2008 period
0
0
50
1
0
00
1
0
50
2
0
00
2
0
50
3
0
00
3
0
50
hectare / year
– Increase of total annual deforestation from 3500 ha/year to 5900 ha/year
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana
Discussion
•
Why this methodology has been chosen
–
–
–
–
–
•
It was the methodology used for the NFI and this methodology has been validated by the IPCC for France => Coherence with
the national territory
Does not require lot of expertise
Saving digitization time and bias
Existing ArcGIS extension for the analysis
Quality control integrated within the statistical process
Application of this methodology in the REDD+ framework?
– Efficiency of the method to monitor Deforestation has been demonstrated
– Possibility to monitor forest degradation? Further investigations needed
• Use of SPOT 5 data (2.5 to 10 m resolution) or Very High Resolution sensors (< 1m)
• Combination with radar data (sensitivity to biomass) / Combination with field data
– Key issues:
• Availability and cost of high resolution satellite imageries
• No localization of the deforestation
24/11/2009
Knowledge-based management of tropical rainforest – Cayenne, French Guiana