Vegetation Change in North Africa through the analysis of satellite data,

1982 - 2006

Professor Stephen Young

Department of Geography, Salem State College

IGC - 2008, Tunis, Tunisia – August 13, 2008

Vegetation Change in North Africa

OUTLINE

Why this research?

Overview of Data Set & Methodology used.

Overview of where land cover change is occurring.

Overview of persistent vegetation change.

Overview of the Driving Forces behind the changes.

Vegetation Change in North Africa

Why this research?

Global Vegetation Change From 1982/83 to 1998/99

Why this research?

Have already mapped vegetation change at the global scale and now focusing on the regional scale.

Have researched Australia, East Asia, South Asia, and Southwest Asia – now looking at North Africa.

Looking for strong temporal signals of PERSISTENT vegetation change.

Trying to understand those signals in context with global environmental change.

Why this research?

In particular

Colleagues at this conference may be able to help me understand the vegetation changes which are occurring in North Africa.

Data Used

GIMMS AVHRR land cover data NOAA / NASA AVHRR data – 8 km resolution

Coarse resolution picks up broad change

Normalized Difference Vegetation Index (NDVI)

(NIR - red) / (NIR + red) High correlation with photosynthesis

Data Pre-Processing

GIMMS AVHRR data Base data: NDVI 15-day MVC

Re-composited: Monthly Max Composites, January 1982 – December 2003

Re-composited: Annual Average Composites

Re-composited endpoints (1982 + 1983) ÷ 2 = 1982/83 (2002 + 2003) ÷ 2 = 2002/03

Global Scale NDVI GIMMS dataAnnual Average 1987

Desert Pixels & All Global Land Pixels

-2

-1

0

1

2

3

4

5

6

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3

Years

Perc

ent

Global Land Cover Sahara 2Linear (Global Land Cover) Linear (Sahara 2)

Data Used

SPOT VEGETATION data (1km) SPOT IMAGE – 1 km resolution

Finer resolution than GIMMS

Normalized Difference Vegetation Index (NDVI) (NIR - red) / (NIR + red) High correlation with photosynthesis

Data Pre-Processing

SPOT VEGETATION data Base data: NDVI 10-day MVC

Re-composited: Monthly Max Composites, April 1998 – Dec 2006

Re-composited: Annual Average Composites 1998 used Jan, Feb, March of 1999

Re-composited endpoints (1998 + 1999) ÷ 2 = 1998/99 (2005 + 2006) ÷ 2 = 2005/06

SPOT VEGETATION NDVI Annual Average 2001

SPOT VEGETATION

0

20

40

60

80

100

120

140

160

180

200

1998 1999 2000 2001 2002 2003 2004 2005 2006

Years

Sca

led

ND

VI

All Africa Sahara Vegetation

Methodology

Pairwise Comparison (Univariate Differencing) GIMMS: 2002/03 minus 1982/83 = change SPOT: 2005/06 minus 1998/99 = change

Percent Change (2002/03 minus 1982/83) / 1982/83 = Percent Change (2005/06 minus 1998/99) / 1998/99 = Percent Change

Profiling Graphing change through the period

Results

All Africa ChangeGIMMS: 1982 to 2003

Table – All Africa Change

Classification (% Change) # of Pixels % of Land PixelsMajor Decrease (decrease > 20%) 3895 0.1%Decrease (decrease 10 to 20%) 22426 3.8%Minor Decrease (decrease 5 to 10%) 60269 9.9%Little Change (between -5 and +5%) 343420 56.9%Minor Increase (increase 5 to 10%) 72695 12.1%Increase (increase 10 to 20%) 70061 11.6%Major Increase (increase > 15%) 33456 5.6%All Land Pixels 606222 100%

North Africa ChangeGIMMS, 1982 to 2003

Table – North Africa Change

Classification (% Change) # of Pixel % of Land PixelsMajor Decrease (decrease > 20%) 502 0.1%Decrease (decrease 10 to 20%) 2081 1.4%Minor Decrease (decrease 5 to 10%) 9173 6.2%Little Change (between -5 and +5%) 125815 85.6%Minor Increase (increase 5 to 15%) 4645 3.2%Increase (increase 10 to 20%) 3067 2.1%Major Increase (increase > 15%) 1710 1.2%All Land Pixels 146993 100%

Profiles of Change from 1982 to 2003

Profiles of Change from 1982 to 2003

Vegetation Change in North AfricaGIMMS Data - 1982 - 2003

Change is highly variable year to year

Few Persistent Changes

All Africa ChangeSPOT: 1998/99 to 2005/06

All Africa ChangeSPOT: 1998/99 to 2005/06

North Africa – Areas of Decline

North Africa – Areas of Decline

60

70

80

90

100

110

120

130

140

150

160

1998 1999 2000 2001 2002 2003 2004 2005 2006

Years

Sca

led

ND

VI

Series1 Series2 Series3

North Africa – Areas of Decline

60

70

80

90

100

110

120

130

140

150

160

1998 1999 2000 2001 2002 2003 2004 2005 2006

Years

Sca

led

ND

VI

Series4 Series5

North Africa – Areas of Decline

North Africa – Areas of Decline

60

70

80

90

100

110

120

130

140

150

160

1998 1999 2000 2001 2002 2003 2004 2005 2006

Years

Sca

led

ND

VI

Series1 Series2 Series3 Series4 Series5

North Africa – Same Areas of DeclineGIMMS Data, 1982/3 – 2002/3

Mesopotamian Wetlands, Iraq Areas of Decline

GIMMS DataWetlands

0.1

0.12

0.14

0.16

0.18

0.2

0.22

0.24

0.26

0.28

0.3

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3

Years

ND

VI

Wetlands

India South Interior Karnataka

Annual Integrated NDVI

y = 0.0222x - 39.313

4.5

5

5.5

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

YEARS

Trend line:

NDVI

5 yr moving average

India South Interior Karnataka

Annual Integrated NDVI Annual Rainfall

y = 0.0222x - 39.313

4.5

5

5.5

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

YEARS

Trend line:

NDVI

5 yr moving average

y = -33.752x + 8499.8

4000

5000

6000

7000

8000

9000

10000

11000

12000

Years

Rainfall in mm

Trend line :

5 yr moving average

North Africa – Areas of Increase1 – West Nile Delta, 2 – North Central Algeria, 3 – Atlas Mountains, 4 – South Morocco

North Africa – Areas of Increase1 – West Nile Delta, 2 – North Central Algeria, 3 – Atlas Mountains, 4 – South Morocco

GIMMS Data – Western Nile Delta

Arc of Irrigation Temporal Profiles

50

70

90

110

130

150

170

190

210

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3

Years

Scal

ed N

DVI

Region - 1 Region - 2 Region - 3 Region - 4 Region - 5

3-year Running Average

50

70

90

110

130

150

170

190

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3

Years

Scal

ed N

DVI

Region - 1 Region - 2 Region - 3 Region - 4 Region -5

Conclusions

Unlike other parts of the world, patterns of declining photosynthesis (NDVI) in North Africa are highly variable – with few areas of persistent change.

Climate must be the major driver of change for most of the region.

Conclusions

Areas in Morocco indicated in the literature as suffering from desertification – also have patterns of great variability.

The influence of human activity is hidden by strong climate variability.

Conclusions

There are some regions in North Africa which do show signs of persistent increase.

Like other regions of the world, the main driver of persistent increases in photosynthesis (NDVI) is agriculture and in particular related water resources.

Future research will focus on analysing precipitation data for North Africa with NDVI data.

.

Thank You