Transcript Peak NDVI

Assessing Climate Changes in Arctic Sweden and
Repercussions on Sami Reindeer Husbandry and Culture:
Using a MODIS Image Time Series and Key Informant Interviews
Gregory N. Taff
The University of Memphis
Department of Earth Sciences
Yang Shao
The University of North Carolina at Chapel Hill
Department of Geography
Research Goals
1. Assess recent climate changes in
Northern Sweden (current study 2000 –
2006)
2. Understand how climate changes impact
and could impact Sami reindeer
husbandry and Sami culture
3. Future work: develop new methods for
stakeholders to use GIS to help manage
land sustainably in this region
Climate Change in Fennoscandia
Høgda et. al (2007)*
• Study area – all of Fennoscandia, 1982 – 1999
• AVHRR
• Climate change assessed through changes in
growing season using NDVI
– Growing season was determined for each pixel by
first calculating a mean NDVI (for NDVI>0) over the
past 18 years. Growing season was defined to begin
and end as the NDVI for the pixel passed this
threshold (the mean).
• This method was found to correlate well with pollen and
climate data indicating growing season
* Høgda, K., Karlsen, S., Tømmervik, H., “5 Changes in growing season in Fennoscandia 1982-1999”, in Arctic Alpine Ecosystems
and People in a Changing Environment, Springer Berlin Heidelberg, pp. 71 – 84, 2007.
Change in Onset of Spring, 1982 - 1999
Høgda et al. (2007)
Fig. Change in onset of spring during the period 1982 to 1999. Position of the pollen stations (star),
phenological observation points (circle), and climatic stations (cross) used in Høgda et al. study.
Change in Onset of Autumn, 1982 - 1999
Høgda et al. (2007)
Fig. Change in onset of autumn during the period 1982 to 1999.
Methods
• Remote sensing 2000 – 2006
– Monitor annual landcover changes
– MODIS vegetation cover (NDVI):
16-day composite (MOD13Q) product (v 5.0).
•
•
•
•
•
Date of first permanent snow cover
Date of snow melt
Date of peak NDVI
Peak NDVI
Average annual NDVI
– Future work:
• Conduct analyses back in time using AVHRR to get longer coverage
• Analyze climate data
• Key Informant Interviews
– In what ways have Swedish Sami reindeer herders noticed local
climate changes?
– How has climate change impacted and how might climate change
impact Sami reindeer husbandry?
MODIS Specifications
Band No.
Resolution (m)
Bandwidth (um)
1
2
250
250
620-670
841-876
3
4
5
6
7
500
500
500
500
500
459-479
545-565
1230-1250
1628-1652
2105-2155
243
228
74
275
110
8
9
10
11
12
13
14
15
16
1000
1000
1000
1000
1000
1000
1000
1000
1000
405-420
438-448
483-493
526-536
546-556
662-672
673-683
743-753
862-877
880
838
802
754
750
910
1087
586
516
(red)
(NIR)
NDVI = (NIR - red) / (NIR + red)
SNR
128
201
Image Processing 1
• Water bodies and permanent snow cover
masked out (pixels with negative NDVI
throughout summer)
• For snow cover date calculations (snow cover
determined by negative NDVI):
– Date of first permanent snow cover:
• First date when at least 75% of study area is covered in snow
(and remains covered for the winter)
– Date of snow melt:
• First date when less than 75% of study area is covered in
snow
Image Processing 2
• Monitoring vegetation changes over time
– All negative NDVI values deleted
– Calculations for Peak NDVI for each year:
• For each image date, all nonnegative NDVI values
were averaged
• Date of peak average NDVI determined for each year
• Peak average NDVI recorded
– Calculations for annual Average NDVI:
• For each year, an average was taken of all
nonnegative NDVI values of all dates in the year
Study Area
•
All remote sensing analyses were conducted
for:
1. Entire study area (Northern and North Central
Sweden, east of high mountains)
2. Intensive Study Area (ISA) in North of Sweden (land
around Övre Soppero)
•
Future work: study area to be defined by
extent of specific Sami village lands
–
–
Large tracts of land where the reindeer herds
owned by members of one “village” use throughout
the year
Some “villages” extend into Norway.
Results
NDVI values averaged for the entire year (Northern Sweden)
Peak NDVI Value for each year (Norhtern Sweden)
Julian Days at NDVI peak values (Northern Sweden)
August 1
July 1
June 1
Snow melt/cover for Northern Sweden
Year
2000
2001
Snow melt
129
129
Snow Cover
321
321
2002
2003
2004
129
49
129
321
321
321
2005
2006
129
97
321
321
NDVI values averaged for the entire year (ISA)
Peak NDVI Value for each year (ISA)
Julian day
Julian Days at NDVI peak values (ISA)
August 1
July 1
June 1
Snow melt/cover for ISA
Year
2000
2001
Snow melt
129
113
Snow Cover
321
321
2002
2003
2004
129
49
129
321
321
321
2005
2006
145
97
321
321
Conclusions from remote sensing
• Average annual NDVI increasing for
– Large Sweden study area
– ISA in north of Sweden
– Shows a likely general warming trend, continuing the trend of
elongated growing season shown by Høgda et al. (2007)
• Date of first snow cover very consistent over time
• Peak NDVI values, date of peak NDVI, date of snow melt
– No clear trend
– Not enough years of data (7 years)
– Trends should be apparent when AVHRR data is processed
Significance of climate change on
reindeer herding
• Lichen availability: video
– Future work: monitor changes in lands
containing lichens
– Grazing lands already in danger
• Mining
• Forestry
• Tourism structures
• Insects
• Layers of ice
Sami Culture
• Cultural history and reindeer husbandry as far back as 7000 years
• Reindeer husbandry
– Gives Sami rights to use land according to state governments
– 10% of Sami herd reindeer
• Small percentage now rely solely on reindeer husbandry for income
– Annual reindeer herding events maintain communities/families,
language and culture
• Reindeer calving – spring
• Ear marking – summer
• Reindeer corralling - autumn
– Source of pride
• World heritage
– Approx. 20,000 Sami
– Potentially dying language and culture
• Sami culture historically oppressed by Scandinavian countries
– Since late 20th century, a revival of Sami cultureh
– Some schools now taught in Sami language
• Sami parliament – GIS mapping to show compromised Sami lands